University of Southern California Dissertations and Theses

The Influence Of Order Information And Stimulus Display Time On Short-Term Retention

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The Influence Of Order Information And Stimulus Display Time On Short-Term Retention

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Content THE INFLUENCE OF ORDER INFORMATION
AND STIMULUS DISPLAY TIME
ON SHORT-TERM RETENTION
by
R ic h a rd F ly n n G a b r ie l
A D i s s e r t a t i o n P r e s e n te d t o th e
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
I n P a r t i a l F u l f i l l m e n t o f th e
R e q u ire m e n ts f o r t h e D e g re e
DOCTOR QF PHILOSOPHY
(P s y c h o lo g y )
J a n u a ry 19&l|.
UNIVERSITY OF SOUTHERN CALIFORNIA
GRADUATE SC HOOL
UNIVERSITY PARK
LOS ANGELES 7, C ALIFORNIA
This dissertation, written by
R ic h a rd F ly n n G a b r ie l
under the direction of hijh....Dissertation C om
mittee, and approved by all its members, has
been presented to and accepted by the Graduate
School, in partial fulfillment of requirements
for the degree of
D O C T O R O F P H I L O S O P H Y
.................
S D ean
Date.............................................................................
DISSERTATION COMMITTEE
.....
■\ " ' C hairm an
ACK NO W LEDG M ENTS
Few m ore i m p o r ta n t d e c i s i o n s a re made by a g ra d u
a te s t u d e n t t h a n t h e s e l e c t i o n o f a g u id a n c e c o m m itte e .
I t h i n k t h a t I h a v e b e e n e x tr e m e ly f o r t u n a t e i n my c h o i c e ^
a b e t t e r one c o u l d n 't b e f o u n d . I f th e q u a l i t i e s m aking
up a good c o m m itte e w e re to b e l i s t e d , my c o m m itte e w ould
r a t e a t th e to p i n a l l . I n t e l l i g e n c e , e x p e r i e n c e , r e
s p o n s i b i l i t y , c o o p e r a t i o n , k in d n e s s • • • ; name i t and
th e y h a d i t #
F o r e x a m p le , due t o e x t e n u a t i n g c ir c u m s ta n c e s ,
tim e becam e c r i t i c a l . S o l e ly f o r my b e n e f i t , th e com
m i t t e e m em bers w ere good en o u g h t o re v ie w th e f i r s t d r a f t
o f th e d i s s e r t a t i o n i n l e s s th a n one w eek. When th e
h e a v y b u rd e n o f t h e i r crow ded s c h e d u l e s , a s w e ll a s t h e i r
s e n s e o f r e s p o n s i b i l i t y t o th e p r o f e s s i o n o f p s y c h o lo g y
and to m e, i s c o n s i d e r e d , t h i s i s t r u l y a n am azin g exam ple
o f t h e i r w i l l i n g n e s s t o e x te n d th e m s e lv e s beyond th e
l i m i t s t h a t c o u ld r e a s o n a b ly b e e x p e c te d . So t o D r . Mark
S . M ay zn er, my c h a ir m a n , D r. J . P . G u i l f o r d , and D r.
H a rry W o lb e rs g o e s my s i n o e r e a p p r e c i a t i o n .
T hanks a re due a l s o t o th e o f f i c e o f N a v a l Re
s e a r c h w h ic h , th ro u g h a c o n t r a c t w ith D r . M a y zn e r, p r o
v id e d f i n a n c i a l a s s i s t a n c e . And to th e many o t h e r s , th e
i i
s u b j e c t s who v o lu n te e r e d t o p a r t i c i p a t e i n th e e x p e r i
m e n ts w i t h o u t an y c o m p e n s a tio n ; t h e i r i n s t r u c t o r s who
a llo w e d me to u s e v a lu a b le c l a s s tim e to s e e k v o l u n t e e r s ;
t o M r. S id n e y C a r l i n and M r. Hugh P e t e r s o n and th e s t a f f
a t P a s a d e n a C ity C o lle g e ; t o M rs. L o r r l e L o c k h a r t, my
t y p i s t , who n o t o n ly p u t up w ith th e tim e p r e s s u r e , b u t
a l s o my h a n d w r itin g ;- and t o a l l th e o t h e r s o f t h e f a c u l t y
and s t a f f o f th e U n i v e r s i t y who h a v e c o n t r i b u t e d t o my
e d u o a t io n , my w a rm e st t h a n k s .
iii
TABLE OF CONTENTS
Pago
ACKNOWLEDGMENTS...................................................................................... 11
LIST OF TA B LES.............................................................................................
LIST OF FIGURES..................................................................................... 1*
C h a p te r
I* INTRODUCTION............................. ...................................... 1
I I . REVIEW OF THE LITERATURE.................................... 8
I n t r o d u c t i o n • 8
E v id e n c e S u g g e s tin g s e p a r a t e Memory
M echanism s . .................................. 9
Amount o f M a t e r i a l .................................. 12
R a te o f P r e s e n t a t i o n a n d /o r R e c a l l • • • 2
D e la y B etw een P r e s e n t a t i o n and R e c a l l . • 3
P o s t s t lm u l u s C u in g .......................... 1+3
R e h e a r s a l . • • • • • • ..................... • • • • 52
S e t ..................................................................................... 60
O r g a n is a t i o n o f t h e S t i m u li a n d /o r
R e s p o n s e s . . . . .......................... • • • • • 67
R edundancy o r V e rb a l C o n te x t • • • • • • 72
p r o a c t i v e and R e t r o a c t i v e I n h i b i t i o n • • 83
F r e q u e n c y , A s s o c ia t io n V a lu e , and
S i m i l a r i t y ......................... 87
S u b j e c t V a r i a b l e s . ........................ 100
R e sp o n se V a r i a b l e s ..................... • • • • • • 102
S tim u lu s M a t e r i a l ..................................................... 106
S e n s o ry Mode o f P r e s e n t a t i o n ...........................112
Im m e d ia te Memory a s a j o i n t T ask • • • • 12k
M is c e lla n e o u s E x p e rim e n ts o r A r t i c l e s . • 126
T h e o ry • • • • • • • • • • • • • • • • • 129
D i s c u s s io n o f t h e L i t e r a t u r e • • • • • • li+0
C o n c lu s io n s S u p p o r tin g a n I n t e r f e r e n c e
P o s i t i o n .................................................................... ll+0
C o n c lu s io n s S u p p o r tin g a D ecay P o s i t i o n
( G e n e r a l ) . ........................................................ li+1
C o n c lu s io n s S u p p o r tin g a L im ite d "C h an
n e l C a p a c ity " a n d /o r a L im ite d Number
o f "C h u n k s" • • • • • • • • • • • • • • ll+2
i v
C hapter Page
E v id e n c e I n d i c a t i n g th e I n f l u e n c e o f
L ong-T erm L e a r n in g on S h o rt-T e rm
Memory ................................................................................. 3i)-3
G e n e r a l C o n c lu s io n s .................................................. lli4
I l l * EXPERIMENT I . . . . ........................................................ 11^5
I n t r o d u c t i o n • • • . . • • • • ll|-5>
M ethod • • • * • • • • • • ..........................................lli-5
R e s u l t s ........................................................................................... 153
D i s c u s s io n ............................. 167
IV* EXPERIMENTS INVESTIGATING INTERPOLATED
A C T IV IT Y .......................................................................................171
I n t r o d u c t i o n .........................................................171
E x p e rim e n t I I .................................................................. 171
E x p e rim e n t I I I ....................................................................... 173
E x p e rim e n t IV . . . . ................................... 17 o
V* DISCUSSION AND CONCLUSIONS...............................................182
T h re e T y p es o f L e a r n in g I n v o lv e d i n
Memory S p a n . • ..............................................................182
E x p e r im e n ta l C o n c l u s i o n s .............................................. 185
G e n e ra l C o n c lu s io n s ....................................................... 191
T h e o r e t i c a l C o n c lu s io n s I m
p r a c t i c a l I m p l i c a t i o n s • • • • • • • • • • 19o
VI* SUMMARY................................................................................................ 200
I n t r o d u c t i o n ............................... • •• •• • •• 200
R eview o f t h e L i t e r a t u r e • • • • • • • • • 200
E x p e rim e n t I .............................. 201
F o llo w -U p E x p e r im e n ts . • • • • • • • • . . 203
D i s c u s s io n .............................. 20I4 .
REFERENCES.......................................................................................................... 206
APPENDICES.......................................................................................................... 217
APPENDIX A ...................................................................................... 218
C a l l f o r S u b j e c t s ........................................ 219
I n s t r u c t i o n s ...................................................... 221
APPENDIX B ...................................................................................... 232
A nsw er F o r m s ........................................ 233
v
C hapter Page
APPENDIX C ............................................. 2l|.8
M urdock’ s D i s t i n c t i o n B etw een L e a r n in g
and M emory............................. 2lf-9
APPENDIX D......................................................................................25> 1
B ro w n 's I n f o r m a tio n T h e o ry F o rm u la s and
t h e D e r i v a t i o n o f t h e Amount o f O rd e r
I n f o r m a tio n T r a n s m itte d •• •• ••• •• 252
v i
LIST OP TABLES
T a b le Page
1* A v e rag e Memory S pan f o r D i f f e r e n t T ypes
o f M a t e r i a l ( B r e n e r , I 9I4 . O ) .................................... 13
2* E x p e r im e n ta l S tim u lu s L i s t s i n th e O rd e r
D i s p l a y e d ......................................................................... 11+9
3* W ords on R e c o g n itio n T a s k . •••••• •• • 15 0
I).* S tim u lu s C a te g o ry and Ite m Summary • • • • . l 5 l
5* Mean S c o r e s ...................................... 151+
6 * A n a ly s is o f V a r ia n c e Summary R e c a ll Number
C o r r e c t* 157
7* A n a ly s is o f V a ria n c e Summary R e c a l l Number
C o r r e c t and I n P o s i t i o n .................................. 158
8 , A n a ly s is o f V a r ia n c e Summary R e c o g n itio n
Number C o r r e c t .............................................. 159
9* A n a ly s is o f V a ria n c e Summary R e c o g n itio n
Number C o r r e c t an d I n P o s i t i o n • • • « • • l 6o
10* A n a ly s is o f V a ria n c e Summary B etw een 11
Word L i s t s • • • • • ..................... • • • • • • l 6 l
11* L i s t M eans i n R ank O rd e r ................................. l 6 l
12* A n a ly s is o f V a ria n c e Summary R e c a l l Number
C o r r e c t ( E x c lu d in g L i s t C) • • • • « • • • 163
13* A n a ly s is o f V a ria n c e Summary 11 Word L i s t s
E x c lu d in g L i s t C • • • .............................. 163
ll+. A n a ly s is o f V a r ia n c e Summary R e c a l l Number
C o r r e c t and i n P o s i t i o n E x e lu d in g L i s t C • 161+
15* A n a ly s is o f V a r ia n c e Summary R e c o g n itio n
Number C o r r e c t ( E x c lu d in g L i s t C)» • • • • 165
v i i
T ab le Page
1 6 . A n a ly s is o f V a ria n c e Summary R e c o g n itio n
Humber C o r r e c t and I n P o s i t i o n
( E x c lu d in g L i s t C) • ............................................... 166
17* A v erag e E x te n t o f O rd e r and P o s i t i o n • • • • 168
18• E x p e rim e n t I I Mean S c o r e s . ....................... 17^
19* E x p e rim e n t I I A n a ly s is o f V a ria n c e Summary • 175
20* E x p e rim e n t I I I Mean S c o re s 177
2 1 . E x p e rim e n t I I I A n a ly s is o f V a ria n c e Summary. 177
2 2 . E x p e rim e n t IV Meazi S c o r e s . •• •• • •• • • 180
2 3 . E x p e rim e n t IV A n a ly s is o f V a ria n c e Summary • l 8 l
▼ iii
LIST OF FIGURES
F ig u r e Page
1« S a n d e r s ' R e s u l t s •••••• •• • ..................... £7
2* B r o a d b e n t's M e c h a n ic a l M o d e l .................................... 137
ix
CHAPTER I
INTRODUCTION
S h o r t - t e r m r e t e n t i o n , o f t e n c a l l e d " im m e d ia te
m em ory," h a s a c o m p a r a tiv e ly lo n g h i s t o r y i n p s y c h o lo g i
c a l e x p e r im e n ta tio n . J a c o b s , f o r e x a m p le , a s lo n g ago as
1887 fo u n d t h a t th e memory s p a n f o r num bers w as g r e a t e r
t h a n t h a t f o r l e t t e r s w h ic h w a s, i n t u r n , g r e a t e r th a n
th e s p a n o f n o n s e n s e s y l l a b l e s ( C r a n n e l l and P a r r i s h ,
1 9 5 7 ).
I n t e r e s t i n memory sp a n h a s o o n tin u e d th ro u g h th e
y e a r s b u t h a s b e e n f o c u s e d , u n t i l r e l a t i v e l y r e c e n t l y , o n
num ber s p a n . T h is h a s p e rh a p s b e e n due to th e i n c l u s i o n
o f t h i s a n i l i t y i n a num ber o f i n t e l l i g e n c e t e s t s .
W ith in t h e p a s t tw e lv e y e a r s t h e r e h a s b e e n an i n
c r e a s i n g i n t e r e s t i n t h i s p ro b le m o f s h o r t - t e r m m em ory.
C e r t a i n l y a l a r g e s h a r e o f t h i s i n t e r e s t h a s b e e n g e n e r
a te d by t h r e e f a c t o r s : (1 ) The a p p l i c a t i o n o f th e
te c h n iq u e s o f in f o r m a ti o n th e o r y t o p ro b le m s i n p s y
c h o lo g y h a s s e rv e d t o f r e s h e n t h e a p p ro a c h t o o ld p r o b
le m s; ( 2 ) th e d e v e lo p m e n t o f c o m p u te rs , w h ic h p e rfo rm
many f u n c t i o n s a n a lo g o u s t o th o s e o f hum ans, and w h ich
h a v e a s h o r t - t e r m o r b u f f e r s t o r a g e , h a s s e r v e d t o c a l l
1
a t t e n t i o n t o t h e f a c t t h a t t h e r e may be s e p a r a t e memory
m echanism s i n h u m an s; and ( 3 ) th e d e v e lo p m e n t o f l a r g e
s c a l e m an -m ach in e s y s te m s w h ic h im p o se new dem ands u p o n
s h o r t - t e r m memory*
The sp e e d and c r i t i c a l n a t u r e o f many o f th e t a s k s
i n m o d ern s y s te m s r e q u i r e s o p tim a l p e r f o r m a n c e . T he
m a rg in o f e r r o r i s o f t e n e x c e e d in g ly s m a ll* C o m p lic a tin g
th e p ro b le m i s th e f a c t t h a t s p a c e f o r e q u ip m e n t* d i s
p la y s * e t c . * i s o f t e n e x tr e m e ly l i m i t e d . I f man i s g o in g
t o be i n th e sy stem * h i s c a p a c i t i e s and l i m i t a t i o n s m u st
be know n and t h e s y s te m d e s ig n e d t o m axim ize h i s p e rfo r m
a n c e .
As a n ex am p le o f t h e n e e d f o r f a c i l i t a t i n g s h o r t
te rm r e t e n t i o n * c o n s i d e r a w eapons d i r e c t o r a t one o f t h e
SAGE c e n t e r s ( t h e U n ite d S t a t e s a i r d e f e n s e s y s te m )* He
i s b e in g c o n t i n u a l l y bom barded w ith i n f o r m a ti o n i n p u t s t o
be u s e d i n d i r e c t i n g o u r d e f e n s iv e s y s te m s a g a i n s t a
p o s s i b l e enemy a t t a c k . The q u e s t i o n a r i s e s * c a n a man be
e x p e c te d t o rem em ber a l l o f t h e s e I n p u t s o r m u st a d i s
p l a y s y s te m o f some s o r t b e d e v is e d ? U n d o u b te d ly a d i s
p l a y o f some s o r t m u st be p ro v id e d * b u t w h at s h o u ld be
th e n a t u r e o f th e d i s p l a y ? I n o r d e r t o d e s ig n th e s y s te m
p r o p e r ly * we m u st know th e c h a r a c t e r i s t i c s o f hum an
m em ory. S in c e m o st o f th e i n f o r m a ti o n i s r e c e i v e d once*
" s t o r e d * f o r a s h o r t tim e * and t h e n may b e l o s t w ith o u t
3
d e c r e a s in g th e s y s te m 's e f f e c t i v e n e s s , " s h o r t- te r m * r e
t e n t i o n i s o f g r e a t im p o rta n c e *
A lo o k a t th e p ro b le m fro m t h e s t a n d p o in t o f i n
f o r m a tio n t h e o r y may b e o f v a l u e . The f a c t t h a t t h e
I m p o rta n t v a r i a b l e s a r e num erous and c h a n g in g m eans t h a t
a c o n s i d e r a b le lo a d may b e im posed on th e m an-m achine
"c o m m u n ic a tio n s y s te m ." A t low r a t e s o f i n p u t th e human
c a n p r o b a b ly u s e a l l o f th e I n f o r m a tio n p r e s e n te d * When
th e i n p u t i s I n c r e a s e d th e am ount o f i n f o r m a tio n t h a t i s
t r a n s m i t t e d w i l l p r o b a b ly a l s o i n c r e a s e . A t some r a t e o f
i n p u t , h o w e v e r, th e am ount o f I n f o r m a tio n t r a n s m i t t e d
r e a c h e s a n a sy m p to te and no m a t t e r how much m ore in fo rm a
t i o n i s p r o v id e d o n ly a g iv e n am ount w i l l be tr a n s m i t te d *
T h is a s y m p to tic v a lu e may b e r e f e r r e d t o as th e " c h a n n e l
c a p a c ity * "
V iew ed i n t h i s w ay, i t a p p e a rs t h a t im p ro v in g
o p e r a t o r p e rfo rm a n c e i n s h o r t - t e r m memory t a s k s may be
a c c o m p lish e d by ( a ) i n c r e a s i n g th e o h a n n e l c a p a o lt y
th ro u g h p e r s o n n e l s e l e c t i o n o r t r a i n i n g i n memory d e v i c e s ;
(b ) p la n n in g d i s p l a y s t o e l i m i n a t e u n d e s i r a b l e re d u n d a n c y ;
( c ) p r e s e n t i n g o n ly i n f o r m a tio n t h a t i s a b s o l u t e l y e s
s e n t i a l t o h i s p e rfo rm a n c e ; a n d /o r (d ) p u t t i n g some o f
th e i n f o r m a tio n i n lo n g - te r m s t o r a g e , th u s f r e e i n g th e
s h o r t - t e r m s t o r a g e c a p a c i t y f o r th e im m e d ia te n e e d s*
S e v e r a l o f th e a p p ro a c h e s c i t e d above h a v e r e c e i v e d
If
a t t e n t i o n fro m p s y c h o l o g i s t s . M i l l e r (1 9 5 6 )* ^or e x a m p le *
h a s s u g g e s te d t h a t t h e r e e re a t l e a s t tw o w ays i n w h ic h
th e l i m i t a t i o n i n s h o r t - t e r m memory c a n be a v o id e d * The
f i r s t * w h ic h h e c a l l s r e c o d i n g v I n v o lv e s m aking a t r a n s
f o r m a tio n fro m u n i t s c o n ta in i n g o n ly a l i t t l e in f o r m a tio n
to u n i t s c o n ta in i n g a l o t o f in f o r m a tio n * ( S e v e r a l e x
p e rim e n ts h a v e i n d i c a t e d t h a t t h e am ount o f in f o r m a tio n *
i n b i t s * p e r s tim u lu s h a s o n ly a s l i g h t e f f e c t on memory*
S p e c i f i c ex am p les w i l l be c i t e d i n C h a p te r I I * ) As an
exam ple o f t h e pow er o f re c o d in g * M i l l e r c i t e s th e s u b
j e c t who* a f t e r b e in g t r a i n e d i n b o th th e b in a r y and
o o t a l num ber sy ste m s* was a b le t o s t o r e and r e p r o d u c e u p
to 1|.0 b in a r y d i g i t s *
A se c o n d way o f a i d i n g memory i s by w h at M i l l e r
c a l l s " c h u n k in g * " T h is in v o lv e s a g ro u p in g o f ite m s and
th e n rem e m b e rin g th e group* A te le g r a p h e r * w hen l e a r n
in g * may o p e r a te i n te rm s o f " d l t s " and "d a h a * " L a t e r
h e may w ork i n u n i t s o f l e t t e r s and e v e n t u a l l y e v e n
w ords and p h ra s e s *
One v a r i a b l e w h ich h a s b e e n s u g g e s te d as p o s s i b l y
b e in g im p o r ta n t i n s h o r t - t e r m r e t e n t i o n * and w h ic h h a s
n o t b e e n e x p e r im e n ta lly i n v e s t i g a t e d * i s t h a t o f o rd e r*
L a s h le y (1 9 5 0 ) c a l l e d a t t e n t i o n t o th e p o t e n t i a l im p o r
ta n c e o f o r d e r a s a v a r i a b l e o v e r a d e c a d e ago* More
r e c e n t l y * G a rn e r (1 9 6 2 ) and Brown (1 9 5 9 ) h a v e e m p h a sise d
5
th e n e e d f o r s t u d i e s d e a l in g w ith o r d e r , p a r t i c u l a r l y i n
r e l a t i o n t o im m e d ia te memory*
Brown i s one o f th e few w r i t e r s t o o f f e r any
r e a s o n a b ly c o m p re h e n siv e t h e o r e t i c a l f o r m u la ti o n f o r
im m e d ia te memory* H is p o s i t i o n i s l a r g e l y d e r iv e d fro m
th e u s e o f i n f o r m a tio n t h e o r y a s a m odel f o r human i n f o r
m a tio n p r o c e s s i n g . A c c o rd in g to B row n, in f o r m a tio n th e o r y
h a s two fo rm u la e w h ich a r e o f im p o rta n c e t o o r d e r . The
f i r s t , n lo g £ N ( s e e A p p en d ix D) i n d i c a t e s th e am ount o f
s e l e c t i v e i n f o r m a tio n w h ic h i s made up o f tw o c o m p o n e n ts:
o r d e r in f o r m a ti o n and Nite m in f o r m a tio n " o r w h at was p r e
s e n te d I r r e s p e c t i v e o f o r d e r . The fo rm u la f o r o r d e r i n
f o r m a tio n i s lo g £ Hi T hus th e " ite m in f o r m a tio n 1 1 may be
o b ta in e d by s u b t r a c t i n g th e o r d e r in f o r m a tio n fro m th e
s e l e c t i v e I n f o r m a tio n . T h e r e f o r e , th e p r e d i c t i o n may be
made t h a t i f th e am ount o f o r d e r in f o r m a ti o n i n a m eabage
c o u ld be r e d u c e d , th e c a p a c i ty f o r ite m i n f o r m a tio n w ould
be in c r e a s e d *
Brown assum es t h a t " s t o r a g e s p a c e " i n hum ans i s
l i m i t e d . The m ore t h a t i s s t o r e d , th e l e s s sp a c e t h a t i s
a v a i l a b l e f o r s t o r a g e o f o t h e r m a t e r i a l o r f o r r e d u n d a n t
m a t e r i a l* Brown h o ld s th e p o s i t i o n t h a t i f e v e r y t h in g
w ere s t o r e d w ith s u f f i c i e n t re d u n d a n c y , t h e r e w ould be no
f o r g e t t i n g . The e f f e c t o f r e h e a r s a l o r r e p e t i t i o n ,
a c c o r d in g t o t h i s v ie w , i s a t l e a s t p a r t l y due t o th e
6
e s ta b lis h m e n t o f r e d u n d a n t t r a c e s * M o re o v e r, a s th e
le n g th o f th e s e q u e n c e i n c r e a s e s , o r d e r in f o r m a ti o n b e
comes a n i n c r e a s i n g p r o p o r t i o n o f th e t o t a l in f o r m a ti o n
t h a t m u st b e s t o r e d . T h u s, i f o p e r a t o r s v e re r e q u i r e d
to rem em ber o n ly th e ite m s ( c o n t e n t i n f o r m a t i o n ) , and
c o u ld I g n o re th e o r d e r , p e rh a p s more ite m s c o u ld be
s t o r e d .
The r e s e a r c h t o b e r e p o r t e d i n t h i s d i s s e r t a t i o n
was p r i m a r i l y d i r e c t e d a t t e s t i n g B ro w n 's p o s i t i o n r e
g a r d in g o r d e r i n f o r m a t i o n . A d d i t io n a l g o a ls w ere to
d e te rm in e i f i n t e r p o l a t e d a c t i v i t y and le n g th o f l i s t
i n f l u e n c e a n d /o r i n t e r a c t w ith o r d e r and t o o b t a i n some
f u n c t i o n a l d e s c r i p t i o n o f t h e r e s u l t s .
The r e s e a r c h w as a ls o d e s ig n e d t o o b t a i n in fo rm a
t i o n p e r t a i n i n g t o w h e th e r o r n o t memory o f t h i s ty p e i s
d e p e n d e n t upon a n a c t i v i t y t r a c e , o r w h e th e r some lo n g e r
l a s t i n g s t r u c t u r a l c h a n g e s may o c c u r . Hebb ( 1961) r e
p o r t s a n e x p e rim e n t s u p p o r tin g th e s t r u c t u r a l c h an g e
p o s i t i o n . I t i s p o s s i b l e t o su p p o se t h a t n o th in g a t
te n d e d t o i s e v e r c o m p le te ly l o s t . Some m a t e r i a l , how
e v e r , may be i n e f f i c i e n t l y " f i l e d away" so t h a t i t s
r e t r i e v a l i s d i f f i c u l t . The f u n c t i o n o f r e h e a r s a l may
be to code th e s t o r a g e l o o a t i o n o f th e m a t e r i a l o r t o
o r g a n iz e i t so t h a t i t may b e m ore r e a d i l y r e t r i e v e d .
I f t h i s i s th e c a s e , a lth o u g h r e c a l l o f th e m a t e r i a l
may seem im p o s s i b l e , a r e c o g n i t i o n t a s k may be f a i r l y
e a s y , e v e n some tim e a f t e r t h e m a t e r i a l was f i r s t p r e
s e n t e d .
CHAPTER I I
REVIEW OP THE LITERATURE
I n t r o d u c t i o n
B la n k e n s h ip (1 9 3 8 ) w ro te a n e x te n s i v e r e v ie w o f
th e l i t e r a t u r e c o n c e rn in g Im m e d ia te m em ory. T h e re h a s
t e e n no summary o f th e w ork I n t h i s a r e a s in c e t h e n .
T h is c h a p t e r r e v ie w s w e l l o v e r 100 p u b l is h e d b e h a v i o r a l
s t u d i e s t h a t h a v e a p p e a re d i n p s y c h o l o g ic a l j o u r n a l s *
b o o k s , o r t e c h n i c a l r e p o r t s s in c e 1 9 3 8 . The m a j o r i t y o f
th e s e h a v e b e e n p u b l is h e d s i n c e 1 9 5 0 . An a tte m p t was
made t o b e e x h a u s t i v e , b u t t h e r e may be s t u d i e s t h a t th e
w r i t e r h a s m is s e d . F o r t h e s e , a n a p o lo g y I s o f f e r e d t o
b o th t h e a u th o r s and r e a d e r s .
The o r g a n i z a t i o n o f th e c h a p t e r I s b a s e d u p o n th e
In d e p e n d e n t v a r i a b l e s t h a t w ere I n v e s t i g a t e d I n t h e
v a r i o u s s t u d i e s . S in c e many o f t h e s e s t u d i e s t r e a t m ore
th a n one In d e p e n d e n t v a r i a b l e , a d e g re e o f a r b i t r a r i n e s s
on th e p a r t o f t h e r e v ie w e r w as n e c e s s a r y r e g a r d i n g w h ic h
s u b - s e c t i o n w o u ld c o n t a i n th e r e p o r t o f th e e x p e r im e n t.
The d e c i s i o n was g e n e r a l l y made o n th e b a s i s o f t h e r e
s u l t s o f th e e x p e r im e n t. An a tte m p t w i l l be m ade a t th e
c o n c lu s io n o f th e c h a p t e r t o draw t h e m a jo r f i n d i n g s
to g e th e r i n t o some r e a s o n a b ly d e f i n i t e c o n c lu s io n s
Evidence S u ggestin g Separate
Memory Mechanisms
L a s h le y (1 9 5 0 ) n o te s t h a t D e s c a r te s was p e rh a p s
th e e a r l i e s t p e r s o n t o a tte m p t t o e x p l a i n memory i n te rm s
o f b r a i n a c tio n * He s t a t e s :
I n th e i n t e r v e n i n g c e n t u r i e s much h a s b e e n l e a r n e d
c o n c e rn in g th e n a tu r e o f th e Im p u ls e s t r a n s m i t t e d
by n e rv e s * In n u m e ra b le s t u d i e s h a v e d e f in e d c o n d i
t i o n s u n d e r w h ic h l e a r n i n g i s f a c i l i t a t e d o r r e
t a r d e d , b u t * * * we seem l i t t l e n e a r e r t o an
u n d e r s ta n d in g o f th e n a tu r e o f th e memory t r a c e
th a n w as D e s c a r te s *
L a s h le y d e s c r i b e s th e d e v e lo p m e n t o f e f f o r t i n
s e a r c h o f th e lo c u s o f memory o r "en g ram " b u t c o n c lu d e s
t h a t t h e s e s t u d i e s h a v e show n o n ly w hat and w here th e
memory t r a c e i s n o t . I t h a s d is c o v e r e d n o th in g d i r e c t l y
o f t h e r e a l n a t u r e o f th e e n g ra m . I n f a c t , he s t a t e s
t h a t , a f t e r r e v ie w in g th e e v id e n c e , " t h e n e c e s s a r y c o n
c l u s i o n i s t h a t l e a r n i n g i s j u s t n o t p o s s i b l e •"
E v id e n tly th e y e a r s s in c e L a s h le y h a v e n o t s i g
n i f i c a n t l y ch an g ed t h i s s i t u a t i o n . Thomas (1 9 6 2 ) s t a t e s
t h a t wno r e s e a r c h f i n d i n g s c a n be s a id t o h a v e e s t a b
l i s h e d a p h y s i o l o g i c a l m echanism o r e v e n th e e x i s t e n c e o f
a memory t r a c e * " I t i s by no m eans c e r t a i n t h a t a l l
memory i s m e d ia te d by a s i n g l e ty p e o f m echanism ; t h a t
m o to r s k i l l s and e i d e t i c im a g e s , f o r e x a m p le , hav e any
p h y s i o l o g i c a l p r o p e r t i e s i n common. I n h i s w o rd s , "The
10
a tte m p t to a c c o u n t f o r a l l memory by any s i n g l e th e o r y
I n v o lv e s a s s u m p tio n s w h ich a r e n o t s u p p o r te d b y any e v i
d en ce now a v a i l a b l e . "
I t I s h i g h ly p r o b a b le t h a t Im m ed iate memory I s
m a in ta in e d by some s o r t o f a f t e r - d i s c h a r g e o f th e o r i g i
n a l l y e x c i t e d n e u ro n s — by a r e v e r b e r a t o r y c i r c u i t , f o r
e x a m p le . One th e o r y b a s e d on t h i s p r i n c i p l e I s t h a t o f
B ro a d b e n t ( 1 9 5 3 ) . He s u g g e s ts t h a t th e c e n t r a l n e rv o u s
s y s te m (CHS) h a s a f i l t e r w h ich c a n h a n d le o n ly one
"c h u n k " o f I n f o r m a tio n a t a t im e . P la c e d e a r l i e r i n th e
CHS i s th e s h o r t - t e r m " s t o r a g e sy ste m " w h ic h i s s e t up a s
a r e v e r b e r a t o r y c i r c u i t . I f a chunk o f in f o r m a ti o n
e n t e r s th e n e rv o u s s y s te m , th e f i l t e r may n o t be o p e n due
to b e in g o c c u p ie d b y s t i m u l i a r r i v i n g e a r l i e r , o r fro m
a n o th e r c h a n n e l* I n t h i s s i t u a t i o n , t h e i n f o r m a tio n may
be c y c le d i n d e f i n i t e l y u n t i l th e f i l t e r l e t s i t th r o u g h
to t h e p e rm a n e n t sy s te m o r u n t i l th e t r a c e d i e s o u t*
W h eth er o r n o t B ro a d b e n t» s f o r m u la ti o n i s th e
c o r r e c t one ( e x p e r im e n ts s u p p o r tin g h i s th e o r y w i l l be
t r e a t e d i n a l a t e r s e c t i o n ) , t h e r e a r e s e v e r a l l i n e s o f
e v id e n c e t o s u p p o r t th e c o n te n ti o n t h a t t h e r e a r e a t
l e a s t tw o s e p a r a te s to r a g e sy s te m s o r m echanism s* Among
t h e s e a r e :
a ) A n e c d o ta l e v id e n c e fro m p e rs o n s s u f f e r i n g fro m
a m n e sia o r s e n i l i t y who c a n o f t e n rem em ber w h at h a p p e n e d
11
y e s t e r d a y , b u t n o t y e a r s ago a n d /o r v ic e v e rs a *
b ) E l e c t r o - c o n v u l s i v e sh o o k e x p e r im e n ts I n w h ic h
a n im a ls , t r a i n e d to make a d i s c r i m i n a t i o n and th e n
sh o c k e d , c a n l a t e r p e rfo r m th e d i s c r i m i n a t i o n I f th e
sh o c k f o l lo w 8 t r a i n i n g b y a r e l a t i v e l y lo n g I n t e r v a l , b u t
n o t i f t h e sh o c k o c c u r s s h o r t l y a f t e r t r a i n i n g (M organ
and S t e l l a r , 1950)*
c ) B r a in a b l a t i o n s t u d i e s I n w h ic h a c a t i s
a llo w e d t o w a tc h th e e x p e r im e n te r p u t fo o d u n d e r a cup*
N orm al c a t s , I f r e s t r a i n e d f o r a l e n g t h o f t im e , w i l l go
to th e cup a f t e r r e l e a s e t o g e t t h e f o o d . B r a in dam aged
c a t s do n o t ( B r a z i e r , 1953)*
d ) An e x p e rim e n t i n w h ich an o c to p u s was t r a i n e d
to d i s c r i m i n a t e b e tw e e n a l o b s t e r e i t h e r acco m p an ied by a
w h ite c a rd o r by i t s e l f * I f th e w h ite c a r d w as p r e s e n t
th e o c to p u s w as s h o c k e d . O th e rw is e , th e o c to p u s c o u ld
e a t th e l o b s t e r . I f p a r t o f th e o c to p u s ' b r a i n was r e
m oved, th e o c to p u s w ould n o t a p p ro a c h th e l o b s t e r i f th e
t e s t t r i a l fo llo w e d s h o r t l y a f t e r t r a i n i n g , b u t w ould I f
t h e r e was a lo n g e r i n t e r v a l b e tw e e n t r a i n i n g and th e
t e s t ( S t e l l a r , 1957)*
T h u s, i t a p p e a rs t h a t t h e r e may be a s e p a r a t e
m echanism f o r Im m ed iate m em ory. The p ro b le m o f d e f i n i n g
th e c o n d it i o n s s e p a r a t i n g Im m ed iate memory fro m m ore
p e rm a n e n t s t o r a g e w i l l be d e f e r r e d u n t i l l a t e r *
12
Amount o f M aterial
B re n e r ( I 9I 4 .O ), u s i n g c o ll e g e s t u d e n t s , d e te rm in e d
th e a v e ra g e memory s p a n f o r a w id e v a r i e t y o f d i f f e r e n t
m a te r ia l* T a b le 1 g iv e s th e r e s u l t s o f h i s e x p e rim e n t*
H is p ro c e d u re fo llo w e d t h e t r a d i t i o n a l m ethod o f d e t e r
m in in g th e memory sp an * T h a t i s , s u b j e c t s l i s t e n e d t o a
s e r i e s o f s t i m u l i and t h e n r e p e a t e d them b a c k , i n t h e i r
o r d e r o f a r r i v a l * G e n e r a ll y , o n ly a few ite m s a re p r e
s e n te d i n i t i a l l y , and t e s t i n g c o n tin u e s u n t i l th e s u b j e c t
m akes h i s f i r s t m is ta k e * I n t h i s way th e l o n g e s t le n g th
o f l i s t t h a t c a n be r e p e a t e d w ith o u t e r r o r i s d e te rm in e d *
The s e n te n c e s u s e d b y B re n e r c o n ta in e d s i x w ords
and e i g h t s y l l a b l e s * T h u s, 1*75 s e n te n c e s c o r re s p o n d to
10*5 w ords o r lij.*0 s y l l a b l e s * A t f i r s t g l a n c e , i t a p
p e a r s t h a t " m e a n in g fu l” m a t e r i a l i s m ore e a s i l y s to r e d *
M ille r (1 9 5 1 ) i n t e r p r e t e d t h e s e d i f f e r e n c e s a s s u g g e s tin g
t h a t a l i m i t i n g f a c t o r may be th e am ount o f i n f o r m a ti o n
( i n b i t s ) s t o r e d r a t h e r t h a n th e t o t a l num ber o f ite m s —
M ille r l a t e r r e v i s e d h i s p o s i t i o n b u t t h i s l a t e r p o s i t i o n
w i l l be d is c u s s e d i n a n o th e r s e c tio n *
The t r a d i t i o n a l memory sp a n e x p e r im e n ts , a lth o u g h
v a lu a b le i n m e a s u rin g a p t i t u d e s , a re n o t g e n e r a l l s a b l e to
s i t u a t i o n s t h a t c o n f r o n t u s i n e v e ry d a y l i f e . A
c h a r a c t e r i s t i c o f m ost r e a l l i f e t a s k s in v o lv in g t h i s
13
TABLE 1
AVERAGE M EM O RY SPAN FOR DIFFERENT
TYPES OF MATERIAL (BRENER, 19l*0)
M a t e r i a l A v erag e S p an
S im p le s e n te n c e s (w h o le — 6 w o rd s ,
6 s y l l a b l e s )
1 .7 5
S im p le commands ( c o r r e c t l y e x e c u te d ) 2 j* 2
N onsense s y l l a b l e s (w h o le CTJC)
2.1*9
P a ir e d a s s o c i a t e s (w hole p a i r s ) 2 .5 0
A b s t r a c t w ords ( v i s u a l ) 5.21*
S im p le g e o m e tr ic a l d e s ig n s
5 .3 1
A b s tr a c t w ords ( o r a l )
5 .5 8
C o n c re te w ords ( v i s u a l ) 5 .7 6
C o n c re te w ords ( o r a l ) 5 .8 6
C o lo rs 7 .0 6
C o n so n a n ts ( o r a l ) 7 .2 1
C o n so n a n ts ( v i s u a l ) 7 .3 0
D i g i t s
7 .9 8
a b i l i t y i s t h e f a c t t h a t t h e s e q u e n c e i s c o n tin u o u s and
c h a n g in g , and t h e o p e r a t o r i s r e q u i r e d to r e t a i n a s muoh
as p o s s i b l e o f t h e m o st r e c e n t l y p r e s e n t e d in f o r m a tio n *
As S h e p a rd and T e g h ts o o n ia n (1 9 6 1 ) n o t e , s u c h s i t u a t i o n s
a re q u i t e common ( p l a y i n g b r i d g e , c o n tin u o u s m o n ito r in g
o f a co m p lex d i s p l a y ) and h a v e a w id e t h e o r e t i c a l b e a r in g *
I n d u c t i v e I n f e r e n c e , d e d u c tiv e r e a s o n i n g , p ro b le m s o l v i n g
and v e r b a l com m unio& tlon a l l r e q u i r e t h a t a p e rs o n * s
r e s p o n s e s be s e l e c t i v e l y m o d u la te d by s t i m u l i p r e s e n t e d
a t v a r y in g i n t e r v a l s *
S h e p a rd and T e c h ts o o n la n i n v e s t i g a t e d th e r e t e n
t i o n o f i n f o r m a ti o n u n d e r c o n d it i o n s a p p ro a c h in g a s t e a d y
s t a t e . S u b j e c t s w ere p r e s e n t e d a d e c k o f 3 x 5 c a rd s *
On e a c h c a r d was a 3 - d l g i t num ber* S u b j e c t s re s p o n d e d
• o l d " o r "new " d e p e n d in g u p o n w h e th e r th e y d id o r d i d n ’ t
rem em ber h a v in g s e e n t h a t num ber a t some e a r l i e r p o i n t i n
th e s e r i e s . E a c h num ber was p r e s e n t e d tw ic e b u t th e
num ber o f o t h e r 3- d i g i t num bers I n t e r v e n i n g b e tw e e n th e
f i r s t and se c o n d p r e s e n t a t i o n was m a n ip u la te d * The r e
s u l t s i n d i c a t e t h a t t h e p r o b a b i l i t y o f c o r r e c t l y c l a s
s i f y i n g an o ld 3- d i g i t num ber as " o ld " i s a d e c r e a s i n g
f u n c t i o n o f th e num ber o f i n t e r v e n i n g p r e s e n t a t i o n s *
E v en a f t e r 60 i n t e r v e n i n g n u m b e rs, h o w e v e r, th e p r o b a
b i l i t y o f c o r r e c t r e c o g n i t i o n was s t i l l w e l l above th e
p r o b a b i l i t y o f c l a s s i f y i n g a new s tim u lu s as o l d , w h ic h
15
was o n ly .3 0 a f t e r 200 p r e s e n t a t i o n s . I t was p o s s i b l e
to make a n e s t im a t e o f th e lo w e r b o u n d a ry o f in f o r m a tio n
t h a t s u b j e c t s w ere a b le t o c a r r y a lo n g a t any one tim e .
T h is tu r n e d o u t t o b e a b o u t $0 b i t s w h ic h was c o n s i d e r
a b ly h ig h e r th a n M ille r * s ( 195&) o r P o lla c k * s (1 9 5 3 )
e s t i m a t e s b u t i t i s p o s s i b l e t h a t t h i s d e v i a t i o n i s due
to th e u s e o f a r e c o g n i t i o n t a s k .
P o lla c k (1 9 5 3 ) d e v is e d m e ssa g e s c o n s i s t i n g o f
c o n s o n a n ts and n u m e r a ls . T h ese m e ssa g e s w ere r e a d , w ith
as l i t t l e rh y th m ic s t r e s s and e m p h a sis as p o s s i b l e , i n t o
a m a g n e tic r e c o r d e r a t th e r a t e o f s i x m essag e u n i t s i n
5 s e c o n d s . The m a t e r i a l was p la y e d b a c k t o s u b j e c t s .
S e r v in g w ith e a c h S was a n a s s i s t a n t who c o r r e c t e d th e
r e s p o n s e . The s u b j e c t 's r e p r o d u c t io n o f t h e m essag e was
sc a n n e d f o r e r r o r s . I f th e f i r s t r e p r o d u c t io n was n o t
c o r r e c t , th e s u b j e c t was i n s t r u c t e d to make s u c c e s s iv e
r e s p o n s e s u n t i l th e m essag e was c o r r e c t l y r e p r o d u c e d . I f
s t i l l n o t c o r r e c t a f t e r th e f o u r t h g u e s s , th e c o r r e c t
re s p o n s e was s u p p l i e d . B o th th e le n g th o f th e m essage
and th e in f o r m a ti o n p e r m essag e u n i t w ere v a r i e d .
The r e s u l t s i n d i c a t e t h a t th e in f o r m a tio n l o s t p e r
m essag e u n i t , i . e . e r r o r o u t p u t , i n c r e a s e s as th e le n g t h
o f th e m essag e i n c r e a s e s and a s th e num ber o f p o s s i b l e
a l t e r n a t i v e s p e r m e s s a g e - u n it i n c r e a s e s . F o r m e ssa g e s o f
a g iv e n l e n g t h ; h o w e v e r, t h e p e r c e n ta g e o f i n f o r m a tio n
16
p r e s e n te d t h a t i s l o s t i s a lm o s t in d e p e n d e n t o f th e
num ber o f p o s s i b l e a l t e r n a t i v e s p e r m e s s a g e - u n i t, and i s
s im p ly a f u n c t i o n o f th e le n g th o f th e m e s s a g e . P o l l a c k
a l s o c o n c lu d e s t h a t th e am ount o f in f o r m a ti o n g a in e d i n
c r e a s e s a s th e l e n g t h o f m e ssa g e s i n c r e a s e s u n t i l & b ro a d
maximum i s r e a c h e d beyond w h ic h in f o r m a ti o n g a in e d d e
c r e a s e s . T h a t i s , t h e r e i s a r e g i o n o f m essag e le n g th s
f o r maximum g a in o f in f o r m a tio n *
One p r i n c i p l e t h a t P o l l a c k d e r i v e s fro m h i s e x p e r i
m ent i s j F o r a g iv e n am ount o f in f o r m a ti o n i n p u t , a
s m a ll e r in f o r m a ti o n l o s s and l a r g e r in f o r m a ti o n g a i n a r e
o b ta in e d fro m s h o r t m essa g e s a s s o c i a t e d w ith a l a r g e
num ber o f a l t e r n a t i v e s p e r m essag e u n i t th a n fro m l a r g e r
m e ssa g e s a s s o c i a t e d w ith a s m a lle r num ber o f p o s s i b l e
a l t e r n a t i v e s *
Y ntem a and M euser (1 9 6 2 ) exam ined th e e f f e c t o f
th e num ber o f s t a t e s t h a t e a c h v a r i a b l e m ig h t assu m e .
The s u b j e c t s w ere r e a d a s e r i e s o f m e ssa g e s e a c h t e l l i n g
h im th e s t a t e o f one o f th e v a r i a b l e s . M essag es w ere r e
c o rd e d o n 3 x 5 c a r d s , th e n p u t a t th e b o tto m o f th e p i l e
so th e y c o u l d n 't be s e e n a g a in * At random I n t e r v a l s th e
s e r i e s o f m e ssa g e s was I n t e r r u p t e d and th e s u b j e c t a sk e d
to r e c a l l w h at t h e l a s t m essag e a b o u t one o f th e v a r i a b l e s
was*
V a rie d a lo n g w ith th e num ber o f ‘• s t a t e s * t h a t e a c h
17
v a ria b le could assume was (a) the number o f v a r ia b le s to
be m onitored; (b) whether a l l v a r ia b le s had the same or
d iffe r e n t s e t o f p o s s ib le s t a te s ; and (c ) the p r o b a b ility
th a t a message would change the s ta te o f one o f the
v a ria b les* In no case did the number o f p o s s ib le a lt e r
n a tiv e s have any s ig n if ic a n t e f f e c t , provided a c o r r e c tio n
fo r chance su ccess was made* The p r o b a b ility o f change,
however, was found to have a la rg e e ffe c t*
In an e a r lie r stu d y, Yntema and Meuser ( i 9 6 0 )
varied the number of v a r ia b le s and whether each v a ria b le
had the same or m utually e x c lu siv e s e t o f p o s s ib le s ta te s
which i t could assume* The su b ject was read a s e r ie s of
m essages, each o f which to ld him th a t one o f th e v a r ia b le s
i s , and u n t il fu r th e r n o tic e would rem ain, in some par
tic u la r sta te * At random in te r v a ls the s e r ie s was in te r
rupted and the su b jec t asked what the p resen t s t a te o f one
of the v a r ia b le s was* There were two, th r e e , fo u r , s ix
or e ig h t v a ria b les*
The fr a c tio n o f the q u estio n s c o r r e c tly answered
decreased as the number o f v a r ia b le s in crea sed and, i f
there were more than two v a r ia b le s , was low er when they
a l l had the same s e t o f four p o s s ib le sta te s* The
p r o b a b ility o f a p a r tic u la r q u estio n b ein g answered
c o r r e c tly depended on the number o f q u estio n s and m essages
in terv en in g between the q u estio n b ein g con sid ered and the
18
m essag e t h a t d e te rm in e d th e c o r r e c t a n s w e r. T h ese r e s u l t s
w ere v e r i f i e d I n th e l a t e r s tu d y c i t e d a b o v e . I t a p p e a rs
t h a t I n t e r f e r e n c e o r i t s o p p o s i t e , v on R e s t o r f f 's i s o l a
t i o n , may p la y a r o l e i n t h i s ty p e o f t a s k .
L lo y d and h i s c o -w o rk e rs h av e a l s o b e e n i n t e r e s t e d
i n th e g e n e r a l s i t u a t i o n i n w h ic h t h e p r e s e n t a t i o n o f
ite m s and t h e i r r e c a l l a re n o t d i s c r e t e l y s e p a r a t e d . I n
a s e r i e s o f e x p e rim e n ts (L lo y d , R e id , and F e a ll o o k , i 9 6 0 )
a se q u e n c e o f ite m s was p r e s e n t e d t o th e s u b j e c t s . E ach
ite m to be rem em bered was f o llo w e d a t some p o i n t i n th e
se q u e n c e by a cue w h ich s p e c i f i e d t h a t th e s u b j e c t m u st
r e c a l l t h a t ite m . The ite m s t o be rem em bered w ere i n
s t a n c e s o f a c l a s s and th e c l a s s name was u s e d a s a r e c a l l
p o i n t . F o r e x a m p le , a se q u e n c e m ig h t c o n s i s t o f th e
w ords " f o x , e lm , C h ic a g o , T re e • • • •" When th e w ord
" T re e " was s a i d , th e s u b j e c t s h o u ld h av e re s p o n d e d w ith
" e lm ."
The f i r s t - e x p e rim e n t s y s t e m a t i c a l l y v a r ie d th e
num ber o f ite m s t h a t th e s u b j e c t s w ere r e q u i r e d t o r e
m em ber. A p r e s e n t a t i o n r a t e o f one ite m o r r e c a l l p o i n t
e v e ry t h r e e se c o n d s was u s e d . R e c a ll p o i n t s w ere p re c e d e d
by a 500 c p s to n e . The a v e ra g e s t o r a g e lo a d was fo u n d t o
be h i g h l y s i g n i f i c a n t .
A se c o n d e x p e rim e n t h e ld th e a v e ra g e s t o r a g e lo a d
c o n s t a n t w h ile th e num ber o f ite m c l a s s e s u s e d i n th e
19
se q u e n c e was v a r i e d ( t h e r e w e re a lw ay s f o u r ite m s p e r
c l a s s ) . O nly th e e f f e c t o f p r a c t i c e tu r n e d o u t t o be
s i g n i f i c a n t .
E x p e rim e n t I I I h e l d c o n s t a n t th e num ber o f c l a s s e s
w h ile v a r y in g th e num ber o f ite m s i n e a c h c l a s s . O nly
a v e ra g e s t o r a g e lo a d and p r a c t i c e w ere s i g n i f i c a n t .
The sam e ty p e o f e x p e r im e n ta l t a s k w as u s e d by
R eid * e t a l . ( I 9 6 I ) , to i n v e s t i g a t e th e a v e ra g e lo a d r e
d u c ti o n (A L R ). T h a t i s * th e s u b j e c t s w ere r e q u i r e d t o
r e c a l l m ore t h a n one s t o r e d ite m a t e a c h r e c a l l p o i n t .
I f " c i t y * w ere t h e r e c a l l word* and i f p r e v io u s c i t i e s i n
th e s e q u e n c e w ere " B e r l i n * and "Moscow*" t h e s u b j e c t
s h o u ld s t a t e b o t h .
The f i r s t e x p e rim e n t i n t h i s s e r i e s v a r i e d a v e ra g e
s t o r a g e lo a d (ASL) w h ile k e e p in g th e a v e ra g e lo a d r e d u c
t i o n c o n s t a n t a t a v a lu e g r e a t e r th a n one (two). H ere*
r e c a l l e r r o r s i n c r e a s e a lm o s t l i n e a r l y w i t h th e ASL.
The n e x t e x p e r im e n t k e p t t h e ASL c o n s t a n t a t 1^.5
ite m s * b u t v a r i e d t h e ALR b e tw e e n 1 .0 and 3*5 i t e m s . I t
w as fo u n d t h a t r e c a l l e r r o r s s y s t e m a t i c a l l y d e c l in e d a s
th e ALR i n c r e a s e d .
Two p o t e n t i a l c a u s e s o f t h i s im p ro v e d p e rfo rm a n c e
w ere o f f e r e d : ( a ) The d e c r e a s e i n th e num ber o f r e c a l l
p o i n t s r e d u c e s th e a v e ra g e am ount o f I n t e r p o l a t e d a c t i v i t y
and ( b ) th e I n c r e a s e d lo a d m e a n t m ore ite m s fro m a s i n g l e
20
c l a s s w ere 'b e in g s t o r e d and may h a v e p r o v id e d a n o p p o r tu
n i t y f o r th e g ro u p in g o f ite m s* More w i l l b e s a i d a b o u t
t h i s l a t e r *
A d d itio n a l e x p e rim e n ts h a v e b e e n p e rfo rm e d w h ich
su p p le m e n t th e b a s i c ASL r e s u l t s * L lo y d ( I 9 6 I ) e x te n d e d
th e ASL to h i g h e r v a lu e s and a ls o u s e d m a t e r i a l ju d g e d t o
be u n r e la te d * An ite m w as a l e t t e r - w o r d p a i r ; a r e c a l l
p o i n t th e l e t t e r a lo n e * S u b j e c t s w ere t o r e c a l l a l l
w o rd s p r e v i o u s l y p a ir e d w ith t h e l e t t e r * B etw een a g iv e n
ite m and i t s r e c a l l p o i n t , o t h e r r e c a l l p o i n t s , o t h e r
i t e m s , o r b o th c o u ld be i n t e r p o l a t e d * The ASL w as v a r i e d
b e tw e e n 2*5 and 12*5 ite m s * A t e a o h r e c a l l p o i n t e i t h e r
o n e , tw o o r t h r e e ite m s w ere r e q u e s te d *
The ASL and p r a c t i c e a g a in r e s u l t e d i n s i g n i f i c a n t
d i f f e r e n c e s * The d a t a s u g g e s te d , h o w e v e r, t h a t th e e f
f e c t s m ig h t be a p p ro a c h in g a n a sy m p to te a t th e h ig h e r
A SL*s.
A n o th e r s tu d y t o b e r e p o r t e d i n t h i s s e c t i o n was
p e rfo rm e d by A l l a n ( 1961)* She was I n t e r e s t e d i n w h at
h a p p en e d when t h e hum an c o m m u n ic a tio n sy s te m was o v e r
lo a d e d * The t a s k was t o l e a r n a c h a n c e o r d e r i n a p a ck
o f 26 c a r d s c o n ta in i n g th e l e t t e r s o f th e a lp h a b e t* E aoh
l e t t e r was p r i n t e d o n a s e p a r a t e c a rd * The s u b j e c t to o k
th e p a c k i n one h a n d and tu r n e d o v e r one c a rd a t a tim e ,
s a y in g i t s name o u t lo u d and t r y i n g w ith o u t s t r a i n t o
2 1
n o te th e o r d e r I n w h ic h t h e y tu r n e d u p . A r a t e o f one
c a r d p e r se c o n d w as m a in ta in e d . As so o n as th e p a c k was
f i n i s h e d th e s u b j e c t c a l l e d o u t th e o r d e r a s n e a r l y a s h e
c o u ld . W ith o u t s h u f f l i n g , t h i s p r o c e d u re w as f o llo w e d
u n t i l t h e o r d e r was l e a r n e d . T h ere w ere no c o r r e c t i o n s
by th e e x p e r im e n te r *
I t to o k an a v e ra g e o f o n ly a l i t t l e o v e r f o u r
t r i a l s to l e a r n th e s e q u e n c e . M o re o v e r, a c c o r d in g t o th e
a u t h o r , t h e s u b j e c t s a t t h e end c o u ld s a y th e se q u e n c e I n
th e r e v e r s e o r d e r o r b e g in a t any p o i n t I n th e se q u e n o e
and go fo rw a rd s o r b a ck w a rd s as d i r e c t e d *
An e x p e rim e n t was p e rfo rm e d to d e te rm in e I f th e
r e s u l t o b ta in e d o c c u rr e d o n ly when th e sy s te m w as o v e r
lo a d e d . F iv e s u b j e c t s w ere a sk e d to m em orize two 2 6 -
l e t t e r s e q u e n c e s by two d i f f e r e n t m e th o d s 3 ( a ) th e
"whole** m ethod a s e x p la in e d a b o v e , o r (b ) th e "part**
m ethod w h ic h m ean t h a v in g th e s e q u e n c e d iv id e d i n t o f i v e
p o r t i o n s , e a c h o f w h ic h w ere m em orized s e p a r a t e l y b y
r e a d in g e a c h s h o r t se q u e n c e and th e n r e c a l l i n g I t fro m
im m e d ia te m em ory. T h is was r e p e a t e d e i g h t t i m e s . The
s u b j e c t s w ere f i n a l l y a sk e d t o r e p e a t a l l 26 l e t t e r s *
A ll s u b j e c t s a s s ig n e d t o th e w hole m ethod h ad
l e a r n e d th e l i s t by th e e ig h t h t r i a l b u t none a s s ig n e d t o
th e p a r t m ethod h ad le a r n e d th e e n t i r e se q u e n c e *
Many c r i t i c i s m s may be d i r e c t e d a t t h i s s t u d y .
22
Too many t h i n g s w ere l e f t u n c o n t r o l l e d . The u s e o f vow els*
f o r e x a m p le , may h a v e f a c i l i t a t e d " c h u n k in g " o f l e t t e r s '
i n t o p ro n o u n c e a b le u n i t s s e v e r a l l e t t e r s lo n g * T he d i v i d
in g up o f th e se q u e n c e i n t o f i v e p a r t s may h a v e m ade t h i s
m ore d i f f i c u l t * The c o n c lu s io n s d raw n b y th e a u th o r seem
te n u o u s a t b e s t* I t i s a l s o i n t e r e s t i n g t o n o te t h a t
e i g h t t r i a l s -w ere u s e d i n th e se c o n d e x p e rim e n t w h e re a s
a n a v e ra g e o f o n ly a l i t t l e o v e r f o u r w e re r e q u i r e d w ith
th e i n i t i a l g ro u p o f s u b j e c t s * I t may w e l l b e t h a t th e
n o v e r lo a d in g ” o f th e hum an f o r c e s h im t o r e c o r d o r u s e
o t h e r d e v ic e s an a p p a r e n t l y l e s s f r u s t r a t i n g t a s k w o u ld
n o t e l i c i t , b u t t h i s s tu d y d o e s n 't a llo w a c l e a r - c u t co n
c l u s i o n o f t h i s *
B o u s f i e l d , e t a l* (1 9 5 8 ) v a r i e d th e l e n g t h o f l i s t
t o i n v e s t i g a t e s e r i a l p o s i t i o n e f f e c t s * The h y p o t h e s i s
th e y w ere t e s t i n g was d e r iv e d fro m a c o n s i d e r a t i o n o f th e
M arbe e f f e c t , i * e * , t h e r e s h o u ld be a n e g a t iv e r e l a t i o n
b e tw e e n th e s e r i a l p o s i t i o n and th e m ean num ber r e c a l l e d *
T h i r t y u n d e r g r a d u a te s u b j e c t s p a r t i c i p a t e d . L i s t s o f
w o rd s w ere s e l e c t e d fro m 75 w o rd s m a tc h e d f o r f r e q u e n c y
o f u s a g e , e t c * , and d is p la y e d s e q u e n t i a l l y b y m eans o f a
p r o j e c t o r * k 2*5 se co n d e x p o s u re tim e w as u s e d . F o u r
l i s t l e n g t h s — 5 » 1 0 , 2 0 , and lj.0 i te m s — w ere ra n d o m ly
s e l e c t e d and e a c h s u b j e c t u n d e rw e n t one t r i a l fro m e a c h
l i s t le n g th * I n t e r p o l a t e d a c t i v i t y f o r tw o m in u te s
23
fo llo w e d e a c h l i s t le n g t h b e f o r e th e p r e s e n t a t i o n o f th e
n e x t l i s t .
As th e le n g th o f l i s t I n c r e a s e d th e num ber r e c a l l e d
p e r s e r i a l p o s i t i o n becam e I n c r e a s i n g l y U s h a p e d . The
m ean s e r i a l p o s i t i o n o f th e w o rd s a s th e y o c c u r r e d I n
r e c a l l was d e te rm in e d and a lth o u g h th e p r e d i c t e d e f f e c t
was n o t o b ta in e d f o r s h o r t l i s t s * th e r e l a t i o n s h i p te n d e d
to go i n th e p r e d i c t e d d i r e c t i o n a t t h e lo n g e r l i s t
l e n g t h s . The o r d e r o f r e c a l l t y p i c a l l y fo llo w e d th e
o r d e r o f p r e s e n t a t i o n .
R a te o f P r e s e n t a t i o n a n d /o r R e o a ll
B oth o f t h e s e v a r i a b l e s h a v e b e e n th e s u b j e c t o f
c o n s i d e r a b le r e s e a r c h . They a r e b e in g t r e a t e d t o g e t h e r
b e c a u s e many o f th e s t u d i e s v a r i e d b o th s i m u lt a n e o u s ly .
The f i r s t s tu d y t o be c o n s id e r e d was p e rfo rm e d by
B e rry ( 1 9 6 1 ) . E ig h te e n e le m e n ta r y p s y c h o lo g y s t u d e n ts
w ere g iv e n a s i n g l e l e a r n i n g t r i a l on a l i s t o f te n * low
a s s o c i a t i o n v a lu e n o n se n se s y l l a b l e s w h ic h w ere p r e s e n te d
on a memory drum . F o r h a l f o f th e s u b j e c t s t h e r e w as a
p r e s e n t a t i o n p e r i o d o f s i x se c o n d s f o llo w e d b y a b la n k
i n t e r v a l o f s i x se c o n d s b e f o r e t h e n e x t w ord a p p e a r e d .
T h ere w ere t h r e e su b g ro u p s w i t h i n t h i s h a l f - g r o u p . The
f i r s t su b g ro u p was in fo rm e d t h a t th e y w ould be r e q u i r e d
to r e c a l l t h e n o n se n se s y l l a b l e s a f t e r one m in u te ; th e
se c o n d su b g ro u p was I n s t r u c t e d to p r i n t e a c h o f th e
2k
s y l l a b l e s a s so o n a s I t o c c u r r e d ; and th e t h i r d su b g ro u p
was t o l d t o p r i n t th e w ord d u r in g th e s ix - s e c o n d " b la n k *
p e rio d *
The o t h e r h a l f o f th e s u b j e c t s w ere s i m i l a r l y
d iv id e d b u t t h e r e w as a c o n tin u o u s tw e lv e -s e c o n d e x p o s u re
w ith no b la n k p e r i o d b e tw e e n s t i m u l i . A t th e end o f one
t r i a l th e drum w as s to p p e d and one m in u te l a t e r th e y w ere
a sk e d to p r i n t th e s y l l a b l e s .
The num ber o f c o r r e c t r e s p o n s e s was u s e d a s t h e
r e s p o n s e m e a s u re . The o v e r a l l F - t e s t d id n o t t u r n o u t
s i g n i f i c a n t b u t i f th e n o - p r i n t i n g g ro u p was e x c lu d e d , a n
a n a l y s i s o f v a r ia n c e o f th e re m a in in g 2 x 2 t a b l e y i e l d e d
a p -v & lu e o f l e s s t h a n *0£* C o n s e q u e n tly a se c o n d e x p e r i
m ent w as p e rfo rm e d u s in g o n ly t h e s e g r o u p s . I t was fo u n d ,
a t l e s s th a n t h e .0 5 l e v e l , t h a t th e s u b j e c t s who p r i n t e d
th e s y l l a b l e a s so o n a s i t a p p e a re d d id s i g n i f i c a n t l y
b e t t e r .
The a u th o r c o n c lu d e s t h a t th e c l o s e r th e r e s p o n s e
t o one ite m i s t o t h e p r e s e n t a t i o n o f t h e n e x t ite m , th e
p o o r e r th e r e c a l l . I s o l a t i o n i s in v o lv e d as an e x p la n a
t o r y c o n c e p t. W ith th e c l o s e r tim e i n t e r v a l s , i n t e r
f e r e n c e h a s a g r e a t e r i n f l u e n c e .
D ecay o f th e memory t r a c e h a s b e e n o f f e r e d a s th e
o t h e r m a jo r t h e o r e t i c a l p o s i t i o n t o a c c o u n t f o r s h o r t - t e r m
memory l o s s . C onrad (195>7) had 30 s u b j e c t s l i s t e n t o
2 $
8- d i g i t num bers w h ich h a d b e e n r e c o r d e d on ta p e a t th e
r a t e o f e i t h e r 30 o r 90 d i g i t s p e r m in u te . Im m e d ia te ly
f o llo w in g e a c h n u m b er, a tim in g d e v io e s t a r t e d c l i c k i n g
l o u d l y , a g a in a t t h e r a t e o f e i t h e r 30 o r 90 tim e s p e r
m in u te . S u b j e c t s w ro te down th e 8 - d i g i t num ber th e y had
j u s t h e a r d , one d i g i t a t a tim e , i n s t e p w ith th e t i m e r .
I n th e c o n d i t i o n i n w h ic h b o th p r e s e n t a t i o n and r e c a l l
w ere a t th e slo w r a t e , f o r any g iv e n d i g i t i n t h e s e r i e s ,
th e i n t e r v a l b e tw e e n p r e s e n t a t i o n r a t e and r e c a l l was
t h r e e tim e s lo n g e r th a n w hen b o th r a t e s w ere f a s t .
The p r o p o r t i o n o f d i g i t s r e c a l l e d was s i g n i f i c a n t l y
g r e a t e r w ith th e s h o r t d e la y (O .lfl to 0 * 3 2 ) . T r e b l in g th e
i n t e r v a l b e tw e e n p r e s e n t a t i o n and r e c a l l a p p ro x im a te ly
d o u b le d th e num ber o f d i g i t s f o r g o t t e n .
S in c e i t seem ed t h a t th e lo n g e r one i s r e s t r a i n e d
fro m r e c a l l i n g , th e g r e a t e r i s th e l i k e l i h o o d o f f o r
g e t t i n g , i t m ig h t be e x p e c te d t h a t r e c a l l a t a f r e e r a t e
w ould be s u p e r i o r t o r e c a l l a t an y c o n s t r a i n e d r a t e . The
m ethod d e s c r ib e d above was u s e d t o t e s t t h i s by a d d in g
a t h i r d , u n p a c e d r e c a l l g r o u p . The p r o p o r t io n s o f w rong
num bers a t p a c e d r e c a l l s o f 30 and 90 d i g i t s p e r m in u te
and th e f r e e r e c a l l c o n d i t i o n w ere 0 . 5 9 * 0 .3 8 and 0 . 6^
r e s p e c t i v e l y . The a u th o r c o n o lu d e s t h a t t h e s e r e s u l t s
a re d i f f i c u l t t o e x p l a i n i n te rm s o t h e r th a n th e d e c a y
t h e o r y .
26
C onrad and H iX le (1 9 5 8 ) s u b j e c t e d th e d e c a y th e o r y
t o a f u r t h e r t e s t . I n an e x p e r im e n ta l s i t u a t i o n g e n e r a l l y
s i m i l a r t o t h e one Im m e d ia te ly p r e c e d i n g , t h i r t y fe m a le
s u b j e o t s l i s t e n e d to ta p e r e c o r d e d d i g i t s p r e s e n t e d i n
b lo c k s o f e i g h t d i g i t s . T h ere w ere tw o p r e s e n t a t i o n
r a t e s , 30 and 90 d i g i t s p e r m in u te , and t h r e e r e c a l l
r a t e s , 30 and 90 d i g i t s p e r m in u te and u n p a c e d . T h ese
s i x c o n d it i o n s w ere p r e s e n t e d i n a f a c t o r i a l a rr a n g e m e n t.
The r e s u l t s a g a in w ere i n th e d i r e c t i o n p r e d i c t e d b y th e
d e ca y t h e o r y . T h ese r e s u l t s d i f f e r fro m some o t h e r s i n
t h a t th e f a s t p r e s e n t a t i o n r a t e g av e b e t t e r p e r f o r m a n c e .
The u n p a ce d r e c a l l s i t u a t i o n o f f e r s s e v e r a l a d v a n ta g e s :
( a ) r e c a l l c a n be c o m p le te d m ore q u ic k ly ; ( b ) th e s u b j e c t s
c a n tim e t h e i r r e s p o n s e s i n a c c o rd w ith m e n ta l p r o c e s s e s ;
and ( c ) t h e r e w as a n o p p o r tu n ity f o r c o m p le te r e h e a r s a l
im m e d ia te ly f o l lo w in g th e p r e s e n t a t i o n . (W ien th e r e c a l l
was p a c e d , th e f i r s t d i g i t was r e q u i r e d a lm o s t im m e d ia te ly
a f t e r th e l a s t d i g i t p r e s e n t e d .)
N ot a l l o f th e r e l e v a n t e x p e rim e n ts h a v e b e e n p e r
fo rm ed w ith v e r b a l m a t e r i a l . S k i l l e d t a s k s h a v e many
c h a r a c t e r i s t i c s s i m i l a r to th o s e fo u n d i n memory s p a n o r
s h o r t - t e r m r e t e n t i o n t a s k s . O b s e r v a tio n i n s k i l l e d t a s k s
u s u a l l y in v o lv e s a n t i c i p a t i o n , i . e . , o b s e r v a t i o n r u n s
a h ea d o f p e rfo rm a n c e . M ackw orth and M ackw orth (1 9 5 9 )
d e s ig n e d two e x p e rim e n ts to s e e how f a r i n a d v an ce
27
I n f o r m a tio n c o u ld be g iv e n I n a s im p le d e c i s i o n m ak in g
ta s k *
E x p e rim e n t I In v o lv e d a n o r d e r s e a r o h ta s k * T w enty
c o u n te r s h ad t o b e moved down t h e i r r e s p e c t i v e colum ns on
a g r i d I n tim e w ith th e t i c k i n g o f a 3 - f i g u r e c lo c k * A t
e a c h tio k * o n e c o u n te r c o u ld b e m oved one s q u a re down i t s
colum n* I n e a c h colum n o f tw e n ty s q u a re s * f o u r s q u a r e s
c o n ta in e d 3- f l g u r e num bers* w h ic h w ere r e g a r d e d a s o b
j e c t i v e s I n tim e and s p a c e . T h ese s q u a r e s w ere a rr a n g e d
i n s u c h a way t h a t I f t h e c o u n te r s w ere m oved c o r r e c t l y *
e a c h one w ould a r r i v e a t e a c h num bered t a r g e t s q u a r e a t
th e moment t h a t num ber w as sh o w in g o n th e c lo c k * T he su b
je c t* s t a s k was to d e c id e w h ic h c o u n te r s h o u ld b e m oved by
co m p a rin g v a r io u s tim e s show n on t h e d is p la y * T h e re w as a
f a s t c o n d it i o n i n w h ic h th e c lo c k t i c k e d e v e r y 1*5 se c o n d s
and a slo w c o n d i t i o n i n w h ic h i t t i c k e d e v e r y 3*0 se c o n d s*
The d i s p l a y c o n s i s t e d o f a s e r i e s o f p i c t u r e s o f
3 - d i g i t num bers p r o j e c t e d on a s c re e n * I n e a c h p i c t u r e
one o b j e c t i v e was o u t l i n e d b y a w h ite sq u a re * s u c c e s s iv e
o b j e c t i v e s b e in g " s p o t l i t 1 1 I n t h i s f a s h i o n by s u c c e s s iv e
p i c t u r e s * The a d d i t i o n a l e m p h a sis g iv e n b y th e a r r i v a l
o f th e " s p o t l i g h t " was r e g a r d e d a s an a d v a n c e d cu e*
A se co n d v a r i a b l e was th e num ber o f m oves t h a t th e
s u b j e c t h ad to " s t o r e * " T h a t i s , i n s t o r a g e s i z e o f
z ero * S h ad n o th in g to rem em ber b e c a u s e th e s p o t l i g h t was
28
alw ay s p o i n t i n g t o t h e p r e s e n t o b j e c t i v e , th e one to w a rd
w hich he s h o u ld be m oving a t t h a t tim e . W ith a s t o r a g e o f
o n e , t h e o b j e c t i v e e m p h a siz e d by th e " s p o t l i g h t * w as th e
one a f t e r th e p r e s e n t o n e . S h ad t o p e r c e iv e and rem em ber
one p o s i t i o n o f th e " s p o t l i g h t * w h ile m oving th e c o u n te r
to w a rd th e p r e v io u s o b j e c t i v e . S to r a g e s o f z e r o , o n e ,
tw o , t h r e e , and f o u r ad v an ce c u e s w ere u s e d . A c o n t r o l
c o n s i s t e d o f a s i t u a t i o n i n w h ic h th e s p o t l i g h t p r o v id e d
u s e l e s s i n f o r m a ti o n .
T w elve s u b j e c t s , n a v a l r a t i n g s b e tw e e n th e a g e s o f
1 8 -2 3 , u n d e rw e n t a l l c o n d it i o n s i n a ra n d o m iz e d L a t i n
S q u a re a rra n g e m e n t. B oth th e ad v an c e c u e s and c lo c k
sp e ed r e s u l t e d i n s i g n i f i c a n t d i f f e r e n c e s w ith th e f a s t e r
sp e e d and m ore ad v an ced c u e s h a v in g d e t r i m e n t a l r e s u l t s .
A dvances o f z e r o , one and tw o gave b e t t e r p e rfo rm a n c e th a n
u n a id e d s e a r c h , h o w e v e r. When th e r e s u l t s w ere c o n s id e r e d
i n te rm s o f ad v an ce tim e , a d v a n c e -tw o was e f f e c t i v e a t th e
s lo w e r p r e s e n t a t i o n sp e e d w h ic h i n d i c a t e s an e f f e c t i v e
s t o r a g e tim e o f t h i r t y s e c o n d s . A t th e f a s t e r s p e e d ,
a d v a n c e -o n e w as th e f u r t h e s t ah ead c u e s w ere e f f e c t i v e
w h ic h r e p r e s e n t s o n ly 7*5 s e c o n d s . The a u th o r s c o n c lu d e
t h a t i t i s h a r d e r t o p e r c e i v e , r e t a i n and r e c a l l ite m s
w h ich a re c o n t i n u a l l y c h a n g in g d u rin g a s e r i a l t a s k th a n
w ith th e same ite m s i n a c l a s s i c a l memory t a s k . B ut fro m
th e d e c a y th e o r y v ie w p o in t, i t i s i n t e r e s t i n g t o n o te t h a t
29
th e r e s u l t s p r e v i o u s l y fo u n d a r e r e v e r s e d * T h a t i s , n o v
th e f a s t e r sp e e d c a u s e s a d e c re m e n t* E v i d e n t l y , t h e r e i s
so m e th in g p r e s e n t i n t h i s s i t u a t i o n w h ich i s q u a l i t a t i v e l y
d i f f e r e n t t h a n i n th e m ore t y p i c a l memory sp a n t a s k s i n
v o lv e d i n th e p r e v io u s s t u d i e s . I s i t c o m p le x ity ? The
e v id e n c e i s n o t c l e a r en o u g h a t t h i s p o i n t t o make a
d e c i s i o n , b u t t h i s c o n t r a d i c t i o n w i l l be c o n s id e r e d a t
g r e a t e r le n g t h a l i t t l e l a t e r *
M ackw orth (1 9 5 9 ) p r e s e n te d e i t h e r l e t t e r s o r l i g h t s
t o s u b j e c t s who w ere t o re s p o n d b y p u s h in g a n a p p r o p r i a te
b u t t o n . The s u b j e c t s w ere n o t t o re s p o n d t o a s p e c i f i c
s t i m u l u s , h o w e v e r, u n t i l a s p e c i f i e d num ber o f l a t e r
s t i m u l i h ad a p p e a re d * T h at i s , th e y had t o rem em ber a
c o n t i n u a l l y c h a n g in g s m a ll g ro u p o f l e t t e r s . The s i z e o f
th e g ro u p t o be rem em bered was v a r i e d fro m one t o f o u r
l e t t e r s i n a d d i t i o n t o th e one to w h ich th e p a r t i c u l a r
re s p o n s e was t o be m ad e. The r a t e o f p r e s e n t a t i o n a t
w h ic h th e s u b j e c t s c o u ld r e a c h a n 80 p e r c e n t c o r r e c t
s c o r e w as d e te r m in e d . I t was fo u n d t h a t s u b j e c t s r e
q u i r e d a p p ro x im a te ly o n e se c o n d p e r s tim u lu s f o r e a c h
member o f th e g ro u p w h ic h th e y h a d t o s t o r e . F o r e x a m p le ,
w hen th e r e s p o n s e was made f i v e l e t t e r s a f t e r i t s s tim u lu s
( f o u r l e t t e r s s t o r e d ) , s u b j e c t s r e q u i r e d f o u r se o o n d s p e r
s tim u lu s t o a c h ie v e t h e 80 p e r c e n t s c o r e . Two l a t e r
e x p e rim e n ts a ls o r e p o r t e d I n t h i s p a p e r i n d i c a t e d t h a t
30
i d e n t i f y i n g l e t t e r s w ere n o t n e c e s s a r y f o r " a d v a n c e s * 0 ,
1 , o r 2 , b u t w ere n e c e s s a r y a t a d v a n c e s 3 and I)..
M ackw orth ( 1 9 6 2 a ) , n o t in g t h a t some s t u d i e s o b
t a i n e d d i v e r g e n t r e s u l t s w ith r e s p e c t t o t h e p r e d i c t i o n s
o f d e ca y t h e o r y , i n v e s t i g a t e d th e r a t e o f th e v i s u a l p r e
s e n t a t i o n o f d i g i t s . The m e ssa g e s c o n s i s t e d o f e i g h t o r
n in e d i g i t s and w ore p r e s e n te d by m oving f i l m . The d i g i t s
w ere p r e s e n t e d one a t a t im e , i n s u c c e s s iv e p o s i t i o n s fro m
l e f t t o r i g h t on th e s c r e e n . A t th e end o f th e s e q u e n c e ,
th e s u b j e c t s w ro te down t h e a n sw e rs i n th e same o r d e r as
th e y a p p e a r e d . The r a t e s w ere 2 . 0 , 1 .5 , 1 * 0 , 0 .5 &nd
0 .2 5 s e c o n d s p e r d i g i t . H er r e s u l t s i n d i c a t e t h a t th e
2*0 se c o n d p e r d i g i t r a t e o b ta in e d th e b e s t p e rfo r m a n c e .
T h is d o e s n o t p r o v id e v e ry good e v id e n c e a g a i n s t th e
d e c a y t h e o r y , h o w e v e r, s i n c e p e r c e p t u a l p ro b le m s may h av e
c o n fo u n d e d th e r e s u l t s . A t v e ry f a s t s p e e d s t h e r e i s
p r o b a b ly d i f f i c u l t y i n r e a d i n g th e d i g i t s , w h ile a t v e ry
slo w sp e e d s t h e r e i s p r o b a b ly an a d d i t i o n a l o p p o r t u n it y
f o r r e h e a r s a l . M o re o v e r, sh e s t a t e s t h a t when th e l a s t
d i g i t s a r e r e c a l l e d f i r s t , p e rfo rm a n c e w as b e t t e r on th e
l a s t d i g i t s . T h is r e s u l t m ig h t s u p p o r t e i t h e r a d e c a y o r
i n t e r f e r e n c e t h e o r y .
A l a t e r e x p e rim e n t was p e rfo rm e d by M aokw orth
(1 9 6 2 o ) u s in g s i m i l a r d i s p l a y m a t e r i a l s . S p e c i f i c a l l y
sh e i n v e s t i g a t e d th e e f f e c t o f lo o k in g f o r th e c o r r e c t
31
r e s p o n s e i n a s i t u a t i o n w here t h e p r e s e n t a t i o n o f th e
s e r i e s was c o m p le te d b e f o r e r e c a l l was r e q u i r e d . Two
ty p e s o f a r e s p o n s e ( d i c t a t i n g and p r e s s i n g b u tto n s
l a b e l l e d fro m z e r o th ro u g h n in e ) , d i s p l a y s p e e d , and
o r g a n i z a t i o n ( b lo c k v e r s u s u n i t s ) w ere v a r i e d . A l l t h r e e
v a r i a b l e s h ad a s i g n i f i c a n t e f f e c t b u t t h e r e w ere no
s i g n i f i c a n t i n t e r a c t i o n s *
A se c o n d e x p e rim e n t a tte m p te d to i n v e s t i g a t e m ore
c l o s e l y th e r a t e o f r e s p o n s e . I t was n o t known how f a s t
th e s u b j e c t s re s p o n d e d i n th e p r e v io u s e x p e r im e n t. The
m an u al re s p o n s e m ig h t h av e ta k e n lo n g e r th a n d i c t a t i n g
and a c c o u n te d f o r th e d i f f e r e n c e . F o u r ty p e s o f r e s p o n s e
w ere u s e d : u n p a c e d d i c t a t i n g , d i c t a t i n g i n tim e w ith a
m etronom e a t th e r a t e o f one d i g i t p e r s e c o n d , w r i t i n g a s
f a s t a s p o s s i b l e , and w r i t i n g i n tim e w ith m etronom e a t
r a t e o f one d i g i t p e r s e c o n d . As b e f o r e , d i s p l a y sp e e d
and o r g a n i z a t i o n w ere a ls o v a r ie d *
The m a in v a r i a b l e s w ere a g a in s i g n i f i c a n t b u t now
some i n t e r a c t i o n s a c h ie v e s i g n i f i c a n c e . The r e s u l t s o f
b o th e x p e rim e n ts i n d i c a t e t h a t th e s e l e c t i o n o f a m a n u a l
r e s p o n s e and a slo w e d r a t e o f d i c t a t e d r e s p o n s e a d v e r s e ly
i n f lu e n c e r e t e n t i o n w h ile th e r a t e o f m an u al r e s p o n s e
d o e s n o t . M oreover g ro u p in g o f th e ite m s on th e d i s p l a y
h a s a p o s i t i v e e f f e c t *
M urdock ( i 9 6 0 ) r e p o r t s a s e r i e s o f tw e lv e e x p e r l -
32
m erits i n w h ic h many v a r i a b l e s w e re s t u d i e d . M ost i n t e n s e
l y i n v e s t i g a t e d w e re t h e l e n g t h o f t h e l i s t and p r e s e n t a
t i o n t i m e . The s t a n d a r d c o n d i t i o n s f o r s e v e r a l e x p e r i
m e n ts w ere a s f o llo w s g T h i r t y w o rd s , w h ic h w e re ra n d o m ly
s e l e c t e d fro m t h e T h o rn d ik e -L o rg e l i s t o f 1000 m o st
commonly u s e d w o rd s , w ere p r e s e n t e d a t t h e r a t e o f tw o
s e c o n d s p e r w o rd . A f t e r e a c h t r i a l s u b j e c t s w ro te down
a s m any o f th e w o rd s a s th e y rem em bered on a n a n sw e r fo rm
i n a sp a o e d e te r m in e d by th e l e t t e r w ith w h ic h th e w ord
b eg an *
H is p rim a ry r e s u l t s may b e su m m arise d a s f o l l o w s :
1* T h ere w as no d i f f e r e n c e b e tw e e n a u d i t o r y and
v i s u a l p r e s e n t a t i o n .
2* T h e re i s no w arm -up e f f e c t i n f r e e r e c a l l
v e r b a l l e a r n i n g .
3* U n e q u a l r e c a l l tim e h ad l i t t l e e f f e c t , an d
k* R i = k (L x PT) * m
w here
R^ ■ t h e num ber r e c a l l e d a f t e r one p r e s e n t a t i o n
L * l e n g t h o f l i s t
PT * p r e s e n t a t i o n tim e p e r ite m
k and m a r e e m p i r i c a l l y d e r i v e d o o n s t a n ts *
He s t a t e s t h a t i n a l l p r o b a b i l i t y "m" i s t h e
memory s p a n and *k* a m e a su re o f th e r a t e a t w h ic h
c h a n g e s a s a f u n o t l o n o f L and P T .
33
M urdock p r e s e n t s o t h e r e m p i r i c a l l y d e r iv e d f o rm u la s
w h ic h p e r t a i n m ore to l e a r n i n g i n g e n e r a l th a n t o im
m e d ia te memory* A p p en d ix C w i l l p r e s e n t t h e s e fo rm u la s *
The n e x t s tu d y t o be r e p o r t e d w as c o n d u c te d by
F o u lto n (1 9 5 3 )* He a tte m p te d t o d e te rm in e w h e th e r th e
d i v i s i o n o f a t t e n t i o n b e tw e e n r e c a l l i n g e a r l i e r ite m s and
m em o riz in g l a t e r ite m s had a n a d v e rs e e f f e c t *
E ach o f 16 s u b j e c t s h ad t o make tw o -h a n d e d , 16
c h o ic e r e s p o n s e s a c c o rd in g t o a random s e r i e s o f v i s u a l
d i s p l a y s w h ic h w ere p r o j e c t e d one a t a tim e o n a s c r e e n *
E a c h s e r i e s o f If? d i s p l a y ite m s was d iv id e d i n t o t h r e e
e q u a l s e c t i o n s . The f i r s t f i v e ( p r e - d i s p l a y ) h ad t o be
re s p o n d e d to as so o n a s th e y a p p e a r e d ; th e n e x t f i v e
( b lo o k o u t) had t o be l e a r n e d ; and w h ile th e l a s t f i v e
( p o s t - d i s p l a y ) w ere b e in g d i s p l a y e d , s u b j e c t s had t o
re s p o n d t o a l l f i v e o f th e p r e c e d in g ite m s h e c o u ld
rem em b er, i n th e o r d e r i n w h io h h e le a r n e d th em . A f t e r
t h i s , th e l a s t f i v e ite m s w ere to b e p r o c e s s e d , a g a in i n
th e o r d e r i n w h ic h th e y w ere p r e s e n te d *
The f i r s t two d i s p l a y g ro u p s w ere p r e s e n t e d a t th e
same s p e e d , w h ic h was a t th e r a t e o f e i t h e r 1 , 2 , 3 , o r I4 .
se c o n d s p e r i te m . The l a s t f i v e w ere p r e s e n t e d a t e i t h e r
th e same o r d i f f e r e n t r a t e a s th e f i r s t t e n i t e m s , b u t i n
e i t h e r o a se a t one o f th e same f o u r d i s p l a y sp e e d s *
The r e s u l t s I n d i c a t e t h a t w hen th e l a s t f i v e ite m s
3h
w ere d is p la y e d a t a f a s t s p e e d , th e s u b j e c t c o u ld e i t h e r
re s p o n d t o th e e a r l i e r d i s p l a y o r n o te th e l a s t Ite m s*
B o th c o u ld n o t b e done e f f e c t i v e l y * No p a r t i c u l a r d i f f i
c u l t y w as e n c o u n te r e d a t t h e s lo w e r sp e e d s* T h is c o m p e ti
t i o n b e tw e e n r e c a l l and m e m o ris a tio n I s i n t e r p r e t e d by
P o u lto n t o s u g g e s t a m echanism b y w h ic h th e a c t i v e r e t e n
t i o n o f e a r l i e r Ite m s c o u ld i n t e r f e r e w ith th e m em o riza
t i o n o f l a t e r Ite m s*
P o u lto n (1951)-) r e p o r t s a n o th e r s tu d y I n w h ich
e i g h t s u b j e c t s w ere p r e s e n t e d w ith a t w o - c i r c l e d i s p l a y
i n w h ic h p o i n t e r s I n d i c a t e d i n w h ich d i r e c t i o n a j o y s t i c k
was t o be moved* The s i x t e e n p o s s i b l e d i s p l a y co m b in a
t i o n s w ere c o m p le te ly ra n d o m iz e d and p r e s e n t e d by m eans
o f a f i l m s t r i p * R e sp o n se s w ere r e c o r d e d g r a p h i c a l l y by
p e n s* The s u b j e c t s h ad to re s p o n d a t " l a g s " r a n g in g fro m
one to th r e e * A t l a g - o n e , a r e s p o n s e w as to be made to
th e d i s p l a y t h a t j u s t d is a p p e a re d * A t l a g - tw o , to th e
d i s p l a y j u s t b e f o r e t h a t , e tc * F iv e s p e e d s o f re s p o n s e
w ere t r i e d a t eao h l a g — o n e , tw o , t h r e e , and f o u r se c o n d s
p e r r e s p o n s e , and a t th e s u b j e c t 's own sp eed * (T he m ean
sp e e d s s e l e c t e d by t h e S s w ere 1*7* 2 . 0 , and 2*2 se c o n d s
p e r r e s p o n s e a t la g s o n e , tw o and t h r e e r e s p e c t i v e l y * )
C o n s id e r a b le p r a c t i c e was g iv e n b e f o r e th e e x p e r i
m ent b egan* P e rfo rm a n c e d u r in g th e t e s t d e c r e a s e d b o th
w ith tim e f o r t h e r e s p o n s e and la g * A l l t i m e s - f o r -
35
r e s p o n s e o f tw o s e c o n d s an d above w ere g ro u p e d s i n c e t h e y
d id n o t d i f f e r s i g n i f i c a n t l y * b u t t h e r e w as a d i f f e r e n c e
b e tw e e n t h e s e and t h e o n e -s e c o n d c o n d itio n * L ag h a d a
r e l a t i v e l y g r e a t e r i n f l u e n c e . P e rfo rm a n c e d e c r e a s e d fro m
98 p e r c e n t c o r r e c t a t th e tw o -se c o n d * la g - o n e c o n d i t i o n
t o o n ly 9 p e r c e n t c o r r e c t a t o n e -s e c o n d , l a g - t h r e e c o n d i
t i o n .
A n o th e r e x p e r im e n t was p e rfo rm e d v a r y i n g tim e p e r
r e s p o n s e and l a g b u t u s i n g a d i f f e r e n t t a s k . A m oving
p a p e r ta p e u p o n w h ic h w as t r a c e d a z i g - z a g c o u rs e c o u ld
be s e e n b y s u b j e c t s th r o u g h a 1 .5 mm. s l i t . T w elve s u b
j e c t s c o p ie d th e z i g - z a g s a t l a g s o f fro m z e r o t o t h r e e
u s i n g a w ir e p o i n t e r w h ic h m oved i n a p a r a l l e l s l i t
s c r e e n e d by a s h i e l d . The tim e p e r r e s p o n s e w as v a r i e d
by m a n i p u l a t in g th e c o u r s e s p e e d . The r e s u l t s d u p l i c a t e d
th o s e o b t a i n e d i n t h e p r e v io u s e x p e rim e n t* b u t i t was
fo u n d t h a t a t a r a t e o f 0 .6 s e c o n d s p e r r e s p o n s e * e r r o r s
a p p r o x im a te ly d o u b le d f o r l a g s o f z e r o and o n e .
P o u lto n c o n c lu d e s t h a t a c c u ra c y i s a d v e r s e l y a f
f e c t e d a t h i g h s p e e d s b e c a u s e a t t h e s e s p e e d s * o p e r a t o r s
m u st s t o r e i n f o r m a t i o n . W ith a c o n s t a n t l a g b u t i n c r e a s e d
sp eed * a c c u r a c y i s a f f e c t e d b e c a u s e t h e r e i s l e s s tim e
f o r r e c a l l .
T e ic h n e r and S a d l e r (1 9 6 2 ) v a r i e d e x p o s u re tim e
and " d e n s i t y . " D e n s ity w as d e f in e d a s t h e num ber o f
36
tim e s th e same l e t t e r was I n c lu d e d on a random d i s p l a y
w h ile k e e p in g t h e num ber o f l e t t e r c a t e g o r i e s c o n s t a n t .
S u b je c ts w ere r e q u i r e d t o r e p o r t l e t t e r c a t e g o r i e s w ith o u t
r e g a r d to how o f t e n th e y a p p e a re d . T hey fo u n d t h a t a t
v e ry s h o r t e x p o s u re tim e s , i d e n t i f i c a t i o n was p o s i t i v e l y
r e l a t e d t o d e n s i t y , b u t a t r e l a t i v e l y lo n g e x p o s u re tim e s
i d e n t i f i c a t i o n w as i n v e r s e l y r e l a t e d t o d e n s i t y . A t e v e r y
d e n s i t y , i d e n t i f i c a t i o n was d i r e c t l y r e l a t e d t o e x p o s u re
tim e . Number o f c a t e g o r i e s a ls o had a n e g a tiv e i n f l u e n c e .
The a u th o rs * i n t e r p r e t a t i o n o f th e s e r e s u l t s w as I n
te rm s o f i n f o r m a ti o n t h e o r y . D e n s i t y , a s d e f in e d h e r e ,
was a fo rm o f re d u n d a n c y . I n a " n o is y 1 1 c h a n n e l, r e d u n
d an cy i n c r e a s e d in f o r m a ti o n t r a n s m i s s i o n . On th e o t h e r
h a n d , i n a n e s s e n t i a l l y n o i s e - f r e e c h a n n e l su c h a s u se d
i n t h i s e x p e r im e n t, re d u n d a n c y i n th e fo rm o f d e n s i ty h a s
a d e c re m e n ta l e f f e c t . W here re d u n d a n c y i n c r e a s e s in f o rm a
t i o n t r a n s m i s s i o n , t h e r e i s a r e l a t i v e l y l a r g e g a i n i n th e
r a t e o f t r a n s m i s s i o n . O th e rw is e , t h e r e i s a m ore im p o r
t a n t i n t e r f e r e n c e w ith s h o r t - t e r m m em ory.
D e la y B etw een p r e s e n t a t i o n and R e c a l l
A t e s t f o r th e im m e d ia te memory o f 8 - d i g i t m e ssa g e s
was g iv e n t o 2 i| . fe m a le te le p h o n e o p e r a t o r s by C onrad
( 1958 )* A d i a l i n g sy ste m was com pared t o a d e c im a l s e t o f
k e y s ( k e y s e n d e r ) . Two a d d i t i o n a l g ro u p s w ere r e q u i r e d t o
37
d i a l th e p r e f i x n0* b e f o r e t h e t e s t o f th e m e s s a g e . The
m e ssa g e s w ere ta p e r e c o r d e d a t th e r a t e o f 100 d i g i t s p e r
m in u te . T h ere w as an I n t e r v a l b e tw e e n e a c h m essag e d u r in g
w h ich S s w ere r e q u i r e d t o r e s p o n d . The m e ssa g e s w ere
c o n s t r u c t e d so t h a t e a c h d i g i t o c c u r r e d an e q u a l num ber
o f tim e 8 and o b v io u s ly e a s y m e ssa g e s w ere e x c lu d e d .
The m essag e was s c o re d c o r r e c t o n ly when a l l d i g i t s
w ere r e c o r d e d i n th e c o r r e c t o r d e r . A dding th e p r e f i x
d i g i t r e s u l t e d i n s i g n i f i c a n t l y fe w e r c o r r e c t m e ssa g e s
w h e th e r th e k e y s e n d e r o r d i a l was u s e d . The p r o p o r t i o n
o f e r r o r s a t e a c h s e r i a l p o s i t i o n was th e same f o r b o th
c o n d i t i o n s . No e r r o r s o c c u rre d i n th e d i a l i n g o f N0n ;
t h u s , i t seem s f a i r l y c e r t a i n t h a t t h e o p e r a t o r s t r e a t e d
th e z e ro a s r e d u n d a n t. E ven th o u g h r e d u n d a n t, th e a d d i
t i o n o f z e ro a s a p r e f i x c a u s e s I n c r e a s e d e r r o r s . T h is
i s e x p la in a b le i n te rm s o f th e d e c a y th e o r y f o r t h e d i a l
in g s i t u a t i o n s in c e t h e r e was a r e l a t i v e l y lo n g d e la y i n
t h i s c o n d i t i o n . B ut w ith t h e k e y s e n d e r t h e r e w as v e ry
l i t t l e d e l a y , and y e t , i n c r e a s e d e r r o r s w ere a lm o s t a s
l a r g e h e r e as i n d i a l i n g .
A n o th e r s e t o f e x p e rim e n ts w ere p e rfo rm e d a t a
l a t e r d a te (C o n ra d , 1960) . S u b je c ts l i s t e n e d t o m e s sa g e s
c o n s i s t i n g o f s e v e n o r e i g h t d i g i t s w h ic h h ad b e e n ta p e
r e c o r d e d a t th e r a t e o f 120 d i g i t s p e r m in u te . They w ere
to r e p e a t b a c k , v e r b a l l y , th e m essag e a t an a p p r o p r i a t e
38
t im e .
T h e re w ere tw o c o n d it i o n s i n E x p e rim e n t I com pa
r a b l e t o th o s e t h a t th e te le p h o n e o p e r a t o r s u n d e rw e n t.
W ith o u t th e p r e f i x " z e r o , " th e m ean num ber r e c a l l e d was
7 2 .5 p e r c e n t . W ith th e p r e f i x , i t was 3 7 P«r c e n t .
E x p e rim e n t I I w as s i m i l a r b u t added a t h i r d g ro u p
who d e la y e d r e c a l l f o r f i v e s e c o n d s . They w ere e n c o u ra g e d
t o r e h e a r s e . The r e c a l l s c o r e s w ere 6 1 .3 p e r c e n t f o r
im m e d ia te r e c a l l ; 57*5 p e r c e n t f o r th e " r e h e a r s a l " g ro u p
and 23*8 p e r c e n t w hen th e p r e f i x was r e q u ir e d *
E x p e rim e n t I I I w as a g a in s i m i l a r b u t th e t h r e e
c o n d it i o n s w ere a s f o l l o w s : ( a ) R e c a ll a f t e r 10 se c o n d s
o f r e h e a r s a l , (b ) th e s u b j e c t s sp o k e th e d i g i t z e r o im
m e d ia te ly a f t e r h e a r i n g th e m essag e and t h e n w ere a llo w e d
10 s e c o n d s o f r e h e a r s a l b e f o r e r e o a l l , and ( c ) r e c a l l w as
p re c e d e d by th e d i g i t z e r o , b o th o f w h ic h w ere p re c e d e d
by 10 se c o n d s o f r e h e a r s a l *
R e s u l t s f o r th e r e s p e c t i v e c o n d it i o n s w ere ( a ) 70*0
p e r c e n t , (b ) 1 ^ .3 p e r c e n t , and ( c ) 1 ^9 .5 p e r c e n t*
One o f th e m ore s y s te m a tic s t u d i e s o f d e la y was
p e rfo rm e d by Brown (19*>8). H is f i r s t e x p e rim e n t h ad two
g r o u p s . S u b j e c t s i n one g ro u p w ere p r e s e n t e d w ith two
s e t s o f s t i m u l i p r e s e n t e d i n im m e d ia te s u c c e s s i o n . The
f i r s t s e t was t o be rem em bered and c o n s i s t e d o f b e tw e e n
one and f o u r p a i r s o f ra n d o m ly s e l e c t e d c o n s o n a n ts o f
39
w h ich no two w ere th e same o n an y one t r i a l * The se c o n d
s e t o f s t i m u l i was f i v e p a i r s o f num bers c o p ie d o u t o f a
t a b l e o f random num bers* S u b j e c t s w ere r e q u i r e d t o r e a d
b o th o u t lo u d , b u t t h e i r memory w as t e s t e d o n ly on th e
f i r s t s t i m u l i * A re s p o n s e was s c o r e d c o r r e c t o n ly i f
l e t t e r was i n i t s p r o p e r p la c e i n se q u en c e*
The c o n t r o l g ro u p d i f f e r e d o n ly i n t h a t th e a d d i
t i o n a l (n u m b er) s t i m u l i w ere d e le te d * T h e re was a n u n
f i l l e d i n t e r v a l in s te a d * The d e c a y th e o r y w as s u p p o r te d
b y th e r e s u l t s * The s e v e r a l se c o n d d e la y p ro d u c e d f o r
g e t t i n g i f r e h e a r s a l w as p re v e n te d *
B ro w n 's se c o n d e x p e r im e n t w i l l be c o n s id e r e d u n d e r
a n o th e r s e c t i o n b u t h i s t h i r d i s r e l e v a n t t o d e la y * The
a u th o r n o te s t h a t i f a n I n t e r v a l i s in tr o d u c e d b e tw e e n
th e r e q u i r e d s tim u lu s and t h e a d d i t i o n a l s t i m u l i w h ic h
I n te r v e n e b e f o r e r e o a l l * t h e s u b j e o t i s l i k e l y to r e
h e a r s e th e r e q u i r e d m a t e r i a l* T h is may c o u n t e r a c t th e
e f f e c t o f d e ca y r a t h e r them s t r e n g t h e n th e t r a c e much*
I f t h i s 1 b tr u e * su c h a n i n t e r v a l w ould n o t d r a s t i c a l l y
re d u c e th e d e c re m e n t* I f a n i n t e r f e r e n c e th e o r y i s i n
e f f e c t * how ever* t h e i n t e r v a l m ig h t be c r i t i c a l f o r t h e r e
i s e v id e n c e t o s u g g e s t t h a t th e l a b i l i t y o f t h e memory
t r a c e i s h i g h e s t im m e d ia te ly a f t e r e x p o s u re and d e c l i n e s
r a p i d l y ( s e e D u n c a n 's e l e c t r o - c o n v u l s i v e s h o c k e x p e rim e n t
c i t e d e a r l i e r ) •
1*0
The same s t i m u l i w ere u s e d a s I n th e p r e v io u s e x
p e rim e n t* T h re e p a i r s o f s t i m u l i w ere p r e s e n t e d a t I n t e r
v a l s o f 0*78 se c o n d s* The i n t e r v a l b e tw e e n th e l a s t p a i r
o f r e q u i r e d s t i m u l i ( c o n s o n a n ts ) and f i r s t p a i r o f num bers
was v a r i e d am o n g st 0 * 7 8 , 2*3Ij., and lf *68 se c o n d s * The
t o t a l l e n g t h o f th e r e t e n t i o n s p a n was h e ld c o n s t a n t a t
s e v e n se c o n d s* The v a r i a n c e a t t r i b u t a b l e t o t h e v a r i a t i o n
o f th e i n t e r v a l b e tw e e n th e r e q u i r e d and e x tr a n e o u s
s t i m u l i w as h i g h l y s i g n i f i c a n t * As t h e i n t e r v a l I n c r e a s e d
r e c a l l Im p ro v ed fro m lf.1 t o 5> 9 Pe r c e n t a n o n - l i n e a r
f a s h io n * The c o n t r o l g ro u p I n E x p e rim e n t I , w hen th e
c o n d i t i o n s w ere a lm o s t I d e n t i c a l e x c e p t f o r th e a d d i t i o n a l
s t i m u l i * r e c a l l e d 9 ^ Po r o e n t o f th e s t i m u l i * The r e
h e a r s a l o n ly m o d e r a te ly r e d u c e s l o s s and may be a t t r i b u
t a b l e t o a s s o c i a t i o n s fo u n d d u r in g r e h e a r s a l *
The r e s u l t s o f C o n rad * s ( i 9 6 0 ) e x p e r im e n ts and
th o s e o f Brown p r o v id e s t r o n g s u p p o r t f o r a d e c a y th e o ry *
The m o st I m p o r ta n t d i f f e r e n c e b e tw e e n th e tw o s t u d i e s i s
th e l e n g t h o f th e m essa g e u se d * A d e la y u n d e r a lo n g
m essag e c o n d i t i o n i s v e ry dam aging* The e f f e c t s o f r e
h e a r s a l a l s o seem t o b e d i f f e r e n t d e p e n d in g u p o n w h e th e r
th e m essag e i s w i t h i n th e memory s p a n o r n o t* I n C o n rad < s
s tu d y r e h e a r s a l d i d n 't im p ro v e p e rfo rm a n c e * n o r d id i t
p r e v e n t damage t o th e s h o r t e r m e ssa g e s o f Brown* b u t
p e rfo rm a n c e d id im p ro v e a s th e r e h e a r s a l p e r i o d le n g th e n e d *
^x
I t seem s I m m a te r ia l w h e th e r th e d e la y came b e f o r e o r a f t e r
r e h e a r s a l . I n th e lo n g e r m e s s a g e s , o f c o u r s e , r e p e t i t i o n
i s m ore a p t t o b e w rong and i f th e s u b j e c t i s u n aw are o f
e r r o r , t h e r e i s a lm o s t no c h a n c e o f th e s u b s e q u e n t m essag e
b e in g c o r r e o t .
H a n aw alt and T a r r ( I 9 6 I ) p e rfo rm e d a s tu d y i n w h ich
th e e f f e c t o f I n t e r p o l a t e d r e c a l l upon r e c o g n i t i o n w as
m e a su re d a t t h r e e tim e i n t e r v a l s : Im m e d ia te ly f o llo w in g
r e c a l l , and I 4.8 o r $2 h o u r s a f t e r r e c a l l . The t a s k w as t o
r e c a l l a d j e c t i v e s i n a t r u e - f a l s e t e s t g iv e n t o th e su b
j e c t s . R e c o g n itio n was m ea su re d by a m u l t i p l e c h o ic e
t e s t . When r e c o g n i t i o n w as d e la y e d t h e r e w as u n e q u lv o o a l
s u p p o r t f o r t h e f a c i l l t o r y e f f e c t o f Im m ed iate r e c a l l .
The e f f e c t o f b o th c o r r e c t and e rr o n e o u s r e c a l l was fo u n d
to I n c r e a s e w ith tim e *
I n t e r e s t i n g r e s u l t s w ere o b ta in e d b y P e t e r s o n and
P e te r s o n (1 9 5 9 ) i n a v e ry s im p le s t u d y . F o r t y - e i g h t co n
s o n a n t s y l l a b l e s w ith a W itm er a s s o c i a t i o n v a lu e o f 33
p e r c e n t o r l e s s w ere s e l e c t e d as s t i m u l i . O nly one o f
t h e s e s y l l a b l e s w as p r e s e n t e d p e r t r i a l . The e x p e r im e n te r
s p e l l e d th e s y l l a b l e and im m e d ia te ly sp o k e a t h r e e - d i g i t
nu m b er. The s u b j e c t was t o s t a r t c o u n tin g b a ck w a rd s fro m
th e num ber i n s t e p s o f t h r e e o r f o u r u n i t s , i n tim e w ith
a m etro n o m e. When a l i g h t f l a s h e d th e s u b j e c t was t o r e
c a l l t h e c o n s o n a n t s y l l a b l e . The d e la y was v a r i e d b e tw e e n
1 + 2
3 and 18 s e c o n d s . The p r o p o r t i o n c o r r e c t l y r e c a l l e d a f t e r
3 s e c o n d s was a l i t t l e b e t t e r t h a n . 5 0 , b u t a t 18 s e c o n d s
I t w as l e s s t h a n .1 0 . The a u th o r s a ls o m ea su re d l a t e n c i e s
and on t h e b a s i s o f t h e s e , th e y c la im t h a t th e d a t a d o e s
n o t s u g g e s t a g r a d u a l ly w e a k e n in g t r a c e b u t h a s a n o s c i l
l a t o r y n a t u r e .
I n th e f i r s t o f a s e r i e s o f e x p e r im e n ts , M urdock
(1 9 6 1 ) r e p l i c a t e d th e P e t e r s o n s ' I n i t i a l s t u d y . S lig jh t
m o d if i c a t io n s In c lu d e d a z e r o - s e c o n d I n t e r v a l w h ic h was
s u b s t i t u t e d f o r th e 15-s e c o n d i n t e r v a l , th e m etronom e w as
s e t f o r one b e a t p e r se c o n d I n s t e a d o f two b e a t s , th e
z e ro p o i n t o f i n t e r p o l a t e d a c t i v i t y was c o n s id e r e d to be
th e f i r s t b e a t o f t h e m etro n o m e, and a l l s u b j e c t s w e re
g iv e n p r e l i m i n a r y p r a c t i c e I n c o u n tin g b a c k w a rd . The
P e t e r s o n s ' r e s u l t s w ere c o m p le te ly c o n fir m e d .
U s in g th e same s u b j e c t s i n l a t e r s e s s i o n s , M urdock
v a r i e d th e ty p e o f m a t e r i a l b e tw e e n s i n g l e , m o n o s y lla b ic ,
nonhom ophonlc w ords and w ord t r i a d s . S i g n i f i c a n t l y m ore
s i n g l e w o rd s w ere r e c a l l e d th a n e i t h e r l e t t e r s o r w ord
t r i a d s w h ic h w ere a b o u t e q u a l . A f o u r t h s e s s i o n m e a su re d
th e l a t e n c y o f r e s p o n s e s w h ich i n c r e a s e d w ith th e d u r a t i o n
o f i n t e r p o l a t e d a c t i v i t y . M ost o f t h i s l a t t e r e f f e c t was
due t o t h e z e r o - s e c o n d i n t e r v a l .
M urdock was n o t c o m p le te ly s a t i s f i e d w ith c o u n tin g
b a c k w a rd . C o u n tin g slo w m ig h t a llo w r e h e a r s a l . I n a
kl
f o llo w - u p e x p e rim e n t h e p r e s e n t e d a l i s t o f w ords w hose
l e n g t h w as unknow n to t h e s u b j e c t s . They w ere r e q u i r e d
t o rem em ber th e f i r s t and l a s t t h r e e w o rd s . The r e q u i r e
m en t t h a t t h e y h a d t o rem em ber th e l a s t t h r e e w o rd s was
in te n d e d t o p r e v e n t r e h e a r s a l * s i x l i s t l e n g t h s w ere u s e d
v a r y in g b e tw e e n Ij. and 19 w o rd s . The r a t e a t w h ic h th e
w o rd s w ere r e a d was a l s o v a r i e d . B oth o f t h e s e v a r i a b l e s
e s s e n t i a l l y v a r i e d d e l a y .
The p r o p o r t i o n o f c o r r e c t r e c a l l s d e c r e a s e d a s th e
r e t e n t i o n I n t e r v a l i n c r e a s e d , b u t r a t e o f r e a d in g was n o t
a n e f f e c t i v e v a r i a b l e .
M urdock r e p o r t s t h a t h i s e x p e rim e n ts do n o t p r o v id e
unam b ig u o u s s u p p o r t f o r e i t h e r a d e c a y o r i n t e r f e r e n c e
t h e o r y . The d i s s i m i l a r i t y o f th e i n t e r p o l a t e d a c t i v i t y
s u g g e s ts t h a t d e c a y may b e p re d o m in a n t f e a t u r e . B u t r a t e
o f i n t e r p o l a t i o n v a r i e d o v e r a ra n g e o f t h r e e o r f o u r to
one and s t i l l p ro d u c e d th e same am ount o f f o r g e t t i n g . He
c la im s t h a t s i n c e i n th e l a s t e x p e rim e n t i t was th e num ber
o f i n t e r p o l a t e d ite m s and n o t t h e i r r a t e o f p r e s e n t a t i o n
t h a t was c r i t i c a l , th e s e r e s u l t s a r e m ore c o m p a tib le w ith
a n i n t e r f e r e n c e t h e o r y .
P o a ts tlm u lu s C u in g
The s t u d i e s t o b e d is c u s s e d i n t h i s s e c t i o n d i f f e r
fro m th o s e c l a s s i f i e d u n d e r D e la y i n one m a jo r r e s p e c t :
I *
O nly a p a r t o f th e m a t e r i a l d i s p l a y e d I s r e q u i r e d to be
r e c a l l e d . U h lch p a r t I s d e te rm in e d by a cue f o l lo w in g
th e p r e s e n t a t i o n o f th e l a s t g ro u p o f s t i m u l i .
A n d e rso n ( i 9 6 0 ) p r e s e n t e d b y m eans o f a ta p e
r e c o r d e r m e ssa g e s o f 12 random num bers r e a d I n g ro u p s o f
f o u r . The s u b j e c t s w ere r e q u i r e d t o r e c a l l f o u r , e i g h t ,
o r tw e lv e d i g i t s a s I n s t r u c t e d by th e I l l u m i n a t i o n o f
t h r e e c u in g l i g h t s . The l i g h t cu e w as p r e s e n t e d a t I n t e r
v a l s o f z e ro ( I m m e d ia te ly ) , £ o r 30 s e c o n d s a f t e r th e l a s t
d i g i t I n E x p e rim e n t I o r 0 , 2 , tj. s e c o n d s I n E x p e rim e n t I I .
The r e s u l t s I n d i c a t e t h a t p e rfo rm a n c e I s h i g h e s t when
o n ly p a r t o f t h e m essag e n e e d b e r e c a l l e d ; s h o r t d e la y s
a re in v o lv e d ; and th e l a s t Ite m s ( r e c e n c y ) a re r e q u e s t e d .
The n e x t s t u d i e s to b e r e p o r t e d w ere p r o b a b ly
d i r e c t e d m ore a t p e r c e p t i o n th a n m em ory, b u t h a v e r e l e
v a n ce f o r th e l a t t e r . As S p e r l i n g ( i 9 6 0 ) n o t e s , th e
s ta te m e n t t h a t "m ore c a n be s e e n t h a n rem em bered1 * I m p lie s
m ore I n f o r m a tio n i s a v a i l a b l e d u r i n g , and p e rh a p s f o r a
s h o r t tim e a f t e r , t h e s tim u lu s p r e s e n t a t i o n th a n c a n be
rem em b ered . T h is p o i n t s a t a "memory l i m i t a t i o n . "
Our n o rm a l mode o f s e e in g g r e a t l y r e s e m b le s a
s e r i e s o f b r i e f e x p o s u re s due t o s a c c a d ic ey e m o v em en ts.
The q u e s t io n o f "how much c a n be s e e n " I n a b r i e f e x p o s u re
h a s b e e n u n s o lv e d m a in ly b e c a u s e o f t h e d i f f i c u l t y o f
c o n fo u n d in g w hat c a n b e s e e n w ith m em ory. S p e r l in g
k s
a t t e m p t e d t o c i r c u m v e n t t h i s d i f f i c u l t y b y r e q u i r i n g o n l y
a p a r t i a l r e p o r t *
A s e r i e s o f s e v e n e x p e r i m e n t s w a s p e r f o r m e d . A
G e r b r a n d s t a c h i s t o s c o p e w i t h a t w o - f i e l d m i r r o r w a s u s e d *
S t i m u l i w e r e p r e s e n t e d f o r 5>0 m i l l i s e c o n d s ( m s e c s . ) e x c e p t
w h e n e x p o s u r e tim e w a s a v a r i a b l e . S p e c i a l l y p r e p a r e d
f o r m s a r r a n g e d i n a g r i d w e r e u s e d t o r e c o r d t h e r e
s p o n s e s . S u b j e c t s w e r e i n s t r u c t e d t o f i l l i n t h e r e q u i r e d
s p a c e s o n t h e g r i d a n d t o g u e s s i f n o t c e r t a i n . B o t h t h e
t o t a l n u m b e r c o r r e c t a n d t h e n u m b e r o f s t i m u l i i n t h e
c o r r e c t p o s i t i o n w e r e r e c o r d e d , b u t s i n c e t h e sam e r e s u l t s
w e r e o b t a i n e d f o r b o t h , o n l y t h e n u m b e r c o r r e c t w a s r e
p o r t e d *
E x p e r i m e n t I d e t e r m i n e d t h e e x t e n t t h a t i m m e d ia te
m em o ry w a s i n d e p e n d e n t o f t h e n u m b e r a n d s p a t i a l a r r a n g e
m e n t o f t h e m a t e r i a l . T h e f o l l o w i n g a r r a y s w e r e u s e d *
( a ) 3$ 5 >» 6 , o r 7 l e t t e r s n o r m a l l y s p a c e d o n t h e sam e
l i n e , ( b ) 6 l e t t e r s c l o s e l y s p a c e d o n t h e sam e l i n e
( m a s s e d ) , ( c ) tw o r o w s o f 3 l e t t e r s ( 3 * 3 ) * (< 0 tw o r o w s
o f \± l e t t e r s (l|. x I4 . ) , ( e ) t h r e e r o w s o f 3 l e t t e r s ( 3 x 3 x
3 )* ( ? ) tw o r o w s o f 2 l e t t e r s a n d 2 n u m b e r s m ix e d 9
a n d ( g ) t h r e e r o w s o f m ix e d l e t t e r s a n d n u m b e r s (I4 ./I4./I1 .) •
F i v e h i g h l y t r a i n e d p e o p l e s e r v e d a s s u b j e c t s *
The memory w as n e a r ly a c o n s t a n t f o r e a c h s u b j e c t ,
and was n e a r ly in d e p e n d e n t o f th e ty p e o f s t im u lu s * The
I*
s u b j e c t i v e i m p r e s s io n w as t h e m ix tu r e o f n u m b ers an d
l e t t e r s w as m ore d i f f i c u l t , b u t o n ly one s u b j e c t show ed
an y d e f i c i t . L a rg e i n d i v i d u a l d i f f e r e n c e s w ere o b t a i n e d .
F o u r e x p o s u re tim e s ( l £ , £ 0 , l£ 0 and £00 m i l l i
s e c o n d s ) w ere v a r i e d i n t h e s e c o n d e x p e r im e n t. T h is
v a r i a b l e was fo u n d t o b e r e l a t i v e l y u n im p o r ta n t o v e r th e
r a n g e u s e d *
The t h i r d e x p e r im e n t ( p o s t s t i m u l u s c u in g ) r e q u i r e d
o n ly a p a r t i a l r e p o r t . A to n e s p e c i f i e d w h ic h row o f th e
a r r a y w as t o b e r e c o r d e d . T ones o f 2 £ 0 , 6 £ 0 , and 2 ,£ 0 0
c y c l e s p e r s e c o n d w ere u s e d f o r t h e b o tto m , m id d le , and
to p row r e s p e c t i v e l y . I f th e s u b j e c t m i s i n t e r p r e t e d th e
to n e and r e c o r d e d th e w rong row h e w as a s k e d t o w r i t e w h a t
h e c o u ld rem em ber o f t h e c o r r e c t ro w . The p a r t i a l r e p o r t
was c o n s id e r e d a random sa m p le o f t h e l e t t e r s w h ic h t h e
s u b j e c t h a d a v a i l a b l e . T h u s, I f a s u b j e c t was 9 0 p e r c e n t
c o r r e c t I n r e p o r t i n g t h r e e o f n i n e l e t t e r s , h e may b e s a i d
t o h a v e 9 0 p e r c e n t o f t h e n in e l e t t e r s a v a i l a b l e . The
r e s u l t s i n d i c a t e t h a t th e lo w e r l i m i t o f t h e a v e r a g e i n
f o r m a t io n a v a i l a b l e i s tw ic e a s g r e a t a s t h e memory s p a n ,
and i s o v e r lj.0 b i t s . T h is i s q u i t e d i f f e r e n t t h a n some
o t h e r e s t i m a t e s b a s e d o n d i f f e r e n t m e th o d s w h ic h h a v e
b e e n i n t h e r e g i o n o f 2£ b i t s .
Experim ent IV v a ried the tim e when th e " p o st
stim u lu s1 1 in s tr u c tio n was g iv en between -100 m illis e c o n d s
(5 0 m secs* b e f o r e th e o n s e t o f th e s tim u lu s ) t o 1*00
se c o n d i n s i x s t e p s . The d e la y was f i x e d r a t h e r th a n
random f o r e a c h s e t o f t r i a l s *
M ost o f th e l e t t e r s I n e x c e s s o f t h e memory s p a n
w ere l o s t w i t h i n 250 m s e c s . R e s u l ts f o r th e a s c e n d in g
and d e s c e n d in g s e r i e s w ere d i f f e r e n t . When th e d e s c e n d in g
s e r i e s w as g iv e n f i r s t , o r d e r l y b e h a v io r d i s i n t e g r a t e d *
M o d if ic a tio n s I n t h e p ro c e d u r e a c h ie v e d r e g u l a r i t y b u t th e
r e s u l t s f o r th e d i f f e r i n g s e r i e s s t i l l d i f f e r e d * I n th e
a s c e n d in g s e r i e s e r r o r s w ere e v e n ly s p l i t b e tw e e n th e to p
and b o tto m ro w s ; i n t h e d e s c e n d in g s e r i e s t h e to p row was
fa v o r e d by a r a t i o o f th r e e t o one* T h is was I n t e r p r e t e d
a s s u g g e s tin g c h a n g e s i n s t r a t e g y o n th e p a r t o f th e su b
j e c t s * A n o th e r s e r i e s was r u n w ith c e r t a i n m o d i f i c a t i o n s
t o e l i m i n a t e t h e s e s t r a t e g y c h an g es* F o r t h i s s e r i e s ,
r e t e n t i o n h ad d e c re a s e d t o th e l e v e l o f th e memory s p a n
by one seco n d *
p r e - and p o s t- e x p o s u r e f i e l d s w ere v a r i e d i n th e
n e x t e x p e r im e n t. The p o s t- e x p o s u r e f i e l d w as e i t h e r th e
same b r i g h t n e s s a s t h e I n f o r m a tio n f i e l d , o r i t was
d a r k e r , and I t was e i t h e r 15 o r 50 m s e c s . i n d u r a tio n *
R e sp o n se a c c u ra c y was re d u c e d b y a b o u t h a l f f o r a l l c o n d i
tio n s *
I n th e s i x t h e x p e r im e n t, a to n e was u s e d t o
i d e n t i f y w h e th e r th e s u b j e c t s w ere t o r e p o r t l e t t e r s o r
1 * 8
n u m e ra ls fro m a m ixed a rr a y * p a r t i a l r e p o r t s o n ly w ere
r e q u i r e d . R e sp o n se s w ere s l i g h t l y m ore a c c u r a t e t h a n
w h o le r e p o r t s o f s i m i l a r s t i m u l i * I t was o o n c lu d e d t h a t
p a r t i a l r e p o r t s by p o s i t i o n a re m ore e f f e o t l v e th a n
p a r t i a l r e p o r t s b y c a te g o ry *
S u b j e c t s i n t h e f i n a l e x p e rim e n t w ere i n s t r u c t e d
t o w r i t e down w h ic h row w as i n d i c a t e d b y th e to n e ( i * e * ,
to p o r b o tto m ) and th e n r e c o r d th e s t i m u l i o o n ta in e d i n
th e o t h e r row* The d e la y b e f o r e th e i n s t r u c t i o n to n e w as
v a rie d * Two s e t s o f t r i a l s w ith a n e u t r a l to n e w ere a ls o
g iv e n I n w h io h th e i n s t r u c t i o n s w ere t o w r i t e down e i t h e r
row b u t t o w a it u n t i l t h e to n e o c c u r r e d b e f o r e b e g in n in g
t o w r ite * I t was a lm o s t im p o s s ib le t o b e g in w r i t i n g b e
f o r e 1*0 se c o n d h ad e la p s e d so th e d a t a was g ro u p ed *
D a ta was a lm o s t th e same a s t h a t f o r th e memory s p a n e x
p e rim e n t* A l l s u b j e c t s r e p o r t e d th e to p row b e t t e r t h a n
th e b o tto m row i f th e y w ere n o t i n s t r u c t e d i n th e o r d e r
o f r e p o r t i n g * The e x p e r im e n ta l i n t e r f e r e n c e d id n o t
c h an g e th e o v e r a l l num ber o f l e t t e r s c o r r e c t l y r e p o r te d *
The a u th o r s t a t e s t h a t th e s e r i e s o f e x p e rim e n ts
i n d i c a t e t h a t m a t e r i a l i s n o t w e ll r e t a i n e d i f n o t r e
p o rte d * No o b v io u s g r a d i e n t s o f a c o u ra c y i n te rm s o f row
p o s i t i o n w ere fo u n d * T h a t i s , i n c o n t r a s t t o t h e m ore
t y p i c a l l e a r n i n g s i t u a t i o n w here t h e b e g in n in g and th e
end a re r e c a l l e d b e t t e r t h a n t h e m id d le , th e m id d le row
k s
w as g e n e r a l l y s l i g h t l y b e t t e r r e p o r t e d t h a n th e o th e r s *
I t I s l i k e l y t h a t th e s tim u lu s t r a o e was s t i l l
o o n ta ln e d on th e r e t i n a and r e a d a b l e w hen th e to n e was
h e a r d . T h is may b e th e r e a s o n t h a t th e m a t e r i a l r e p o r t e d
f i r s t was m ore a c c u r a t e . A c c o rd in g t o S p e r l in g i t i s
d o u b tf u l i f th e e n t i r e v i s u a l im age was tr a n s fo r m e d i n t o
a s e q u e n t i a l ( a u d i t o r y ) r e p o r t f o r s t o r a g e . T h e re was
some i n d i c a t i o n t h a t p r o a c t i v e i n t e r f e r e n c e had an i n
f lu e n c e *
A v e rb ac h and C o r i e l l ( 1 9 6 1 ) r e p o r t a s e r i e s o f e x
p e r im e n ts s i m i l a r t o S p e r l i n g 1s s t u d y . The e s s e n t i a l
d i f f e r e n c e was th e u se o f a v i s u a l s i g n a l t o d e s ig n a te
th e p a r t o f t h e a r r a y to be r e p o r t e d . T h is a s s u r e d t h a t
th e a r r a y and s i g n a l a re t r a n s m i t t e d t o th e p r o c e s s in g
c e n t e r ( s ) a t th e same r a t e *
A 2 x 8 a r r a y o f ran d o m ly s e l e c t e d l e t t e r s was
e x p o se d f o r $0 m s e c s . A f t e r a v a r i a b l e d e la y a b la c k b a r
was p r e s e n te d f o r f>0 m s e c s . e i t h e r above one o f th e
l e t t e r s o f t h e to p row o r below one o f t h e l e t t e r s o f th e
b o tto m ro w . The s u b j e c t s 1 t a s k w as t o name th e l e t t e r
d e s ig n a te d by th e b a r . A 70 f o o t la m b e rt f i e l d was m ain
t a i n e d t h r o u g h o u t. A f i x a t i o n p o i n t was p r o v id e d i n th e
c e n t e r o f th e v i s u a l f i e l d . The s u r ro u n d was a l a r g e r
f i e l d w ith a lu m in a n ce o f 30 f o o t la m b e r t s . A N e ils o n
t a c h ls to s c o p e u s i n g m u lt i - c h a n n e l TV e q u ip m e n t w ith g a te s
$ 0
c o n t r o l l e d toy t im e r s p r e s e n t e d th e s e q u e n t i a l d i s p l a y o f
p i c t u r e s on a s i n g l e p i c t u r e m o n ito r*
O ver 70 p e r c e n t o f th e l e t t e r s w ere c o r r e c t l y
i d e n t i f i e d when t h e m a rk e r a p p e a re d fro m 100 m s e c s . b e f o r e
th e a r r a y en d ed t o 10 m s e c s . a f t e r . (A c o r r e c t i o n f o r
c h a n c e was u s e d .) A n e g a t iv e l i n e a r s lo p e d e s c r i b e d th e
r e c a l l up t o 100 m s e c s . a f t e r th e a r r a y when r e c a l l w as
a p p ro x im a te ly 35 p e r c e n t . A f t e r 100 m s e c s . . t h e r e w as
no f u r t h e r d e c re m e n t. T h is s u g g e s ts t h a t some o f th e
m a t e r i a l w as t r a n s f e r r e d t o a m ore p e rm a n e n t s t o r a g e .
The r e a s o n t h a t 100 p e r c e n t " r e c a l l * was n o t
a c h ie v e d w hen th e m a rk e r p re c e d e d th e end o f th e a r r a y may
b e due t o I l l e g i b i l i t y o f l e t t e r s , n o t b y th e m s e lv e s , b u t
i n th e c o n te x t o f th e a r r a y . The f i r s t and l a s t l e t t e r s
i n e a c h row w ere r e c a l l e d b e t t e r th a n th o s e i n th e m id d le .
A se c o n d e x p e rim e n t was p e rfo rm e d i n w h ich th e
m a rk e r was a c i r c l e s u r r o u n d in g th e a r e a w here th e d e s i r e d
l e t t e r was d i s p l a y e d a n I n s t a n t e a r l i e r . When th e c i r c l e
p re c e d e d o r f o llo w e d c l o s e l y th e a r r a y , p e rfo rm a n c e was
s i m i l a r t o t h a t o b ta in e d i n th e f i r s t e x p e r im e n t. When
th e d e la y w as a ro u n d 100 m s e c s .. h o w e v e r, c o n s id e r a b le
d i f f e r e n c e s a p p e a re d w ith p e rfo rm a n c e b eco m in g q u i t e p o o r .
W ith a lo n g e r d e l a y , p e rfo rm a n c e Im p ro v ed u n t i l i t e v e n
t u a l l y re s e m b le d th e b a r m a rk e r e x p e r im e n t.
T h is e x p e rim e n t d e m o n s tra te s t h a t a l a t e r s tim u lu s
$1
c a n d r a s t i c a l l y I n f lu e n c e t h e p e r c e p t i o n o f a n e a r l i e r
o n e . I t a l s o i m p lie s r e t i n a l " s t o r a g e . " The i n f l u e n c e
o f th e c i r c l e was a t t r i b u t e d t o th e r e l a t i v e d i s t a n c e o f
th e tw o m a rk e rs — th e c i r c l e was c l o s e , t h e b a r f u r t h e r
away ( r e t i n a l f i e l d s ? ) . I n p r e l i m i n a r y e x p e r im e n ts when
th e b a r m a rk e r was c l o s e , th e p a r t o f t h e l e t t e r n e a r e s t
th e b a r was s t r o n g l y d i s t u r b e d . I t i s i n t e r e s t i n g t h a t
when th e c i r c l e and l e t t e r a p p e a re d t o g e t h e r t h e r e was no
a p p a r e n t d i s t u r b a n c e . E v id e n tl y th e se c o n d s tim u lu s
l i m i t s th e tim e t h a t th e f i r s t s tim u lu s may u n d e rg o
f u r t h e r p r o c e s s i n g .
The d e t r i m e n t a l i n f lu e n c e o f th e c i r c l e was n o t
in d e p e n d e n t o f th e num ber o f l e t t e r s d i s p l a y e d . I f a
s i n g l e l e t t e r was d is p la y e d i n any p o s i t i o n ( w i t h th e
f i x a t i o n p o i n t ) and th e c i r c l e p r e s e n te d w ith th e 100
m se c , d e la y , th e l e t t e r was r e a d p e r f e c t l y . W ith f o u r
l e t t e r s e x p o s e d , p e rfo rm a n c e was d i s t u r b e d d r a m a t i c a l l y .
The a u th o r s te rm e d th e a d v e r s e i n f l u e n c e o f th e
c i r c l e a s " e r a s u r e E v i d e n t l y , t h e e f f e c t i v e n e s s o f
e r a s u r e i s r e l a t e d to how much m u st be " r e a d o u t ." When
th e c i r c l e w as f i l l e d w ith g r i d l i n e s , r e s u l t s f o r d e la y s
lo n g e r t h a n 100 m s e c s . a re s i m i l a r . W ith s h o r t e r d e la y s
th e d i s t u r b a n c e w as e v e n g r e a t e r .
The a u th o r s c la im t h a t p r e l i m i n a r y w ork h a s demon
s t r a t e d t h a t w hen th e a r r a y i s p r e s e n t e d to one eye and
52
th e c i r c l e m a rk e r t o t h e o t h e r * e r a s u r e o c c u rs *
G e n e ra l c o n c lu s io n s t h a t w ere draw n fro m t h e s e
s t u d i e s a re t h a t th e v i s u a l p r o c e s s I n v o lv e s a b u f f e r
s t o r a g e t h a t h a s a v e ry f a s t " r e a d - i n * b u t v e r y slow
" r e a d - o u t •* The s y s te m I n c lu d e s e r a s u r e w h ere new I n
f o r m a tio n te n d s to e r a s e t h a t p r e v i o u s ly s to r e d *
Klemmer ( 1961) n o t e s t h a t i f t h e r e i s a d i f f e r e n c e
b e tw e e n p e r c e iv e d and s t o r e d in f o r m a tio n * p r o p e r o o d ln g
may im prove th e tr a n s m is s io n *
R e h e a r s a l
The P e te r s o n s (1959) u s e d th e same t a s k s p e c i f i e d
i n t h e im m e d ia te ly p r e c e d in g s e c t i o n t o i n v e s t i g a t e th e
i n f lu e n c e o f r e h e a r s a l * One g ro u p o f 2lj. s u b j e c t s w as i n
s t r u c t e d to r e p e a t th e c o n s o n a n t s y l l a b l e i n tim e w ith a
m etronom e u n t i l t h e e x p e r im e n te r gave t h e num ber a t w h ich
tim e th e y w ere to s t a r t c o u n tin g b a ck w a rd s* A n o th e r g ro u p
r e c e i v e d no i n s t r u c t i o n s c o n c e r n in g how th e y w ere t o u s e
t h i s i n t e r v a l * No r e h e a r s a l * one o r t h r e e r e h e a r s a l s
w ere a llo w e d * F o r th e v o c a l g ro u p r e h e a r s a l im p ro v e d
p e rfo rm a n c e s l i g h t l y * The r e s u l t s o f t h e "n o i n s t r u c t i o n "
g ro u p s w ere n o t c o n s i s t e n t l y o rd e re d *
H e l ly e r (19& 2) a l s o s t u d i e d r e h e a r s a l * A t h r e e -
c o n s o n a n t s y l l a b l e and a s e r i e s o f d i g i t g ro u p s w ere d i s
p la y e d on a memory drum* The s u b j e c t s w ere i n s t r u c t e d t o
53
r e a d a lo u d th e s y l l a b l e a s I t a p p e a r e d . They w ere a ls o
t o r e a d th e t h r e e - d i g i t num bers a s th e y a p p e a re d . The
e x p e r im e n te r v a r i e d th e num ber o f tim e s th e same s y l l a b l e
a p p e a re d on th e ta p e a s w e ll a s t h e d e la y i n t e r v a l .
S tim u li w ere d is p la y e d a t th e r a t e o f one s tim u lu s p e r
s e c o n d . A f te r t h e e n t i r e l i s t was p r e s e n t e d , th e s u b j e c t s
w ere r e q u i r e d t o r e c a l l th e c o n s o n a n ts and t o make two
ju d g m e n ts a b o u t t h e n u m b ers. T h is w as to make th e num ber
t a s k m e a n in g fu l and c o n s i s t e d o f e s t i m a t i n g w h ic h d i g i t s
o c c u r r e d m o st and l e a s t f r e q u e n t l y .
An ite m was c o n s id e r e d t o be c o r r e c t o n ly i f e v e r y
c o n s o n a n t was c o r r e o t and i n t h e p r o p e r p o s i t i o n . T h e re
was b e t t e r r e c a l l w ith an I n c r e a s e i n th e num ber o f
s tim u lu s p r e s e n t a t i o n s and w ith s h o r t e r p e r i o d s o f d e l a y .
An e x p e rim e n t was p e rfo rm e d b y H ero n (1 9 6 2 ) i n
w h ich h e i n v e s t i g a t e d th e e f f e c t s o f s im p le r e h e a r s a l on
im m e d ia te memory i n te le p h o n e d i a l i n g . D i a li n g was
c a r r i e d o u t ( a ) im m e d ia te ly a f t e r t h e m essa g e was p r e
s e n t e d , (b ) a f t e r th e m essag e h a d b e e n v o c a l l y r e h e a r s e d
one tim e , o r (o ) a f t e r i t h a d b e e n w r i t t e n down w h ile
b e in g v o c a l ly r e h e a r s e d . One c o n d i t i o n p r e s e n t e d th e
m e ssa g e s v i a th e a u d i t o r y m ode, a n o th e r th ro u g h th e
v i s u a l . The fo rm e r w as p r e s e n t e d s e q u e n t i a l l y and th e
l a t t e r s i m u lta n e o u s ly .
W ith a u d ito r y p r e s e n t a t i o n , im m e d ia te v o c a l
r e h e a r s a l and im m e d ia te d i a l i n g a r e e q u a l and s u p e r i o r t o
d i a l i n g w h ic h f o llo w e d v o c a l r e h e a r s a l * The v i s u a l p r e
s e n t a t i o n p e rfo rm a n c e d i f f e r e d s i n c e i n t h i s c o n d i t i o n
im m e d ia te v o c a l r e h e a r s a l was s u p e r i o r t o d i a l i n g w ith o r
w i t h o u t r e h e a r s a l * P e rfo rm a n c e a f t e r w r i t t e n r e h e a r s a l
w as p o o r e s t i n b o th m o d es. Some s u b j e c t s s p o n ta n e o u s ly
g ro u p e d d i g i t s d u r in g v o c a l r e h e a r s a l and th o s e g r o u p in g
th e d i g i t s i n t o tw o f o u r - d i g i t g ro u p s d id s i g n i f i c a n t l y
b e t t e r t h a n th e o t h e r s . N in e ty p e r c e n t o f th e e r r o r s
m ade i n d i a l i n g w e re a lr e a d y m ade d u r in g r e h e a r s a l f o r th e
a u d i t o r y g ro u p w h ile 7 6 p e r o e n t was th e o o m p a ra b le f i g u r e
f o r th e v i s u a l g ro u p * The a u th o r s t a t e s t h a t th e r e s u l t s
w ere i n g e n e r a l a c c o rd w i t h th e d e o a y th e o r y *
Hebb ( I 9 6 I ) r e p o r t s a n e x p e rim e n t i n w h ic h th e s u b
j e c t s u n d e rw e n t r e h e a r s a l w ith o u t k now ing i t . T h ey w ere
in fo rm e d t h a t t h e p u rp o s e o f t h e e x p e rim e n t was t o s e e i f
memory s p a n im p ro v e s w ith p r a c t i c e * T w e n ty -fo u r s e r i e s o f
n in e d i g i t s w ere r e a d a lo u d a t th e r a t e o f one d i g i t p e r
s e c o n d . The s u b j e c t s w ere t o l i s t e n c a r e f u l l y and r e p e a t
b a c k th e d i g i t s i n th e sam e o r d e r . The s u b j e c t was n o t
in fo rm e d t h a t on e v e r y t h i r d t r i a l th e same s e r i e s w as
r e p e a te d * I f Im m e d ia te memory i s m e d ia te d s o l e l y by a n
a c t i v i t y t r a c e w ith no s t r u c t u r a l c h a n g e s , e a c h new
se q u e n c e w ould be e x p e c te d t o "w ip e th e s l a t e d e a n * " No
c u m u la tiv e l e a r n i n g w ould o c c u r . The d e p e n d e n t v a r i a b l e s
55
w ore th e num ber o f t r i a l s I n w h ic h th e n in e d i g i t s w ere
r e p e a t e d w ith o u t e r r o r and a ls o * w hen th e s u b j e c t was
s to p p e d a s so o n a s h e g a v e one d i g i t o u t o f th e p r o p e r
o r d e r , t h e num ber o f d i g i t s c o r r e c t l y r e p e a t e d on e a c h
t r i a l . B o th m e a su re s i n d i c a t e d t h a t c u m u la tiv e l e a r n i n g
o c c u r r e d .
A f t e r th e n i n e t e e n t h t r i a l th e f o r t y s u b j e c t s w ere
a sk ed i f th e y n o tio e d a n y th in g ^ u n u s u a l. T w en ty -tw o r e
p o r t e d t h e r e h a d b e e n some r e p e t i t i o n and t h r e e o f t h e s e
c o u ld r e p e a t th e c r i t i c a l se q u en c e w ith o u t e r r o r . When
th e o th e r s w ere s p e c i f i c a l l y a sk e d a b o u t r e p e t i t i o n , t h r e e
m ore r e p o r t e d t h e r e h a d b e e n some and one o f th e s e c o u ld
g iv e th e se q u e n c e w ith o u t e r r o r .
A lth o u g h t h i s l a s t i n f o r m a tio n o a s t s some d o u b t,
th e c o n c lu s io n Hebb r e a c h e d w as t h a t a s i n g l e r e p e t i t i o n
p ro d u c e s a s t r u c t u r a l t r a c e w h io h o a n b e c u m u la tiv e .
A g ro u p o f f o u r e x p e rim e n ts w ere p e rfo rm e d by
S a n d e rs ( I 9 6 I ) i n v e s t i g a t i n g b o th r e h e a r s a l and i n t e r
p o l a t e d r e c a l l . I n h i s f i r s t e x p e r im e n t, a c o m b in a tio n o f
e i g h t d i g i t s was p r e s e n t e d t o s u b j e c t s f o r f i v e se c o n d s
d u r in g w h io h th e y w ere t o m em orize th e m . One c o n d i t i o n
h a d a r e c a l l r i g h t a f t e r th e s tim u lu s m a t e r i a l was rem oved
f o llo w e d by 35 se c o n d s o f r e h e a r s a l and th e n a se c o n d r e
c a l l . A se c o n d c o n d i t i o n h ad I 4.0 se c o n d s o f s t r a i g h t r e
h e a r s a l , th e n a r e c a l l . A n o th e r g ro u p r e h e a r s e d f o r 12
5 > 6
s e c o n d s , r e c a l l e d , th e n r e h e a r s e d f o r 23 se c o n d s b e f o r e a
f i n a l r e c a l l *
Im m ed iate r e c a l l seem ed t o i n t e r f e r e w ith r e t e n t i o n
w hen oom pared w ith th e g ro u p s who w ere a llo w e d t o r e h e a r s e
b e f o r e r e c a l l *
The same p ro c e d u re was fo llo w e d i n a se c o n d e x p e r i
m ent e x c e p t r e c a l l was r e q u i r e d e v e ry f o u r s e c o n d s u n t i l
t e n r e p r o d u c t io n s h a d b e e n g i v e n . S c o r in g was i n te rm s o f
th e am ount o f c h an g e b e tw e e n one r e c a l l and t h e n e x t*
S i g n i f i c a n t c h a n g e s s to p p e d a f t e r th e f o u r t h r e o a l l .
T h u s, i t a p p e a rs t h a t a g r a d u a l te n d e n c y to w a rd s t a b i l i t y
em erg es w ith e a c h s u c c e s s iv e r e h e a r s a l and r e c a l l .
E x p e rim e n t I I I a g a in p r e s e n te d d i g i t s . S u b je c ts
w ere a llo w e d t o r e h e a r s e and t h e n w ere p r e s e n te d w ith th e
t a s k o f r e a d in g o t h e r d i g i t s q u io k ly and a lo u d . Im m edi
a t e l y p r e c e d in g th e i n t e r p o l a t e d a c t i v i t y a r e c a l l was
i n s e r t e d t o p r o v id e a c r i t e r i o n f o r f i n a l r e c a l l . I n
t h r e e g ro u p s r e h e a r s a l was v a r i e d and i n t e r f e r e n c e h e ld
c o n s t a n t ; i n a n o th e r t h r e e g ro u p s th e s i t u a t i o n w as r e
v e r s e d . R e c a ll was b e t t e r a f t e r p ro lo n g e d r e h e a r s a l *
C u rv e s ( s e e F ig u re 1) r e l a t i n g I n t e r f e r e n c e t o r e h e a r s a l
seem t o s u g g e s t t h a t w hen I n t e r f e r e n c e s t a r t s , m a t e r i a l
s t i l l i n th e s h o r t - t e r m s to r a g e d e c a y s im m e d ia te ly * The
f a c t t h a t p l a t e a u x e x i s t was I n t e r p r e t e d b y t h e a u th o r to
i n d i c a t e t h a t t r a n s f e r r e d d i g i t s h a v e a f a i r d e g re e o f
M ISTAKES
Figure 1
S7
Sanders* R esu lts
R ehearsal C onstant, In terp o la ted A c tiv ity Varied
Complete Blank
8" R ehearsal
12" R ehearsal
20" R ehearsal
40" R ehearsal
t
10
- - 0 - - - 0 — - O
60 o 30 120
15
INTERFERENCE TIM E (Seconds)
58
p e rm a n e n c y . W ith a d d i t i o n a l r e h e a r s a l , th e m a t e r i a l I s
n o t o n ly t r a n s f e r r e d b u t a d d i t i o n a l l y s t r e n g t h e n e d . A l
th o u g h d e c a y r e a c h e s a maximum w ith th e 12 and 8 se c o n d
r e h e a r s a l t im e s , a c o m p le te b la n k was n o t p r o d u c e d . F o r
t h r e e t r i a l s th e maximum num ber o f m is ta k e s a llo w in g f o r
c h an c e w as 2 2 . The maximum num ber o f m is ta k e s a c t u a l l y
o b ta in e d was o n ly t e n . Some p a r t s o f th e m a t e r i a l m u st be
p la c e d q u ic k ly and p e rm a n e n tly I n th e lo n g - te r m s t o r a g e
sy stem *
E x p e rim e n t IV a tte m p te d t o d e te rm in e i f t h e im
m e d ia te memory s y s te m i n f l u e n c e s m a t e r i a l a lr e a d y i n
p e rm a n e n t s t o r a g e . One g ro u p o f s u b j e c t s w ere e x p o se d t o
and r e h e a r s e d d i g i t s f o r I 4 .O s e c o n d s , r e c a l l e d th e m , w e re
e x p o se d t o a se c o n d s e t o f d i g i t s , r e c a l l e d t h i s s e t , t h e n
a tte m p te d t o r e c a l l th e f i r s t s e t . Two o t h e r g ro u p s d i f
f e r e d o n ly i n th e ty p e o f m a t e r i a l u s e d i n th e s e c o n d s e t ;
th e se c o n d g ro u p u s e d l e t t e r s , and th e t h i r d r e a d d i g i t s
f o r l£ se c o n d s*
T h ree a d d i t i o n a l g ro u p s f o llo w e d th e same p a ra d ig m
b u t r e h e a r s e d f o r o n ly 12 s e c o n d s . T h ere was no e v id e n c e
f o r any i n f l u e n c e o f th e l a t e r l e a r n i n g on th e I n i t i a l
l e a r n i n g a f t e r I4.0 s e c o n d s o f r e h e a r s a l , b u t i n th e 12-
se c o n d c o n d i t i o n , t h e m ore s i m i l a r th e s e c o n d t a s k th e
p o o r e r was th e p e rf o r m a n c e . The a u th o r c o n c lu d e s r e h e a r s a l
m u st s t r e n g t h e n m a t e r i a l i n t h e lo n g -te rm s t o r a g e s y s te m ,
b u t p r o b a b ly n o t b y m ere r e p e t i t i o n * S u b j e c t s seem ed to
r e s o r t t o d e v ic e s s u c h as rh y th m and a r t i f i c i a l r u l e s *
S a n d e rs s u g g e s t s t h a t a s so o n a s som e m a t e r i a l i s t r a n s
f e r r e d an d t h e im m e d ia te lo a d l e s s e n e d * th e r e p e t i t i o n
n e c e s s a r y t o c o u n t e r a c t d e c a y o f im m e d ia te memory b eco m es
s e o o n d a ry t o r e p e t i t i o n aim ed a t l o n g - te r m a s s i m i l a t i o n *
P e t e r s o n an d h i s a s s o c i a t e s (1 9 6 2 ) i n v e s t i g a t e d
th e s t a g e o f l e a r n i n g d u r in g w h io h a s s o c i a t i o n s b e tw e e n
s t i m u l i and r e s p o n s e s a r e le a r n e d * T he c o u n t e r p a r t o f
t h i s , th e " r e s p o n s e r e c a l l " s t a g e ( s e e U nderw ood and
S c h u lz * i 9 6 0 )* d u r in g w h ic h ite m s c o m p r is in g th e l i s t a re
le a r n e d * w as m in im iz e d by s p e c i f y i n g i n t h e i n s t r u c t i o n s
a s e t o f n u m b ers w h ic h w e re t h e n u s e d a s r e s p o n s e s r e
p e a t e d l y th r o u g h o u t t h e e x p e rim e n t*
P a i r e d a s s o c i a t e l e a r n i n g w as u s e d . The s t i m u l i
w ere w o rd s p r e s e n t e d o n a memory drum * D i g i t s w h ic h w ere
t o b e th e r e s p o n s e s w e re p r e s e n t e d w i t h t h e w o rd s e x c e p t
d u r in g th e i n t e r s p e r s e d t e s t s w hen o n ly t h e w ord a p p e a re d *
The d e la y b e tw e e n a p a i r a n d a t e s t w hen o n ly t h e w ord
a p p e a re d w as v a r i e d i n th e f i r s t e x p e r i m e n t . R e t e n t i o n
d e c r e a s e d r e g u l a r l y o v e r i n t e r v a l s u p t o l 6 s e c o n d s . A
se o o n d e x p e r im e n t show ed t h a t a t e s t w i t h o u t k n o w le d g e o f
r e s u l t s v a r i e d i n i t s e f f e c t w i t h i t s p o s i t i o n b e tw e e n
p r e s e n t a t i o n and a s e c o n d t e s t . C o r r e c t r e c a l l o n th e
s e c o n d t e s t * g iv e n c o r r e c t r e c a l l o n th e f i r s t * i n c r e a s e d
6o
a s tim e b e tw e e n p r e s e n t a t i o n and th e f i r s t t e s t I n c r e a s e d *
C o r r e c t r e c a l l on T e s t 2 , g iv e n l n o o r r e c t r e c a l l o n T e s t
1 , d e c r e a s e d a s tim e b e tw e e n p r e s e n t a t i o n and T e s t 1 I n
c re a s e d *
Two o t h e r s t u d i e s I n v e s t i g a t e d th e I n f l u e n c e o f
I n t e r f e r e n c e and u n p ro m p te d r e s p o n s e . The c o n c lu s io n
w h ic h t h e a u th o r s p r e s e n t I s t h a t some o f th e same p h e
nom ena, e * g « , I n c r e a s e d r e c a l l th ro u g h r e p e t i t i o n , r e t r o
a c t i v e I n t e r f e r e n c e , s p o n ta n e o u s r e c o v e r y , e t c . , o c c u r I n
s h o r t - t e r m r e t e n t i o n a s h a v e b e e n d e m o n s tra te d I n s t u d i e s
o v e r lo n g e r I n t e r v a l s . T h e r e f o r e , th e y s u g g e s t t h a t an
a s s u m p tio n b e made t h a t t h e r e I s o n ly one ty p e o f memory
u n t i l th e e x p e r im e n ta l e v id e n c e d i c t a t e s o th e r w is e *
S e t
Kay and P o u lto n (1 9 5 1 ) h y p o th e s iz e d t h a t one f a c t o r
a f f e c t i n g m e m o riz a tio n i s th e s u b j e c t 's a n t i c i p a t i o n o f
th e c o n d l t i o n ( s ) u n d e r w h ic h th e l e a r n e d m a t e r i a l w i l l be
r e q u ir e d *
T h ir ty - tw o s u b j e c t s u n d e rw e n t a t a s k I n w h ic h two
j o y s t i o k - k e y s , one f o r e a c h h a n d , h ad t o b e m oved I n
r e s p o n s e t o a d i s p l a y . Two c i r c l e s w ere p r o j e c t e d on a
s c r e e n s i d e by s i d e . I n e a c h c i r c l e was a n a rro w w hich
was p o in te d i n one o f th e f o u r m a jo r com pass d i r e c t i o n s .
S u b je c ts w ere t o l d t h a t th e c i r c l e s c o rre s p o n d e d t o th e
tw o k e y s and t h e a rro w s I n d i c a t e d th e d i r e c t i o n t h e jo y
s t i c k s w e re t o b e mowed* The e x p e r im e n t c o n s i s t e d o f 20
e p i s o d e s . D u rin g e a c h o f t h e s e t h e s u b j e o t s h a d t o
m em orize e i g h t d i s p l a y Ite m s p r o j e c t e d a t th e r a t e o f tw o
se o o n d s p e r d i s p l a y . S u b j e c t s l a t e r h ad t o re s p o n d a t
th e sam e r a t e . A L a t i n s q u a re a rra n g e m e n t d e te rm in e d th e
o r d e r o f f o u r d i f f e r e n t c o n d i t i o n s . U n d er c o n d i t i o n
th e s u b j e c t r e c a l l e d th e f i r s t s e r i e s o f f o u r d i s p l a y
ite m s im m e d ia te ly a f t e r l e a r n i n g th em ; t h e n l e a r n e d and
r e c a l l e d th e n e x t f o u r ; i n B ^ , th e s u b j e c t l e a r n e d t h e
f i r s t f o u r , t h e n th e n e x t f o u r , t h e n r e c a l l e d them I n th e
same o r d e r ; i n o o n d i t i o n Bg th e I te m s w ere l e a r n e d a s i n
Bj_, b u t t h e l a s t f o u r ite m s w ere r e c a l l e d b e f o r e th o s e
l e a r n e d f i r s t ; c o n d i t i o n G was th e same a s B , e x c e p t i n
th e B c o n d i t i o n s t h e s u b j e c t d id n o t know w h e th e r I t was
& o r B2 s e r i e s w h ile I n C , h e w as t o l d I n a d v a n c e .
The ite m s I n th e B2 a e r i e s w ere e q u a l l y w e l l r e
c a l l e d . I n B^ and C , h o w e v e r, t h e f i r s t ite m s le a r n e d
w ere b e t t e r r e c a l l e d t h a n th e l a t e r i t e m s . W ith C t h e r e
o c c u r r e d t h e t y p i c a l U -sh a p e d c u r v e . W ith B ^, ite m s w ere
r e o a l l e d w ith d e c r e a s in g c o r r e c t n e s s f o r ite m s * > th r o u g h
8.
T h u s, a lth o u g h B^ and C w e re i d e n t i c a l , th e y r e
s u l t e d i n d i f f e r e n t c u r v e s . The a u th o r s a s c r i b e d t h i s t o
d i f f e r e n t s t r a t e g i e s .
62
Brown (195>lj.) p r e s e n te d a s e r i e s o f ite m s c o n s i s t i n g
o f b o th a rro w s and num bers* S u b je c ts a tte m p te d t o r e c a l l
( a ) e i t h e r th e a rro w s o r n u m b e rs* (b ) t h e a rro w s f i r s t and
t h e n th e n u m b ers* o r (o ) th e num bers and t h e n th e a rro w s*
T hey w ere t o l d w h ic h a l t e r n a t i v e e i t h e r j u s t b e f o r e o r
j u s t a f t e r th e s e r i e s was p r e s e n te d * A se c o n d e x p e rim e n t
w as e x a c t l y th e same e x c e p t i n s t r u c t i o n s w ere g iv e n o n ly
a f t e r t h e s e r i e s and l e t t e r s and num bers w ere u s e d i n s t e a d
o f a rro w s and num bers*
E ach num ber o r a rro w was s c o r e d c o r r e c t o n ly i f
p la c e d i n th e c o r r e c t s e q u e n t i a l p o s i t i o n * P e rfo rm a n c e
w as b e t t e r when s u b j e c t s knew w h a t w ould be r e q u i r e d i n
a d v an ce* b u t im provem ent seem s t o h a v e o c c u r r e d o n ly w ith
th o s e ite m s t o b e r e c a l l e d f i r s t *
An a tte m p t t o d e te rm in e i f i n s t r u c t i o n s f a c i l i t a t e d
r e c a l l th ro u g h p e r c e p t u a l m o d if ic a tio n * memory t r a c e
m o d if ic a tio n * o r a v a i l a b i l i t y o f r e s p o n s e w as m ade by
- L aw rence and C o le s (19514-) • S t i m u li c o n s i s t e d o f $0
p i c t u r e s o f f a m i l i a r o b j e c t s c u t fro m m a g a z in e s w h ic h
w ere t a c h i s t o s c o p i c a l l y p r e s e n te d f o r I n t e r v a l s b e tw e e n
20 and $00 m secs* F o r e a c h p i c t u r e tw o s e t s o f a l t e r n a
t i v e s w ere d e v e lo p e d * E ach s e t c o n s i s t e d o f th e nam es o f
f o u r o b j e c t s I n c lu d in g th e c o r r e c t o n e . One s e t c o n s i s t e d
o f d i s c r e t e a l t e r n a t i v e s w h ile t h e se c o n d w as m ade u p o f
s i m i l a r a l t e r n a t i v e s . One g ro u p saw th e a l t e r n a t i v e s
63
b e f o r e th e s t i m u l i ; th e se c o n d a f t e r th e s t i m u l i ; w h ile a
t h i r d ( c o n t r o l ) g ro u p w ere n o t show n t h e a l t e r n a t i v e s *
I t made no d i f f e r e n c e w h e th e r th e a l t e r n a t i v e s
w ere g iv e n b e f o r e o r a f t e r th e s t i m u l i , e v e n w hen a c o r
r e c t i o n w as made f o r g u e s s in g * The d i s c r e t e a l t e r n a t i v e s
p r o v id e d m ore h e lp t h a n th e s i m i l a r a l t e r n a t i v e s * The
a u th o r s i n t e r p r e t th e s e r e s u l t s t o i n d i c a t e t h a t t h e
f a c i l i t a t i n g e f f e c t o p e r a t e s e i t h e r o n th e memory t r a c e
o r by f a c i l i t a t i n g r e s p o n s e s , s i n c e , i f p e r c e p t u a l m o d if i
c a t i o n was r e s p o n s i b l e , th e e f f e c t w ould h a v e o c c u r r e d
o n ly when th e a l t e r n a t i v e s w ere g iv e n p r i o r t o t h e
s t i m u l i *
I n a r e l a t e d s t u d y , L aw ren ce and L a b e rg e (195>6)
a tte m p te d t o t e s t o n ly th e p e r c e p t u a l a c t i o n o f i n s t r u c
t io n s * One g ro u p o f s u b j e c t s w as i n s t r u c t e d t o p a y e q u a l
a t t e n t i o n t o a l l a s p e c t s o f t h e s tim u lu s m a t e r i a l*
A n o th e r g ro u p w as i n s t r u c t e d t o p a y p rim a ry a t t e n t i o n t o
one a s p e c t o f th e s tim u lu s b u t to r e p o r t o n th e o t h e r i n
f o r m a tio n a v a i l a b l e as w e ll* A t h i r d g ro u p was t o p a y
a t t e n t i o n t o , and r e p o r t , o n o n ly one d im e n sio n * F i n a l l y ,
a f o u r t h g ro u p w as i n s t r u c t e d t o r e o o r d i n f o r m a tio n o n a l l
t h r e e a s p e c t s b u t i n t h e o r d e r s p e c i f i e d a f t e r t h e
s tim u lu s was ex p o sed *
S t i m u l i w ere two c a r d s fro m th e W is c o n s in C ard
S o r t i n g t a s k p la c e d s id e by s id e * T h ese c a r d s v a r i e d i n
*
c o l o r , s h a p e , and num ber o f d i g i t s and w ere p r e s e n t e d
t a c h i s t o s c o p i c a l l y f o r 100 m secs*
The a v e ra g e a c c u ra c y o f t h e r e p o r t s o n a l l t h r e e
d im e n s io n s com bined d i f f e r e d o n ly s l i g h t l y b e tw e e n th e
v a r io u s g ro u p s* The a c c u ra c y o f r e p o r t w as c o n s id e r a b ly
g r e a t e r f o r th e d im e n s io n to w h ic h s u b j e c t s h a d b e e n I n
s t r u c t e d t o p ay p a r t i c u l a r a t t e n t i o n , b u t th e a c c u ra c y on
t h i s d o m in a n t d im e n s io n w as n o t i n c r e a s e d u n d e r th e wo n e -
o n ly " i n s t r u c t i o n * When t h e o r d e r o f r e p o r t was s p e c i f i e d
th e d i f f e r e n c e I n a c c u ra c y b e tw e e n t h e f i r s t r e c o r d e d d i
m e n sio n and th e o t h e r tw o d im e n s io n s was a s l a r g e a s t h a t
o c c u r r in g when one d im e n s io n h ad b e e n em p h a size d * T h u s,
i t a p p e a rs t h a t th e e f f e c t o f th e i n s t r u c t i o n s was m e re ly
to d e te rm in e th e o r d e r o f r e p o r t i n a l l c o n d itio n s * T h is
c a s t s d o u b t on w h e th e r I n s t r u c t i o n s i n f l u e n c e p e r c e p tio n *
Brown (1 9 5 6 ) p r e s e n t e d f i v e p a i r s o f a b s t r a c t g e o
m e t r i c a l f i g u r e s t o s u b j e c t s * The se c o n d member o f th e
p a i r was p r e s e n t e d t e n se c o n d s a f t e r th e f i r s t and th e
s u b j e c t s ju d g e d w h e th e r a s p e c i f i e d f e a t u r e h ad ch an g ed
i n one o f two p o s s i b l e d i r e c t i o n s * Unknown t o th e s u b
j e c t s w as th e f a c t t h a t m em bers o f e a c h p a i r w ere i d e n
t i c a l * One g ro u p o f 32 s u b j e c t s w as n o t t o l d w h ic h
f e a t u r e o f th e f i g u r e w ould be c r i t i c a l u n t i l th e p r e
s e n t a t i o n o f th e se c o n d member* A n o th e r g ro u p knew th e
c r i t i c a l f e a t u r e b e f o r e th e f i r s t f i g u r e w as p r e s e n te d *
65
The s u b j e c t s , h o w e v e r, w e re le d t o e x p e c t c h a n g e s I n t h e
f i g u r e s . R e c a l l d i s t o r t i o n s w ere t y p i c a l l y i n th e d i r e c
t i o n o f th e c o n v e n tio n a l and e x p e c te d .
Brow n r e p o r t s a n o th e r e x p e rim e n t aim ed a t d e t e r
m in in g w h e th e r a s e l e c t i v e p r o c e s s c a n o p e r a te d u r in g
p e r c e p t i o n ( I 9 6 0 ) , Two s e t s o f s t i m u l i w ere p r e s e n t e d
s i d e by s i d e f o r a b r i e f I n s t a n t on e a c h t r i a l . The s u b
j e c t s 1 t a s k w as t o r e p o r t th e s e t s p e c i f i e d by h i s
c r i t i c a l i n s t r u c t i o n . C o n d itio n I e n a b le d s u b j e o t s t o
s e l e c t I n f o r m a tio n on t h e b a s i s o f i t s c l a s s ( d i g i t s o r
c o n s o n a n t s ) , p o s i t i o n o r c o l o r ; c o n d i t i o n I I , o n ly b y th e
m a te r ia l* s c l a s s ; c o n d i t i o n H I , o n ly by i t s p o s i t i o n ;
and c o n d i t i o n IV , o n ly b y i t s c o l o r , A n e u t r a l i n s t r u c
t i o n was p r o v id e d and s p e c i f i e d w h e th e r t h e r e s p o n s e was
to b e r e c o r d e d o n t h e r i g h t o r l e f t s i d e o f t h e an sw er
fo rm . I f t h e c r i t i c a l i n s t r u c t i o n w as g iv e n b e f o r e th e
s t i m u l u s , t h e n e u t r a l i n s t r u c t i o n f o llo w e d t h e s t im u lu s
p r e s e n t a t i o n and v i c e v e r s a .
The a c c u ra c y o f r e p o r t was s i g n i f i c a n t l y h i g h e r
when th e c r i t i c a l i n s t r u c t i o n w as g iv e n i n ad v an c e f o r
c o n d it i o n s I and I I , b u t n o t f o r I I I and IV , E v id e n tl y
s e l e c t i v e p e r c e p t i o n w as a b le t o o p e r a te d u r in g p e r c e p t i o n
on th e b a s i s o f c l a s s b u t n o t t h a t o f p o s i t i o n o r c o l o r .
The n e u t r a l i n s t r u c t i o n e q u a te d th e tim e a f t e r p r e s e n t a
t i o n w hen s u b j e c t s c o u ld r e c o r d t h e i r r e s p o n s e s , w h ic h
66
has been a m ethodological weakness In o th er sim ila r ex
perim ents* Thus, I t i s p o ssib le th a t s e le c tiv e p ercep tio n
operates during p ercep tio n , but s t i l l not a c e rta in ty *
Whether or not su b je c ts knew how long a message
would be was a major v a ria b le in another study (P o llo ck ,
Johnson, and K naft, 1959) • The ta sk was to li s te n to a
tape containing in s tru c tio n s and 16 spoken messages which
co n sisted of random d ig its* The messages were 25, 30,
35, or IfO d ig its in len g th and were presented a t a r a te
of l|., 2 , 1, or 0*5 d ig its per second* S ubjects were re
quired to r e c a ll as many of the la s t numbers in the group,
in o rd e r, as they could*
Mean s c o r e s o f lj.*7 and a p p ro x im a te ly 7*0 w ere
o b ta in e d f o r t h e u n c e r t a i n and c e r t a i n l e n g t h g ro u p s
r e s p e c t i v e l y * The r a t e o f p r e s e n t a t i o n a l s o i n f lu e n c e d
th e r e s u l t s , w ith t h e f a s t e r r a t e s r e d u c in g th e num ber o f
d i g i t s r e c a l l e d * T h e se r e s u l t s w ere i n t e r p r e t e d b y th e
a u th o r i n te rm s o f th e b e h a v i o r a l s t r a t e g y o f th e s u b j e c t s
a s w e ll a s p r o a c t i v e i n t e r f e r e n c e *
T e ic h n e r , R e i l l y and S a d le r ( I 9 6 I ) p r e s e n t e d su b
j e c t s w ith v i s u a l d i s p l a y s c o n ta in i n g ra n d o m ly s a m p le d ,
ran d o m ly p o s i t i o n e d g ro u p s o f a lp h a b e t i c l e t t e r s . One
g ro u p r e p o r t e d th e num ber o f d i f f e r e n t l e t t e r s d is p la y e d
( c o u n tin g g ro u p ) w h ile a n o th e r r e p o r t e d th e nam es o f th e
l e t t e r s (n am in g g ro u p )* The num ber o f l e t t e r s named by
67
t h e nam ing g ro u p was th e n c o u n te d and com pared w ith t h a t
r e p o r t e d by t h e c o u n tin g gro u p * I t was fo u n d t h a t th e
num ber c o u n te d was m ore a c c u r a t e I n e s t im a t i n g t h e num ber
d is p la y e d * As th e num ber o f l e t t e r s w h ich w ere d is p la y e d
i n c r e a s e d , t h e e r r o r o f th e nam ing g ro u p i n c r e a s e d m ore
r a p i d l y * S in c e l e t t e r d e t e c t i o n and d i s c r i m i n a t i o n w ere
common to b o th g r o u p s , b u t th e memory r e q u ir e m e n t o f th e
nam ing g ro u p was much g r e a t e r , th e a u th o r s b e li e v e th e
r e s u l t s i n d i c a t e t h a t v i s u a l sym bol i d e n t i f i c a t i o n d ep en d s
u p o n b o th v i s u a l p e r c e p t i o n and s h o r t - t e r m m em ory, and
t h a t th e p e r c e p t u a l c a p a c i t y I s g r e a t e r th a n th e s h o r t
te rm memory c a p a c ity *
O r g a n iz a tio n o f th e S t i m u li
a n a / o r h e s p o u s e s
G e s t a l t p s y c h o l o g is ts h a v e lo n g m a in ta in e d t h a t
o r g a n i z a t i o n i s a p o t e n t v a r i a b l e i n l e a r n i n g as w e ll as
p e r c e p tio n * G ro u p in g , w h ic h i s a fo rm o f o r g a n i z a t i o n ,
may b e e s t a b l i s h e d i n many w a y s; u s in g a rh y th m , p a i r i n g
s t i m u l i s p a t i a l l y , e t c * , a re g iv e n as e x am p le s b y K a to n a
(191+0) * From th e G e s t a l t v ie w p o in t, t h i s g ro u p in g i s d e
p e n d e n t on f e a t u r e s o f o r g a n i z a t i o n w h ic h a r e e x p re s s e d
by th e p r i n c i p l e s o f e q u a l i t y , n e a r n e s s , s p a t i a l and
te m p o ra l d i s t r i b u t i o n , e tc * K a to n a c i t e s l e a r n i n g e x p e r i
m e n ts t o s u p p o r t h i s p o i n t o f view b u t m o st o f th e s e a re
o f th e m ore t r a d i t i o n a l " lo n g - te r m * n a tu r e *
68
S i e g a l (1 9 ^ 3 )# h o w e v e r, p e rfo rm e d a n e x p e rim e n t
t e s t i n g th e v o n R e s t o r f f ( I s o l a t i o n ) phenom enon, I n a
p a ra d ig m w h ic h may b e c l a s s i f i e d a s s i m i l a r t o th o s e a l
r e a d y c o n s i d e r e d . T en n o n se n se s y l l a b l e s and t e n 3 - d l g l t
num bers w ere u s e d . Two l i s t s w ere c o n s t r u c t e d fro m th e
same 20 i te m s . The se c o n d l i s t w as th e m ir r o r Im age o f
th e f i r s t , I . e . , w here a s y l l a b l e a p p e a re d i n th e f i r s t
l i s t , a num ber a p p e a re d i n t h e s e c o n d , and v ic e v e r s a .
E a c h s e r i e s was p r e s e n te d t o th e same 70 s u b j e c t s . E ac h
s tim u lu s was p r i n t e d o n a c a r d w h ic h was h e ld u p f o r f i v e
s e c o n d s . F o llo w in g th e l a s t c a r d i n th e s e r i e s t h e su b
j e c t was a sk e d t o r e c a l l a s many ite m s as h e c o u ld .
The d e p e n d e n t v a r i a b l e was th e sum o f th e t o t a l
num ber r e o a l l e d f o r e a c h s e r i a l p o s i t i o n . O rd e r was n o t
c o n s i d e r e d . The e x p e r im e n te r was i n t e r e s t e d o n ly i n th e
t o t a l num ber r e c a l l e d and a s s ig n e d th e r e s p o n s e s t o th e
c o r r e c t p o s i t i o n . T hose ite m s t h a t w ere i s o l a t e d , i . e . ,
su rro u n d e d on e a c h s i d e by a se q u e n c e o f th e s t i m u l i o f a
d i f f e r e n t k i n d , w ere m o st f r e q u e n t l y r e c a l l e d . Ite m s
s u rro u n d e d b y s i m i l a r m a t e r i a l w ere l e a s t f r e q u e n t l y r e
c a l l e d . A c o n t r o l e x p e rim e n t u s in g a d i f f e r e n t o r d e r
v e r i f i e d th e r e s u l t s .
One o f th e s e r i e s o f e x p e rim e n ts r e p o r t e d by M ack-
w o rth and M aokw orth (1959) and c i t e d e a r l i e r ( s e e p a g e 26)
u se d th e same t a s k b u t g ro u p e d th e ad v an ce c u e s i n g ro u p s
69
o f f o u r o r f i v e b e f o r e th e c lo o k s t a r t e d * I n o t h e r w o rd s *
th e s u b j e c t w as t o l d th e c o r r e c t o r d e r f o r th e f i r s t f o u r
o r f i v e c o u n te r s * The o b j e c t i v e was t o b e re a c h e d i n t h i s
num ber o f c u e s* A f t e r t h e f i r s t f o u r m oves h ad b e e n made*
th e s u b j e c t l i s t e n e d t o th e n e x t f o u r c u e s* T hese g ro u p e d
c u e s le d to b e t t e r a v e ra g e s t o r a g e th a n d id t h e s i n g l e
cu es* w hen ad v an ce s t o r e s o f two o r t h r e e w ere r e q u ir e d *
M ackw orth p e rfo rm e d tw o s t u d i e s ( 1962b )* i n v e s t i
g a t i n g b o th th e sp e e d o f p r e s e n t a t i o n and t h e num ber o f
d i g i t s p r e s e n te d s im u lt a n e o u s ly . The f i r s t i n t h i s s e r i e s
was s i m i l a r t o h e r e a r l i e r s tu d y e x c e p t f o r th e a d d i t i o n
o f a b lo c k ( a l l d i g i t s p r e s e n te d s im u lta n e o u s ly ) p r e
s e n t a t i o n a s w e ll a s th e s e q u e n t i a l * Tim e i n t e r v a l s o f
0*2f>* 0*£* and 1*0 se c o n d s p e r d i g i t w ere u s e d . The b lo c k
d i s p l a y h ad a t o t a l tim e e q u i v a l e n t t o th e num ber o f
d i g i t s tim e s t h e tim e p e r d i g i t i n t h e s e q u e n t i a l s i t u a
tio n * B e t t e r s c o r e s w ere o b ta in e d w ith th e b lo o k d i s p l a y
and w ith th e lo n g e r tim e i n t e r v a l s *
The se c o n d e x p e rim e n t v a r i e d th e num ber o f d i g i t s
p r e s e n te d s im u lta n e o u s ly * M essag es w ere e i t h e r e i g h t o r
tw e lv e d i g i t s and w ere p r e s e n te d e i t h e r one* two* o r f o u r
a t a tim e* o r e l s e th e w hole m essa g e a p p e a re d s im u lta n e
o u sly * D i g i t s w ere show n i n two o r t h r e e l i n e s o f f o u r
d i g i t s each * F iv e tim e s p e r d i g i t w ere u s e d v a r y in g fro m
0*0675 t o 0*50 se c o n d s p e r d i g i t *
70
F o r e a c h d i s p l a y , th e am ount r e c a l l e d was a p p r o x i
m a te ly p r o p o r t i o n a t e t o t h e lo g a r i th m o f th e d u r a t i o n o f
e a c h m essag e e x p r e s s e d a s tim e p e r d i g i t * The am ount r e
c a l l e d a ls o I n c r e a s e d a s th e am ount d is p la y e d s im u lta n e
o u s ly in c r e a s e d *
The a u th o r e x p r e s s e s t h e o p in io n t h a t th e b lo c k
d i s p l a y was s u p e r i o r b e c a u s e o f v i s u a l f a c t o r s * W h ile
t h i s may b e a f a c t o r i n h e r s i t u a t i o n , M ayzner and G a b r ie l
( I 9 6 3 ) h a v e fo u n d e v id e n c e t h a t t h e g ro u p in g o f d i g i t s by
I t s e l f f a c i l i t a t e s r e c a l l * T h is l a s t s tu d y p r e s e n t e d th e
same f i v e s e q u e n c e s o f 12 d i g i t s , e i t h e r i n a v e r t i c a l
colum n o r g ro u p e d i n t o tw o s , t h r e e s , f o u r s o r s ix e s *
C a rd s w ere d is p la y e d f o r s i x se c o n d s* The s u b j e c t was
r e q u i r e d to f i l l i n th e a p p r o p r i a t e s p a c e s on an sw er fo rm s
h a v in g th e sam e o r g a n i z a t i o n as th e m a t e r i a l t h a t w as p r e
s e n te d * I t was fo u n d t h a t th e num ber r e c o r d e d i n th e
c o r r e c t p o s i t i o n I n c r e a s e d a s th e num ber p e r group*
L a t e r , a n o th e r g ro u p o f s u b j e c t s was t e s t e d on th e
same se q u e n c e s b u t o r g a n iz e d i n one row o f 12 d i g i t s
a rr a n g e d h o r i z o n t a l l y * P e rfo rm a n c e w as n o t as good a s
t h a t o b ta in e d p r e v i o u s l y f o r d i g i t s a r r a n g e d i n g ro u p s o f
e i t h e r f o u r o r s ix * S in c e i f v i s u a l f a c t o r s w e re r e s p o n
s i b l e , p e rfo rm a n c e w ould h a v e c o n tin u e d t o I n c r e a s e w ith
th e h o r i z o n t a l d i s p l a y , i t a p p e a rs t h a t t h i s s t u d y p r o
v id e s a d d i t i o n a l e v id e n c e o f t h e i n f l u e n c e o f g ro u p in g *
71
The s u r p r i s i n g t h i n g w as t h a t g ro u p in g c o n tin u e d t o
f a c i l i t a t e p e rfo rm a n c e e v e n when m ore th a n t h r e e d i g i t s
a p p e a re d i n a g r o u p . T h is s u g g e s t s t h a t memory s p a n may
p l a y a r o l e h e r e a ls o *
M i l l e r (1 9 5 6 ) h a s r e c o g n iz e d t h e r o l e t h a t g r o u p in g
su c h a s t h a t u s e d i n t h e p r e v io u s s tu d y may p l a y . He u s e d
th e te rm " c h u n k in g " t o d e s c r i b e i t . A m ore c o m p le te d i s
c u s s i o n o f t h i s phenom enon w i l l t a k e p l a c e a t t h e c o n c lu
s i o n o f t h i s c h a p te r *
O r g a n iz a t i o n n e ed n o t n e c e s s a r i l y be b u i l t i n t o th e
d i s p l a y t o f a c i l i t a t e r e c a l l . E x p e rim e n ts by M athew s
(l9 £ l|-)« end H e ls o n and C over ( 19f>6) d e m o n s tr a te t h a t i f a
l i s t o f ite m s a r e p r e s e n t e d ra n d o m ly f o r th e s u b j e c t t o
c l a s s i f y o r c a t e g o r i z e * r e c a l l f o r t h e s e ite m s I n c r e a s e s
a s d o e s t h e num ber o f c a t e g o r i e s o r th e s p e c i f i c i t y o f
c a t e g o r i e s •
I n Mathews* e x p e rim e n t* t h e s u b j e c t s c l a s s i f i e d
nam es o f fam ous p e o p le i n t o 2* 3 * o r 6 c a t e g o r i e s * The
d i f f e r e n t l i s t s o f nam es t h a t w ere I n c lu d e d w ere e q u a te d
on th e b a s i s o f c o n t r o l l e d a s s o c i a t i v e d a t a . On r e c a l l
t e s t s a f t e r 10 m in u te s o f i n t e r p o l a t e d a c t i v i t y * th e
num ber o f nam es r e c a l l e d v a r i e d d i r e c t l y w ith th e num ber
o f c a t e g o r i e s u s e d . I n t r u s i o n s v a r i e d I n v e r s e l y w i t h th e
num ber o f c a t e g o r i e s . The a u th o r r e c o g n iz e d th e f a c t t h a t
th e e x p e rim e n t h a d l i m i t e d g e n e r a l i t y . He n o te d t h a t th e
72
c a t e g o r i e s u s e d w ere d i s t i n c t and t h a t i n c r e a s i n g th e
num ber o f c a t e g o r i e s may e v e n d e c r e a s e r e c a l l i f t h e c a t e
g o r i e s w ere s i m i l a r *
He I s o n and C o v e r 's e x p e r im e n t u s e d a s i m i l a r ta s k *
One g ro u p w as a sk e d t o c l a s s i f y nam es i n t o th e f o l lo w in g
g e n e r a l c a t e g o r i e s : a c to r * m u s ic ia n * p a i n t e r * s c i e n t i s t *
s ta te s m a n * w r i t e r * k se c o n d g ro u p * u s i n g th e same nam es*
c l a s s i f i e d t h e nam es i n t o th e m ore s p e c i f i c c a t e g o r i e s o f :
E n g li s h m o v le - a c to r * o p e ra -c o m p o s e r* p o r t r a i t - p a i n t e r ,
p h y s i c i s t * r e v o l u t i o n a r y le a d e r * and p l a y w r i g h t . Fam ous
nam es w ere u s e d and t h e r e w ere f o u r nam es t o e a c h c a t e
g o ry *
The tw o g ro u p s w e re c o m p a ra b le on th e c l a s s i f i c a
t i o n ta s k * A f t e r 10 m in u te s o f i n t e r p o l a t e d a c t i v i t y *
how ever* s i g n i f i c a n t l y m ore w ere r e c a l l e d b y th e s p e o l f l c
c a t e g o r y g ro u p th a n b y t h e g e n e r a l c a te g o r y g ro u p . The
m ean s c o r e s w ere llj.*30 and 11*08 r e s p e c t i v e l y *
R edundancy o r V e r b a l C o n te x t
C lo s e ly r e l a t e d t o th e o r g a n i z a t i o n o f th e s t i m u l i
a s i t was t r e a t e d i n th e l a s t ba c t i o n a r e e x p e r im e n ts i n
v e s t i g a t i n g re d u n d a n c y o r v e r b a l c o n te x t* V e r b a l c o n te x t
h a s b e e n d e f in e d a s t h e e x t e n t t o w h ic h a c h o ic e o f a
p a r t i c u l a r w ord d e p e n d s u p o n t h e w ords t h a t p r e c e d e i t
( M i l l e r and S e l f r l d g e * 1 9 5 0 )* D e fin e d i n t h i s way v e r b a l
73
c o n te x t l a a lm o s t synonym ous w ith re d u n d a n c y w h ic h M ille r
( 1951) e x p la in s a s f o l l o w s ;
I f t h e s u c c e s s iv e u n i t s I n a m essag e a re r e l a t e d .
I f th e p r o b a b i l i t y o f a u n i t d e p e n d s upon th e u n i t s
t h a t p re c e d e I t , th e s e r e l a t i o n s re d u c e th e am ount
o f I n f o r m a tio n t h a t a s i n g l e u n i t c a n c a r r y * When
• • • r e l a t i o n s o f t h i s s o r t e x i s t • • • th e same
am ount o f I n f o r m a tio n c o u ld b e co d ed m ore r a p i d l y I n
a la n g u a g e t h a t h a d t h e same num ber o f In d e p e n d e n t
a l t e r n a t i v e s * • • • M ore sy m b o ls a r e b e in g u s e d to
e n c o d e th e m essa g e th a n a r e t h e o r e t i c a l l y n e c e s s a r y *
We e x p r e s s t h i s f a c t b y s a y in g t h a t m o st la n g u a g e s
a re re d u n d a n t*
T h u s, th e m ore wo rg a n iz e d " a m essag e th e g r e a t e r
th e re d u n d a n c y *
T h e o r e t i c a l l y , c o n s t r u c t i o n o f m a t e r i a l s t o i n
c o r p o r a t e th e s t a t i s t i c a l s t r u c t u r e o f th e la n g u a g e o v e r
s e q u e n c e s o f s e v e r a l w ords w o u ld be n e c e s s a r y t o I n v e s t i
g a te th e I n f l u e n c e o f r e d u n d a n c y . T h is w ould r e q u i r e th e
t a b u l a t i o n o f t h e r e l a t i v e f r e q u e n c y o f su c h se q u e n c e s*
T h is w ould b e a t e d i o u s u n d e r t a k in g a n d , as y e t , no su c h
i n f o r m a ti o n i s a v a i l a b l e . M i l l e r and S e l f r i d g e (1 9 5 0 )
d e v is e d a way o f g e t t i n g a ro u n d t h i s p ro b le m . I n s t e a d o f
d ra w in g e a c h word fro m a s t a t i s t i c a l d i s t r i b u t i o n , w ords
w ere draw n fro m a d i f f e r e n t p e r s o n who h ad s e e n " n " p r e
c e d in g w o rd s . (A z e ro o r d e r a p p ro x im a tio n was d e f in e d as
a c o m p le te ly random se q u e n c e o f w o rd s* ) A seo o n d o r d e r
a p p ro x im a tio n , f o r e x a m p le , in v o lv e d p r e s e n t i n g a common
w ord ( b e , i t , th e ) t o a p e r s o n who was i n s t r u c t e d t o u se
th e w ord i n a s e n t e n c e . The w ord h e u s e s d i r e c t l y a f t e r
th e one g iv e n t o h im i s n o te d and l a t e r p r e s e n t e d to
a n o th e r p e r s o n who h a s n o t h e a rd th e s e n te n c e g iv e n by
th e f i r s t p e r s o n , and h e I n t u r n I s a sk e d t o u s e t h a t
w ord i n a s e n te n c e * T h u s, a se q u e n c e o f any d e s i r e d
l e n g t h i s b u i l t u p . E ac h s u c c e s s iv e p a i r o f w ords c o u ld
go t o g e t h e r i n a s e n t e n c e . E a c h word i s d e te rm in e d i n
th e c o n te x t o f o n ly one p r e c e d in g w o rd .
A h i g h e r o r d e r o f a p p ro x im a tio n c o u ld b e d e v is e d by
l e t t i n g a p e r s o n se e a se q u e n c e o f w o rd s and a sk h im to
u s e th e s e q u e n c e i n a s e n t e n c e . T hen th e w ord d i r e c t l y
a f t e r th e se q u e n c e w ould b e a d d e d , t h e f i r s t one d ro p p ed
and th e new se q u e n c e b e g iv e n t o a n o th e r p e r s o n , e t c .
The f i r s t o r d e r was d e f in e d as a random d ra w in g o f w ords
fro m a o o n t e x t u a l l y d e te rm in e d l i s t .
M i l l e r and S e l f r i d g e u s e d e i g h t d i f f e r e n t o r d e r s
o f c o n t e x t u a l c o n s t r a i n t , fro m z e ro t o a p a s s a g e ta k e n
d i r e c t l y fro m c u r r e n t f i c t i o n . A t e a c h o r d e r o f a p p r o x i
m a tio n , f o u r l i s t s o f d i f f e r e n t l e n g t h — 10, 2 0 , 30 and $0
w o rd s—w e re d is p la y e d by m eans o f a w ire r e c o r d e r . S u b
j e c t s l i s t e n e d u n t i l th e l i s t was f i n i s h e d and t h e n w ro te
w h a t th e y h a d h e a rd a s n e a r l y as th e y c o u ld i n th e sam e
o r d e r .
The p e r c e n t r e c a l l e d i n c r e a s e d a s th e o r d e r o f
a p p ro x im a tio n in c r e a s e d and d e c r e a s e d as t h e le n g th o f
l i s t i n c r e a s e d .
75
R ic h a r d s o n and V oss (19& 0) r e p l i c a t e d th e above
s t u d y . T hey a l s o e v a l u a t e d t h e o r d i n a l p o s i t i o n o f th e
w o rd , and th e se q u e n c e s w h ic h w ere c o n fo u n d e d i n th e
e a r l i e r s t u d y . The r e s u l t s s u p p o r te d th o s e p r e v i o u s l y
o b ta in e d and a l s o fo u n d a s i g n i f i c a n t I n t e r a c t i o n . The
v a r i a b l e s o f o r d i n a l p o s i t i o n and se q u en c e w ere n o t s i g
n i f i c a n t .
A n o th e r a u th o r ( S h a r p , 1958) a ls o e x te n d e d M i l l e r
and S e l f r i d g e 's s t u d y . M essag es t h i r t y w ords lo n g w ere
g e n e r a te d by s u b j e c t s f o r th e s e c o n d , t h i r d , f i f t h and
n i n t h o r d e r s o f a p p r o x im a tio n . The e x p e r im e n te r added
f i r s t o r d e r an d t e x t u a l p a s s a g e s .
P a s s a g e s w e re p r e s e n t e d b y m eans o f a ta p e r e c o r d e r
t o new s u b j e c t s . E a c h s u b j e c t l e a r n e d b u t one p a s s a g e ,
w h ic h was p r e s e n t e d f i v e s u c c e s s iv e tim e s w ith im m e d ia te
r e c a l l a f t e r e a o h p r e s e n t a t i o n . O nly th e r e s u l t s o f th e
f i f t h t e s t w ere r e c o r d e d . One w eek l a t e r s u b j e c t s w ere
p r e s e n te d w ith th e m a t e r i a l o n ce fo llo w e d by an im m e d ia te
r e c a l l t e s t . The t o t a l num ber o f c o u p le ts r e c a l l e d and
th e t o t a l num ber o f w ords r e c a l l e d w ere th e d e p e n d e n t
v a r i a b l e s .
From th e p r o b a b i l i t y v a lu e s o f th e m odal r e s p o n s e s
i n e a c h d i s t r i b u t i o n o f w o rd s, th e u n c e r t a i n t y v a lu e ( i n
b i t s ) was d e te r m in e d . An a n a l y s i s o f v a r ia n c e u s i n g th e
u n c e r t a i n t y v a lu e s f o r th e 30 m odal w o rd s i n e a c h p a s s a g e
76
r e v e a l e d s i g n i f i c a n t d i f f e r e n c e s i n c o n t e x t u a l c o n s t r a i n t
b e tw e e n a l l b u t th e se c o n d and t h i r d o r d e r s o f a p p ro x im a
tio n * The o d d -e v e n c o r r e l a t i o n was fo u n d t o b e s e r o ,
i n d i c a t i n g th e 30 w o rd s w ere in d e p e n d e n t*
The a u th o r c la im s t h a t u n c e r t a i n t y was m ore s e n s i
t i v e th a n f r e e r e c a l l as an i n d i c a t i o n o f c o n te x tu a l co n
s t r a i n t , and r e l e a r n i n g was m ore s e n s i t i v e th a n im m e d ia te
r e c a l l a s an in d e x o f c o n te x tu a l c o n s t r a i n t . The r e s u l t s ,
i n g e n e r a l , s u p p o r t th e r e s u l t s o f th e e a r l i e r e x p e r i
m en ts •
M arks and J a c k (1 9 5 2 ) o b j e c te d t o M i l l e r and
S e l f r i d g e 's s tu d y o n th e b a s i s o f m e th o d o lo g y . S p e c i f i
c a l l y , th e y o b j e c te d t o ( a ) th e f a c t t h a t a p r a c t i c e
e f f e c t c o u ld h a v e b e e n p r e s e n t , (b ) th e d i s r e g a r d o f
o r d e r i n s c o r in g may h a v e a llo w e d s u b j e c t s t o fo rm t h e i r
own a s s o c i a t i o n s , and ( c ) t h a t p a r t s o f th e same s e n te n c e
a p p e a re d i n th e lo n g e r l i s t s *
C o n s e q u e n tly , th e y p e rfo rm e d a m o d if ie d s tu d y t o
overcom e t h e s e o b j e c t i o n s . I n m o st o t h e r r e s p e c t s th e
s t u d i e s w ere s i m i l a r ; i n f a c t , some o f th e same m a t e r i a l
w as u s e d . S e q u e n c e s w ere b ro k e n down i n t o c o n s e c u tiv e
se g m en ts o f 6 , 7» 8 • • . 2 3 w o rd s . I n d i v i d u a l s u b j e c t s
w ere p r e s e n te d w ith se g m e n ts o f i n c r e a s i n g l e n g t h u n t i l
two c o n s e c u tiv e se g m e n ts w ere m is s e d . A f a i l u r e w as d e
f i n e d a s any o m is s io n , I n v e r s i o n , o r a d d i t i o n . The s c o r e
77
was th e num ber o f w o rd s i n th e l o n g e s t se g m en t t h a t was
r e c a l l e d c o r r e c t l y *
The r e s u l t s c l e a r l y s u p p o r te d th e p o s i t i v e i n
f lu e n c e t h a t o r d e r o f a p p ro x im a tio n h a s o n t h e num ber o f
ite m s r e o a l l e d * The a u t h o r s , h o w e v e r, c o n te n d t h a t a l
th o u g h M i l l e r and S e l f r i d g e ’ s s ta te m e n t t h a t nth e s i g n i f i
c a n t d i s t i n c t i o n i s n o t t o be draw n b e tw e e n m ea n in g and
n o n s e n s e , b u t b e tw e e n m a t e r i a l s t h a t u t i l i s e p r e v io u s
l e a r n i n g and p e rm it p o s i t i v e t r a n s f e r and m a t e r i a l s t h a t
do n o t" may be t r u e , th e d a t a on w h ic h th e c o n c lu s io n i s
b a se d a r e o f a v e ry s p e c i a l i z e d k in d * They c o n c lu d e t h a t
w hen a d i f f e r e n t m e a su re o f r e t e n t i o n i s u s e d a s i n t h e
p r e s e n t s tu d y , " r e o a l l seem s to be v e ry m uch a f u n c t i o n o f
th e »a p r i o r i 1 r e l a t i v e m e a n in g fu ln e s s o f th e m a t e r i a l s * n
A s tu d y d e s ig n e d t o exam ine th e i n f l u e n c e o f
s e q u e n t i a l s t r u c t u r e u p o n o r d e r o f r e c a l l and th e s e r i a l
p o s i t i o n c u rv e was p e rfo rm e d by D eese and K aufm an (1957)*
The f i r s t e x p e rim e n t fo u n d t h a t f o r l i s t s o f w ords i n
w h ic h t h e r e was no s e q u e n t i a l s t r u c t u r e , a T J-shaped s e r i a l
p o s i t i o n c u rv e was o b ta in e d * F o r p a s s a g e s o f c o n n e c te d
d i s c o u r s e , th e o r d e r o f r e c a l l was th e same a s t h e o r d e r
o f p r e s e n t a t i o n and th e s e r i a l p o s i t i o n c u rv e was l i k e
t h a t o b ta in e d by th e m ethod o f s e r i a l a n t i c i p a t i o n * A
se c o n d s tu d y v e r i f i e d and g e n e r a l i z e d t h e s e r e s u l t s *
T h ese e x p e rim e n ts i n d i c a t e t h a t t h e s e r i a l p o s i t i o n
78
c u rv e o f f r e q u e n c y o f r e c a l l v a r i e s w ith t h e s e q u e n t i a l
s t r u c t u r e o f t h e m a t e r i a l* S u b je c ts do m ore th a n " c h u n k ,"
h o w e v e r. A c c o rd in g to D eese and K aufm an, th e y r e o r g a n iz e
th e p a t t e r n s t o co n fo rm t o lo n g e s t a b l i s h e d i n d i v i d u a l
v e r b a l h a b i t s *
Jo h n s o n and L lo y d ( i 9 6 0 ) i n v e s t i g a t e d th e v e r b a l
c o n te x t i n c o n ju n c ti o n w ith t h e a v e ra g e s to r a g e l o a d . The
v e r b a l c o n t e x t was v a r i e d b o th I n th e o r d e r t h a t th e
s t i m u l i w ere p r e s e n t e d end i n th e o r d e r t h a t r e s p o n s e s
w ould be r e q u i r e d . (S e e s e c t i o n on "A m ount" f o r th e
e x p e r im e n ta l p ro c e d u re in v o lv e d i n m e a s u rin g th e a v e ra g e
s to r a g e lo a d * )
The ite m s w ere l e t t e r - w o r d p a i r s and th e r e c a l l
p o i n t s w ere th e l e t t e r s a l o n e . I t was d e te rm in e d t h a t
v e r b a l c o n te x t was p o s i t i v e l y r e l a t e d t o r e c a l l f o r th e
r e s p o n s e o r d e r g ro u p , b u t n o t i n th e s tim u lu s o r d e r group*
The a u th o r s c o n c lu d e d t h a t th e r e l a t i o n s h i p mey be i n t e r
p r e t e d a s a r e s u l t o f p o s i t i v e t r a n s f e r and l e a r n e d
re s p o n s e p r o b a b i l i t i e s * The i n f l u e n c e o f c o n te x t i n t h i s
s e q u e n t i a l t a s k was s l i g h t when com pared t o memory sp a n
e x p e r im e n ts .
A il o f th e s t u d i e s r e p o r t e d up t o t h i s p o i n t p e r
t a i n i n g to c o n t e x t u a l c o n s t r a i n t h a v e u se d w ords as
s t i m u l i . A born and R u b e n s te in (195>2) and R u b e n s te in and
A born ( I 95I4 .) u s e d n o n se n se (CVC) s y l l a b l e s . I n t h e i r
79
f i r s t s tu d y a v o o a b u la ry o f 16 s y l l a b l e s w as e v e n ly
d iv id e d i n t o f o u r c l a s s e s . To f a c i l i t a t e l e a r n i n g th e
s y l l a b l e s w ere c o n s t r u c t e d so t h a t th e m em bership i n e a c h
c l a s s was c h a r a c t e r i z e d by some f o r m a l f e a t u r e . F o r
e x a m p le , a l l th e u n i t s i n th e f i r s t c l a s s b e g a n w ith nZ$n
e tc * S ix p a s s a g e s , 30 t o 32 s y l l a b l e s i n l e n g t h , w ere
c o n s t r u c t e d so t h a t a l l o f th e s y l l a b l e s w ere em ployed
w ith a p p ro x im a te ly th e same fre q u e n c y *
More l i m i t a t i o n s w ere Im posed on some p a s s a g e s th a n
o t h e r s . I n th e f i r s t p a s s a g e t h e s y l l a b l e s w ere ra n d o m ly
a s s ig n e d ; i n t h e s e c o n d , th e s y l l a b l e s w ere g ro u p e d by
p a i r s , and th e se c o n d member o f th e p a i r b e lo n g e d t o th e
n e x t h i g h e r c l a s s th a n th e f i r s t ; t h e o t h e r p a s s a g e s i n
c r e a s e d i n c o n s t r a i n t s . T h u s, e a c h s u c c e s s iv e p a s s a g e
c o n ta in e d fe w e r b i t s o f in f o r m a tio n *
E a c h s u b j e c t was r e q u i r e d t o m em orize t h e " i n
v e n to r y " o f s y l l a b l e s b e f o r e th e s t a r t o f t h e e x p e rim e n t*
As h y p o th e s iz e d , th e m ean num ber o f s y l l a b l e s c o r r e c t l y
r e c a l l e d in c r e a s e d a s th e d e g re e o f o r g a n i z a t i o n ( r e d u c
t i o n i n b i t s ) in c r e a s e d *
The a u th o r s i n t e r p r e t e d t h e s e r e s u l t s a s i n d i c a t i n g
t h a t t h e am ount o f in f o r m a tio n c o n ta in e d i n th e p a s s a g e
in f lu e n c e d r e c a l l * T h e ir se c o n d s tu d y ( H u b e n s te ln and
A b o rn , 19514-) a tte m p te d to s e a r c h f o r a n e x p l a n a t i o n o f th e
d e c r e a s e i n i n f o r m a tio n r e c a l l e d i n th e m ore h i g h ly
80
r e d u n d a n t p a s s a g e s * They r e a d m in i s t e r e d th e e a r l i e r
m a t e r i a l w ith m ore h i g h ly t r a i n e d s u b j e c t s and th e le n g t h
o f t h e p a s s a g e s was a ls o i n c r e a s e d . S u b j e c t s t r i e d t o
m em orize a s e r i e s o f p a s s a g e s o v e r a s u c c e s s io n o f s tu d y
p e r i o d s r a n g in g fro m one to tw e n ty m in u te s i n l e n g t h .
They o b ta in e d r e s u l t s w h ic h i n d i c a t e d t h a t : R e c a ll
s c o r e s w ere a lw a y s h i g h e r ( i n te rm s o f b i t s ) f o r p a s s a g e s
w ith h ig h in f o r m a tio n c o n t e n t ; t h e r e w as no c o n s ta n c y i n
t h e am ount o f I n f o r m a tio n r e c a l l e d ; t h e r e seem ed t o be a
r e g u l a r I n v e r s e r e l a t i o n s h i p b e tw e e n d e g re e o f o r g a n iz a
t i o n and am ount o f in f o r m a tio n r e c a l l e d In d e p e n d e n t o f th e
s tu d y p e r i o d ; and th e am ount o f in f o r m a ti o n r e c a l l e d p e r
u n i t o f tim e d e c re a s e d a s le n g th o f s tu d y i n c r e a s e d .
Thus* a lth o u g h th e s u b j e c t s knew th e r u l e s o f
f o r m a tio n and th e re d u n d a n t s e q u e n c e s w ere e a s i e r t o
m em o riz e , th e y w ere n o t a s much e a s i e r a s w ould h a v e b e e n
p r e d i c t e d on th e b a s i s o f an h y p o t h e s is t h a t th e am ount
o f i n f o r m a tio n a c q u ir e d i s i n v a r i a n t .
M i l l e r (1 958) e x p lo r e d th e r e c a l l o f r e d u n d a n t as
o p p o sed to random s t r i n g s o f s y m b o ls . An a l g e b r a f o r
g e n e r a t i n g s t r i n g s o f sym bols a c c o r d in g t o e x p l i c i t r u l e s
was d e f in e d and a s e t o f re d u n d a n t s t r i n g s was g e n e r a t e d .
A s u b s e t o f t h e s e s t r i n g s was m em orized b y e a c h s u b j e c t ,
u s in g th e m ethod o f f r e e r e c a l l . The c o n t r o l s i t u a t i o n
was i d e n t i c a l e x c e p t f o r th e u se o f s t r i n g s g e n e r a te d by
81
random num bers • I t v a s fo u n d t h a t e v e n th o u g h th e su b
j e c t s knew n o th in g o f th e r u l e s o f f o r m a t io n , th e re d u n
d a n t s t r i n g s w ere m ore e a s i l y m em orized*
B e ca u se th e re d u n d a n t s t r i n g s h a d g r e a t e r i n t e r -
l i s t s i m i l a r i t y , m ore i n t e r f e r e n c e m ig h t h a v e b e e n e x
p e c te d i n t h i s o o n d itlo n * M i l l e r c o n c lu d e d th e s u b j e c t s
m u st h a v e g ro u p e d and re c o d e d th e r e d u n d a n t s t r i n g s th u s
a v o id in g t h e s e I n t e r f e r e n c e e f f e o t s *
T h u s, s e v e r a l s t u d i e s h a v e show n t h a t th e am ount
o f m a t e r i a l le a r n e d i n c r e a s e s w ith re d u n d a n c y b u t th e
am ount o f I n f o r m a tio n , i n b i t s , d e c r e a s e s * The e x a c t
f u n c t i o n d e s c r i b i n g t h i s r e l a t i o n s h i p h a s n o t b e e n d e t e r
m ined* Many v a r i a b l e s u n d o u b te d ly i n f l u e n c e t h i s r e l a
tio n * H ogan (1 9 8 1 ) s u g g e s ts t h a t t h e num ber o f s t a t e s ,
r u l e s o f t r a n s i t i o n , th e s u b j e c t s ' e x p e r i e n c e , and am ount
o f m a t e r i a l a s p r o b a b ly i n f l u e n t i a l f a c t o r s * He d e v is e d
a n o th e r e x p e rim e n t t o i n v e s t i g a t e th e r e l a t i o n s h i p b e
tw een th e re d u n d a n c y o f m e ssa g e s and th e am ount o f i n
f o r m a tio n p r o c e s s e d *
A f i n i t e s t a t e gram m ar w ith v a ry in g t r a n s i t i o n a l
p r o b a b i l i t i e s was u se d to g e n e r a t e s t r i n g s o f sy m b o ls o f
f o u r r e d u n d a n c ie s : 5 3 *3 # 7 f>*9 * 8 3 *6 , and 89*6 p e r c e n t*
An e s s e n t i a l l y random s t r i n g was a ls o c o n s tr u c te d * The
v o c a b u la r y c o n s i s t e d o f e i g h t c o n s o n a n ts and a n a s t e r i s k *
A l l m essa g e s w ere ty p e d on 3 x £ c a r d s w ith tw o m e ssa g e s
82
p e r c a rd * The t a s k v a a t o co p y th e m e s sa g e s b u t s u b j e c t s
c o u ld w r i t e o n ly w hen n o t lo o k in g a t t h e c a rd * A box
h e ld th e c a r d s and a b u t t o n h a d t o b e p u sh e d b y th e s u b
j e c t I n o r d e r to s e e t h e m essag e* A t im e r m e a su re d how
lo n g t h e b u t t o n w as h e ld down*
T h ere w as a s t r i k i n g am ount o f d i f f e r e n c e I n th e
num ber o f lo o k s f o r th e v a r i o u s d e g re e s o f re d u n d a n c y
w ith th e num ber o f sy m b o ls p e r lo o k I n c r e a s i n g w ith r e
dundancy* The d i f f e r e n c e s I n th e am ount o f tim e p e r
lo o k w ere s m a ll b u t s i g n i f i c a n t . A se c o n d e x p e r im e n t
u s e d th o r o u g h ly t r a i n e d s u b j e c t s and fo u n d t h a t s o p h is
t i c a t e d s u b j e o t s te n d e d t o p r o o e s s m ore sy m b o ls p e r lo o k *
A s tu d y a tt e m p t in g t o r e l a t e d e g re e o f re d u n d a n c y
to t h e d e g re e o f a u to m a t i z a ti o n t h a t c a n b e r e a c h e d
d u r in g e x te n d e d p r a c t i c e was p e rfo rm e d by B a h r lc k and
S h e l ly (1 9 5 8 )* A u to m a tiz a tio n w as d e f in e d a s a ch an g e
fro m e x t e r o c e p t i v e to p r o p r l o o e p t l v e c o n t r o l o f t h e ta s k *
S u b j e c t s w ere g iv e n p ro lo n g e d t r a i n i n g o n one o f
f o u r v e r s i o n s o f a s e r i a l r e a c t i o n t a s k t o l i g h t s t i m u l i *
The t a s k s d i f f e r e d I n t h e d e g re e o f re d u n d a n c y o f th e
s tim u lu s se q u en c e* A t t h r e e s t a g e s o f t h e t r a i n i n g a
se c o n d a u d it o r y t a s k w as ad d ed and th e s u b j e c t s w ere r e
q u ir e d t o p e rfo rm b o th c o n c u r r e n tly * The d e g re e o f r e
d undancy h ad no e f f e o t on t h e v i s u a l t a s k a lo n e i n te rm s
o f w h e th e r a re s p o n s e was m ade w i t h i n th e a p p r o p r i a t e
83
tim e l i m i t * I n t e r f e r e n c e e f f a c t s dua t o tlm a s h a r i n g ,
h o w e v e r, v a r i e d I n v e r s e l y w ith th e d e g re e o f re d u n d a n c y *
R e l a t i v e l y s m a ll am ounts o f re d u n d a n c y p ro d u c e d s i g n i f i
c a n t r e d u c t i o n s I n I n t e r f e r e n c e * T h ese d i f f e r e n c e s d id
n o t d im in is h u n d e r c o n tin u e d t r a i n i n g *
P r o a c t i v e and R e t r o a c t i v e I n h i b i t i o n
E a r l y I n t h i s c h a p t e r I t w as p o i n te d o u t t h a t
t h e r e w as some e v id e n c e t o I n d i c a t e t h e e x i s t e n c e o f a t
l e a s t tw o d i f f e r e n t memory m echanism s* The n e x t two
s e c t i o n s r e p o r t e x p e r im e n ts p e rfo rm e d i n Im m e d ia te memory
s i t u a t i o n s b u t w h ic h h a v e lo o k e d a t v a r i a b l e s fo u n d t o be
I m p o r ta n t I n th e m ore t r a d i t i o n a l l e a r n i n g e x p e rim e n ts *
One o f th e r e a s o n s a d v an c ed t o e x p l a i n f o r g e t t i n g
h a s b e e n t h a t o f r e s p o n s e c o m p e titio n * The o c c u r r e n c e o f
s e r i a l o r d e r i n t r u s i o n s h a s s u p p o rte d t h i s p o s i t i o n *
S u p p o s e d ly , i n t r u s i o n s a r e a r e s u l t o f p r o a c t i v e i n h i b i
tio n * I f t h i s i s t r u e , u n l e s s th e e f f e o t s o f p r o a c t i v e
i n h i b i t i o n c e a s e a t t h e n e x t m e s s a g e , r e c a l l o u g h t t o
becom e p r o g r e s s i v e l y w o rse th ro u g h o u t t h e t e s t *
On th e o t h e r h a n d , I t may be t h a t t h e s e s e r i a l
o r d e r i n t r u s i o n s do n o t d i r e c t l y le a d t o f o r g e t t i n g , b u t
t h a t th e s u b j e c t , h a v in g f o r g o t t e n , s e l e c t s fro m a s e t
o f a l t e r n a t i v e s * From th e p o i n t o f v iew o f r e s p o n s e
c o m p e ti t io n , one w ould p r e d i c t t h a t lo n g i n t e r v a l s
b e tw e e n s u c c e s s iv e m e ssa g e s w ould r e s u l t i n fe w e r i n t r u
s i o n s and t h u s fe w e r r e c a l l e r r o r s * A o c o rd ln g t o d eo ay
t h e o r y , h o w e v e r, one w o u ld e x p e c t lo n g I n t e r v a l s b e tw e e n
m e ssa g e s t o le a d t o f e w e r I n t r u s i o n s b u t t o no c h an g e i n
th e num ber o f r e c a l l e r r o r s *
C onrad ( 1960a ) t e s t e d 2l|. s u b j e c t s u n d e r t h r e e
c o n d it i o n s d i f f e r i n g o n ly i n th e I n t e r v a l b e tw e e n s u c c e s
s i v e m e ssa g e s* The m e ssa g e s o o n s l s t e d o f s e q u e n c e s o f
e i g h t d i g i t s sp o k e n a t th e r a t e o f tw o d i g i t s p e r seco n d *
T he d e p e n d e n t v a r i a b l e was th e num ber o f s e r i a l o r d e r
i n t r u s i o n s fro m t h e p r e v io u s l i s t * A s e r i a l o r d e r i n
t r u s i o n w as d e f in e d a s t h e o c c u rre n c e o f a n e r r o r i n
w h ic h th e c o r r e o t d i g i t w as r e p l a c e d by a d i g i t th e s u b -
j e o t p r o v id e d f o r t h e same s e r i a l p o s i t i o n i n a p r e v io u s
m e s sa g e , w h e th e r i t h a d b e e n r i g h t o r w rong*
No I n t r u s i o n s o c c u r r e d i n t h e lj.0-seoond g ro u p , and
fe w e r o c c u r r e d f o r th e 2 5 -s e o o n d g ro u p t h a n f o r th e 15-
se o o n d g ro u p * The num ber o f I n t r u s i o n s d id n o t a f f e o t
th e num ber o f e r r o r s * T h ese r e s u l t s s u g g e s t t h a t f o r
g e t t i n g h a s o c c u r r e d b e f o r e t h e i n t r u s i o n s o o c u r*
Waugh ( i 9 6 0 ) n o t e s t h a t a s a n im m e d ia te memory
s e r i e s becom es l o n g e r , th e t o t a l num ber o f ite m s c o r r e c t
l y r e o a l l e d r i s e s t o a maximum, t h e n f a l l s o f f * She
p e rfo rm e d tw o e x p e rim e n ts w h lo h s t u d i e d t h e i n f l u e n c e o f
s e r i e s l e n g t h on th e " t e r m i n a l sp a n * " T h a t i s , sh e
85
v a r ie d t h e t o t a l number o f it e m s i n t h e s e r i e s (e x p o s u r e
s e r i e s ) * end a sk ed t h e s u b j e c t s t o r e c a l l a s p e c i f i c
number o f t h e l a s t p r e s e n t e d I te m s ( r e c a l l s e r i e s ) * w h ic h
a l s o v a r ie d * The s t i m u l i w ere d i g i t s p r e s e n t e d i n an e s
s e n t i a l l y random o r d e r * b u t u n d e r c o n s t r a i n t s t o e l i m i n a t e
o b v io u s ly e a s y s e q u e n c e s * The s u b j e c t s a lw a y s k n e v t h e
le n g t h o f t h e r e c a l l s e r i e s b u t n e v e r t h a t o f t h e e x p o s u r e
s e r i e s * D i g i t s c o u ld b e r e o o r d e d i n any o r d e r . B a ch
r e c a l l a e r i e s w as p r e o e d e d b y a p r e - r e c a l l s e r i e s o f fro m
0 t o 20 d i g i t s *
The r e s u l t s s u g g e s t e d t h a t t h e memory sp a n i s a t
l e a s t p a r t i a l l y d e te r m in e d b y a e r i a l p o s i t i o n e f f e c t s *
W ith a s h o r t l i s t * r e c e n c y and p r im a c y I n t e r a c t * W ith a
lo n g l i s t th e y o a n 't * and b o th t h e t e r m in a l and i n i t i a l
sp a n s a r e r e l a t i v e l y s h o r t * One e x p la n a t io n o f t h e r e
s u l t s w h ic h w as s u g g e s t e d i s t h a t r e o e n o y r e s u l t s fro m th e
s h o r t e r d e la y b e tw e e n e x p o s u r e and r e o a l l w h ile t h e e f f e o t s
o f p rim a cy r e s u l t fro m t h e m ore I n t e n s e r e h e a r s a l o f th e
e a r l y ite m s * T h is v ie w p o in t w as o f f e r e d i n o p p o s i t i o n t o
th e i n t e r f e r e n c e e f f e c t s o f p r o - and r e t r o - a o t i v e i n h i b i
t i o n *
A n o th e r s t u d y b y Waugh ( 1 9 6l ) com pared f r e e and
s e r i a l r e c a l l o f l i s t s o f m o n o s y lla b io E n g li s h w ord s o v e r
th e c o u r s e o f s i x t r i a l s * The l e a r n i n g c u r v e f o r s e r i a l
l e a r n in g w as l i n e a r w h ile t h a t f o r f r e e r e o a l l w as
86
n e g a t iv e ly a c c e le r a t e d . F ree r e c a l l was n o t fou n d t o
depend I n any way on v h e th e r w ords t o be le a r n e d w ere
scram b led b e fo r e e v e r y t r i a l o r p r e s e n te d i n th e same
o r d e r on a l l t r i a l s . She c o n clu d ed t h a t s e r i a l le a r n in g
r e p r e s e n t s a c u m u la tio n o f memory sp an s* b u t t h a t f r e e
r e o a l l i s n o t e a s i l y e x p la in e d *
The l a s t stu d y t o be r e p o r te d i n t h i s s e c t i o n was
perform ed by Murdook ( 1 9 6 1 ) . L i s t s o f p a i r e d - a s s o o i a t e s
w ere p r e s e n te d once* th e n th e s u b j e c t s w ere t e s t e d f o r
r e o a l l o f one o f th e p a ir s i n t h e l i s t . The s u b j e c t s w ere
n o t in form ed ab ou t w hloh p a ir w ould b e s e l e o t e d f o r r e
c a l l . The number o f p a ir s p r e c e d in g th e to-b e-rem em b ered
p a ir was v a r ie d ( P . I . l e v e l ) and was e i t h e r 0* 1* 2* o r
3 p a ir s o f w o rd s. The r e t r o a c t i v e i x d iib it io n l e v e l was
v a r ie d a ls o and was e i t h e r 0 * 1 * 2 * 3 * o r 5 p a ir s o f
w o r d s. Words w ere c h o se n from th o s e w ith a T h o rn d ik e -
L orge c o u n t o f 20 o r b e t t e r . The p r e s e n t a t io n r a t e was
8 se c o n d s p er p a ir w h ile th e r e c a l l i n t e r v a l was 1$
s e c o n d s .
The r e s u l t s in d ic a t e d t h a t p r o - and r e t r o - a c t i v e
i n h i b i t i o n were v e r y s i g n i f i c a n t * b u t t h e i r i n t e r a c t i o n
was n o t . How much o f t h i s i s due t o tim e i n th e r e t r o
a c t iv e i n h i b i t i o n c o n d it io n i s d i f f i c u l t t o a s s e s s . The
P I v a lu e s o f one and g r e a t e r w ere com bined s in c e th e y
were v e r y s im ila r * so th e e f f e c t h e r e was b etw een h a v in g
87
no Ite m b e f o r e th e d e s i r e d ite m o r h a v in g one o r m ore
ite m s p r e c e d in g i t *
F requency* A s s o c ia t io n V a lu e ,
and s i m i l a r i t y
T h ere h a v e b e e n a num ber o f s t u d i e s i n v e s t i g a t i n g
th e f r e q u e n c y t h a t a n ite m i s e i t h e r e n c o u n te re d o r u s e d
o n s h o r t - t e r m r e t e n t i o n * I n a n o th e r o f t h e s e r i e s o f
s t u d i e s i n v e s t i g a t i n g a v e ra g e s t o r a g e lo a d * L lo y d and
J o h n s to n ( i 9 6 0 ) a ls o v a r i e d th e f r e q u e n c y t h a t ite m s o c
c u r r e d i n a s e q u e n c e . A t a p e r e c o r d e r p r e s e n t e d l e t t e r -
v o rd p a i r s . When t h e s u b j e c t h e a r d a l e t t e r a lo n e * he w as
i n s t r u c t e d t o r e c a l l a l l o f th e w o rd s p r e v i o u s l y p a i r e d
w ith th e l e t t e r . One g ro u p h e a r d ite m s p a i r e d w i t h e q u a l
f re q u e n c y w h ile a n o th e r g ro u p h e a r d some Ite m s p a i r e d f r e
q u e n tly and o t h e r s p a i r e d i n f r e q u e n t l y * R e c a l l e r r o r s
d e c r e a s e d a s th e ite m s o c c u r r e d m ore f r e q u e n t ly *
T u lv ln g and P a tk a n (1 9 6 2 ) I n v e s t i g a t e d t h e co n
c u r r e n t e f f e c t s o f w ord f r e q u e n c y and c o n t e x t u a l c o n s t r a i n t
on th e r e c a l l o f w o rd s o n s u c c e s s iv e p r a c t i c e t r i a l s *
T h e re w ere tw o l e v e l s o f fre q u e n o y and f i v e l e v e l s o f
c o n t e x t u a l c o n s t r a i n t * B ach o f tw o e x p e r im e n ta l g ro u p s
l e a r n e d f i v e l i s t s a t one l e v e l o f w ord fre q u e n c y * B o th
th e num ber o f w ords c o r r e c t l y r e c a l l e d and th e o r d e r o f
r e o a l l o f w ords com pared w ith t h e o r i g i n a l l i s t w ere
d e te r m in e d . S u b j e c t s l i s t e n e d t o 2l|. w o rd s w h ic h w ere
88
p r e s e n te d b y m eans o f a ta p e r e c o r d e r and th e n w ro te a s
many o f th e w ords a s th e y o o u ld rem em ber i n any o r d e r *
Then t h e same l i s t w as r e p e a t e d w ith a n o th e r r e o a l l b e f o r e
th e n e x t l i s t w as p r e s e n te d *
The r e s u l t s i n d i c a t e d t h a t a lth o u g h th e num ber o f
low f r e q u e n c y w ords c o r r e o t l y r e c a l l e d i n c r e a s e o n ly
s l i g h t l y a s th e o r d e r o f a p p ro x im a tio n t o E n g lis h i n
c r e a s e s * h i g h f r e q u e n c y w ords show a f a s t e r im provem ent*
A t low l e v e l s o f c o n t e x t u a l c o n s t r a i n t t h e r e i s v e ry
l i t t l e d i f f e r e n c e *
F o r t h e i r s e q u e n t i a l a n a l y s i s o f th e o r d e r o f r e
c a l l th e a u th o r s u s e d w hat t h e y te rm e d t h e " a d o p te d
c h u n k *1 1 i* e * * an y g ro u p o f one o r m ore ite m s w h ic h o c
c u r r e d i n t h e r e o a l l i n th e same se q u e n o e a s th e y o e e u r r e d
i n th e o r i g i n a l l i s t . An a n a l y s i s o f v a r ia n c e o f t h i s
d a t a y i e l d e d a s i g n i f i c a n t F - v a lu e o n ly f o r o r d e r o f ap
p ro x im a tio n * The o v e r a l l m eans f o r h ig h and low f r e q u e n c y
l i s t s w ere a lm o s t i d e n t i c a l * A lth o u g h th e num ber o f
c h u n k s w as r e l a t i v e l y i n v a r i a n t * th e s i z e o f e a c h chunk
grew * Thus th e a d v a n ta g e i n m ore m e a n in g f u l m a t e r i a l may
b e due t o th e o c c u r r e n c e o f l a r g e r ch u n k s*
Two l i s t s o f 60 n o u n s e a c h w ere s e l e c t e d b y B o u s-
f i e l d and C ohen (1 9 5 5 ) to m e e t t h e f o llo w in g c o n d i t i o n s :
( a ) T h ere w ere 15 w ords i n e a o h o f f o u r c a t e g o r i e s
(a n im a ls * nam es* p r o f e s s i o n s * and v e g e t a b l e s ) ; ( b ) one
89
l i s t contained h igh frequency words w hile another had on ly
low frequency words; (c ) the mean word frequency fo r eaoh
category was the same w ith in each l i s t ; (d) eaeh oategory
used matched words in re sp ect to the number o f s y ll a b le s .
A p ro jecto r d isp layed each word fo r three seoon d s.
The su b je c ts were req u ired to r e o a ll the whole l i s t in
the order in which they remembered i t . There were f i r e
columns on the answer sh e e t and su b jec ts were requ ired to
change to a new column each two m in u tes.
The r e o a ll o f h igh -freq u en cy words was s ig n if ic a n t
ly g rea ter than th a t obtained fo r low -frequency words.
The t o t a l amount o f " c lu ste r in g ." i . e . . occurrences o f
two or more words o f the same category as a sequence in
r e o a ll. was a ls o s ig n if lo a n tly g rea ter fo r h igh frequency
words, as was the average number o f words per " c lu ste r ."
The authors contend th a t in order to aocount fo r
" clu sterin g " we must go beyond the p o stu la ted h a b it
stren g th s o f in d iv id u a l words, and must assume th e func
tio n in g o f some h igher order m ediating p r o c e ss. They
in te r p r e t th e ir r e s u lt s in terms o f Hebb's "superordinate
p ercep tio n s."
A ccording to t h is p o s it io n , repeated arou sal of a
group o f r e la te d subordinate p ercep tio n s has as a con se
quence the developswnt o f a superordinate stru o tu re whose
a c t iv it y c o n s titu te s the p ercep tio n o f the whole c a te g o r y .
90
The occurrence o f a s in g le subordinate may a c tiv a te th e
auperordinate w hich, in turn* f a c i l i t a t e s resp on ses o f
su b o rd in a tes. The word "leopard" may lead to "animal"
which i n turn lea d s to " lio n s ," " o a ts," e t c .
Such str u c tu r e s are supposed to develop w ith use
and memory may In volve th e r e -a c tiv a tio n o f both sub
ord in ate and su perordin ate s tr u c tu r e s . Furtherm ore, the
p o s s i b i l i t y th a t "meaning" i s dependent upon th e a c tiv a
tio n o f th ese str u c tu r e s was o ffe r e d as a p o s s ib ilit y *
D eese (1 9 5 9 ) b a d s u b j e c t s l i s t e n t o a ta p e r e c o r d e r
w h ic h p r e s e n t e d 36 l i s t s o f 12 w o rd s e a c h . W ords w ere
r e c a l l e d o r a l l y a t th e end o f e a c h l i s t . E ac h l i s t co n
s i s t e d o f th e 12 h i g h e s t fr e q u e n c y r e s p o n s e s g iv e n t o a
p a r t i c u l a r s tim u lu s on t h e E e n t- R o s e n o f f w o r d - a s s o c i a t l o n
l i s t . The p a r t i c u l a r l i s t s u s e d w ere s e l e c t e d b e c a u s e
some o f them v e ry r e l i a b l y p ro d u c e d a te n d e n c y f o r s u b
j e c t s t o r e c a l l th e w ord a s s o c i a t e d w ith th e l i s t , b u t
n o t h e a r d , w h ile o t h e r s d id n o t .
For each l i s t i t was determined how o fte n the
o r ig in a l X-R stim u lu s word was e l i c i t e d when th e su b je c ts
attem pted to r e c a ll th e l i s t . The problem was to d eter
mine the ex ten t to whioh the tendency to em it th ese
p a r tic u la r In tr u sio n s was p red ic ta b le from the frequency
w ith which th ese words were g iv e n as a s s o c ia tio n s to the
words on the l i s t . Another sim ila r sample o f su b jec ts
91
was used to o b ta in word a s s o c ia tio n norms*
The p ro d u o t-m o m en t c o r r e l a t i o n b e tw e e n f r e q u e n c y o f
o c c u rre n c e o f t h e s e w o rd s a s i n t r u s i o n s and t h e i r f re q u e n c y
o f a s s o c i a t i o n w as *873* T h u s, t h i s p r o v id e s a d d i t i o n a l
e v id e n c e t h a t i n t h e p r o c e s s o f r e c o l l e c t i o n , w ords and
c o n o e p ts a s s o c i a t e d w ith rem em bered ite m s w i l l be added*
Ite m s w h ic h a re f o r g o t t e n a r e p r o b a b ly th e ite m s w h ich
h a v e a low p r o b a b i l i t y o f b e in g e l i c i t e d by th e rem em bered
l i s t ite m s *
Another study was reported by Deese ( 1960 a ) in
which the frequency o f usage o f the words in th e l i s t was
v a ried as was the number o f words p resen ted in each l i s t *
I t was found th a t th e mean number o f words r e c a lle d in
creased w ith b oth . There was a lso a s ig n if ic a n t in t e r
a c tio n o f the two major v a r ia b le s . R ec a ll was dispropor
tio n a te ly g rea ter fo r th e h ig h frequenoy words*
Although the words were chosen a t random exoept fo r
the r e s t r ic t io n of frequenoy o f u sa g e, c e r ta in o f the
l i s t s were d iscovered to co n ta in words a s s o c ia t iv e ly r e
la te d to each o th e r . An index o f the average tendency o f
a l l words in each l i s t to be e l i c i t e d as an a s s o c ia tio n by
a l l other words in the l i s t was computed, and i t was
determined th a t the index was la rg er fo r th e h igh frequency
l i s t . O ils evidence ten ds to support th e h y p o th esis th a t
the v a r ia tio n in f r e e - r e c a ll sco res w ith frequency was
92
l a r g e l y th e r e s u l t o f d i f f e r e n c e s b e tw e e n th e f re q u e n c y
i n in te r - w o r d a s s o c i a t i o n s as w as th e i n t e r a c t i o n b e tw e e n
l i s t le n g t h an d fre q u e n c y *
D eese ( 1960b ) d e d u o ea fro m some o f t h e s e r e s u l t s
t h a t once a w ord i s e n c o d e d i n a n in d iv id u a l* s v o c a b u la r y ,
th e g e n e r a l fr e q u e n c y o f u s a g e o f t h a t w ord i s u n im p o rta n t
t o t h e i n d i v i d u a l * s a b i l i t y to r e c a l l t h a t w ord* F r e
q uency o f u s a g e , a c c o r d in g t o h im , i s a m ea su re o f th e
p r o b a b i l i t y o f p r o d u c t i o n , and i n th o s e s i t u a t i o n s i n
w h ic h s h e e r p r o d u c t i o n f r e q u e n c y c o u ld i n f lu e n c e th e r e
c a l l o u tco m e, f r e q u e n c y w o u ld p l a y a r o l e . S uch may b e
th e c a s e i n f i n d i n g d i f f e r e n c e s b e tw e e n z e ro and f i r s t
o r d e r a p p ro x im a tio n s t o E n g lis h *
A n o th e r s tu d y b y D eese (1 9 5 9 * ) p r o v id e s f u r t h e r
s u p p o r t f o r h i s p o s i t i o n . He v a r i e d th e i n t e r - i t e m
a s s o c i a t i v e s t r e n g t h ( i . e . , t h e a v e ra g e r e l a t i v e f r e q u e n c y
w h ich a l l ite m s i n th e l i s t te n d to ev o k e a l l o t h e r ite m s
i n th e l i s t a s f r e e a s s o c i a t e s ) t o t e s t th e f o llo w in g
h y p o th e s e s : ( a ) The num ber o f ite m s r e c a l l e d i s p r o p o r
t i o n a l t o t h e i n t e r - i t e m a s s o c i a t i v e s t r e n g t h ; (b ) e x
tr a n e o u s I n t r u s i o n s a r e I n v e r s e l y r e l a t e d t o th e i n t e r -
ite m a s s o c i a t i v e s t r e n g t h ; ( c ) th e num ber o f d i f f e r e n t
i n t r u s i o n s i s i n v e r s e l y r e l a t e d t o I n t e r - i t e m a s s o c i a t i v e
s t r e n g th *
A m nem onic d e v ic e was b u i l t i n t o s e e w h e th e r
93
a s s o c ia tiv e stre n g th d ir e c tly in flu en ced r e c a ll or whether
i t was used sim ply as a mnemonic. A name was g iv e n to
each l i s t which the su b je c ts wrote on the data sh eet be
fo re r e c a l l . Under some co n d itio n s the name provided
a s s o c ia tiv e oues fo r the item s on the l i s t , fo r oth ers i t
was o f no h e lp .
In phase I , the Immediate fr e e r e c a l l of l i s t s of
words were o b ta in ed . S ix o f th e l i s t s were con stru cted
o f words fre q u en tly g iv en as a s s o c ia tio n s to p a r tic u la r
K ent-R osanoff s t im u li. S ix other l i s t s c o n sis te d o f low
frequency a s s o c ia tio n s to th e same s i x s t im u li, w h ile s ix
other l i s t s c o n sis te d o f worda never g iv en as a s s o c ia tio n s
to th e se same s t im u li. The l i s t s were matched fo r
Thorndike-Lorge freq u en cy. For o n e-h a lf o f the su b jec ts
the l i s t names were the appropriate K ent-R osanoff s t im u li,
w h ile fo r the o th ers the l i s t name was u n r e la te d .
In phase I I , fr e e a s s o c ia tio n norms were obtained
fo r the words u sed . There were more item s r e c a lle d fo r
the h igh-freq u en cy a s s o c ia tio n s to the K-R s tim u li than to
e ith e r the low or zero frequenoy ite m s, (liv in g the sub-
je o t the appropriate K-R stim u lu s as a l i s t name had no
e f f e c t on the number r e c a lle d . This su g g e sts that the
in te r -ite m a s s o c ia tiv e stre n g th i s the major v a ria b le
determ ining the number o f item s r e o a lle d . The c o r r e la tio n
between the mean number o f In tr u sio n s and in te r -ite m
9 i*
a s s o c i a t i v e s t r e n g t h was - 0 . ^ 8 . T h e re was n o t o n ly a
te n d e n c y f o r I n t r u s i o n s t o be l e s s f r e q u e n t on th e h ig h *
a s s o c i a t i o n l i s t s , b u t th e I n t r u s i o n s o f d i f f e r e n t su b
j e c t s te n d e d t o be th e same*
D eese c la im s t h a t i t i s p r o b a b le t h a t th e s u b j e c t s
f r e e - a s s o c i a t e to w ords th e n e d i t t h e i r a s s o c i a t i o n s b e
f o r e p ro d u c in g them a s o v e r t ite m s i n r e c a l l * T h ere
seem ed t o b e no i n t e n t i o n a l u s e o f m nem onios* The su b
j e c t s may re p ro d u c e fro m im m e d ia te memory a s m a ll o o re o f
ite m s and f r e e a s s o c i a t e t o t h e s e , th e s t r o n g e s t o f w h ich
a re e m itte d a s r e s p o n s e s i n r e c a l l *
P e t e r s o n , P e t e r s o n , and H i l l e r ( 19&1) v a r i e d t h e
A rc h e r a s s o c i a t i o n v a lu e f o r tr lg r a m s * T h re e v a lu e s w ere
u s e d } 1 3 .1 , 8l{.*9, and 99*2 p e r o e n t* (The tr lg r a m s i n
th e l a s t g ro u p w ere a l l t h r e e - l e t t e r w o rd s* ) A t h r e e -
l e t t e r ite m was e x p o se d o n a memory drum f o r 1*1 s e c o n d s ,
d u r in g w h ic h tim e th e s u b j e c t was t o s p e l l i t a lo u d * The
drum tu r n e d t o a 3- d i g i t num ber and th e s u b j e c t c o u n te d
b ackw ard by e i t h e r t h r e e o r f o u r fro m t h i s num ber f o r s i x
se c o n d s* The drum th e n t u r n e d , e x p o s in g a b la n k sp a c e
and th e s u b j e c t s to p p e d c o u n tin g and t r i e d t o r e c a l l th e
ite m b y s p e l l i n g i t a lo u d * T w elve se c o n d s l a t e r th e drum
tu rn e d t o a new b la n k sp a c e and th e n t o a new ite m * E a c h
o f th e t h r e e ty p e s o f ite m s a p p e a re d e q u a l ly o f t e n w i t h i n
e a c h b lo c k o f s i x , b u t w ere ran d o m ly a s s ig n e d w i t h i n t h i s
9 $
b lo c k *
Marked d i f f e r e n c e s i n r e c a l l d ir e c t ly r e la t in g the
number r e c a lle d to a s s o c ia tio n valu e were obtained*
The se c o n d e x p e rim e n t b y t h e s e a u th o r s d o e s n o t
s u p p o r t th e h y p o t h e s is o f D eese m e n tio n e d above* T h ese
a u th o r s r e a s o n e d t h a t i f a h ig h a s s o c i a t i o n v a lu e f a c i l i
t a t e d r e c a l l th r o u g h m e d ia tin g a s s o c i a t i o n s * th e l a t e n c y
o f c o r r e c t r e c a l l s s h o u ld v a r y w ith t h e a s s o c i a t i o n v a lu e
o f th e ite m r e c a l l e d * T w e n ty -fo u r n o n s e n s e s y l l a b l e s
w ith an A ro h e r v a lu e o f 11 p e r c e n t w e re com pared w ith Z]\.
s y l l a b l e s h a v in g a v a lu e o f 100 p e r c e n t* A tim e r was
ad d ed t o t h e c i r c u i t w h ic h w as a u t o m a t i c a l l y a c t i v a t e d
w hen th e ite m w as t o be r e c a l l e d an d s to p p e d by t h e ex
p e r im e n te r a f t e r th e t h i r d l e t t e r was sp o k e n b y th e s u b
j e c t * R e te n ti o n tim e s o f 1 and 6 s e c o n d s w ere u se d * I n
o t h e r r e s p e c t s th e e x p e rim e n t w as l i k e th e one im m e d ia te ly
p re c e d in g *
D i f f e r e n c e s i n r e c a l l w e re o b ta in e d o n ly a t t h e 6-
s e c o n d i n t e r v a l * The l a t e n c i e s d id n o t d i f f e r s i g n i f i
c a n t l y f o r t h e a s s o c i a t i o n v a lu e s * Thus* th e h y p o t h e s is
t h a t m e d ia tin g a s s o c i a t i o n s f a c i l i t a t e r e o a l l was n o t
s u p p o rte d *
A t h i r d e x p e rim e n t v a r i e d th e r e c a l l i n t e r v a l o v e r
f o u r v a lu e s r a n g in g fro m one t o s i x s e c o n d s * I n m o st
o t h e r r e s p e c t s * t h i s s tu d y w as s i m i l a r t o th e f i r s t two*
96
The l a t e n c y o f o a r r e o t r e c a l l s I n c r e a s e d g r a d u a l l y a s th e
i n t e r v a l in c r e a s e d *
B o u s f ie ld and Cowan v a r i e d th e a s s o c i a t i o n v a lu e
o f t r ig r a m s a s w e l l a s th e ty p e o f re s p o n s e m ad e. One
g ro u p o f s u b j e c t s s p e l l e d t h e t r i g r a a s w h ile a n o th e r
g ro u p p ro n o u n c e d th e m . W h eth er r e c a l l w as t o b e i n th e
same o r d e r a s th e s t i m u l i w ere p r e s e n t e d o r i n any o r d e r
w as a l s o v a r ie d * The memory s p a n te c h n iq u e w as u se d *
Pronounoiation y ie ld e d ap preciably high®** memory
span than did s p e llin g . There were no d iffe r e n c e s in the
m agnitudes o f th e spans th a t could be a ttr ib u te d to the
change from ordered to fr e e r e c a l l . The su b jec ts tended
to reproduce the item s in the order o f p r e se n ta tio n any
way*
The n e x t few s t u d i e s t o be r e p o r t e d v a ry some
a s p e c t o f s i m i l a r i t y . The f i r s t s tu d y i n t h i s g ro u p was
by H o ro w its ( 1961) who ex am in ed th e j o i n t i n f l u e n c e o f
i n t r a l i s t s i m i l a r i t y an d t h e n a tu r e o f th e s u b je c ts * ta s k *
Two l i s t s o f 3 - c o n s o n a n t t r i g r a m s w ere u s e d . The l i s t s
w ere 12 u n i t s lo n g . The t r lg r a m s o f th e h i g h - s i m i l a r l t y
l i s t c o n ta in e d o n ly f o u r d i f f e r e n t l e t t e r s $ w h ile th o s e
o f t h e l o w - s l m l l a r l t y l i s t c o n ta in e d 12 d i f f e r e n t l e t t e r s *
Two g ro u p s o f s u b j e o t s r e c a l l e d a s many s y l l a b l e s a s th e y
c o u ld a f t e r e a c h o f t e n p r e s e n t a t i o n s , w h ile two o t h e r
g ro u p s l e a r n e d th e o r d e r o f t h e s y l l a b l e s b u t n o t th e
97
s y l l a b l e s th e m s e lv e s .
H ig h i n t r a l i s t s i m i l a r i t y w as fo u n d t o f a c i l i t a t e
f r e e r e o a l l e a r l y i n t r a i n i n g b u t t h i s s u p e r i o r i t y was
l o s t o n l a t e r t r i a l s . Low i n t r a l i s t s i m i l a r i t y u n if o r m ly
f a c i l i t a t e d l e a r n i n g .
B e lb in and Cane (1 9 5 6 ) h a d s u b j e c t s lo o k a t 12
s i m i l a r p h o t o s . T he s u b j e c t s w e re t h e n g iv e n a r e c o g n i
t i o n t e s t o f 12 p h o to s i n w h ic h a num ber r a n g i n g fro m 1
t o 12 h a d b e e n show n I n t h e o r i g i n a l g r o u p . A l l o f th e
p h o to s w e re s u f f i c i e n t l y a l i k e t o r e q u i r e some g u e s s i n g .
The s u b j e c t s te n d e d t o s e l e c t a p p r o x im a te ly $0 p e r c e n t
a s h a v in g b e e n s e e n p r e v i o u s l y and t o r e j e c t t h e o t h e r $0
p e r c e n t . When a s e c o n d and s i m i l a r d i s p l a y and r e c o g n i
t i o n t e s t f o llo w e d im m e d ia te ly , t h e r e w as a te n d e n c y f o r
s u b j e c t s t o m ake m ore " y e s * r e s p o n s e s w i t h o u t an y im p ro v e
m en t i n a c c u r a c y . I t w as d e te rm in e d t h a t w hen a c o r r e c t
d e c i s i o n was p o s s i b l e b u t d i f f i c u l t , a p o s i t i v e l y o o r r e e t
r e s p o n s e ( r e c o g n i s i n g s o m e th in g s e e n b e f o r e ) w as e a s i e r
th a n r e j e c t i n g s o m e th in g n o t s e e n b e f o r e .
A s e c o n d e x p e r im e n t r e v e a l e d t h a t th e a c c u ra c y and
c e r t a i n t y o f a d e c i s i o n v a r i e d w i t h t h e n a t u r e o f t h e
c h o ic e s i t u a t i o n . The r a n g e o f s t i m u l i and t h e f i n e n e s s
o f t h e d e s o r i m l n a t i o n r e q u i r e d u n d o u b te d ly i n f l u e n c e t h e
r e s u l t s o f b o th o f t h e s e s t u d i e s .
The h y p o t h e s i s t h a t la n g u a g e h a b i t s a f f e c t th e
98
e a s e w ith w h ic h p a i r s o f s y l l a b l e s o a n b e l e a r n e d was
t e s t e d b y B a d d e le y (1 9 6 1 )* E ig h t p a i r s o f n o n s e n s e s y l
l a b l e s w ere s e l e o t e d fro m G la z e * s l i s t , l h e s e p a i r s w ere i
I
ohosen so th a t in one order th e l a s t l e t t e r o f the f i r s t
s y lla b le and th e f i r s t l e t t e r o f the second s y lla b le oc
curred fr e q u e n tly in th e language (com p atib le) , but when
the s y lla b le s were rev ersed th e se in t e r - s y lla b le digrams
ocourred in fr e q u e n tly (in com p atib le)*
Two l i s t s were formed from th ese s y lla b le s * In
the f i r s t l i s t th e f i r s t four p a ir s were com patible but
the l a s t fo u r were incom patible * The seoond l i s t reversed,
the order* Two groups* u sin g the a n tic ip a tio n method*
learn ed u n t il th ey had achieved a record o f th r ee erro r
le s s t r i a l s or u n t il a t o t a l o f 20 t r i a l s had ooourred*
The performance was measured in terms o f the t o t a l error
d iffe r e n c e between the f i r s t and la s t four p a ir s o f s y l
la b le s* Of the e ig h t p airs* seven were learned more
r e a d ily in the com patible situ a tio n * The author con
cluded th a t S-R c o m p a tib ility e f f e c t s analogous to those
found fo r sen sorl-m otor s k i l l s occur in verb al learn ing*
Brown (1 9 5 8 ) performed an experim ent in whioh the
stim u li th a t the su b jec ts were required to lea rn c o n sis te d
o f four p a ir s o f consonants* A d d ition al stim u li* which
were presen ted e ith e r ju s t b efo re or ju s t a fte r th e r e
quired stim u li* c o n siste d o f three p a ir s o f consonants or
99
t h r e e p a i r s o f n u m b e rs. No c o n s o n a n t o r d i g i t w as r e
p e a te d on any one t r i a l * A o o n t r o l g ro u p was e x p o se d
o n ly t o t h e r e q u i r e d s t i m u l i * P a i r s o f sy m b o ls w ere p r e
s e n te d a t I n t e r v a l s o f 1*33 se c o n d s* The i n t e r v a l b e tw e e n '
th e s t a r t o f e a c h t r i a l an d r e c a l l w as a lw ay s 5*33
se c o n d s * B o th s i m i l a r an d d i f f e r e n t a d d i t i o n a l m a t e r i a l
p r e s e n t e d a f t e r t h e r e q u i r e d m a t e r i a l r e s u l t e d I n l a r g e
am o u n ts o f I n t e r f e r e n c e , w ith s i m i l a r h a v in g s l i g h t l y b u t
s t a t i s t i c a l l y s i g n i f i c a n t m ore o f a d e t r i m e n t a l e f f e c t *
S i m i l a r m a t e r i a l p r e s e n t e d b e f o r e th e r e q u i r e d m a t e r i a l
h ad a s l i g h t i n t e r f e r e n c e e f f e c t b u t d i f f e r e n t m a t e r i a l
d id n o t*
U n d er t h e s e c o n d i t i o n s , t h e n , i t a p p e a rs t h a t
s i m i l a r i t y d o e s n o t p la y a v e r y iiq p o r ta n t r o l e * On th e
b a s i s o f th e t r a c e - d e c a y t h e o r y , i t w ould b e p r e d i c t e d
t h a t any e f f e c t o f s i m i l a r i t y w ould be due t o o o n f u s io n
I n r e c a l l * I n t r u s i o n s fro m s t i m u l i o f t h i s ty p e i n th e
p r e s e n t s tu d y w ere a l i t t l e h i g h e r th a n a t a o h a n c e l e v e l
w hen su o h s t i m u l i f o llo w e d t h e r e q u i r e d m a t e r i a l * B u t
w hen th e s i m i l a r m a t e r i a l p r e c e d e d t h e r e q u i r e d m a t e r i a l ,
i n t r u s i o n s w ere s l g n i f i o a n t l y l e s s th a n w ould b e e x p e c te d
by o h an ce* The e x p la n a t i o n f o r t h i s l a t t e r r e s u l t may be
t h a t w hen t h e u n w a n ted s t i m u l i I n t r u d e t h i s w i l l te n d to
d e la y r e c a l l o f t h e r e q u i r e d s t i m u l i , e v e n th o u g h t h e su b
j e c t s r e c o g n iz e them a s i n t r u s i o n s and do n o t in c l u d e them
1 0 0
I n th e o v e r t r e p o r t . T h is w ould I n p a i r r e o a l l a c c o r d in g
t o t h e t r a o e - d e c a y h y p o t h e s is and y e t le a d t o fe w e r in *
t r u s i o n s . T h is e x p e rim e n t seem s t o p r o v id e f u r t h e r su p
p o r t f o r th e d e e a y h y p o th e s is *
S u b j e c t V a r ia b le s
An e x p e rim e n t w as p e rfo rm e d b y F r a s e r (1958) i n
v e s t i g a t i n g t h e d i f f e r e n c e i n memory s p a n s b e tw e e n y o u n g
and o l d e r m en. One g r o u p 's a g e s ra n g e d fro m 18 t o 29*
w h ile t h e o t h e r g ro u p w as com posed o f men w hose age w as
b e tw e e n 30 an d 55 y e a r s . A l l w ere t e a c h e r s and w e re
m a tc h e d w ith r e s p e c t to g e n e r a l i n t e l l i g e n c e * e tc * S i g h t
d i g i t num bers w e re p r e s e n t e d a t a r a t e o f e i t h e r 120 o r
lj.0 d i g i t s p e r m in u te and re p ro d u c e d a t t h e same r a t e .
D i f f e r e n c e s i n th e m ean num ber r e c a l l e d o c c u r r e d w ith th e
f a s t r a t e b e in g s u p e r i o r . A lth o u g h t h e r e was no d i f f e r
e n c e b e tw e e n m ean s c o r e s o b ta in e d b y th e tw o age g ro u p s
w hen th e f a s t r a t e w as u se d * o l d e r men d id s i g n i f i c a n t l y
p o o r e r u n d e r t h e slow c o n d i t i o n . Thus* i t w ould a p p e a r
t h a t th e sp a n i s th e sam e f o r d i f f e r e n t age g ro u p s* b u t
th e r a t e o f d e c a y te n d s t o i n o r e a s e w ith age*
S c h w a rts ( I 96I ) t e s t e d tw o s u b j e c t s f o r d i g i t sp an
once a d ay f o r e i g h t d a y s* The b e s t d i g i t s p a n t h a t w as
o b ta in e d was e i g h t . E ac h s u b j e c t r e c e i v e d t e n p r a c t i c e
t r i a l s p e r d ay a f t e r th e i n i t i a l t e s t t r i a l on a d i f f e r e n t
n i n e - d i g i t s e r i e s . The r e s u l t i n g d i s t r i b u t i o n s w e r e
n e a r l y n o r m a l I n form *
F o u r new s u b j e c t s f o l l o w e d t h e sam e p r o c e d u r e f o r
18 d a y s * T h r e e o f t h e s e s u b j e c t s Im p ro v ed s u f f i c i e n t l y
w i t h t h e p r a c t i c e t o b e a b le t o rem em ber n in e d i g i t s *
N o t o n l y d id t h e memory s p a n I n c r e a s e b u t t h e t o t a l num ber
r e c a l l e d o f t h e p r a c t i c e s e r i e s n e a r l y t r i p l e d * T he s u b -
J e c t s b e l i e v e d t h a t t h e Im p ro v em en t w as I n t h e u s e o f
b e t t e r m nem onic d e v i c e s * V a r i a b i l i t y r e m a in e d c o n s t a n t *
One g r o u p o f e x p e r im e n t e r s ( G r is s o m , S u e d f l e l d and
V e r n o n , 1 9 6 2 ) h y p o t h e s i s e d t h a t a l o n g , u n d is t u r b e d p o s t *
a c q u i s i t i o n p e r i o d w o u ld f a c i l i t a t e r e t e n t i o n o f v e r b a l
m a t e r i a l * T h is p r e d i c t i o n w a s m ade o n t h e b a s i s o f th e
f i n d i n g t h a t t h e r e i s b e t t e r r e t e n t i o n w hen t h e l e a r n i n g
t a k e s p l a c e J u s t b e f o r e s l e e p * T w en ty v o l u n t e e r s p a r t i c i
p a t e d I n a 2l4 .-h.our I s o l a t i o n e x p e r im e n t* The s u b j e c t s
w e r e i s o l a t e d I n d i v i d u a l l y i n a s o u n d p r o o f , d a r k room and
r e s t r i c t e d t o b e d s * T h ey w e r e t o l d t o s t a y r e l a t i v e l y
s t i l l and t o t a l l y s i l e n t d u r in g t h e i r c o n fin e m e n t* B e d
p a n s and f o o d w e re a v a i l a b l e a t t h e e d g e o f t h e b ed*
A f t e r o n e m in u te o f c o n f in e m e n t t h e y w e r e a u r a l l y
p r e s e n t e d w i t h a 1 8 2 -w o r d p a s s a g e fr o m T o l s t o y * s War and
P e a c e * T h ey w e r e I n s t r u c t e d t o p a y s t r i c t a t t e n t i o n and
t o l i s t e n c a r e f u l l y t o a l l o f t h e d e t a i l s s i n c e t h e y w o u ld
b e a sk e d t o r e p e a t t h e p a s s a g e * I m m e d ia t e ly a f t e r t h e e n d
1 0 2
o f th e p a ssa g e th ey were asked to attem pt a v erb a tim r e
t e l l i n g * The ex p erim en ta l su b je o ts were th en l e f t un
d istu rb ed w h ile th e c o n tr o l group was r e le a s e d and t o ld
to r e tu r n 2lf hours la t e r fo r " fu rth er w ork,* and were
th en r e te s te d * The i s o l a t i o n group was asked to r e p e a t
th e p a ssa g e Ju st b e fo r e r e le a s e *
Only one su b je o t a n tic ip a te d th e r e t e s t , a cco rd in g
to th e auth ors* The re sp o n se s were scored f o r th e number
o f c o r r e c t ly reproduced words from th e p a s s a g e , ir r e s p e c
t i v e o f th e correspondenoe o f th e sequence* The e x p e r i
m ental group perform ed s i g n if i c a n t l y b e t te r on th e r e t e s t
th an d id th e c o n tr o l group* T his was I n te r p r e te d by th e
au th ors to in d ic a te th a t le a r n in g in u e d ia te ly fo llo w e d by
q u ie sc e n c e and th e c e s s a t io n o f new e x p e r ie n c e i s b e t t e r
r e ta in e d ( t h e ir word was " p e r fe c tly * ) and th u s , su p p o rts
an in te r fe r e n c e th eory o f fo r g e ttin g *
R esponse V a r ia b le s
There have been many d if f e r e n t re sp o n se v a r ia b le s
u sed in exp erim en ts on sh o rt-ter m r e te n tio n * Only a few
s t u d ie s , how ever, have attem pted to determ ine d if f e r e n c e s
a ttr ib u ta b le to th e type o f r e sp o n se . S e v e r a l o f th e se
have a lr ea d y b een c it e d (c f* s e o tlo n on o r g a n iz a tio n )
s in c e th e major r e s u l t o f th e stud y seemed more p e r t in e n t
to sn o th er v a r ia b le * The th r e e experim ents t o be d es
cr ib ed i n t h is s e c t io n had th e type o f re sp o n se made as a
103
m a jo r In d e p e n d e n t v a r i a b le *
K o rn and Jah n k e (1 9 6 2 ) v a r ie d th e l e n g t h o f th e
l i s t and ty p e o f m a t e r i a l u s e d a s s t i m u l i as w e ll as
w h e th e r th e r e q u i r e d re s p o n s e was th e r e c a l l o r r e c o g n i
t i o n o f th e m a t e r i a l* L i s t le n g th s w ere fro m 3 t o 9 u n i t s
f o r d i g i t s and c o n s o n a n ts w h ile th e h ig h and low a s s o c i a
t i o n v a lu e s y l l a b l e s w ere fro m ^ t o 10 u n i t s lo n g *
The r e c o g n i t i o n t a s k c o n s i s t e d o f h a v in g s u b j e o ts
l i s t e n t o one s e r i e s o f I t e m s * th e n a se c o n d s e r i e s and
f i n a l l y t o c h e c k an an sw er s h e e t a s t o w h e th e r th e se c o n d
s e r i e s was th e same a s th e f i r s t * Unknown to t h e s u b j e o t s
was th e f a c t t h a t t h e se c o n d s e r i e s was alw ay s th e same
b u t on h a l f o f th e t r i a l s th e o r d e r o f th e Ite m s I n th e
s e r i e s was d i f f e r e n t * T h e re w ere two t r i a l s o f e a c h
l e n g t h f o r e a c h ty p e o f m a t e r i a l and t e s t i n g was te r m in
a te d when t h e s u b j e c t was u n a b le on e i t h e r t r i a l t o
p e rfo rm p e r f e c t l y * A ta p e r e c o r d e r p r e s e n te d th e s t i m u l i
a t th e r a t e o f one u n i t p e r seco n d *
R e c o g n itio n was fo u n d t o b e s i g n i f i c a n t l y b e t t e r
th a n r e c a l l * and th e s p a n v a r i e d a s a f u n c t i o n o f th e
ty p e o f m a t e r i a l* The a u th o r s s t a t e t h a t i n s p e c t i o n s u g
g e s t s t h a t f o r d i f f e r e n t re s p o n s e m ethods* memory s p a n w as
m o st s i m i l a r f o r th e d i g i t s w ith d e c r e a s in g s i m i l a r i t y f o r
c o n s o n a n ts * h ig h a s s o c i a t i o n v a lu e s y l l a b l e s * and low
a s s o c i a t i o n v a lu e s y l l a b l e s i n t h a t o rd e r* The memory
10k
s p a n f o r high, a s s o c i a t i o n v a lu e s y l l a b l e s v a s s i g n i f i o a n t -
l y g r e a t e r t h a n t h a t f o r low a s s o c i a t i o n v a lu e s y l l a b l e s
w hen r e c a l l w as r e q u i r e d , b u t n o t i n th e r e c o g j i i t l o n
c o n d itio n *
The s ta te m e n t t h a t b o th r e c a l l and r e c o g n i t i o n a re
c o n fo u n d e d e s t i m a t e s o f r e t e n t i o n due t o t h e c o n ta m in a tin g
e f f e c t s o f r e t r i e v a l h a s b e e n a d v a n c e d by B usohke ( 1 9 6 3 )*
He d e v is e d a n o th e r m ethod o f m e a s u rin g r e t e n t i o n w h ic h h e
c a l l s th e " m is s in g s c a n " m ethod*
B a s i c a l l y h i s p ro c e d u r e sim p ly r e q u i r e d th e s u b
j e c t s t o r e p o r t w h ic h num ber o f a s e t was n o t in c lu d e d
w hen th e s t i m u l i w ere p r e s e n te d * A c o n t r o l t a s k w as a
d i g i t s p a n t e s t m o d ifie d so t h a t s u b j e c t s w ere r e q u i r e d
o n ly t o r e c a l l th e s t i m u l i i n th e l i s t w ith o u t r e g a r d t o
th e o r d e r o f p r e s e n t a t i o n *
T en s u b j e o t s p a r t i c i p a t e d i n b o th t a s k s i n a
c o u n te r b a la n c e d s e r i e s * The t e s t ite m s w ere th e num bers
fro m one t o s i x t e e n , ran d o m ly o r d e r e d , and w ere p r e s e n te d
i n g ro u p s o f fro m I 4 . to li) . d i g i t s . O nly one num ber was
m is s in g and w h ic h num ber t h i s w ould b e w as d e te rm in e d
ran d o m ly * The num ber s e r i e s w ere th e same i n b o th c o n d i
tio n s *
The m is s in g s c a n e s tim a te o f r e t e n t i o n w as g r e a t e r
th a n t h a t o f th e m o d ifie d d i g i t sp a n f o r a l l s u b j e o ts *
M ost o f th e f o r g o t t e n ite m s i n th e d i g i t s p a n w ere i n th e
105
se c o n d h a l f o f th e s e r i e s a s I t w as p r e s e n te d * b u t f o r th e
m is s in g s c a n m ethod* m o st o f th e e r r o r s w ere I n t h e f i r s t
h a lf * S u b je c ts u s u a l l y r e p o r t e d t h e num bers I n th e m o d i
f i e d d i g i t s p a n t e s t I n th e o r d e r o f p r e s e n t a t i o n * o r
n e a r l y so*
The a u th o r c o n c lu d e s t h a t t h e m is s i n g s c a n m eth o d
I s a m ore s e n s i t i v e m ea su re o f r e t e n t i o n * He a l s o n o t e s
t h a t th e r e v e r s a l o f th e e r r o r d i s t r i b u t i o n f o r t h e tw o
t a s k s may I n d i c a t e e i t h e r : ( a ) d i f f e r e n t m odes o f s h o r t
te rm s t o r a g e a r e In v o lv e d ; (b ) t h a t d i f f e r e n t o p e r a t i o n s
may be p e rfo rm e d on I n f o r m a tio n p r i o r t o s t o r a g e ! o r
( c ) d i f f e r e n t ty p e s o f s c a n n in g a r e u s e d on th e same
s to r a g e *
D a v is and h i s c o -w o rk e rs (1 9 6 1 ) a tte m p te d t o d e t e r
m ine I f t h e d i f f e r e n c e s o b ta in e d w hen a r e c o g n i t i o n t a s k
I s com pared w i t h a r e c a l l t a s k w ere due t o t h e g r e a t e r
num ber o f a l t e r n a t i v e s fro m w h ic h th e s u b j e c t s h a d t o
ch o o se u n d e r th e r e o a l l c o n d itio n * T w e n ty -fo u r women
s e r v e d a s s u b je o ts * The s t i m u l i w ere e i t h e r t w o - l e t t e r
s y l l a b l e s w h ich b e g a n w ith a v o w el and e n d ed w ith a
c o n so n a n t* o r t w o - d i g i t num bers* R andom ly s e l e o t e d l i s t s
w ere d is p la y e d on a memory drum a t a r a t e o f 1*5 s e c o n d s
p e r u n i t* and w ere 15 u n i t s lo n g *
U nder th e r e c a l l c o n d it i o n t h e s u b j e c t s w ere a sk e d
t o r e c a l l a s many o f th e s t i m u l i a s th e y c o u ld * T h e re
106
w ere t h r e e r e c o g n i t i o n c o n d i t i o n s . I n th e f i r s t t h e s u b
j e c t ! w ere p r e s e n te d w i t h a l i s t o f 30 s t i m u l i and m arked
a l l th o s e t h a t th e y th o u g h t a p p e a re d on th e o r i g i n a l l i s t *
The two o t h e r r e c o g n i t i o n t a s k s w ere s i m i l a r b u t h a d
e i t h e r 60 o r 90 s t i m u l i fro m w h ich th e o r i g i n a l 15 w ere t o
be p ic k e d *
Raw s c o r e s w ere c o n v e r te d t o a n in f o r m a ti o n o o n te n t
m e a su re w h ic h ig n o r e d t h e am ount o f i n f o r m a tio n t r a n s
m it t e d b y t h e o r d e r o f t h e s t i m u l i * p e rfo rm a n c e m e a su re d
by t h i s te c h n iq u e was no b e t t e r f o r r e c o g n i t i o n th a n f o r
r e c a l l *
S tim u lu s M a t e r i a l
A t e s t o f t h e n o t i o n t h a t a m ore l i m i t e d p o o l o f
ite m s m akes r e c a l l e a s i e r w as p e rfo rm e d by C ra n n e l and
P a r r i s h (1 9 5 7 )* They t e s t e d th e im m e d ia te memory s p a n f o r
n in e d i g i t s ; p r e - s e l e c t e d g ro u p s o f n in e l e t t e r s and n in e
r e a l w o rd s; a n u n l im i te d p o o l o f a l l 26 l e t t e r s ; and a
la r g e num ber o f r e a l w o rd s . T h i r t y - s i x d i f f e r e n t l i s t s *
f o u r e a c h c o n ta in i n g fro m f o u r th r o u g h tw e lv e u n i t s * w ere
p r e p a r e d f o r e a c h d i f f e r e n t g ro u p o f s t i m u l i * The l e t t e r s
w ere th o s e fro m "A* th ro u g h * 1 ,* and w ords w ere a l l t h r e e
l e t t e r s i n l e n g t h . The s t i m u l i w ere p r e s e n t e d by m eans o f
a ta p e r e c o r d e r a t th e r a t e o f one p e r se co n d *
F a i l u r e c o n s i s t e d o f I n c o r r e c t r e c a l l o f th e
107
s t i m u l i i n t h e s e q u e n c e h e a r d f o r any f o u r c o n s e c u tiv e
l i s t s * When one ty p e o f m a t e r i a l w as f a i l e d , th e s u b j e c t
a d v an c ed t o t h e n e x t ty p e o f m a t e r i a l * The o r d e r o f th e
m a t e r i a l was c o u n te r b a la n c e d *
The sp a n f o r d i g i t s h a d th e h i g h e s t p e r c e n ta g e o f
c o r r e c t r e c a l l s f o r e a c h l i s t l e n g t h w h ile b o th l i m i t e d
and u n lim ite d w o rd s h ad t h e lo w e s t v a lu e * The l i m i t i n g
o f th e p o o l o f ite m s d id n o t seem to h a v e any in f lu e n c e *
T h u s , t h e h y p o th e s is t h a t th e d i f f e r e n c e s i n memory sp a n
f o r d i f f e r e n t m a t e r i a l s a r e b r o u g h t a b o u t by th e d i f f e r
e n ce i n th e num ber o f ite m s fro m w h ich th e s u b j e o t h a d t o
s e l e c t was n o t s u p p o rte d *
A n d e rso n and R o ss (1 9 5 5 ) p r e s e n t e d a $ x m a t r ix
w ith e a c h o e l l c o n t a i n i n g , o n d i f f e r e n t t r i a l s , e i t h e r
w o rd s, l e t t e r s , n u m b e rs, o r sy m b o ls i n o r d e r t o t e s t t h e
h y p o th e s is t h a t t h e r e i s a r e l e v a n t l y i n v a r i a n t r e l a t i o n
s h ip b e tw e e n t h e s p a t i a l l o c a t i o n o f th e s t i m u l i and e a s e
o f le a r n in g * T h a t i s , w ith th e s t i m u l i p r e s e n t e d s im u l
t a n e o u s ly i n th e m a t r i x , a r e t h e r e any f a v o r e d l o c a t i o n s ?
The t w o - d i g i t num bers w ere ra n d o m ly s e l e c t e d , th e
g e o m e tric f i g u r e s p r e t e s t e d f o r d i s c r i m i n a t i o n , w ords
m atch e d f o r T h o rn d llc e -L o rg e c o u n t, and th e sym bols w ere
s e l e c t e d fro m th o s e i n t h e W e o h s le r-B e lle v u e t e s t * F iv e
fo rm s o f e a c h ty p e o f m a t e r i a l w ere c o n s t r u c t e d by random
a s s ig n m e n t o f th e ite m s t o th e 2£ c e l l s * No ite m a p p e a re d
1 0 8
I n th e sam e c e l l o n any two f o rm s . The s u b j e c t s lo o k e d
a t th e fo rm f o r one m in u te , t h e n tu r n e d I t o v e r and th e
5 x 5 r e s p o n s e fo rm on th e b a c k w as f i l l e d I n . One m in u te
was a llo w e d t o o a m p le te t h e form * T h e re w ere f i v e o n e -
h o u r s e s s io n s f o r e a c h o f f i v e s u b j e c t s * D u rin g e a c h
s e s s i o n e a c h s u b j e c t w as g iv e n f i v e t r i a l s w ith one form
o f e a c h ty p e o f m a t e r i a l* A L a t i n S q u a re d e s ig n was u s e d .
The r a n k in g s f o r t h e t o t a l num ber o f c o r r e c t r e -
sp o n s e s was a s f o l l o w s : l e t t e r s , sy m b o ls, w o rd s , num bers*
and g e o m e tr ic f i g u r e s * A l l o f th e m a t e r i a l s b u t th e sym
b o ls show ed a s te a d y ro w -b y -ro w d e c r e a s e I n th e o o r r e c t
r e s p o n s e s th r o u g h th e f o u r t h row* The f i f t h row was a t
l e a s t e q u a l t o th e f o u r t h row and p e rh a p s s l i g h t l y s u p e
r i o r * The r e s u l t s f o r t h e sy m b o ls f o llo w e d a d i f f e r e n t
p a t t e r n w ith th e f i r s t tw o colum ns sh o w in g th e b e s t p e r
fo rm a n c e , w ith a m arked d e o re m e n t I n th e c e n t e r o f th e
m a tr ix *
The a u th o r s c o n c lu d e d t h a t t h e r e a r e some f a i r l y
c o n s t a n t r e l a t i o n s h i p s b e tw e e n l e a r n i n g and s p a t i a l l o c a
tio n * Row o r d e r , colum n o r d e r and th e num ber o f a d ja c e n t
c e l l s a l l seem t o b e r e l a t e d t o th e s u b j e c t s 1 r e s p o n s e *
An e x t e n s i o n o f t h i s s tu d y w as p e rfo rm e d by A s t l n
and R o ss ( 1 9 5 6 ) . The same e x p e r im e n ta l s t i m u l i w ere u s e d
b u t a f i v e m in u te d e la y f i l l e d w i t h u n r e l a t e d r e a d i n g w as
i n s e r t e d b e f o r e th e l a s t l e a r n i n g t r i a l * The e x p e r l -
109
m e n te rs r e c o r d e d t h e te m p o ra l o r d e r i n g o f th e a n s w e ra .
E v e ry c e l l w as g iv e n a n a c c u ra c y r a n k o n th e b a s i s
o f th e t o t a l num ber o f c o r r e c t r e s p o n s e s I n t h a t c e l l on
a l l t r i a l s * T em p o ral o r d e r r a n k s w ere a ls o a s s ig n e d o n
th e b a s i s o f t h e m ean te m p o ra l r e s p o n s e num ber* The ra n k
o r d e r c o r r e l a t i o n b e tw e e n th e t o t a l num ber c o r r e c t and th e
m ean te m p o ra l r e s p o n s e w as 0*90* T h e re was no s i g n i f i c a n t
d i f f e r e n c e b e tw e e n th e f i f t h and s i x t h t r i a l s * I n f a c t ,
th e s i x t h w as s l i g h t l y b e t t e r *
C o n rad (1 9 6 2 a ) d e s ig n e d a n e x p e rim e n t t o a n sw e r th e
q u e s t i o n o f w here f i g u r e s s h o u ld o c c u r i n coded m a t e r i a l
c o n s i s t i n g o f f o u r l e t t e r s and two d i g i t s * F i f t y s e
q u e n c e s w ere d e v is e d b y s e l e o t i n g f o u r l e t t e r s a t a tim e
fro m a c o n t i n u a l l y s h u f f l e d p a c k o f l e t t e r s and b y u s in g
a t a b l e o f random num bers t o d e te rm in e t h e d i g i t s * The
d i g l t - p a l r s w ere a l l o c a t e d to g ro u p s o f l e t t e r s t o make
up f i v e e a c h o f f i v e d i f f e r e n t ty p e s o f se q u e n c e s * The
d i g i t s w ere e i t h e r f i r s t o r p re c e d e d by o n e , tw o , t h r e e
o r f o u r l e t t e r s , b u t w ere a lw a y s p r e s e n te d a s a p a ir *
T h ese s e q u e n c e s w ere ta p e r e c o r d e d and p r e s e n t e d a t a
r a t e o f 100 c h a r a c t e r s p e r m in u te * S u b j e c t s l i s t e n e d t o
e a o h se q u e n c e and im m e d ia te ly w ro te down w hat th e y th o u g h t
i t was* O ld e r men r e o a l l e d a p p ro x im a te ly o n e - h a l f o f th e
s e q u e n c e s c o r r e c t l y b u t y o u n g e r men fo u n d th e t a s k to o
e a sy * Two new g ro u p s o f s u b j e o t s w ere r e q u i r e d t o p r e f i x
1 1 0
t h e i r a n sw e rs w i t h t h e l e t t e r *&•*
T h is m o d i f i c a t i o n r e s u l t e d I n a s i g n i f i c a n t d i f
f e r e n c e b e tw e e n t h e se q u e n c e w h ic h h a d o n ly one l e t t e r
f o llo w in g th e d i g i t s and a l l o f t h e o t h e r se q u e n c e s *
i
F i f t y - o n e p e r c e n t w ere c o r r e c t l y r e c a l l e d f o r t h i s g ro u p
w h ile o n ly I4.3 p a r c e n t w ere c o r r e o t f o r t h e n e x t b e s t s e - f
q u o n o e . I n e v e r y s e r i a l p o s i t i o n b u t o n e , th e f i g u r e s
w ere e a s i e r t o r e c a l l t h a n th e num bers* The a u th o r a t
t r i b u t e d th e r e s u l t s t o t h e e f f e c t s o f i s o l a t i o n c o u n te r
a c t i n g t h e s e r i a l o r d e r e f f e c t s *
I n a n o th e r a r t i c l e C onrad ( 1962b) n o te d t h a t th e
D ecay T h e o ry o f im m e d ia te memory dem ands t h e e x ls te n o e o f
p a r t i a l l y d e c a y e d memory t r a c e s h a v in g a s y s te m a tic r e l a
t i o n s h i p t o t h e o r i g i n a l t r a c e s * To t e s t t h i s h e v i s u a l l y
p r e s e n t e d s i x - l e t t e r s e q u e n c e s f o r im m e d ia te r e c a l l t o
387 s u b j e c t s * C e r t a i n s y s te m a tic s u b s t i t u t i o n s o c c u rr e d
when t h e l e t t e r s w ere i n c o r r e c t l y r e c a l l e d *
I n a s s o c i a t e d s tu d y ex am in ed th e c o n f u s io n s r e
p o r t e d when t h e sam e v o c a b u la r y o f l e t t e r s was u s e d i n a n
a u d it o r y i n t e l l i g i b i l i t y t e s t w ith a w h ite n o is e b a c k
g ro u n d * A h i g h l y s i g n i f i c a n t c o r r e l a t i o n w as fo u n d b e
tw e en t h e l e t t e r s c o n fu s e d i n t h i s s tu d y and th o s e p r e
s e n te d i n th e v i s u a l s e q u e n c e s f o r im m e d ia te r e c a l l *
B ro a d b e n t ( 19& 2 ) n o te d t h i s s i m i l a r i t y and s t a t e s
t h a t one e x p l a n a t i o n m ig h t b e t h a t th e s u b j e c t r e p e a t s
Ill
th e l e t t e r s w h ic h h e s e e s en d i s , i n f a c t , rem e m b e rin g
t h i s i n t e r n a l p r o c e s s r a t h e r th a n th e o r i g i n a l s i g h t o f
th e l e t t e r s * T h u s, th e r e a c t i o n w h ic h i s made t o t h e
in f o r m a ti o n may b e j u s t a s im p o r ta n t as th e way th e ite m s
a re p r e s e n t e d i n d e c id in g w h at w i l l be a v a i l a b l e f o r
s to r a g e *
A n d e rso n and F i t t s (1 9 5 8 ) r e a s o n e d t h a t s i n c e a
s u b j e c t 's a b i l i t y t o i d e n t i f y s t i m u l i o n a n a b s o lu te b a s i s
i s l i m i t e d , t h e maximum num ber o f s tim u lu s c a t e g o r i e s t h a t
c a n b e u s e d w hen ite m s a r e v a r i e d a lo n g a s i n g l e d im e n sio n
i s s m a ll* The m o st f e a s i b l e m eans o f i n c r e a s i n g th e s i s e
o f a c o d in g a lp h a b e t i s t o I n c r e a s e th e d i m e n s i o n a l i t y o f
th e s tim u lu s *
T hey t e s t e d t h i s h y p o th e s is by v a r y i n g t h e l e v e l s
o f s tim u lu s c o m p le x ity * They p r e s e n te d g ro u p s o f n in e
c o lo r p a t c h e s , n in e b la c k n u m e r a ls , o r b la c k n u m e ra ls on
a c o lo r e d b a c k g ro u n d t a o h i s t o s c o p l c a l l y f o r 0*10 se c o n d s*
The am ount o f i n f o r m a tio n t r a n s m i t t e d ( i n b i t s ) w as d e t e r
m in ed f o r th e d i f f e r e n t s t i m u l i * I t was fo u n d t h a t i n
f o r m a tio n I n c r e a s e d w ith c o m p le x ity b u t n o t a s much as
m ig h t b e e x p e c te d * T h a t i s , t h e d im e n sio n s d id n o t co n
fo rm t o an a d d i t i v e r e l a t i o n s h i p * The d a t a a l s o s u g
g e s te d t h a t t h e am ount o f i n f o r m a tio n t r a n s m i t t e d f o llo w s
a n i n v e r t e d N < U" f u n c t i o n w ith l i s t le n g th * A l i s t l e n g t h
o f f o u r c o l o r s was b e t t e r th a n s i x , f o r ex am p le* The
1 1 2
com plex s t i m u l i h a d n o t r e a c h e d a p e a k u n d e r th e c o n d i
t i o n s u s e d i n t h i s e x p e rim e n t*
S e r i e s o f t a p e r e c o r d e d s e n te n c e s w e re p r e s e n t e d
t o v a r i o u s g ro u p s o f l i s t e n e r s by L a d e fo g e d and B ro a d b e n t !
(I9 6 0 )* D u rin g e a o h s e n te n c e a n e x tr a n e o u s so u n d was
p r e s e n t on t h e r e c o r d i n g and s u b j e c t s w ere t o i n d i c a t e
th e e x a c t p o i n t i n th e s e n te n c e a t w h ic h t h i s so u n d o c
c u r r e d . I t w as fo u n d t h a t e r r o r s w ere made w h ic h w ere
l a r g e com pared w ith t h e d u r a t i o n o f a s i n g l e s p e e c h sound*
The a u th o r s s u g g e s t t h a t t h i s i n d i c a t e s s u b j e o t s do n o t
d e a l w ith e a c h so u n d s e p a r a t e l y , b u t w ith a g ro u p o f
s o u n d s . The e r r o r s w ere re d u c e d i f d i g i t s w ere u s e d
i n s t e a d o f w o rd s o r i f t h e s u b j e o t s w ere t r a i n e d i n
p h o n e t i c s . The p o s s i b i l i t y o f r e g a r d i n g t h e r e s u l t s as
a n e x te n s i o n o f T i t o h e n e r 's "Law o f P r i o r E n tr y " w h io h
s t a t e s t h a t " t h e s tim u lu s f o r w h ic h we a r e p r e d is p o s e d
r e q u i r e s l e s s tim e t h a n a l i k e s t i m u l u s , f o r w h ic h we a r e
u n p r e p a r e d , t o p ro d u c e i t s f u l l c o n s c io u s e f f e c t , " was
o f f e r e d by th e a u th o rs *
Sensory Mode o f P resen ta tio n
Broadbent (195lf) in it ia t e d a s e r ie s o f experim ents
which have had s ig n if ic a n t im p lic a tio n s fo r th eory in
sh ort-term memory. He used a d u a l-tra ck tape record er
and s p l i t earphones to p resen t two d iffe r e n t 3 - d lg it
113
s e r i e s s im u lta n e o u s ly t o t h e d i f f e r e n t e a r s o f h i s su b
j e c t s * F o r e x a m p le , th e s e r i e s *7» 3> k* m ig h t a r r i v e a t
th e l e f t e a r w h ile " 2 , 1 , w as a r r i v i n g a t t h e r i g f r t
e a r* T h u s, * 7 " and "2 * a r r i v e d a t d i f f e r e n t e a r s a t th e
sam e tim e and so on* T h is ty p e o f t a s k h a s b e e n te rm e d
" d i c h o t i c l i s t e n i n g " b y M oray (19f> 9). One g ro u p w as i n
s t r u c t e d t o w r i t e down t h e d i g i t s i n a n y o r d e r w h ile
a n o th e r w as t o l d t o w r i t e th em down a s t h e y a r r i v e d , i * e * ,
7* 2 , 3 , 1 , if, 5* T he f r e e i n s t r u c t i o n g ro u p t y p i c a l l y
w ro te down a l l t h e s t i m u l i fro m one e a r b e f o r e th o s e fro m
th e o th e r * The o t h e r g ro u p fo u n d i t e x tre m e ly d i f f i c u l t
t o r e c o r d th e d i g i t s i n t h e o r d e r o f a r r i v a l a t th e f a s t
sp e e d s b u t when t h e r a t e w as s lo w e d , t h i s t a s k becam e
p o s s ib le * .
B ro a d b e n t d e d u ce d fro m t h e s e r e s u l t s t h a t s p a t i a l l y
s e p a r a te d so u n d s may p a s s th r o u g h th e p e r c e p t u a l m echanism
s u c c e s s i v e l y r a t h e r t h a n s im u lta n e o u s ly * T h is s u g g e s ts
t h a t in f o r m a tio n fro m th e o t h e r e a r m u st b e s t o r e d
te m p o r a lly an d I s p e r c e iv e d a f t e r a p a s s a g e o f tim e * The
p r a c t i c a l i m p l i c a t i o n , i n w h ic h h e w as m o st i n t e r e s t e d a t
th e t im e , w as t h a t some d e g re e o f s p a t i a l s e p a r a t i o n i s
d e s i r a b l e w hen a n i n d i v i d u a l m u st d e a l w ith two o r m ore
c h a n n e ls , b u t i f r a p i d a l t e r n a t i o n b e tw e e n c h a n n e ls i s
r e q u i r e d , a s e p a r a t i o n may becom e a h in d ra n c e *
I n a n a r t i c l e p u b lis h e d i n 195&, h o w e v e r, B ro a d b e n t
lib
p r e s e n te d more t h e o r e t i c a l l y o r i e n t e d e x p e rim e n ts * He
n o te d t h a t th e e x t e n t t o w h ic h m ore th a n one p r o o e s s c a n
go on s im u lta n e o u s ly w i t h i n t h e n e rv o u s sy ste m i s im
p o r t a n t f o r a t h e o r y s u c h a s H e b b 's* w h ic h h o ld s t h a t
d i f f e r e n t s t i m u l i a c t i v a t e p h y s i c a l l y d i f f e r e n t e le m e n ts
i n th e b r a i n and m ore th a n one* t h e r e f o r e * m ig h t b e a c t i v e
s im u lta n e o u s ly * On th e o t h e r hand* a "m ass a c t io n " ty p e
o f th e o r y m ig h t h o ld t h a t th e w hole c o r t e x i s in v o lv e d i n
re s p o n s e t o one s tim u lu s and so c a n n o t s im u lta n e o u s ly
p r o c e s s tw o s tim u li*
I n th e f i r s t e x p e rim e n t h e u s e d a m ethod s i m i l a r
to t h e e a r l i e r s tu d y b u t p r e s e n t e d d i g i t s s im u lta n e o u s ly
t o b o th t h e e y e s and e a r s * T h ree d i g i t s w ere p r e s e n te d
on a ta p e r e c o r d e r w h ile a n o th e r t h r e e w e re s e e n th ro u g h
a s l o t o v e r a m oving b e l t * The r e s u l t s i n d i c a t e d t h a t
th e e y e and e a r c a n r e c e i v e d i f f e r e n t s t i m u l i s im u lta n e
o u s ly b u t a g a in t h e r e s p o n s e f o llo w e d th e o r i g i n a l p a t
te r n * th e t h r e e d i g i t s fro m one s e n s e b e in g r e p o r t e d b e
f o r e t h e t h r e e d is p la y e d t o t h e o t h e r s e n se * T h e re was
no te n d e n c y * how ever* f o r e i t h e r s e n s e t o be th e one u n i
v e r s a l l y d e la y e d *
A se c o n d e x p e rim e n t u s e d f i l t e r e d v o ic e s p r e s e n t e d
s im u lta n e o u s ly o v e r t h e same lo u d s p e a k e r* W ith n a iv e
s u b j e c t s and tw o v o ic e s s h a r p ly d i s t i n g u i s h e d by th e
f i l t e r * one b e in g p r e s e n t e d i n a h ig h f r e q u e n c y and th e
115
seco n d i n a lo w , th e phenomenon a g a in occu rred *
T h ese r e s u l t s ad d g e n e r a l i t y to t h e o r i g i n a l f i n d
in g * I t was c o n o lu d e d t h a t a te m p o ra ry s t o r a g e o f i n f o r
m a tio n i s p o s s i b l e w ith a num ber o f d i f f e r e n t s e n s e s *
k f a i r l y s o p h is t ic a t e d th e o r y em erged w ith B road-
bent* s n e x t p ap er (1 9 5 7 )* He s t a t e s t h a t th e f a c t t h a t
s t im u li from one se n s e w i l l appear i n r e sp o n s e b e fo r e
th o s e from a n o th er s e n s e im p lie s some m echanism w it h in
th e s u b j e c t w h ich ca n p a s s In fo r m a tio n o n ly s u c c e s s iv e ly *
There m ust a ls o be a n o th er s to r a g e m echanism w h ich can
s im u lta n e o u s ly c o n t a in in fo r m a tio n from two c h a n n e ls and
th a t t h i s l o g i c a l l y l i e s on th e s e n s e s id e o f th e p e r c e p
t u a l m echanism * He assum es t h a t t h i s sy stem i s th e same
one t h a t o p e r a te s i n th e norm al Im m ediate memory e x p e r i
m ents*
H is f i r s t e x p e rim e n t a sk e d t h e q u e s t io n o f w h e th e r
t h i s s t o r a g e sy s te m i s o p e r a t i v e i n n o rm al Im m ed iate
memory o r w h e th e r i t i s a n em erg en cy d e v ic e o p e r a t i v e
o n ly i n " o v e r lo a d * o r s im u lta n e o u s s i t u a t i o n s . He m a in
t a i n e d t h a t i f t h e s y s te m i s m e re ly a s ta g e i n th e n o rm a l
p r o c e s s in g o f i n f o r m a t i o n , i t s h o u ld be p o s s i b l e t o p r e
s c r i b e a n o r d e r o f r e c a l l a t any tim e b e f o r e r e c a l l , e v e n
a f t e r s t i m u l a t i o n w ith o u t i n f l u e n c i n g t h e r e s u l t s * I f ,
h o w e v e r, t h i s s t o r a g e s y s te m i s an " o v e r lo a d " m ech an ism ,
th e n one o r t h e o t h e r c h a n n e l w o u ld d e l i v e r in f o r m a tio n
1 1 6
im m e d ia te ly u p o n s tim u la tio n * An l n e t r u o t l o n to r e c a l l
i n a p a r t i c u l a r o r d e r a r r i v i n g a f t e r s t i m u l a t i o n w ould
n o t i n f l u e n c e p r o c e s s in g b u t o n ly o u t p u t , and th e d i f f e r
e n c e b e tw e e n th e o r d e r s w ould n o t r e s u l t i n a s e r i a l
o r d e r e f f e c t *
Two g ro u p s o f s u b j e c t s w e re p r e s e n t e d w ith a 4 1 -
c h o t l c l i s t e n i n g ta s k * One g ro u p knew i n ad v an ce w h e th e r
th e d i g i t s p r e s e n t e d to t h e l e f t o r r i g h t e a r w ere t o be
r e p o r t e d f i r s t . The se c o n d g ro u p d id n * t know u n t i l a f t e r
t h e s t i m u l i h ad b e e n p r e s e n t e d . On th e f i r s t d ay b o th
c o n d it i o n s g a v e a te n d e n c y t o r e c o r d t h e e a r i n d i c a t e d by
t h e e x p e r im e n te r m ore a c c u r a t e l y . On th e se c o n d d a y ,
h o w e v e r, t h e g ro u p w h ich r e c e i v e d th e i n s t r u c t i o n b e f o r e
th e s t i m u l i s t i l l show ed a p r e f e r e n c e f o r th e i n d i c a t e d
e a r w h ile t h e p o s t - s t i m u l u s g ro u p d id n o t* The a u th o r
c o n c lu d e s t h a t th e c e n t r a l n e rv o u s sy s te m i s c a p a b le o f
p r o c e s s in g i n f o r m a tio n i n b o th w a y s. The s u b j e c t s who
r e c e i v e d t h e I n s t r u c t i o n a f t e r s t i m u l a t i o n ch an g ed
s t r a t e g i e s b e c a u se a g r e a t e r t o t a l num ber o f c o r r e c t r e
sp o n s e s c o u ld b e a c h ie v e d by p a s s i n g one s e t o f d i g i t s
th ro u g h t h e sy ste m f i r s t * On th e f i r s t d ay th e p r e
i n s t r u c t i o n g ro u p g a v e s u p e r i o r o v e r a l l p e rfo rm a n c e * On
th e seco n d d ay th e g ro u p s w ere a b o u t e q u a l i n e f f i c i e n c y *
T h is m eans t h a t th e s t r a t e g y o f h o ld in g a l l i n f o r m a tio n
i n t h i s s h o r t - t e r m s t o r a g e s y s te m p r o b a b ly i s n o t th e one
117
used in ty p ic a l Immediate memory exp erim en ts, s in c e , a l
though i t i s p o s s ib le to do s o , i t i s le s s e f f i o i e n t .
A second experim ent used b in au ral stim u la tio n but
varied the d ela y before th e d ig it s from th e second ear
could be reported* This was accom plished by p resen tin g
s ix d ig it s to th e f i r s t ear w ith th e two d ig it s p resen ted
to th e oth er ear occurring e ith e r e a r ly or la te in th e
f i r s t s e r ie s . Under a l l c o n d itio n s, the su b je c t was to
w r ite down the s ix d ig it s p resen ted to th e f i r s t e a r , and
then the oth er two d i g i t s . Two r a te s o f p r e s e n ta tio n ,
o n e -d ig it or tw o -d ig its per second, were used in order to
d is tin g u is h la p se o f tim e from in te r p o la te d a c t iv it y .
Storage tended to become in e f f i c ie n t i f th e two
d ig it s had to be stored fo r the longer tim e s, a t le a s t
fo r th e f a s t - r a t e c o n d itio n . When m a teria l was p resen ted
at the slow r a t e , however, performance when the two d ig it s
were p resen ted e a r ly a c tu a lly im proved.
Broadbent (1958) has w r itte n a book e la b o r a tin g on
h is theory o f short-term memory but which goes fa r beyond
the scope o f t h is stu d y . I t i s h ig h ly recommended as
b ein g w e ll worth read in g fo r anyone In te r e ste d in the
gen eral problems o f in form ation p ro cessin g in humans.
Not everyone agrees w ith a l l o f Broadbent*s in t e r
p r e ta tio n s . Moray ( i 9 6 0 ) argued th a t Broadbent*s o r ig in a l
experim ent was not a f a ir t e s t o f a s u b je c t’ s a b ilit y to
1 1 8
s w itc h b e tw e e n s i g n a l s . He c la im e d t h a t w hat a s u b j e c t
w as r e q u i r e d t o do w as s w itc h fro m a s i g n a l h e h e a r d and
th e t r a c e o f t h e o t h e r , n o t th e se c o n d s i g n a l i t s e l f . A
m ore g e n u in e m ea su re m e n t o f a s u b j e c t 's p e rfo rm a n c e i n a
s w itc h in g t a s k , a c c o r d in g t o h im , w ould o o e u r i f t h e s i g
n a l s came n o t i n s im u lta n e o u s p a i r s , b u t s ta g g e r e d so th e y
n ew er a c t u a l l y o v e rla p p e d *
M oray p r e s e n t e d l i s t s o f s i x d i g i t s t o s u b j e c t s i n
g ro u p s o f 10 l i s t s . T h ere w as a 1 0 -se c o n d p a u s e b e tw e e n
e a c h g ro u p o f s i x d i g i t s d u r in g w h ic h th e s u b j e c t r e c a l l e d
th e ite m s J u s t p r e s e n t e d . A ta p e r e c o r d e r was u s e d and
s u b j e c t s w e re a sk e d t o r e o a l l a l l th e d i g i t s fro m one e a r
f o llo w e d b y t h e o t h e r ; i n any o r d e r t h a t th e y w is h e d ; o r
a l t e r n a t i n g fro m e a r t o e a r . The d l c h o t i c c o n d i t i o n s w ere
p r e s e n t e d e i t h e r s im u lta n e o u s ly , s t a g g e r e d , o r w i t h o v e r
l a p p i n g .
The r e s u l t s f o r th e s u c c e s s iv e and a l t e r n a t e r e c a l l
f o r s im u lta n e o u s d i g i t s s u p p o r te d t h e r e s u l t s o f B ro a d
b e n t . No s i g n i f i c a n t d i f f e r e n c e was o b t a i n e d , h o w e v e r,
w hen t h e d i g i t s w ere s t a g g e r e d . T h a t i s , i f s i g n a l s do
n o t o v e r l a p , th e y c a n be r e c a l l e d p e r f e c t l y w e l l b y a l t e r
n a tin g * T h e re w ere no d i f f e r e n c e s b e tw e e n s ta g g e r e d and
s im u lta n e o u s c o n d it i o n s u n d e r th e s u c c e s s iv e r e c a l l s i t u a
t i o n so th e s ta g g e r e d w ere p r o b a b ly n o t e a s i e r t o p e r
c e i v e .
^ 119
Moray o f f e r s an a l t e r n a t i v e t o B ro a d b e n t* s th e o ry *
He s u g g e s ts t h a t w hen s i g n a l s o v e r la p t h e tw o s e t s a r e
p r o c e s s e d s im u lta n e o u s ly b u t a r e s t o r e d I n s e p a r a t e
r e g i s t e r s a c c o r d in g t o t h e s o u r c e fro m w h ic h th e y came*
D u rin g r e c a l l th e y a re p ro d u c e d r e g i s t e r by r e g i s t e r *
A . se c o n d e x p e rim e n t b y M oray s t u d i e d th e e f f e c t o f
r a t e o f p r e s e n t a t i o n on s u c c e s s iv e r e c a l l f o l lo w in g s im u l
ta n e o u s p r e s e n t a t i o n * T h ree sp e e d s* two p a i r s p e r seco n d *
one p a i r p e r seco n d * and one p a i r e v e r y tw o se c o n d s* w ere
u se d * T en s u b j e c t s p a r t i c i p a t e d * h a l f o f w h ic h p r o g r e s s e d
fro m t h e slow s p e e d to t h e f a s t * and t h e o t h e r s f o llo w in g
th e r e v e r s e d p ro c e d u re * B ro a d b e n t h y p o th e s is e d a t r a c e
l a s t i n g a b o u t one se c o n d (1 9 5 8 )* I f t r u e * th e n d i g i t s
s t o r e d f o r lo n g e r th a n a se c o n d w ould te n d t o fa d e * The
r e s u l t s f o r th e f a s t e s t r a t e s I n t h i s e x p e rim e n t show a
t r e n d I n th e o p p o s ite d i r e c t i o n * T he m id d le o f th e
''s t o r e d * d i g i t s a c t u a l l y show ed t h e l a r g e s t num ber o f
e r r o r s * The t o t a l num ber o f e r r o r s a ls o was to o low*
a c c o rd in g t o th e a u th o r* t o s a t i s f y B ro a d b e n t* s th e o ry *
T r a n s p o s i ti o n e r r o r s b e tw e e n th e tw o e a r s m ade up
a b o u t t h r e e - f o u r t h s o f t h e num ber due t o a l l o t h e r c a u s e s *
I t I s d i f f i c u l t t o a c c o u n t f o r t h e s e o n th e b a s i s o f
B ro a d b e n t* s th e o ry * a t l e a s t f o r M oray*
M oray*s p o i n t I s t h a t B ro a d b e n t* s m odel (1 9 5 8 ) i s
w rong I n r e g a r d t o s w itc h in g t im e . B a s i c a l l y h e f a v o r s
1 2 0
th e th e o r y b u t m a in ta in s t h a t e i t h e r s w it c h in g tim e i s
much l e s s th a n B ro a d b en t s u g g e s t s o r d o e s n 1t o c c u r i n
t h i s t y p e o f s i t u a t i o n . B ro a d b en t and G reg o ry ( 1 9 6 1 ) d e
s ig n e d some e x p e r im e n ts in te n d e d t o exam in e t h e s e p o s s i
b i l i t i e s *
T h e ir f i r s t e x p e r im e n t a tte m p te d t o d e te r m in e w hy,
i f s w it c h in g tim e i s e x t r e m e ly s h o r t , e a r - b y - e a r r e c a l l i s
s u p e r i o r . Moray s u g g e s t e d t h a t s im u lt a n e o u s ly p r e s e n t e d
d i g i t s te n d e d t o i n t e r f e r e w it h ea c h o t h e r and t o a v o id
t h i s a re p a s s e d on t o s e p a r a t e s t o r e s a s s o o n a s t h e y
a r r i v e . R e c a l l i s t h e n s t o r e by s t o r e . When d i g i t s w ere
p r e s e n t e d i n r a p id a l t e r n a t i o n t h e i n t e r f e r e n c e w as
e lim in a t e d and a l l in fo r m a t io n e n t e r s one s t o r e , and
t h e r e f o r e c a n be r e p r o d u c e d i n th e a c t u a l o r d e r o f a r r iv a l *
S u ch a th e o r y p la c e s g r e a t em p h a sis on t h e s t r a t e g y o f th e
l i s t e n e r and a c c o r d in g t o t h e p r e s e n t a u t h o r s , i t w ou ld
f o llo w t h a t i f a str e a m o f d i g i t s w ere p r e s e n t e d a l t e r
n a t e l y t o e i t h e r e a r , and th e o r d e r o f r e c a l l w as n o t
know n, t h e l i s t e n e r w ould b e i n a q u a n d a ry .
T w enty l i s t s o f s i x d i g i t s w ere p r e s e n t e d t o su b
j e c t s . A lt e r n a t e d i g i t s w ere p r e s e n t e d t o d i f f e r e n t e a r s
i n a s t a g g e r e d s e q u e n c e . One d i g i t w as p r e s e n t e d t o e a c h
e a r e v e r y se c o n d ( 0 . 5 s e c o n d s p e r d i g i t ) . E ach s u b j e c t
r e c e iv e d tw o I n s t r u c t i o n s on e a c h l i s t , t h e f i r s t s p e c i f y
in g th e s i d e o f t h e p a p er t h a t th e answ er was t o b e p la c e d
o n , an d t h e o t h e r w h e th e r t h e d i g i t s w e re t o h e r e c a l l e d
i n t h e o r d e r o f a r r i v a l o r e a r - b y - e a r • o n e c o n d i t i o n
g a v e t h e I n s t r u c t i o n p e r t a i n i n g t o o r d e r o f r e c a l l b e f o r e
t h e s t i m u l i w e re p r e s e n t e d an d t h e o n e a b o u t w h e re a n s w e r s
w e re t o b e r e c o r d e d a f t e r t h e s t i m u l i * T he o t h e r c o n d i
t i o n r e v e r s e d t h e o r d e r o f t h e i n s t r u c t i o n s *
T he r e s u l t s i n d i c a t e d t h a t r e c a l l i n t h e a l t e r
n a t i n g o r d e r w as n o m o re d i f f i c u l t t h a n e a r - b y - e a r * T h u s ,
t h e s p e c i a l s t r a t e g y d o e s n 't se e m t o e n t e r *
E x p e r im e n t IX t e s t e d t h e sam e h y p o t h e s i s i n a
s i t u a t i o n i n v o l v i n g a l t e r n a t i o n b e tw e e n e a r s a n d e y e s *
T h r e e d i g i t s w e re p r e s e n t e d b y t a p e r e c o r d e r . A p a p e r
s c r e e n w as f i x e d t o t h e r e c o r d e r s o t h a t t h e t a p e p a s s i n g
fro m t h e p l a y b a c k h e a d t o t h e r e c e i v i n g s p o o l w as v i s i b l e
f o r a b o u t 1 * 7 5 i n c h e s ( o n e - h a l f s e c o n d ) * T he v i s u a l
d i g i t s w e re w r i t t e n o n t h e t a p e i n s u c h a way t h a t e a c h
b e ca m e v i s i b l e a f t e r t h e p r e v i o u s a u d i t o r y d i g i t h a d
f i n i s h e d s o u n d in g *
S u b j e c t s w e re a s k e d t o r e c o r d t h e i r a n s w e rs e i t h e r
i n t h e a c t u a l o r d e r o f a r r i v a l o r b y w r i t i n g t h e t h r e e
p r e s e n t e d a u r a l l y f o l l o w e d b y t h o s e p r e s e n t e d t o t h e e y e *
T he l a t t e r s i t u a t i o n w as m uch s u p e r i o r t o t h e f i r s t *
T h u s i t a p p e a r s t h a t a l t e r n a t i o n i s d i f f i c u l t b e tw e e n t h e
e a r an d e y e b u t p o s s i b l e b e tw e e n t h e tw o e a r s *
B r o a d b e n t an d G re g o ry t r y t o a n s w e r m o s t o f M o r a y 's
1 2 2
d i f f e r e n c e s i n t h e i r d i s c u s s i o n , M oray ( 1 9 6 1 ) , a lth o u g h
s t a t i n g t h a t h e w ould now a l i g n h i m s e l f m ore c l o s e l y w ith
B ro a d b e n t* s v ie w s , s t i l l m a in ta in s t h a t some o f t h e tim e s
f o r p r o c e s s in g I n f o r m a tio n a r e much l e s s th a n th o s e su g
g e s te d by B ro a d b e n t,
R a b b l t t (1 9 6 2 ) p r e s e n te d s u b j e c t s w ith a s e r i e s o f
l e t t e r s p r i n t e d I n one o f two d i f f e r e n t c o l o r s . S u b j e c t s
w ere th e n r e q u i r e d t o r e c a l l t h e s e l e t t e r s and t h e i r
c o lo r s in d e p e n d e n tly I n t h e i r o r d e r o f p r e s e n t a t i o n . The
e f f e c t s o f p r e - and p o s t - i n s t r u e t i o n a s t o th e o r d e r o f
r e c a l l p a r a l l e l th o s e o b ta in e d by B ro a d b e n t ( 1 9 5 7 ) , who
u s e d b l n a u r a l l y p r e s e n te d m a t e r i a l . T h u s , s o m e th in g
w h ic h seem s t o be a s i n g l e Ite m o f i n f o r m a ti o n may be
rem em bered s e l e c t i v e l y .
An e x p e rim e n t d e s ig n e d to i n v e s t i g a t e t h e s p e e d
and a c c u ra c y o f r e c a l l a s a f u n c t i o n o f (a) f i v e d i f f e r e n t
b i n o c u l a r v ie w in g c o n d i t i o n s ; (b ) r e h e a r s a l t i m e , and
( c ) th e e y e t o w h ic h th e in f o r m a ti o n i s p r e s e n t e d , was
p e rfo rm e d by Sam pson and Spong (1 9 6 l ) • T en r l g h t - e y e
d o m in a n t s u b j e c t s u s e d a b i n o c u l a r v ie w e r t o s e e m a t e r i a l
p r o j e c t e d on a s c r e e n . I n s i d e th e v ie w e r a se o o n d s c r e e n
p r e s e n te d f i x a t i o n p o i n t s . The s t i m u l i w ere d i g i t s *
T h ere w ere f o u r d i f f e r e n t ty p e s o f s l i d e s u s e d w ith d i g i t s
p la c e d b elo w th e f i x a t i o n p o i n t s i n d i f f e r e n t p a r t s o f t h e
v i s u a l f i e l d . E ach t r i a l c o n s i s t e d o f e i g h t d i g i t s p r e
123
s e n te d I n f o u r p a i r s , one d i g i t to e a c h eye* One ey e
m ig h t h a v e a d i g i t p r e s e n te d t o th e te m p o ra l s id e o f t h e
f i x a t i o n p o i n t w h ile th e o t h e r d i g i t was p r e s e n t e d
n a s a l l y , o r b o th m ig h t be p r e s e n te d o n th e same s id e * A
o o n t r o l c o n d i t i o n c o n s i s t e d o f no f i x a t i o n p o i n t and t h e
d i g i t s p la c e d i n th e c e n t e r o f th e r e s p e c t i v e f i e l d s * A
f i n a l r e d s l i d e w h ich o c c u r re d e i t h e r 0*8 o r 1*1 s e c o n d s
a f t e r th e l a s t d i g i t s s i g n i f i e d t h a t th e e i g h t num bers
w ere t o b e c a l l e d o u t i n any o rd e r* The d u r a t i o n o f e a c h
s tim u lu s p a i r w as 0*3 se c o n d s and th e i n t e r v a l b e tw e e n
s t i m u l i was 1*1 se c o n d s*
S i g n i f i c a n t l y m ore d i g i t s w ere r e o a l l e d b y th e
d o m in a n t ey e* A s i g n i f i c a n t I n t e r a c t i o n b e tw e e n v ie w in g
c o n d i t i o n and eye w as a ls o o b ta in e d * The d i f f e r e n c e i n
r e c a l l b e tw e e n e y e s was a lm o s t e n t i r e l y due to t h e c o n t r o l
c o n d i t i o n ; i . e . , w ith b i n o c u l a r f i x a t i o n t h e r e w as no
d i f f e r e n c e b e tw e e n t h e e y e s* D i g i t s t o th e l e f t (n o n
d o m in a n t) e y e w ere r e p o r t e d s i g n i f i c a n t l y slo w e r* D i g i t s
p r e s e n te d n a s a l l y w ere s i g n i f i c a n t l y b e t t e r r e c a l l e d *
U nder c e r t a i n c o n d i t i o n s , "w hen th e c e n t r a l m echan
ism w as t a x e d , ” a te m p o ra l g ro u p in g o f re s p o n s e o c c u r r e d
and t h i s p a i r i n g was i n t e r p r e t e d as r e p r e s e n t i n g th e
a c t i o n o f th e c e n t r a l m echanism * T h is s u g g e s ts t h a t
g r o u p in g d o e s n o t depend o n ly on th e s p a t i a l a rra n g e m e n t
o f th e s t i m u l i *
1 2 1 4 -
Im m ed iate Memory a s > J o i n t T ask
Brown and P o u lto n (1 9 6 l ) u s e d a s h o r t - t e r m memory
t a s k w h ic h s u b j e c t s w e re t o p e rfo rm when t h e y c o u ld w h ile
d r i v i n g a c a r t o m e a su re th e d e g re e t o w h ic h th e d r i v e r i s
a b s o rb e d u n d e r v a r y in g d r i v i n g c o n d i t i o n s . The s u b s i d i a r y
t a s k f o r t h e d r i v e r s w as a s f o l lo w s : A ta p e r e c o r d e r
d e l i v e r e d 8 - d l g i t m e s s a g e s , one g ro u p e v e r y f o u r s e c o n d s .
E ac h num ber g ro u p d i f f e r e d by o n ly one d i g i t fro m th e
p r e v io u s g ro u p . The new d i g i t s w ere ta k e n a t random f r a a
a t a b l e and t h e s e r i a l p o s i t i o n i n w h ic h th e new num ber
o o c u rre d was a l s o r a n d o m is e d . T he s u b j e c t was t o d e t e o t
e a c h new d i g i t and s p e a k i t i n t h e 2 -a e o o n d d e la y b e f o r e
th e n e x t g ro u p o f d i g i t s a r r i v e d .
The a u th o r s c o n c lu d e d t h a t t h i s te c h n iq u e seem s
s u i t a b l e f o r m e a s u rin g th e d e g re e o f a u t o m a t i s a t i o n , th e
r e l a t i v e d i f f i c u l t y o f t a s k s , and a s a m eans o f c o m p a rin g
s y s te m s . The t h e o r e t i c a l b a s i s f o r th e te c h n iq u e i s th e
a s s u m p tio n t h a t t h e r e l a a l i m i t t o th e r a t e a t w h ic h a n
o p e r a to r c a n d e a l w i t h i n f o r m a ti o n . I n o t h e r w o rd s , he
h a s a l i m i t e d " c h a n n e l c a p a c i t y . " When t h e dem ands o f th e
p rim a ry and s u b s i d i a r y t a s k s t o g e t h e r e x o e e d t h i s r a t e ,
e r r o r s m u st o c c u r . I f t h e dem ands o f th e s u b s i d i a r y t a s k
re m a in c o n s t a n t , th e e r r o r s m ust r e f l e c t f l u c t u a t i o n s i n
th e dem ands o f th e p rim a ry t a s k . I n th e t a s k u s e d h e r e ,
125
th e memory r e q u ir e m e n t d id n o t seem to a f f e e t p e rfo rm a n c e
o n th e p rim a ry ta s k * The d r i v e r s d id n o t d e c r e a s e sp eed *
e t c • * i n r e l a t i o n t o a c o n t r o l group*
Two a d d i t i o n a l m eth o d s I n v o lv in g s h o r t - t e r m memory
a a a s u b s i d i a r y t a s k w ere d e s c r ib e d by I* D . Brown (1 9 6 2 )* ;
I
The f i r s t method Involved lis t e n in g to a continuous s e r ie s j
o f random d ig its * The ta sk was to p ick out any th ree
s u c c e ssiv e d ig it s which occurred In the order "even* odd*
even*" The second method required the su b jec t to l i s t e n
to te n le tte r s * one occurrin g every f iv e seco n d s. E ig h t
le t t e r s In the s e r ie s were d iffe r e n t w h ile one was r e
p ea ted . The su b ject was to p ick out the l e t t e r which
occurred tw ice*
B ro a d b e n t and H e ro n (1 9 6 2 ) com bined t a s k s t o
m e a su re th e memory p e rfo rm a n c e d e c re m e n t. One g ro u p o f
s u b j e c t s w ere g iv e n s h e e t s o f p a p e r on w h ic h random 1 0 -
d i g l t s t r i n g s w ere ty p e d * one row b e n e a th a n o t h e r . A
s h e e t o f c a rd b o a rd w ith a s l o t was p la c e d o v e r th e p ag e s o
o n ly one 1 0 - d l g i t row c o u ld b e s e e n a t a tim e . S u b j e c t s
w ere t o s t a r t a t th e to p o f th e f i r s t row and w ork down
u n t i l a l l num bers h a d b e e n ex am in ed and p u t a p e n c i l l i n e
th ro u g h e v e ry d i g i t o f a p a r t i c u l a r ty p e ( e * g .* 2 )* A
se c o n d g ro u p u s e d th e same m a t e r i a l b u t a lth o u g h th e s u b
j e c t s t a r t e d c r o s s i n g o u t one num ber* he w ould p e r i o d i c a l
l y d is c o v e r some o t h e r num ber w h ich had a r e d c i r c l e
1 2 6
a ro u n d I t and w as th e n t o s t a r t c r o s s i n g o u t t h i s new
num ber I n s t e a d . S u b je c ts I n th e t h i r d g ro u p w ere t o l d t o
c r o s s o u t th e f i r s t • l * th e y oame t o , th e n th e f i r s t * 2 "
w h ie h f o llo w e d , e t c . When * 0 " w as r e a c h e d , s u b j e c t s w ere
t o s t a r t w ith nl N a g a i n .
A ta p e r e c o r d i n g i n w h ic h one l e t t e r o f t h e a lp h a
b e t o c c u r r e d e v e ry f i v e s e c o n d s s e rv e d to p r o v id e th e
s e c o n d , d i s t r a c t i n g t a s k . I n e v e ry t e n l e t t e r s , one o c
c u r r e d t w i c e . A f te r e a c h t e n l e t t e r s , a v o ic e a sk e d th e
s u b j e c t to w r i t e down th e l e t t e r t h a t h ad b e e n r e p e a t e d .
H a ls t a s k was o m itte d on h a l f o f th e t r i a l s .
I t w as d e te rm in e d t h a t c o n tin u o u s t a s k s w h ic h i n
v o lv e e v e n a s l i g h t memory lo a d a r e v e r y v u l n e r a b le to
d i s t r a c t i o n w hen com pared w ith s i m i l a r t a s k s w h ic h a v o id
t h i s l o a d . O ld e r p e o p le w ere fo u n d t o d i f f e r m a rk e d ly ,
some o f t h i s g ro u p b e in g s e r i o u s l y i n f e r i o r t o a y o u n g e r
g ro u p a lth o u g h no c o r r e s p o n d in g d i f f e r e n c e o c c u rs i n t a s k s
w ith o u t th e d i s t r a c t i o n . O ld e r p e o p le te n d e d t o do b a d ly
on one t a s k o r th e o t h e r w h ile y o u n g e r p e o p le te n d e d to do
r e a s o n a b ly w e ll a t b o t h . Some f e a t u r e s o f th e r e s u l t s
w ere r e p o r t e d to e m p h a siz e t h e im p o rta n c e o f i n t e r f e r e n c e
r a t h e r th a n d e c a y . R e h e a r s a l was o f f e r e d a s a p o s s i b l e
m eans o f r e d u c in g t h i s i n t e r f e r e n c e .
M is c e lla n e o u s E x p e rim e n ts o r A r t i c l e s
Games (1 9 6 2 ) g av e 100 s t u d e n t s a b a t t e r y o f t e s t s
127
t o I n v e s t i g a t e th e l o a d in g s o f a s e r i e s o f v e r b a l l e a r n i n g
t a s k s on t h e R o te Memory and Memory S pan f a c t o r s * The
m ethod o f p r e s e n t a t i o n , th e c o n s ta n c y o f o r d e r , and th e
ty p e o f t a s k w ere v a r i e d on d i f f e r e n t t e s t s u s i n g c o n s o
n a n t l e t t e r s a s s t i m u l i * The e f f e c t s o f p r a c t i c e o v e r
s i x t r i a l s on t h e f r e e r e c a l l mode o f r e s p o n s e w ere a l s o
i n v e s t i g a t e d * A s e t o f r e f e r e n c e f a c t o r s and a s e t o f
s p e c i f i c f a c t o r s w ere e x t r a c t e d by f a c t o r a n a ly s is *
O rth o g o n a l r o t a t i o n u s in g t h e c r i t e r i o n o f s im p le s t r u c
t u r e was u s e d *
B o th t h e R o te and M em ory-Span f a c t o r s w ere c l e a r l y
d e fin e d * The e x p e r im e n ta l v e r b a l l e a r n i n g t a s k s d is p la y e d
s u b s t a n t i a l lo a d in g s o n th e r o t e f a c t o r and n e g l i g i b l e o r
low lo a d in g s on th e S p a n f a c t o r * V a r i a t i o n s i n th e
m eth o d s o f p r e s e n t a t i o n ( a n t i c i p a t i o n o r p r o s e n t - r e c a l l )
and c o n s ta n c y o f o r d e r h a d no c o n s i s t e n t s y s te m a t i c e f f e c t
on th e lo a d in g s o f e i t h e r f a c t o r * The o n ly s u b s t a n t i a l
c h an g e o f f a c t o r i a l c o m p o s itio n a t t r i b u t a b l e t o p r a c t i c e
w as a s h i f t o f t h e r e p e a t e d S p an t e s t s fro m t h e S pan
f a c t o r t o t h e R o te f a c t o r *
Z a n g w ill (1 9 5 6 ) c i t e s a s tu d y b y G o m u llc k l, w h ic h
h e c la im s may th ro w new l i g h t on th e n a t u r e o f im m e d ia te
memory* I n G o m u lio k l's e x p e rim e n t n a r r a t i v e s v a r y in g i n
le n g t h b e tw e e n 15 and 200 w o rd s w ere r e a d a lo u d t o su b
j e c t s who w e re t o re p ro d u c e a s a c c u r a t e l y a s p o s s i b l e e a c h
1 2 8
m essa g e Im m e d ia te ly a f t e r i t h ad b e e n r e a d , R e p ro d u c tio n s
w ere r e c o r d e d v e rb a tim *
S t r i k i n g and c o n s i s t e n t c h a n g e s w ere o b s e rv e d i n
th e r e p r o d u c tio n s * O nly f i v e o f th e 5 0 s u b j e c t s r e p r o
d u ced a s p e c i f i c p a s s a g e v e rb a tim * The o t h e r s u b j e c t s
re p ro d u c e d o e r t a i n p a r t s e s s e n t i a l l y u n a l t e r e d w h e re a s
o t h e r p a r t s u n d e rw e n t s i g n i f i c a n t c h an g e s* The c h a n g e s
seem ed to be c l a s s i f i a b l e i n t o f o u r p r i n c i p l e t y p e s :
( a ) o m is s io n s , i n w h ich a w ord o r p h r a s e a t v a r i a n c e w ith
t h e l i s t e n e r ' s e x p e c t a t i o n s i s d ro p p e d o u t w ith o u t h i s
a w a re n e s s o f so m e th in g h a v in g b e e n f o r g o t t e n ; (b ) m in o r
a l t e r a t i o n s i n w ord o r d e r o r s y n ta x ; ( c ) s u b s t i t u t i o n s ; o r
(d ) d is p la c e m e n t* I n a l l c a s e s , " c o n v e n t i o n a l i s a t i o n *
o o c u rre d w h o lly w ith o u t th e know ledge o r I n t e n t i o n o f th e
s u b j e c t s *
The a u th o r c la im s t h a t th e s e c h a n g e s r e f l e c t a c t i v e
p r o c e s s e s o f th e r e o r g a n i s a t i o n o f p e r c e p t i o n and r e c a l l *
The o m is s io n s and in o r e a s e d b r e v i t y o f th e r e p r o d u c t io n s
a re d i f f i c u l t t o a s o r ib e to p a s s i v e deoay* An i n t e r p r e t a
t i o n i n te rm s o f F r e u d ia n r e p r e s s i o n was s u g g e s te d *
The r e s u l t s o f a num ber o f e x p e rim e n ts d e s ig n e d t o
exam ine th e e f f e c t s on r e c a l l o f d i f f e r e n t p r e s e n t a t i o n
and r e c a l l c o n d it i o n s w ere a n a ly s e d by C o n rad (1959)*
The g e n e r a l fo rm o f a l l o f th e e x p e rim e n ts w as th e sam e*
D i g i t m e ssa g e s o f d i f f e r e n t le n g t h s w ere r e c o r d e d , and
129
t h e n s u b j e c t s l i s t e n e d t o t h e m e s s a g e s a n d e i t h e r w r o t e
t h e m e s s a g e o r r e s p o n d e d b y d i a l i n g t h e n u m b e r o n a t e l e
p h o n e d i a l o r p r e s s i n g b u t t o n s o n a 2 x 5 d i g i t a l k e y
b o a r d * I t w as f o u n d t h a t f o u r t y p e s o f e r r o r s t y p i c a l l y
o c c u r *
T h e s e a r e t r a n s p o s i t i o n e r r o r s , o m i s s i o n s , s u b s t i
t u t i o n s , a n d s e r i a l o r d e r i n t r u s i o n s . T he a u t h o r a n a l y z e s
t h e s e e r r o r s a n d c o n c l u d e s t h a t n o o n e h a s a t t e m p t e d t o
e x p l a i n n e u r o l o g i c a l l y how p a t t e r n s o f n e u r o n a l e x c i t a t i o n
c a n l o s e t h e i r s e q u e n t i a l c h a r a c t e r * I n t e r e s t i n g l y
e n o u g h , a l l o f t h e e r r o r t y p e s w h e n p l o t t e d p r o d u c e t h e
c h a r a c t e r i s t i c s e r i a l o r d e r c u r v e , I . e . , a u - s h a p e d c u r v e
sk e w e d to w a r d t h e e n d *
T h e o r y
T he p r e v i o u s s e c t i o n s h a v e d e a l t w i t h t h e o r y o n l y
t o t h e e x t e n t t h a t i t w as n e c e s s a r y t o m ake t h e e x p e r i
m e n t a l s t u d i e s m e a n in g f u l o r w h e re t h e c o n c l u s i o n s o f t h e
a u t h o r s to u c h e d o n i t . S e v e r a l a u t h o r s , h o w e v e r , h a v e
p u b l i s h e d a r t i c l e s n o t r e p o r t i n g e x p e r i m e n t a l s t u d i e s b u t
p r e s e n t i n g o n l y t h e o r e t i c a l c o n s i d e r a t i o n s . T h e s e a r t i c l e s
a r e t r e a t e d i n t h i s s e c t i o n .
Brown* s t h e o r y *— B row n ( 1 9 5 9 ) s t a t e s t h a t t h e r e a r e
s e v e r a l r e a s o n s t h a t a " B e c a y " t h e o r y h a s se e m e d u n p r o f i t
a b l e * Among t h e s e a r e s ( a ) T he tim e c o u r s e o f f o r g e t t i n g
i s n o t f i x e d b u t v a r i a b l e * T he d e c r e m e n t i s m o re r a p i d
i f f u r t h e r s i m i l a r m a t e r i a l i s l e a r n e d i n th e I n t e r v a l
b e f o r e r e o a l l ( R e t r o a c t i v e I n h i b i t i o n ) and d i f f e r e n o e s
o c c u r d e p e n d in g u p o n w h e th e r p r a c t i c e t r i a l s a r e m assed
o r d i s t r i b u t e d * (b ) Memory i s f r e q u e n t l y d i s t o r t e d * I t
i s n o t c l e a r how a d e c a y t h e o r y c o u ld le a d t o a n am biguous
o u tp u t w h lo h d o e s n o t c o r r e s p o n d t o t h e i n p u t • ( o ) Ite m s
a t th e b e g in n in g an d en d o f a s e r i e s a r e m ore e a s i l y r e
c a l l e d t h a n th o s e I n t e r v e n i n g ( S e r i a l P o s i t i o n E f f e c t ) •
He p ro p o s e d a t h e o r y w h ic h a tte m p te d t o a c c o u n t
f o r some o f th e s e d i f f i c u l t i e s . O nly f u n c t i o n a l p r o p e r
t i e s o f h y p o th e s iz e d i n t e r n a l s t r u c t u r e s w ere o f c o n c e rn
t o B row n.
I n r e a l i t y , th e o r y i s p r o b a b ly a m isn o m e r. Brown* s
p o s i t i o n i s b a s e d u p o n a num ber o f c o n c e p ts . The f i r s t
o o n o e p t i s t h a t o f s t o r a g e s p a c e . T h is i s v iew ed i n a
g e n e r a l i z e d fo rm and d o e s n o t im p ly a l o c a l i z e d a r e a o f
th e b r a i n i n w h ic h i n f o r m a ti o n i s s t o r e d . S to r a g e sp a c e
may be e i t h e r g e n e r a l o r s p e c i f i c . T h a t la , some " s p a c e *
may b e u s e d f o r th e s t o r a g e o f any k in d o f in f o r m a ti o n
w h ile o t h e r s e c t i o n s may be u s e d f o r t h e s t o r a g e o f o n ly
one s p e c i f i c ty p e o f i n f o r m a t i o n . L im ite d g e n e r a l i t y o r
s p e c i f i c i t y i s a l s o p o s s i b l e . T h is l a s t may be u s e d i n
" o v e rlo a d * s i t u a t i o n s .
The Memory T ra c e c o n c e p t r e f e r s t o th e p a r t o f th e
s t o r a g e s p a c e w h ic h i s u s e d t o r e c o r d a p a r t i c u l a r e v e n t
or message* The decay o f t h is tr a c e la p o stu la ted * The
time a t which each p art or a sp ec t of an even t I s recorded
I s p o te n t ia lly s ig n ific a n t* One e v e n t, a spoken senten ce
fo r exam ple, may e s ta b lis h a s e r ie s o f tr a c e s which are
not recorded sim u ltan eou sly*
The s t o r a g e s p a c e o c c u p ie d by t h e t r a c e I s l i m i t e d
by th e c h a n n e l c a p a c i t y o f t h e t r a c e * T h is c a p a c i t y I s
n o t f i x e d b u t l e s s e n s a s tim e c o n ti n u e s and t h e t r a o e
d e c a y s* F o r exan$>le, 100 b i t s o f s t o r a g e s p a c e may be
n e e d e d a f t e r one s e c o n d , b u t o n ly one b i t a f t e r one h o u r*
The r e s i d u a l I n f o r m a tio n I n t h e t r a c e I s c o n s id e r e d t h a t
p a r t o f th e o r i g i n a l I n f o r m a t io n w h ic h may b e e x t r a c t e d
a t any s t a g e I n t h e d e ca y * C h a n g e , a s s u c h , I n th e t r a c e
d o e s n o t n e c e s s a r i l y Im p ly t h a t I n f o r m a t io n i s l o s t * I f
th e t r a c e s t a r t s a s r e v e r b e r a t i o n and e n d s a s s y n a p tlo
c h a n g e , th e i n i t i a l s t a t e may s t i l l b e u n i q u e l y d e d u c ib le
fro m t h e f i n a l s t a t e *
R edundancy I s a n I m p o r ta n t c o n c e p t t o Brown* The
p o s i t i o n t h a t h e t a k e s i s t h a t w hen t h e t r a c e i s fo rm ed
m ore s t o r a g e s p a c e may b e u s e d t h a n i s n e c e s s a r y f o r th e
im m e d ia te r e p r e s e n t a t i o n o f th e i n f o r m a t i o n t o b e s to r e d *
T h e r e f o r e , t h e t r a c e h a s re d u n d a n c y . A t r a c e w h ic h s t a r t s
w ith re d u n d a n c y may b e a b le t o w i th s ta n d d e c a y w ith o u t a
l o s s o f in f o r m a tio n * The re d u n d a n c y i s l o s t i n s t e a d *
The amount o f redundancy In th e tra ce does not n e c e s s a r ily
132
depend upon the amount in th e Input to th e s e n s e s . This
Input may be reooded to e lim in a te redundancy* and a non-
re dundent input may be coded redundantly*
The even ts sto red in tra o es w i l l o fte n be r e la te d
to one another* As a r e s u lt* d iffe r e n t tr a c e s may oarry* ;
at le a s t in part* some o f the same inform ation* Thus*
a tra ce system may co n ta in redundancy independently o f
the redundancy w ith in in d iv id u a l traoes* This traoe
system can o fte n supply some o f th e in form ation l o s t
through th e decay o f an in d iv id u a l trace* The word "AND,*
fo r example* may be rep resen ted in the tra ce system as
*AHD* but s t i l l be r e c a lle d as "AND*”
Coding determ ines both the amount o f redundancy and
how i t i s used* These two fa c to r s r e g u la te how long the
tra ce can w ithstand decay w ithout the lo s s o f inform ation*
The decay o f th e traoe i s assumed to be due to an
in cr ea se in random n o ise* and i s rap id at f i r s t but then
slows* I t i s a ls o assumed th a t i f everyth in g were stored
w ith s u f f ic ie n t redundancy* the decay would not lead to
fo r g e ttin g * But redundancy u ses up storage space and
sin c e the b rain i s o f lim ite d s iz e * th ere must be con
s tr a in ts on the amount o f sto ra g e space th a t i s used at
any one time* I t i s lik e l y th a t the amount o f redundancy
can be varied but th ere must be some o v e r a ll lim it on the
amount o f storage space th a t i s to be u sed . This may s e t
133
up com p etition both between sim ultaneous m essages and
between co n secu tiv e m essages not separated by an in te r v a l
o f r e s t*
Order Inform ation i s supposedly stored w ith r e la
t i v e l y l i t t l e redundancy* Thus* i t I s e a s ily fo rg o tten *
R e p e titio n may stren g th en a tra ce by e ith e r e s ta b lis h in g
a new traoe or by r e c o n s titu tin g th e ohanges which form
the tra ce whloh then become more la stin g *
The tim e course o f fo r g e ttin g does not depend only
on th e h yp oth esised tim e course of decay* A ccording to
Brown* th e f a ilu r e to ap p reciate t h is has been a primary
reason fo r th e lack o f acceptance o f the tra ce-d eca y
h y p o th esis* F actors in flu e n c in g the tim e course o f fo r
g e ttin g in clu d e redundancy* oodlng* tr a n sfe r o f tr a in in g
(sup p ly o f in form ation from the traoe system )* and p ro-
and r e tr o -a c tiv e in h ib itio n *
When Inform ation i s l o s t through deoay o f an
in d iv id u a l trace* i t may be a v a ila b le from the tra ce s y s
tem* For example* the memory o f th e order from words in
a q u o ta tio n may depend upon the in form ation in the trace
system concerning probable word orders*
Traoe deoay may be the reason th at p ro- and r e tr o
a c tiv e in h ib itio n cause a decrem ent. I f a number o f
th in g s are learned a t d iffe r e n t times* tra ce decay may
make the su b jec t fo r g e t which th in g s were learned when*
13k
I f tvo d iffe r e n t l i s t s o f nonsense s y lla b le s are learn ed
in su c c e ssio n , fo r g e ttin g o f e ith e r l i s t may be a c c e le r
ated by co n fu sio n between them* The lo s s o f order in fo r
m ation, th en , i s seen as a source fo r th e in flu e n c e o f
p ro- and r e tr o -a c tiv e in h ib itio n , but Brown doubts i f
only order in form ation i s l o s t through decay*
The average amount of sto ra g e space a v a ila b le per
item i s seen as f a llin g when the number o f item s to be
learned in cr ea ses* This may be th e rea so n th a t i t i s
d isp ro p o rtio n a tely more d i f f i o u l t to le a rn as th e amount
to be learned in crea ses*
D is to r tio n s in memory are lia b le to ooour whenever
a tra ce has become inadequate through decay* R eo a ll then
la r g e ly becomes r e c o n str u c tiv e in oharaoter* This may
lead to an unambiguous output but error may a lso be con
tained*
The memory span i s viewed as b ein g lim ite d la r g e ly
by th e rap id decay (or low redundancy) o f order informa
tion * Although i t might appear th a t r a te o f p r e se n ta tio n
would in flu e n c e the span, two fa c to r s h elp s t a b i liz e i t :
(a) Order in form ation f a l l s more than p ro p o rtio n a tely
when the len g th o f the sequenoe i s reduced; and (b ) when
the p r e se n ta tio n ra te i s slow , re h ea rsa l may take plaoe*
Brown1s theory i s intended to have Im p lica tio n s be
yond those In v o lv in g immediate memory* I t i s la r g e ly
1 3 5
" a fte r -th e -fa c t" but view s memory from a new p o in t of
view . As such i t may lead to fu rth er exp erim en tation .
I t already h a s, In so fa r as the experim ent reported in the
n ext chapter i s concerned.
Broadbent's th eo ry . —As was the case w ith Brown's
fo rm u la tio n s, on ly the b a sic te n e ts of Broadbent1s theory
w i l l be p resen ted . Broadbent s t a r t s w ith the concept th a t
the human p ercep tu al ca p a city i s lim ite d . In consequence,
a s e le c t iv e op eration i s performed on a l l in p u ts to the
system . This op eration takes the form o f s e le c tin g a l l
Inputs having some c h a r a c te r is tic in common. Such an
op eration e x tr a c ts r e la t iv e ly l i t t l e inform ation from the
s ig n a l and i s econom ical o f the nervous system 's c a p a c ity .
The c h a r a c te r is tic s on which the s e le c tio n may operate are
termed "sensory ch an nels." The p a r tic u la r s e le c tio n made
a t any one time w i l l depend p a r tly on the c h a r a c te r is tic s
of the input ( in t e n s it y , e a r lin e s s in tim e, absence o f
recen t in p u ts on th at ch an nel, p o s itio n o f the channel in
the h ierarch y of ch an n els, e t ce tera ) and p a r tly on in fo r
m ation in th e permanent s t o r e . The change from one s e le c
tio n to another takes a determ inate tim e.
Incoming inform ation may be h eld in a temporary
sto r e at a sta g e p revious to th a t of the s e le c t iv e opera
t io n . Such in form ation may pass through the p ercep tu al
system on th e next subsequent s e le c tio n of the sensory
c h a n n e l o f I t s a r r i v a l , i f i t i s s t i l l s t o r e d . A f t e r
p a s s a g e th r o u g h th e p e r c e p t u a l s y s te m , t h e i n f o r m a ti o n
may b e r e t u r n e d t o t h e te m p o ra ry s t o r e . The s e l e c t i o n o f
i n f o r m a ti o n f o r s u c h a r e t u r n i s d e te rm in e d b y i n f o r m a ti o n
i n t h e m ore p e rm a n e n t s t o r e .
I n im m e d ia te memory e x p e rim e n ts a s tre a m o f s t i m u l i
i s d e l i v e r e d b e f o r e any o v e r t r e s p o n s e i s r e q u i r e d . A l l
o f th e i n f o r m a ti o n i n t h e s tr e a m i s w i t h i n th e o rg a n is m
a t one t im e . B ro a d b e n t (195713) u s e s a s e r i e s o f b a l l s t o
r e p r e s e n t t h e I n f o r m a tio n u n i t s and a n e tw o rk o f tu b e s to
r e p r e s e n t t h e c e n t r a l n e rv o u s s y s te m t o c l a r i f y some o f
th e o p e r a t i o n s . (S e e F ig u r e 2 . ) W ith a s m a ll num ber o f
b a l l s , t h e tim e b e tw e e n i n s e r t i o n and em erg en ce o f i n
f o r m a tio n c a n be v a r i e d w ith o u t any a p p a r e n t e f f e c t on
e f f i c i e n c y .
I f a s h o r t s e r i e s o f b a l l s i s k e p t w a i t i n g i n one
b ra n o h beyond t h e c r i t i c a l tim e , t h e b a l l w h ic h h a s b e e n
t h e r e l o n g e s t w i l l le a v e t h e s y s te m . The b r a n c h w i l l n o t
s e r v e a s a s t o r e f o r a n u n l im i te d le n g t h o f tim e b e f o r e
th e r e s p o n s e i s a llo w e d . I t i s p o s s i b l e , how ever* f o r
th e s e r i e s o f b a l l s t o d ro p down t h e ste m and come b a c k
up a n o th e r tu b e t o a n o th e r b r a n c h . As so o n as t h e f u l l
s e r i e s h a s c o m p le te d t h i s , th e p r o c e s s c a n be r e p e a t e d so
t h a t t h e s e t o f b a l l s may b e k e p t i n th e s y s te m f o r any
d e s i r e d t im e . The i n s e r t i o n o f any o t h e r b a l l d u r in g
Figure 2
137
Broadbent's Mechanical Model
(After Broadbent., 1957b)
138
t h a t tim e w i l l e i t h e r mean t h a t th e e x t r a b a l l w i l l n e v e r
em erge o r e l s e th e c i r c u l a t i o n o f th e s e r i e s w i l l m ee t
I n t e r f e r e n c e . The sy ste m w i l l w ork o n ly w ith a c e r t a i n
maximum num ber o f b a l l s . Above t h a t num ber e a c h b a l l
w i l l h a v e t o re m a in I n th e b ra n c h f o r m ore th a n th e
c r i t i c a l tim e and a s e v e r e b reak d o w n o f s t o r a g e w i l l
o c c u r . The i n t e r f e r i n g e f f e c t o f a n e x t r a b a l l d u r in g
a d e la y w i l l d ep en d on th e s i z e o f th e s e r i e s b e in g c i r
c u l a t e d . G r e a t e r I n t e r f e r e n c e o c c u rs I f th e num ber o f
b a l l s i s n e a r th e l i m i t .
I f b o th b ra n c h e s c o n t a i n b a l l s , th e m ovem ent o f
th e d o o r w i l l p u t one g ro u p i n t o c i r c u l a t i o n b e f o r e th e
o t h e r . To move th e d o o r w h ile a g ro u p I s a c t u a l l y p a s s i n g
w ould r i s k a jam m ing. So a l l b a l l s i n one b ra n c h p a s s
down th e ste m b e fo r e any o f th e o t h e r i f th e b a l l s a re
c lo s e t o g e t h e r ( i . e . , r a t e o f p r e s e n t a t i o n I s f a s t ) . I f
b a l l s a r e I n s e r t e d w ith a s i z e a b l e i n t e r v a l i n b e tw e e n
s u c c e s s iv e b a l l s , th e d o o r may be swung b a c k and f o r t h t o
d e a l w ith e a c h b ra n c h a l t e r n a t e l y .
I f a le n g th y s e r i e s i s I n s e r t e d th r o u g h one b r a n c h ,
th e d o o r b e in g h e ld o p en f o r th e m , and a c o u p le o f b a l l s
a re d e l i v e r e d t o th e o th e r b ra n c h i n t h e m e a n tim e , t h i s
se co n d g ro u p o f b a l l s w i l l w a it t h e r e u n t i l th e ste m I s
c l e a r f o r them t o p a s s . T h ere i s a r i s k t h a t t h e s e e x t r a
b a l l s may be r e q u i r e d to w a it I n th e b r a n c h b ey o n d th e
139
c r i t i c a l tim e and w i l l t h e r e f o r e be l o s t , e s p e c i a l l y i f
th e e x t r a b a l l s o c c u r e a r l y i n th e f i r s t s e r i e s *
S e r i a l o r d e r e f f e c t s d ep en d upon th e r a t e s o f p r e
s e n t a t i o n o f th e s t i m u l i and t h e r e q u i r e d r e s p o n s e as
com pared t o t h e r a t e o f r e c i r c u l a t i o n . T hey a l s o d ep en d
u p o n th e s t r a t e g y o f t h e s u b j e c t . I f th e r a t e o f r e s p o n s e
i s b e lo w t h a t o f r e o i r c u l a t i o n , b u t n o t so slo w as t o
a llo w c o m p le te r e c i r c u l a t i o n b e f o r e t h e n e x t r e s p o n s e , th e
f i r s t ite m s w i l l be s t o r e d f o r a s h o r t e r p e r i o d o f tim e
t h a n th e l a t e r ite m s and th e f i r s t p a r t o f t h e l i s t w i l l
be r e c a l l e d b e t t e r *
I t m ust b e rem em bered t h a t th e b a l l s r e p r e s e n t
in f o r m a ti o n , n o t s t i m u l a t i o n . Two s t i m u l i may be d e a l t
w ith s im u lta n e o u s ly i f th e y c o n t a i n l i t t l e enough in f o rm a
t i o n . The tim e f o r in f o r m a ti o n t o p a s s d e p e n d s , a t l e a s t
i n p a r t , u p o n th e am ount o f i n f o r m a tio n p e r item *
T h is b r i e f a c c o u n t o f B ro a d b e n t1s th e o r y c a n n o t
do i t j u s t i c e . The c a r e f u l r e a d e r w i l l n o t i c e how g r e a t
a r o l e h i s e x p e rim e n ts u s in g d i c h o t l o l i s t e n i n g t a s k s
h a v e p la y e d i n i t s f o r m u l a t i o n . N o n e th e le s s , h i s m odel
seem s to h a v e some p r e d i c t i v e pow er and may p o s s i b l y be
d e s c r i p t i v e o f c e n t r a l n e rv o u s sy s te m p r o c e s s in g * B ro a d
b a n d s m o d el p r o b a b ly i s m ore c l o s e l y t i e d t o th e c e n t r a l
n e rv o u s sy s te m th a n th e m odel s u g g e s te d by Brown*
Ii*0
D la c u a a lo n o f th e L i t e r a t u r e
The s t u d i e s r e p o r t e d I n t h i s c h a p t e r h a v e a l l d e a l t
w ith s h o r t - t e r m m em ory. Two t r a d i t i o n a l t h e o r i e s , d e c a y
and i n t e r f e r e n c e , h a v e b e e n s u g g e s te d to e x p l a i n phenom ena
a s s o c i a t e d w ith t h i s ty p e o f t a s k . R e c e n tl y , two a d d i
t i o n a l t h e o r i e s , p e rh a p s m ore a p p r o p r i a t e l y c a l l e d m o d e ls ,
h a v e b e e n o f f e r e d * B o th o f t h e s e (B ro a d b e n t* s and
B ro w n 's) h a v e r e l i e d o n d e c a y and w ere p r e s e n t e d i n th e
l a s t s e c tio n * Many o f th e s t u d i e s r e v ie w e d , h o w e v e r,
p r o v id e e v id e n c e t o s u p p o r t an i n t e r f e r e n c e th e o ry *
The p u rp o s e o f t h i s s e c t i o n i s t o p u l l t o g e t h e r
th e t h r e a d s o f a l l t h e e x p e r im e n ts re v ie w e d t o d e te rm in e
th e o v e r a l l i m p l i c a t i o n s o f t h e s e s t u d i e s * E a c h e x p e r i
m ent was re v ie w e d t o f i n d a sim p le summary s ta te m e n t d e s
c r i b i n g th e c o n c lu s io n s t h a t m ig h t b e i n d i c a t e d by th e
s tu d y * T h ese w ere g ro u p e d d e p e n d in g u p o n th e p o s i t i o n
t h a t th e y seem ed t o s u p p o rt* T h ese c o n c lu s io n s a r e p r e
s e n te d b e lo w .
Not e v e r y s tu d y i s r e p r e s e n te d * Some s t u d i e s d id
n o t seem t o a llo w an y c l e a r l y d e f in e d c o n c lu s io n *
C o n c lu s io n s S u p p o r tin g an
i n t e r f e r e n c e P o s i t i o n
1* D i s c r e t e a l t e r n a t i v e s a re b e t t e r t h a n s i m i l a r a l t e r
n a ti v e s *
2 . S tim u li d is p la y e d i n c e r t a i n l o c a t i o n s a r e rem em bered
1 l * .i
b e t t e r t h a n o th e r s * The c h a r a c t e r i s t i c w h ic h seem s
t o d e te rm in e t h i s f a c i X i t a t i o n i s r e l a t i v e i s o l a t i o n ,
3* The c X o se r t h e r e s p o n s e t o one ite m i s t o t h e a p p e a r-i
anoe o f th e n e x t , t h e g r e a t e r t h e d if f io u X ty *
If.* The r e t r o a c t i v e i n h i b i t i o n i s sX ig h tX y g r e a t e r i f
s i m i l a r m a t e r i a l i s u se d a s th e in te r p o X a te d
a o t i v i t y ,
5* L a t e r s t i m u l i c a n d r a s t i c a l l y i n f l u e n c e th e p e r c e p
t i o n o f e a r l i e r s t i m u l i , e . g « , " e r a s u r e * "
6* R a te o f in te r p o X a te d a c t i v i t y i s n o t an i n f l u e n t i a l
v a r i a b l e *
7* I n c r e a s e d p r o b a b i l i t y o f a c h a n g e i n th e s t a t e o f
a v a r i a b l e i n a " r u n n in g memory" t a s k h a s a l a r g e
d e t r i m e n t a l e f f e c t *
8 * S e r i a l o r d e r e f f e c t s a r e o b t a i n e d f o r a l l ty p e s o f
e r r o r s *
9* The l a r g e r th e num ber o f v a r i a b l e s w i t h i n a g iv e n
am ount o f m a t e r i a l , t h e fe w e r t h e e r r o r s t h a t o c c u r*
10* I f d i f f e r e n t v a r i a b l e s c a n assum e d i f f e r e n t s t a t e s
r a t h e r t h a n s i m i l a r s t a t e s , th e num ber o f e r r o r s i s
re d u c e d *
11* A d d in g s ti m u l u s d im e n s io n s f a c i l i t a t e s p e rfo rm a n c e *
C o n c lu s io n s S u p p o r tin g a D ecay
P o s i t i o n ( g e n e r a l ) — 35----------- ^
1* W ith d i g i t s , r e h e a r s a l o n ly m o d e r a te ly r e d u c e s t h e
1 1 4 . 2
l o s s duo t o d e la y *
2* Some s t u d i e s h a v e fo u n d t h a t p e rfo rm a n c e Im p ro v e s I f
a f a s t r a t e o f p r e s e n t a t i o n a n d /o r r e c a l l I s u s e d .
F o r s t u d i e s I n d i c a t i n g o t h e r w i s e , r e h e a r s a l may b e
in v o lv e d a s a n e x p l a n a t i o n .
3 . F o r p o s t - s t i m u l u s c u in g s i t u a t i o n s , m o st o f t h e i n
f o r m a tio n bey o n d th e memory sp a n i s l o s t 250 m i l l i
se c o n d s a f t e r th e s tim u lu s p r e s e n t a t i o n .
C o n c lu s io n s S u p p o r tin g a L im ite d
" C h a n n e l C a p a c ity ^ a n d /o r a
L im ite d Number o f wc h u n k s^
1 . D e la y w i t h lo n g m e ssa g e s i s v e ry dam aging and i t
do es n o t make any d i f f e r e n c e i f d e la y com es b e f o r e
o r a f t e r r e h e a r s a l . I f a m essag e a s lo n g a s th e
sp a n i s to be rem em b ered , a d d in g a s i n g l e r e d u n d a n t
d i g i t t o be r e p o r t e d b e f o r e th e m essag e d r a s t i c a l l y
i n t e r f e r e s w ith m em ory.
2 . More I s p e r c e iv e d t h a n c a n b e rem em bered ( p o s t -
a tlm u lu s c u i n g ) •
3 . E x p o su re tim e up t o 500 m il l i s e c o n d s may be v a r i e d
w ith o u t g r e a t l y I n f l u e n c i n g t h e am ount r e c a l l e d f o r
s im u lta n e o u s p r e s e n t a t i o n .
l^. R edundancy i s e f f e c t i v e i n a n o is y c h a n n e l b u t n o t
i n a n o i s e - f r e e c h a n n e l.
5 . A . s m a lle r in f o r m a ti o n l o s s and a l a r g e r g a in i s o b
t a i n e d fro m s h o r t m essa g es w ith h ig h in f o r m a ti o n
H j-3
c o n te n t th a n th e r e v e r s e .
6 . E r r o r o u tp u t i n c r e a s e s as t h e le n g t h o f th e m essa g e
i n c r e a s e s .
7* A lth o u g h p r a c t i c e i n c r e a s e s th e t o t a l num ber o f
ite m s r e c a l l e d , th e d i g i t - s p a n i n c r e a s e s o n ly s l i g h t
l y .
8 . I t d o e s n 't seem t o make any d i f f e r e n c e w h e th e r one
o r m ore ite m s p re c e d e th e d e s i r e d o u tp u t i n a p r o
a c t i v e i n h i b i t i o n p a ra d ig m .
9 . I f a m essag e i s w i t h i n th e s p a n , a d e la y i s n o t
n e c e s s a r i l y d a m a g in g .
E v id e n c e I n d i c a t i n g th e I n f l u e n c e
o f L ong-T erm L e a rn in g on g jh o rt-
erm Memory
1* H igh i n t e r - s y l l a b l e d ig ra m fr e q u e n c y p o s i t i v e l y i n
f l u e n c e s th e num ber o f ite m s r e c a l l e d .
2 . R edundancy f a c i l i t a t e s r e c a l l w hen th e num ber o f
ite m s r e c a l l e d i s th e d e p e n d e n t v a r i a b l e .
3 . An i n t e r a c t i o n e x i s t s b e tw e e n fre q u e n c y o f th e
m a t e r i a l and l i s t l e n g t h .
ll. I n t e r - i t e m a s s o c i a t i v e s t r e n g t h o f t h e w o rd s i n th e
l i s t p o s i t i v e l y I n f l u e n c e r e c a l l .
5 . P r a c t i c e on i n f r e q u e n t m a t e r i a l im p ro v e s p e rfo rm a n c e
i n a s h o r t - t e r m memory t a s k .
6 . I f " c l u s t e r i n g * i s p o s s i b l e , th e num ber r e c a l l e d i n
c r e a s e s .
HA
7 . When m a t e r i a l i s p a r t i a l l y f o r g o t t e n , " c o n v e n tio n
a l i z a t i o n 1 1 ta k e s p la c e *
G e n e ra l C o n c lu s io n s
1* L im i ti n g t h e p o o l o f ite m s d o e s n o t seem to f a c i l i
t a t e r e c a l l *
2* M a t e r i a l i s n o t w e ll r e t a i n e d i f n o t r e p o r te d *
3* R e d u n d a n t s t r i n g s a r e m ore e a s i l y le a r n e d e v e n i f
s u b j e c t s do n o t know th e r u l e s *
Ij.* G ro u p in g o f u n i t s i s e f f e c t i v e *
There i s a tendency toward g re a te r s t a b i l it y a f te r
re h earsa l*
6 * M a t e r i a l p r e s e n te d o n ly o n ce may h a v e a l o n g - l a s t i n g
e f f e c t (H ebb*s r e s u l t s ) a lth o u g h m a t e r i a l c a n n o t be
r e c a l l e d *
7 . p a r t i a l r e p o r t by p o s i t i o n i s b e t t e r th a n t h a t by
c a te g o ry *
8 * S e l e c t i v e p e r c e p t i o n d o e s n o t o p e r a te on th e b a s i s
o f p o s i t i o n o r c o lo r a lth o u g h i t may o p e r a te on th e
b a s i s o f c la s s *
9* S e r i a l o r d e r e f f e c t s a r e i n f lu e n c e d b y th e s e q u e n t i a l
s t r u c t u r e o f th e m a t e r i a l *
10* The s t r a t e g y o f th e s u b j e c t I n f l u e n c e s th e r e s u l t s *
11* F o r " l a g s " up t o f i v e , s t i m u l i m u st b e d is p la y e d f o r
a p p ro x im a te ly one se c o n d p e r ite m i n s to r a g e t o a llo w
s u b j e c t s t o r e c a l l 80 p e r c e n t o f th e ite m s *
CHAPTER III
EXPERIMENT I
I n t r o d u c t i o n
As s t a t e d I n t h e i n t r o d u c t o r y c h a p t e r , th e p u rp o s e
o f t h e f i r s t e x p e rim e n t w as t o d e te rm in e i f th e rem em ber
in g o f o r d e r i n f o r m a tio n le s s e n e d th e am ount o f ite m i n
f o r m a tio n t h a t c o u ld b e r e t a i n e d . T h is h y p o th e s is w as
d e r iv e d by Brown (1 9 5 9 ) a f t e r a c o n s i d e r a t i o n o f In fo rm a
t i o n T h eo ry a s a m odel f o r hum an i n f o r m a tio n p r o c e s s in g *
M ethod
T a s k . - - S u b j e c t s w ere e x p o se d t o a se q u e n c e o f
w o rd s , e i t h e r s e v e n o r e le v e n w o rd s lo n g . A t th e c o n c lu
s i o n o f t h e l i s t th e y w ere a sk e d t o r e c o r d th e w ords i n
t h e o r d e r t h a t th e y a p p e a re d , i f p o s s i b l e , b u t to I n c lu d e
a l l o f th e w ords t h a t th e y rem e m b e red . One g ro u p w ro te
t h e i r a n sw e rs down on a b la n k fo rm . A n o th e r g ro u p * s
an sw er fo rm s l i s t e d th e c a t e g o r i e s fro m w hich th e w ords
w ere s e l e c t e d i n th e o r d e r t h a t th e w ords o c c u r r e d . F o r
e x a m p le , i f th e w ords t h a t w ere d is p la y e d w ere " e lm , f i f e ,
f o i l , s h i f t • • • ,* th e an sw er fo rm l i s t e d " t r e e , m u s ic a l
i n s t r u m e n t , w eapon, b o a t , • . • ." I n t h i s way o r d e r
memory n e e d n o t p l a y a r o l e s in c e th e I n f o r m a tio n was
l W
1 1 * 6
p r o v id e d , and t h u s , a c c o rd in g to th e h y p o t h e s i s , m ore
tts to r a g e s p a c e 1 * was a v a i l a b l e f o r c o n te n t i n f o r m a ti o n . A
t h i r d g ro u p c o n t r o l l e d f o r th e p o s s i b i l i t y t h a t s e e in g
th e c a t e g o r i e s m ig h t f a c i l i t a t e th e c o n te n t memory b y
l i s t i n g th e c a t e g o r i e s i n a l p h a b e t i c a l o rd e r*
A se c o n d v a r i a b l e was i n t e r p o l a t e d a c t i v i t y * Sub
j e c t s w ere r e q u i r e d t o c o u n t b a ck w a rd s by t h r e e s fro m a
t h r e e - d i g i t num ber d is p la y e d a f t e r th e l a s t w ord i n th e
se q u e n c e f o r z e r o , f i v e , o r tw e n ty s e c o n d s . F o r e x a m p le ,
i f th e num ber was *395>»N a s so o n as he saw th e s l i d e th e
s u b j e c t w ould sa y o u t lo u d and a s f a s t as h e c o u ld " 3 9 2 *
3 8 9 , 386 • • .** u n t i l s to p p e d by th e e x p e r im e n te r . T im in g
s t a r t e d w hen t h e f i r s t d i g i t was c a l l e d o u t by th e s u b j e c t
and th e d u r a t i o n o f th e a c t i v i t y w as m ea su re d by a s to p
w atch * A t th e end o f th e i n t e r p o l a t e d a c t i v i t y , th e s u b
j e c t c o u ld s t a r t w r i t i n g h i s r e s p o n s e s *
L i s t s w ere e i t h e r s e v e n o r e le v e n w ords lo n g . A ll
s u b j e c t s w ere m ea su re d on th e se v e n -w o rd l i s t f i r s t . T h is
w as f o llo w e d by a t l e a s t a f i v e m in u te b r e a k d u r in g w h ich
th e s u b j e c t and e x p e r im e n te r c o n v e rs e d a b o u t t o p i c s o f
g e n e r a l i n t e r e s t . The s u b j e c t was th e n m ea su re d on th e
e le v e n -w o rd l i s t . The s u b j e c t was a llo w e d one m in u te t o
r e c a l l t h e s e v e n w ords and l*f>0 m in u te s t o r e c a l l th e
e le v e n w o rd s . P r e t e s t i n g e s t a b l i s h e d t h a t t h e s e tim e
v a lu e s w ere m ore th a n enough f o r s u b j e c t s to w r i t e down
lltf
a l l t h a t t h e y rem em bered* A t th e end o f th e r e c a l l p e r i
od* s u b j e c t s w ere a sk e d to t u r n t h e i r an sw er fo rm s o v e r*
No c a te g o r y i n f o r m a ti o n w as p ro v id e d o n th e b a c k o f th e
fo rm f o r any group* b u t s u b j e c t s w ere t o l d t o p u t th e
w ords i n th e same o r d e r as th e y w ere d is p la y e d i f th e y
c o u ld * The s l i d e p r o j e c t o r was th e n tu r n e d on a g a in and
ad v an ced t o th e n e x t s l i d e * T h is s l i d e l i s t e d f o u r w ords
fro m e a c h o f th e c a t e g o r i e s t h a t w ere in c lu d e d i n th e
s e q u e n c e . One o f th e f o u r w ords i n e a c h o a te g o r y w as th e
w ord t h a t h ad b e e n p r e v i o u s ly d is p la y e d * The s u b j e c t s
w ere a sk e d to w r i t e down i n o rd e r* w ith t h i s a d d i t i o n a l
h e lp * a l l o f th e w ords t h a t h ad b e e n on th e o r i g i n a l l i s t *
D e s ig n . —A L in d q u i s t Type I I I d e s ig n ( L in d q u is t*
1953) w as u se d * T h a t is * th e f i r s t tw o v a r i a b l e s w ere
t r e a t e d i n a ra n d o m iz e d g ro u p f a c t o r i a l m anner* b u t th e
t h i r d , l i s t l e n g t h , was a " w i t h in s u b j e c t s " e f f e c t .
S tim u lu s m a t e r i a l *— To c o n t r o l f o r th e p o s s i b i l i t y
t h a t some u n f o r e s e e n and u n c o n tr o l le d f a c t o r w i t h i n th e
s p e c i f i c l i s t c h o s e n c o u ld a c c o u n t f o r th e r e s u l t s * f i v e
d i f f e r e n t w ord l i s t s f o r e a c h o f th e tw o l i s t le n g t h s
w ere u s e d . E ac h l i s t c o n s i s t e d o f w ords s e l e c t e d fro m
s p e c i f i c c a t e g o r i e s i n th e f o llo w in g m a n n e r. C a te g o r ie s
fro m Cohen* e t a l . (1 9 5 7 ) i n w h ic h th e c a te g o r y c o n ta in e d
a t l e a s t f o u r nonhom ophonlc* m o n o s y lla b ic w ords w ere
l i s t e d * The T h o rn d ik e -L o r ge ( I 9I 4 J4 .) and C ohen v a lu e s w ere
lij.8
o b ta in e d f o r e a c h o f th e w o rd s . The e le v e n c a t e g o r i e s
w h ic h h ad th e m o st h o m o g e n e ity f o r th e s e v a lu e s w i t h i n
and b e tw e e n c a t e g o r i e s w ere s e l e c t e d . Two a d d i t i o n a l
c r i t e r i a w ere t h a t th e w ords o c c u r r e d l e s s t h a n £0 tim e s
i n one m i l l i o n w ords a c c o rd in g t o th e T h o rn d ik e -L o rg e
d a ta and w ere w e ll down th e l i s t i n th e h i e r a r c h y o f
r e s p o n s e s a s i n d i c a t e d b y C ohen1s d a ta *
An e q u a l ra n g e o f num bers w as a s s ig n e d t o e a c h
c a te g o r y and th e f i v e c a te g o r y s e q u e n c e s w e re s e l e c t e d by
r e f e r r i n g to a t a b l e o f random n u m b e rs. S p e c i f i c w ords
w ere s e l e c t e d i n a s i m i l a r m a n n e r. An e q u a l ra n g e o f
num bers was a s s ig n e d t o e a c h o f th e f o u r w o rd s w i t h i n a
c a te g o r y and a random num ber t a b l e d e te rm in e d th e s p e c i f i c
w ord t o b e in c lu d e d on e a c h l i s t *
The se v e n and e le v e n w ord l i s t s w ere th e n g ro u p e d
i n p a i r s so t h a t th e same w ord d id n o t o c c u r i n b o th
l i s t s f o r any p a i r . T a b le s 2 and 3 l i s t th e s t i m u l i
w h ile T a b le Ij. p r o v id e s th e T h o rn d ik e -L o r ge and C ohen
v a lu e s *
A p p a ra tu s . — The w o rd s w ere d is p la y e d b y m eans o f a
Kodak nC a ro u s e ltt s l i d e p r o j e c t o r . E ach w ord was ty p e d on
a s h e e t o f p a p e r and a p h o to g ra p h was ta k e n u s i n g K oda-
chrom e Type I I ( P r o f e s s i o n a l ) f i l m , fro m w h ic h s l i d e s w ere
m ade. When p r o j e c t e d th e w ords a p p e a re d i n b l a c k p r i n t
a g a i n s t a n o f f - w h i te b a c k g ro u n d . A H u n te r i n t e r v a l t im e r
TABLE 2
EXPERIMENTAL STIMULUS LISTS IN
THE ORDER DISPLAYED
A
B C D E
A .
S e v e n Word S tim u lu s L i s t s
Tim R a f t H ip S l i n g Mace
W r is t H ip F o i l L y re S k u l l
Mole Hog N ick G orge Mole
F i f e L ance L u te Hog F i f e
Mace G orge Dune G len N ick
S k i f f L y re B arge S k i f f R e ef
R e e f M a tt Lynx W T ist B arge
B . E le v e n Word S tim u lu s L i s t s
K e to h G len S k u l l Gown G nat
S to v e F i f e S l i n g G nat M att
F l e a K e tc h Cab B arg e Rug
G orge Lynx L y re E lk L u te
G le n S l i n g
Tim Tim S l e ig h
C lo a k W r is t G nat Mace R a f t
S k u l l Gown V ase H ip Hog
F o i l B u tte Gown Dune C lo ak
S l e ig h S l e ig h E lk H oarse> S l i n g
Lynx V ase R e ef S to v e B u tte
L u te Moth R a f t F i f e W r is t
150
TABLE 3
W ORDS ON RECOGNITION TASK
A* S e v e n Word L i s t
A nim al G e o l. Form Name
E lk B u tte G le n
Hog Dune M att
L ynx G orge N ick
Mole R e e f Tim
B o a t M usic • I n s t r . W eapon Body P a r t
B arg e F i f e F o i l C a lf
K e to h L u te L ance H ip
R a f t L y re Mace S k u l l
S k i f f Reed S l i n g W l*ist
B . E le v e n Word L i s t
A n im al F u r n i t u r e G e o l. Form
E lk B ench B u tte
Hog Rug Dune
Lynx S to v e G orge
Mole V ase R e e f
B o at I n s e c t V e h ic le Body P a r t
B arg e F l e a Cab C a lf
K e tc h G nat H e a rs e H ip
R a f t M oth S l e i g h
W r is t
S k i f f Wasp Van S k u l l
M u s ic . I n s t r . W eapon C lo th in g Name
F i f e F o i l Cape G le n
L u te L ance C lo a k M a tt
L yre Mace Gown N ick
R eed S l i n g S t o l e Tim
TABLE
STIMULUS CATEGORY AND ITEM SUM M ARY
C a te g o ry
T h o rn d ik e -L o rg e C o u n t C o h en , e t a l * , Norms
Mean A ve. Dev* Mean A ve. D e v . H igh* R ank
A nim al 10*50 3 .5 0 1 .5 0 0 .5 0
29
B o a t 5 .2 5 14-25
6 .2 5
2 .1 2 20
Body P a r t
1 5 .2 5 2 .2 5 2 .7 5
0*88 28
C lo th in g
3 3 .2 5 2 * 7 5
1 .2 5 0 .3 8
25
F u r n i t u r e 3 ^ .5 0 1 1 .2 5 9 .5 0
U-.25
11
G eol* Form*
5 .2 5
2 .2 5
1^.25
3 .8 8
19
I n s e c t 7 .5 0 3 .0 0 3 6 .5 0 9 .0 0 8
Mus* I n s t *
9 .2 5
6 .3 8 3 .5 0
2 .7 5
22
Name
7 .2 5 3 .3 0 2 .5 0 0 .5 0
6i*
V e h ic le 1 3 .0 0 9 .0 0
1 .2 5
0 .3 8 2 6
W eapon 8*50
3 .7 5 1 .2 5
0 .3 8
1 £ > 2
was c o n n e c te d I n s e r i e s to th e p r o j e c t o r th ro u g h th e r e
m ote c o n t r o l I n p u t to p r o v id e a s tim u lu s d u r a t i o n o f one
se co n d p e r w o rd . The tim e r e q u i r e d t o c h an g e s l i d e s was
0 .6 se c o n d s so t h e t o t a l tim e b e tw e e n th e o n s e t o f one
s tim u lu s and t h a t o f t h e n e x t was a p p ro x im a te ly 1 .6
s e c o n d s .
S u b j e c t s . — N in e ty v o l u n t e e r s o b ta in e d fro m I n t r o
d u c to r y p s y c h o lo g y c l a s s e s p a r t i c i p a t e d i n th e e x p e r im e n t.
Ten s u b j e c t s w ere a s s ig n e d to e a c h o f th e n in e c e l l s i n
v o lv e d f o r th e r e s p e c t i v e l i s t l e n g t h s . The p a r t i c u l a r
l i s t and e x p e r im e n ta l c o n d i t i o n w ere ra n d o m ly a s s ig n e d t o
th e s u b j e c t s a s th e y a p p e a r e d .
P ro c e d u re . — The s u b j e c t was s e a t e d i n a t a b l e t - a r m
c h a i r p la c e d a p p ro x im a te ly s i x f e e t fro m th e s c r e e n .
Typed I n s t r u c t i o n s w ere p ro v id e d f o r h im to r e a d ( s e e
A p p en d ix A) w h ile th e e x p e r im e n te r r e a d i e d th e e q u ip m e n t.
A l l o f th e s l i d e s c o r r e s p o n d in g t o th e r e s p e c t i v e l i s t s
w ere a lr e a d y i n s e q u e n c e i n s l i d e c a r t r i d g e s , one f o r e a c h
l i s t l e n g t h . The a p p r o p r i a te c a r t r i d g e was i n s e r t e d i n t o
th e m ach in e and r o t a t e d t o th e a s s ig n e d l i s t .
The e x p e r im e n te r t h e n d is c u s s e d th e I n s t r u c t i o n s
w ith th e s u b j e c t , p r o v id e d an a p p r o p r i a te an sw er fo rm f o r
th e s u b j e c t t o s i g n , and i f r e q u i r e d , g a v e th e s u b j e c t
some p r a c t i c e i n c o u n tin g b a ck w a rd s by t h r e e s .
The e x p e rim e n te r s a t I n a c h a i r s l i g h t l y b e h in d
153
and to one s i d e o f t h e s u b j e c t , and a f t e r a r e a d y s i g n a l ,
s t a r t e d th e p r o j e c t o r . The p r o j e c t o r a u to m a t i c a ll y c y c le d
u n t i l t h e t h r e e - d i g i t num ber a p p e a re d and w as t h e n
s to p p e d . F o r th e g ro u p s who h ad n o i n t e r p o l a t e d a c t i v i t y
t h e a p p e a ra n c e o f t h i s s l i d e w as th e s i g n a l t o b e g in r e
c o rd in g t h e i r r e s p o n s e s . F o r th e o t h e r g r o u p s , c o u n tin g
b a ck w a rd s s t a r t e d a s so o n as th e y saw th e n u m b er.
R e s u l ts
F o u r m e a su re s w ere a c q u ir e d fro m e a c h s u b j e c t .
T h ese w e re s The num ber c o r r e c t r e c a l l e d i r r e s p e c t i v e o f
o r d e r ( N .C .R .) ; th e num ber c o r r e c t l y r e c a l l e d i n th e
p o s i t i o n o r i g i n a l l y d i s p l a y e d ( I . P . R . ) j th e num ber r e c o g
n iz e d i r r e s p e c t i v e o f o r d e r (N .C . R e ) ; and th e num ber
r e c o g n iz e d and c o r r e c t l y p l a c e d ( I . F . R e ) . T a b le 5 l i s t s
th e m ean s c o r e s f o r e a c h o f t h e s e d e p e n d e n t v a r i a b l e s .
A L in d q u i s t Type I I I a n a l y s i s o f v a r i a n c e was u s e d
to d e te rm in e s i g n i f i c a n c e v a lu e s f o r e a c h o f th e d e p e n d e n t
v a r i a b l e s . F o r th e NCR m e a s u r e , o n ly th e l i s t l e n g t h was
s i g n i f i c a n t (F s I4.3• 87I 4 ., d f = 1 , 81) w ith m ore w ords b e in g
r e c a l l e d fro m th e lo n g e r l i s t l e n g t h .
F o r th e IPR m e a s u re , s i g n i f i c a n c e w as o b ta in e d f o r
o r d e r (F * 1^3.895, d f • 2 , 8 l ) and th e L e n g th by O rd e r
i n t e r a c t i o n (F ■ 1 ^ .7 5 8 , d f * 2 , 8 1 ) . The g ro u p w h ic h h ad
th e " O rd e r I n f o r m a tio n 1 1 p r o v id e d n a t u r a l l y p la c e d m ore
1£1+
TABLE 5
M EAN SCORES
Number C o r r e c t
C o r r e c t and
I n P o s i t i o n
L i s t L e n g th
7 11 7 11
A . R e c a ll
o»
1^.67 6 .3 7 I+.JL3 1+.17
5"
5 .0 0 6 .3 0 3 4 3 3 .7 7
20" k .9 0
6 .1 3 3 .9 0 3 .5 7
No o r d e r in f o r m a tio n
U-.97 6 .3 7 3 .7 7 3 .3 0
A lp h a b e tiz e d
c a t e g o r i e s l+.6o
5 .9 3
2 .7 0
1 .7 3
O rd e r I n f o r m a tio n
p ro v id e d 5 .2 0 6 .5 0 5 .0 0
6 4 7
G rand m eans
M 9
6 .2 7
3 .8 2
3.81+
B. R e c o g n itio n
0" 6 .5 0 9 .0 0 M 3
3 .0 7
2 *
6 .6 0 9 .2 0 3 4 0
3 .3 3
20" 6 .6 3
9 .5 ° 3 .9 7
2 .8 0
No o r d e r in f o r m a tio n 6 . 6o 8 .7 0 l+.oo 3 .2 7
A lp h a b e tiz e d
c a t e g o r i e s 6 .5 0
9.1+0
2 .1 0 2 .0 3
O rd e r in f o r m a tio n
p r o v id e d
6 .6 3
9 .6 0
M 3 3 .9 0
G rand Means
6 .5 8 9*23 3 .6 9 3 .0 7
c o r r e c t l y o n r e c a l l * w i t h t h e "N o O r d e r I n f o r m a t i o n * an d
" A l p h a b e t i z e d C a t e g o r i e s " f o l l o w i n g I n t h a t o r d e r *
E v i d e n t l y * p r o v i d i n g t h e c a t e g o r i e s i n t h e w ro n g o r d e r h a d
a n i n t e r f e r e n c e e f f e c t * F e w e r w o rd s w e re c o r r e c t l y p l a c e d
f o r t h e e le v e n - w o r d l i s t e x c e p t w h en t h e o r d e r i n f o r m a t i o n
w a s p r o v i d e d * T h i s p r o b a b l y a c c o u n t s f o r t h e s i g n i f i c a n t
i n t e r a c t i o n * T he l e n g t h o f t h e l i s t d i d n o t se e m t o i n
f l u e n c e t h e o v e r a l l n u m b e r o f w o rd s c o r r e c t l y p l a c e d * a t
l e a s t s i g n i f i c a n t l y * b u t t h i s i s p r o b a b l y d u e t o t h e
i n t e r a c t i o n b e i n g s i g n i f i c a n t *
F o r t h e r e c o g n i t i o n m e a s u r e s n o o r d e r i n f o r m a t i o n
w as p r o v i d e d * T h e s u b j e c t s s i m p ly lo o k e d a t t h e s l i d e
c o n t a i n i n g t h e f o u r w o rd s g r o u p e d i n t h e i r r e s p e c t i v e
c a t e g o r i e s f r o m w h ic h t h e y h a d t o s e l e c t t h e w o rd t h e y h a d
p r e v i o u s l y s e e n . T h ey w e re t o l d t o p u t t h e w o rd s i n t h e
c o r r e c t o r d e r i f t h e y c o u l d , b u t t o i n c l u d e a l l o f t h e
w o rd s t h a t t h e y re m e m b e re d * F o r t h e NCRe m e a s u r e * s i g
n i f i c a n c e o c c u r r e d f o r L i s t L e n g t h ( F s 3 6 3 * 5 0 0 , d f ■ 1*
8 1 ) a n d t h e L e n g th b y O r d e r i n t e r a c t i o n . (F ■ 3 . 3 9 6 , d f ■
2 , 8 1 ) • T h e n u m b er c o r r e c t l y r e c a l l e d w as n o t i n f l u e n c e d
b y t h e o r d e r i n f o r m a t i o n f o r t h e s h o r t e r l i s t l e n g t h *
B o th g r o u p s * h o w e v e r* w h ic h h a d som e i n f o r m a t i o n a b o u t t h e
c a t e g o r i e s p e r f o r m e d b e t t e r t h a n t h e "N o O r d e r I n f o r m a t i o n "
g r o u p o n t h e l o n g e r l i s t l e n g t h u n d e r t h e r e c o g n i t i o n
c o n d i t i o n *
156
F o r t h e IPR e d e p e n d e n t v a r i a b l e b o t h O rd e r (F ■
8 .3 7 0 , d f « 2 , 8 1 ) and L i s t L e n g th (F ■ 1 0 .6 7 0 , d f ■ 1 ,
8 1 ) w e re s i g n i f i c a n t . A l l g ro u p s d id p o o r e r i n o o r r e o t l y
p l a c i n g t h e i r r e s p o n s e s w hen t e s t e d w i t h t h e lo n g e r l i s t .
When c o r r e c t o r d e r i n f o r m a t i o n was p r o v id e d u n d e r r e c a l l
c o n d i t i o n s , r e c o g n i t i o n o r d e r w as f a c i l i t a t e d . I n t h i s
o a s e , h o w e v e r, a l p h a b e t i z e d c a t e g o r i e s a g a i n h a d a n
i n t e r f e r e n c e e f f e o t .
A n o th e r a n a l y s i s o f v a r i a n c e w as p e rfo rm e d t o
d e te r m in e i f s i g n i f i c a n t d i f f e r e n c e s o c c u r r e d b e tw e e n t h e
f i v e d i f f e r e n t l i s t s . S i g n i f i c a n c e w as o b t a i n e d an d t -
t e s t s r e v e a l e d t h a t t h e e le v e n - w o r d *C" l i s t and th e
se v e n -w o rd *B" l i s t w ere s i g n i f i c a n t l y e a s i e r t h a n t h e
o t h e r s . (S e e T a b le s 10 and 1 1 .)
T h e re w as a p o s s i b i l i t y t h a t t h e ran d o m a s s ig n m e n t
o f t h e l i s t s t o th e d i f f e r e n t g r o u p s m ay h a v e r e s u l t e d i n
o n e o r s e v e r a l g ro u p s b e in g f a v o r e d b y h a v in g m ore th a n
t h e i r s h a r e o f t h e s e e a s i e r l i s t s . S in c e t h e l i s t l e n g t h s
w ere a " w i t h i n " e f f e c t , i t w ould b e n e c e s s a r y t o e l i m i n a t e
th o s e s u b j e o t s who h a d u s e d e i t h e r t h e 1 1 -w o rd "C* l i s t o r
t h e 7 -w o rd " b " l i s t f o r b o th l i s t l e n g t h s . T h is w o u ld
h a v e r e s u l t e d i n t h e l o s s o f a b o u t l{.0 p e r c e n t o f t h e
d a t a . I n s p e c t i o n r e v e a l e d t h a t t h e g r e a t e s t d i f f e r e n c e
w as o b t a i n e d f o r t h e 1 1-w ord l i s t s . C o n s e q u e n tly , i t w as
d e c id e d t o r e p e r f o r m t h e a n a l y s i s a f t e r re m o v in g o n ly
157
TABLE 6
ANALYSIS OP VARIANCE SUM M ARY
RECALL
NUMBER CORRECT
S o u rc e d f 33 M S
P
B etw een s u b j e c t s
89 2 7 5 .8 9 9
3 .0 8 9
1 .6 7 7 1 (NS)
O rd e r i n f o r m a ti o n 2 1 0 .6 8 2
5 .3 5 1
I n t e r p o l a t e d a c t i v i t y
( ! • * . )
2 .5 8 2 .2 9 1
I n t e r a c t i o n
5
5 .6 8 5 1 .5 2 1
E r r o r (b ) 81 2 5 7 .9 5 0
2 3 6 .5 0 0
8 1 .3 5 3
O .07L
3 .1 8 5 6
W ith in s u b j e c t s
L i s t le n g t h
90
1
8 1 .3 5 3 5 3 .8 7 5 *
L e n g th x o r d e r 2
0 .0 3 7
L e n g th x a c t i v i t y 2
0 .5 7 5 0 .2 8 7
L e n g th x o r d e r x
a c t i v i t y
5
5 .3 6 0 I .0 9 0
E r r o r (w) 81
1 5 0 .1 5 9 1 .8 5 5
T o ta l
179 5 1 1 .3 9 9
ap < .0 0 1
158
TABLE 7
ANALYSIS OP VARIANCE SUM M ARY
RECALL
NUMBER CORRECT AND IN POSITION
S o u rc e d f S3 M S p
B etw een s u b j e c t s
O rd e r I n f o r m a t io n
89
2
7 1 4 .1 6 1
3 7 8 .8 1 1 1 8 9 . 1+06
l+ 3.895a
I n t e r p o l a t e d a c t i v i t y 2 9 .8 7 8
I n t e r a c t i o n
k , £ .9 2 2 1.1+805
E r r o r (b ) 81 31+9.550 1+.315
W ith in s u b j e c t s 90 1 9 5 .5 0 0
L i s t l e n g t h 1 0 .0 0 5 0 .0 0 5
L e n g th x o r d e r 2
1+9.51+5
21+.772 l 5 .7 5 8 a
L e n g th x a c t i v i t y 2
3.314-5
1 .6 7 2
L e n g th x o r d e r x
a c t i v i t y
1 + 1 5 .2 5 5
3 . 8 4 2 4 2 6
E r r o r (w) 81 1 2 7 .3 5 0 1 .5 7 2
T o t a l
179
9 3 9 .6 6 1
ap < *001
159
TABLE 8
ANALYSIS OP VARIANCE SUM M ARY
RECOGNITION
NUMBER CORRECT
Source df
s s ms P
Between su b jects
Order
89
2
I 6Q .39I4 .
6 .7 1 1 3 .3 5 6 1 .8 2 0
A c tiv ity 2 3 .0 1 1 1 .5 0 6
Order x a c tiv ity
k
, 9 .3 2 2
2 *2 ?,°
E rro r (b) 81 .lil-9.350
I . 8 4 J 4.
W ithin su b je c ts
Length
90
1
H .05.000
3 1 7 .3 3 8
6 .9 7 8
3 1 7 .3 3 8 3 6 3 . 500J
Length x order 2
3 .£ 8 9 3 .3 9 6 b
Length x a c tiv ity 2 1 .0 7 8
0 .5 3 9
Length x a c tiv ity x
order
k
8 .8 5 6 2 .2 3 4 2 .5 3 6
E rro r (w) 81 7 0 .7 5 0 0 .8 7 3
T otal
179 573.3914-
a P < .0 5
b P < .0 0 1
160
TABLE 9
ANALYSIS OF VARIANCE SUM M ARY
RECOGNITION
NUM BER CORRECT AND IN POSITION
S o u rc e d f S3 M S F
B etw een s u b j e c t s
O rd e r
89
2
61^*700
1 0 8 .1 3 3 55.. 067 8 .3 7 0 *
A c t i v i t y 2
1 .2 3 3 0 .6 1 7
O rd e r x a c t i v i t y
k 13.035- 3 .2 5 8
E r r o r (b ) 81 5 2 3 .3 0 0 o.li-oO
W ith in s u b j e c t s
L e n g th
90
1
2 1 9 .5 0 0
2 li.2 0 0 2 li.2 0 0 1 0 .6 7 0 a
L e n g th x o r d e r 2 0 .0 0 0 0 .0 0 0
L e n g th x a c t i v i t y 2 1 0 .3 0 0 5 .1 5 0 2 .2 7 1
L e n g th x a c t i v i t y x
o r d e r
k
1 .3 0 0
0 .3 2 5
E r r o r (w) 81 1 8 3 .7 0 0 2 .2 6 8
T o ta l
179
8 6 5 .0 0 0
®P < .0 1
TABLE 10
ANALYSIS OF VARIANCE SUM M ARY
BETWEEN 11 W O RD LISTS
Source df SS M S F
Between
1 +
36*86
9 .2 1 5
3 . 2 & a
W ithin
85 2 1 4 .0 *7 1 4 .
2 .8 3 2
T otal
89
2 7 7 .6 0
a
• 0 £ > <*> .01
TABLE 11
LIST MEANS IN RANK ORDER
L i s t 11 Words L i s t 7 W ords
E 5 . 6S E I4.I4O
A 5. 8 k
A If. 67
D 6 .1 0 D
U-.95
B 6 . y
C 5 .0 0
Ca Ba 5 .8 0
S i g n i f i c a n t l y d i f f e r e n t fro m
o th e r s *
162
those su b jects who had been te s te d w ith the ttC* l i s t*
(See Tables 12 th r o u g h 1 6 .)
The r e s u lts from these analyses d iffe re d In only
one re sp e c t from those performed e a r l ie r u sin g a l l of the
l i s t s ; fo r the NCRe v a ria b le , the Length by Order I n te r
a c tio n did not q u ite reach sig n ifican ce*
As a fu rth e r check on the major h y p o th esis, another
a n a ly sis of v ariance was perform ed using only the 11-word
l i s t s excluding nC." The r e s u lts of th is a n a ly sis d if f e r
In no way from the o th e rs. Although scores fo r the p o s i
tio n v a ria b le were low, considerable order e x iste d In the
answers* In an attem pt to measure th e e x te n t of th is
order two a d d itio n a l analyses were perform ed. The f i r s t
t a l lie d the number of word p o sitio n s answers would have
to be moved to o b tain p e rfe c t correspondence w ith the
p o s itio n of th e answers as they were d isp lay ed . The
second an a ly sis t a l l i e d th e number of words th a t would
have to be moved to o b tain a c o rre c t order fo r those words
th a t were r e c a lle d . These d ata do not provide any in f o r
m ation about In d iv id u al performance since th e su b je c ts did
not a l l r e c a ll the same number of w ords. Comparisons be
tween groups, however, seem le g itim a te since th e re were no
s ig n ific a n t d iffe re n c e s in the mean number of words r e
c a lle d by the various groups.
These d a ta were not su ita b le fo r fu rth e r analyses
163
TABLE 12
ANALYSIS OP VARIANCE SUM M ARY
RECALL
NUMBER CORRECT (EXCLUDING LIST C)
S o u rc e d f
s s M S P
B etw een s u b j e c t s
O rd e r
70
2
" S i S
2 .7 2 0
A c t i v i t y 2 9 4 0 6
I*-.703
O rd e r x a c t i v i t y
k
1 2 .0 5 0 3 .0 1 2
E r r o r (b ) 62 1 7 2 .2 5 8 2 .7 7 8
W ith in s u b j e c t s
L e n g th
71
1
1 3 8 .0 0 0
3 8 .5 6 3 3 8 .5 6 3 27.23l|-a
L e n g th x o r d e r 2 0 .2 6 6
0 .1 3 3
L e n g th x a c t i v i t y 2
3 .3 9 9
1 .7 0 0
L e n g th x o r d e r x
a c t i v i t y
h r
1 .9 9 6
E r r o r (w) 62
8 7 .7 8 7
1 ^ 1 6
T o ta l llj-l
3 3 7 .1 5 5
a P < *001
TABLE 13
ANALYSIS OP VARIANCE SUM M ARY
11 W O RD LISTS EXCLUDING LIST C
S o u rc e d f S3 M S
O rd e r 2
2 .3 1 ^
A c t i v i t y
( C e l l s )
2
( 8 ) < 2!
^ . 6 biv
O rd e r x a c t i v i t y
h
2 0 . 761* .
W ith in 62
1 5 4 .3 1 3 2 . 14.089
T o ta l 70 1 8 2 .7 3 4
1 6 1 *
TABLE ll*
ANALYSIS OF VARIANCE SUM M ARY
RECALL •
NUMBER CORRECT AND IN POSITION
EXCLUDING LIST C
S o u rc e d f SS M S F
B etw een s u b j e c t s
O rd e r I n f o r m a tio n
70
2
1*97.732
2 3 0 .6 0 5
1 1 5 .3 0 2 2 9 . 2 1 2 a
I n t e r p o l a t e d a c t i v i t y 2 7 .0 3 8
3 .5 1 9
O rd e r x a c t i v i t y
E r r o r (b ) 6^
1 5 .3 5 9
2l*l*.730
3 .8 k 0
3 .9 k 7
W ith in s u b j e c t s
L e n g th
71
1
1 2 9 .0 0 0
0.1*50 0.1*50
9 . 9 6 6 a L e n g th x o r d e r 2 2 8 .2 0 5 li* .1 0 2
L e n g th x a c t i v i t y 2 2 .9 1 8
1.1*59
L e n g th x o r d e r x
a c t i v i t y
h
9 .7 1 8 2.1*30
E r r o r (w) 62
8 7 .7 0 9 1.1*15
T o ta l
H*1
*P < .0 0 1
165
TABLE 15
ANALYSIS OF VARIANCE SUM M ARY
RECOGNITION
NUMBER CORRECT (EXCLUDING LIST C)
S o u rc e d f s s M S F
B etw een s u b j e c t s
O rd e r
70
2
1 1 8 . 6 6 2
3 . # 7
1 .7 7 8
0 . 6 0 8 A c t i v i t y 2
1 .2 1 7
2 .l ( . 6 6 O rd e r x a c t i v i t y 1 5 .6 3 ? 3 .9 0 8
E r r o r (b ) 6 2 9 8 . 2 5 6
1 .5 8 5
W ith in s u b j e c t s
L e n g th
71
1
2 7 5 .0 0 0
2 0 8 .3 3 8 2 0 8 .3 3 8 23l4-.09a
L e n g th x o r d e r 2
3 .0 5 5
1 . 5 2 8
L e n g th x a c t i v i t y 2 0 . 5 0 8
0.2514-
L e n g th x o r d e r x
a c t i v i t y
>
7 .9 2 8 1 .9 8 2
E r r o r (w ) 6 2
5 5 .1 7 1
O .8 9 O
T ot a l 1 1 4 .1
3 9 3 . 6 6 2
*P < .0 0 1
166
TABLE 16
ANALYSIS OF VARIANCE SUM M ARY
RECOGNITION
NUMBER CORRECT AND IN POSITION
(EXCLUDING LIST C)
S o u rc e d f SS M S F
B e tw ee n s u b j e c t s 70 lj.62.Q l5 2 Q .170 lj-.635a
O rd e r 2 5 8 .3 3 9 1 .6 7 2
A c t i v i t y 2 3*3&3 2.7lj.2
O rd e r x a c t i v i t y L j. 1 0 .9 8 0 6.29l|.
E r r o r (b ) 62 3 9 0 .2 5 3
W ith in 7 1 1 9 1 .0 0 0
Length 1 2 0 .5 3 5 2 0 .5 3 5 8 .0 5 3 *
Length x order 2 0 .0 5 3 0 .0 2 b
Length x a c t iv it y 2 1 0 .1 1 2 5*056
Length x order x
a c t i v i t y lj. 2 .1 7 6 0 . 5141-
E r r o r (w) 62 I 5 8 . 12lj. 2 .5 5 0
T o ta l II4 .I 6 5 3 .9 1 5
aP < .0 5
bp < .0 0 1
b u t m ean s c o r e s a r e in c lu d e d I n T a b le 17 t o i n d i c a t e th e
e x t e n t t h a t o r d e r w as m a in ta in e d *
D is c u s s io n
A c c o rd in g to t h e fo rm u la s g iv e n b y Brown (195>9)>
f o r a se q u e n c e e l e v e n ite m s lo n g w ith a v o c a b u la r y o f
f o u r p o s s i b l e w ords f o r e a c h Item * th e o r d e r i n f o r m a tio n
w ould a c c o u n t f o r o v e r o n e - h a l f o f th e t o t a l I n f o r m a tio n
t r a n s m i t te d * (S e e A p p en d ix D*) E v en f o r a v o c a b u la r y o f
32 w ords p e r item * th e am ount o f o r d e r i n f o r m a ti o n w ould
be o v e r o n e - f o u r t h o f th e t o t a l i n f o r m a tio n tr a n s m i t te d *
And y e t i n t h i s e x p e r im e n t, t h e r e was no s i g n i f i c a n t
d i f f e r e n c e b e tw e e n g ro u p s i n w h ic h th e am ount o f o r d e r
i n f o r m a ti o n p r o v id e d v a r i e d fro m n one to t o t a l o r d e r r e
dundancy* T h is w as t r u e f o r a l i s t le n g t h t h a t j u s t ex
c e e d e d th e memory sp a n as w e ll a s f o r a lo n g e r l i s t *
I t i s a w e ll known f a c t t h a t i f m a t e r i a l i s to be
m em orized t o a c r i t e r i o n o f e r r o r l e s s r e c a l l , th e tim e
r e q u i r e d I n c r e a s e s d i s p r o p o r t i o n a t e l y as th e p a s s a g e i s
le n g th e n e d . T h ere i s a p o s s i b i l i t y t h a t t h i s ty p e o f
t a s k w o u ld b e n e f i t a s i n f o r m a tio n th e o r y w ould p r e d i c t *
T h a t i s , i f th e o r d e r was p r o v id e d , t h i s may r e s u l t i n
s u b s t a n t i a l s a v in g s f o r a t a s k in v o lv in g m e m o riz a tio n to
p e r f e c t r e c a l l * The f o rm u la p r o v id e d by B row n, h o w e v e r,
r e t a i n s t h e c o n c e p t o f " b i t s * o f i n f o r m a tio n w h ic h a re
TABLE 17
AVERAGE EXTENT OF ORDER AND PO SITIO N
L i s t L e n g th
G roup
7 11
A* A v e ra g e N um ber o f S p a c e s t h e Re
m em b ered W ords H ad t o b e M oved t o b e
I n t h e C o r r e c t P o s i t i o n
0* 1 .2 7 5 * 6 3
S "
2 .^ 0
7 .1 7
2 0 " 2 .1 7
7 . 9 3
No o r d e r I n f o r m a t i o n 2 .0 0 7 . o 0
A l p h a b e t i z e d c a t e g o r i e s 3 * 3 0 1 3 .0 7
O r d e r I n f o r m a t i o n p r o v i d e d 0 .0 0
0 .0 3
B . A v e ra g e N um ber o f R em em bered W ords
T h a t Had t o b e M oved t o O b t a i n
P e r f e c t O r d e r I g n o r i n g P o s i t i o n
0*
0 .2 7 1 .0 0
S n
0 .5 2 *
2 0 * 0 .3 0 0 . 6 8 *
No o r d e r I n f o r m a t i o n
o J b .
1 .0 3
1.144* A l p h a b e t i z e d c a t e g o r i e s 0 . 6 0 *
O rd e r i n f o r m a t i o n p r o v i d e d
0 .0 3
0 .0 0
£
A v e ra g e f o r t h e s e g r o u p s w as
a c t u a l l y h i g h e r b u t I n d e t e r m i n a t e . One o r
m o re s u b j e c t s I n t h e s e c o n d i t i o n s s t a t e d
t h e y c o u ld n o t p u t t h e w o rd s I n t h e o r d e r
p r e s e n t e d an d p u t th e m I n t h e a l p h a b e t i s e d
c a t e g o r y o r d e r * T h e s e p e r s o n s w e re e x
c lu d e d I n c a l c u l a t i n g t h e a v e r a g e s l i s t e d *
169
l a r g e l y d e p e n d e n t u p o n t h e s i z e o f th e v o c a b u la ry fro m
w h ic h th e Ite m I s s e l e c t e d . S e v e r a l e x p e rim e n ts c i t e d
i n C h a p te r U r e v e a l t h a t t h i s c o n c e p t i s n o t d e s c r i p t i v e
o f hum an memory p e rf o r m a n c e . I n f a c t , s e v e r a l a u th o r s
c o n c lu d e t h a t one way o f f a c i l i t a t i n g memory p e rfo rm a n c e
i n te rm s o f th e am ount o f i n f o r m a tio n t r a n s m i t t e d i s t o
p a c k a s much i n f o r m a tio n i n e a c h ite m as p o s s i b l e .
M i l l e r ’ s (1 9 ^ 6 ) c o n c e p t o f "ch u n k * seem s t o be a m ore
a p p r o p r i a te d e s c r i p t i o n o f p e rfo rm a n c e . E v i d e n t l y , m an’ s
s h o r t - t e r m memory i s l i m i t e d t o c a r r y i n g a b o u t s e v e n ,
p lu s - o r - m in u s tw o , c h u n k s o f i n f o r m a ti o n .
I t i s i n t e r e s t i n g t o n o te t h a t w hen th e r e s p o n s e
m e a su re d was th e num ber o f ite m s p la c e d i n th e c o r r e c t
p l a c e , o r d e r d o e s h a v e a s i g n i f i c a n t e f f e c t . T h is s u g
g e s t s t h a t a lth o u g h th e ite m s a r e r e t a i n e d , th e o r d e r h a s
b e e n l o s t . P e rh a p s B r o a d b e n t’ s " f i l t e r * a d m its o n ly
ite m s o r t h a t th e ite m s a re a d m itte d fro m th e s h o r t - t e r m
s t o r e a s th e f i l t e r becom es c l e a r e d . I f th e l a t t e r i s
t r u e , and i f r e v e r b e r a t i n g c i r c u i t s a c c o u n t f o r t h i s
s h o r t - t e r m s t o r e , t h e r e i s no c e r t a i n t y t h a t ite m s w i l l
be a d m itte d th r o u g h th e f i l t e r i n th e same o r d e r a s th e y
w ere p r e s e n t e d . A m ore e x te n s i v e d i s c u s s i o n o f th e s e
r e s u l t s w i l l be in c lu d e d i n C h a p te r V.
One s u r p r i s i n g r e s u l t o f th e e x p e rim e n t was th e
i n e f f e c t i v e n e s s o f i n t e r p o l a t e d a c t i v i t y i n i n t e r f e r i n g
w ith t h e memory f o r th e i t e m s . S e v e r a l e x p e r im e n ts h a v e
i n d i c a t e d t h a t su c h a r e q u ir e m e n t r e s u l t e d i n a s u b
s t a n t i a l d e c re m e n t i n a s s h o r t a tim e a s 20 s e c o n d s * e v e n
w hen o n ly one th r e e - c o n s o n a n t s y l l a b l e w as u s e d a s i n th e
P e t e r s o n and P e t e r s o n s t u d y . M ajo r d i f f e r e n c e s b e tw e e n
t h e i r s tu d y and th e p r e s e n t one w h ich m ig h t a c c o u n t f o r
t h e d i f f e r e n c e s in c lu d e t h e i r r e q u ir e m e n t t h a t th e
s y l l a b l e b e r e p e a t e d b a c k i n e x a c t l y t h e same s e q u e n c e
a s g iv e n * and a p o s s i b i l i t y t h a t t h e i r r a t e o f p r e s e n t a
t i o n w as m uch s h o r t e r t h a n t h a t u s e d h e r e . I t was d e
c id e d t h a t a f o llo w - u p s tu d y i n v e s t i g a t i n g t h i s l a t t e r
p o s s i b i l i t y a s w e l l a s t h e l e n g t h o f i n t e r p o l a t e d
a c t i v i t y s h o u ld b e p e rf o r m e d .
CHAPTER IV
EXPERIMENTS INVESTIGATING INTERPOLATED ACTIVITY
I n t r o d u c t i o n
The e x p e r im e n ts r e p o r t e d I n t h i s c h a p te r w ere d e
s ig n e d t o c l a r i f y t h e r e a s o n t h a t I n t e r p o l a t e d a c t i v i t y
d id n o t r e s u l t I n a d e c re m e n t I n th e f i r s t e x p e rim e n t*
The d e c a y t h e o r y h a s b e e n s u p p o r te d by many e x p e r im e n ts ,
in o lu d in g th o s e o f t h e P e te r s o n s (1 9 5 9 )* M urdock ( I 96 I ) ,
C onrad (1 9 5 7 )* and Brown ( 1 9 5 8 ) . I n E x p e rim e n t I , how
e v e r , th e num ber o f w o rd s c o r r e c t l y r e c a l l e d d id n o t v a r y ,
a lth o u g h I n t e r p o l a t e d a c t i v i t y w as m a in ta in e d f o r p e r i o d s
u p t o 20 se c o n d s* W ith su c h s t r o n g e v id e n c e I n f a v o r o f
a d e c a y in g t r a c e th e o r y th e p ro b le m o f a c c o u n tin g f o r no
d e c re m e n t o c c u rs *
E x p e rim e n t I I
One p o s s i b i l i t y was t h a t th e d u r a t i o n o f s tim u lu s
e x p o s u re a llo w e d s u f f i c i e n t r e h e a r s a l t o overcom e th e
d e c a y p r o c e s s e s f o r t h e d u r a t i o n o f th e i n t e r p o l a t e d
a c t i v i t y * I t was d e c id e d t o I n v e s t i g a t e t h i s p o s s i b i l i t y *
M ethod*— The same a p p a r a tu s was u s e d a s i n th e
f i r s t e x p e rim e n t* The s ti m u l u s d u r a t i o n w as v a r i e d b e
tw e e n 1*0 s e c o n d s and 0*ij. se c o n d s * Due t o th e l i m i t a t i o n s
171
172
o f th e s l i d e p r o j e c t o r I n t e r s t i m u l u s tim e w as a c o n s t a n t
0 .6 se c o n d s* T h e r e f o r e , th e t o t a l tim e b e tw e e n th e o n s e t
o f s u c c e s s iv e s t i m u l i w as 1*0 and 1*6 s e c o n d s f o r th e two
c o n d itio n s *
I n t e r p o l a t e d a c t i v i t y was e i t h e r z e r o o r 20 se c o n d s
and a g a in c o n s i s t e d o f c o u n tin g b a c k w a rd s by t h r e e s fro m
th e num ber d is p la y e d a s th e f i n a l I te m I n th e se q u en c e*
O nly t h r e e o f t h e o r i g i n a l f i v e s e q u e n o e s w ere
u s e d , th e two w h ic h w ere fo u n d t o be d i f f e r e n t b e in g
o m itte d * O nly th e e le v e n -w o rd se q u e n c e was u se d * B o th
th e r e c a l l end r e c o g n i t i o n t a s k s w ere I n c lu d e d as b e fo re *
The p ro c e d u re w as th e same a s I n E x p e rim e n t I i n m o st
o t h e r r e s p e c t s , b u t a l l s u b j e c t s w ere t e s t e d i n th e *no
o r d e r in f o r m a tio n 1 1 c o n d itio n *
S u b j e c t s *— P r e v i o u s l y u n t e s t e d v o l u n t e e r s u b j e c t s
from P a sa d e n a C ity C o lle g e w ere u s e d f o r a l l o f th e e x
p e r im e n ts t o b e r e p o r t e d I n t h i s c h a p te r * T h ese s u b j e c t s
w ere sophom ore o r fre s h m a n s t u d e n t s e n r o l l e d i n i n t r o
d u c to r y p s y c h o lo g y c l a s s e s * F o r t y s u b j e c t s , t e n s u b j e c t s
p e r g ro u p , w ere ra n d o m ly a s s ig n e d t o one o f th e f o u r
c o n d itio n s *
R e s u l t s *— When th e tim e b e tw e e n s u c c e s s iv e s t i m u l i
w as one s e c o n d , m ean r e c a l l s c o r e s f o r th e z e ro and tw e n ty
se c o n d i n t e r p o l a t e d a c t i v i t y g ro u p s w as ^ * 6 and 1^*9 r e
s p e c t i v e l y * C om parable s c o r e s f o r th e 1*6 s e c o n d g ro u p
173
w are £ •£ and 5*2 w ords r e s p e c t i v e l y * A g a in , i n t e r p o l a t e d
a c t i v i t y seem ed to h a v e no I n f l u e n c e when th e d e p e n d e n t
v a r i a b l e was t h e num ber o f ite m s c o r r e c t l y r e c a l l e d i r
r e s p e c t i v e o f o rd e r* R e c o g n itio n s c o r e s show ed th e same
r e s u l t a lth o u g h t h e r e was a g r e a t e r num ber o f w ords c o r
r e c t l y re c o g n iz e d * F o r th e r e c o g n i t i o n t a s k , m eans o f
8*3 and 9«1 w ere o b ta in e d u n d e r th e one se o o n d c o n d i t i o n
and 9*6 and 9*3 f o r th e 1*6 se c o n d c o n d i t i o n f o r th e z e r o
and 2 0 -s e c o n d I n t e r p o l a t e d a c t i v i t y g ro u p s r e s p e c t i v e l y
( s e e T a b le 1 8 )*
A n a ly s is o f v a r ia n c e ( s e e T a b le 19) r e v e a l e d t h a t
th e tim e b e tw e e n th e o n s e t o f s u c c e s s iv e s t i m u l i was n o t
a s i g n i f i c a n t c o n d i t i o n f o r e i t h e r th e r e c a l l o r r e c o g n i
t i o n t a s k s a lth o u g h i t a p p ro a c h e d s i g n i f i c a n c e a t th e *0£
l e v e l when th e num ber o f ite m s c o r r e c t l y r e c o g n iz e d was
th e d e p e n d e n t v a r i a b l e (F a i|* 0 7 , d f a 1 , 3 6 )* T h u s, i t
a p p e a rs t h a t r e c o g n i t i o n i s a m ore s e n s i t i v e m e a su re th a n
r e o a l l and t h a t t h e r e i s r e l a t i v e l y good r e a s o n to s u p
p o se t h a t th e t o t a l tim e t h a t e a c h s tim u lu s may be r e
h e a r s e d d o e s h a v e a n I n f lu e n c e e v e n a t th e s e s h o r t tim e
i n t e r v a l s *
E x p e rim e n t I I I
I t i s p o s s i b l e t h a t th e d e c a y f o r w ords i s s lo w e r
th a n t h a t f o r o t h e r ty p e s o f m a t e r i a l* I f t h i s i s t r u e
X 7lf
TABLE 18
EXPERIMENT I I
MEAN SCORES
I n t e r p o l a t e d A c t i v i t y
0* 20*
A* Mean R e c a l l S c o re s
Tima b e tw e e n o n s e t 1 .0 * 1^.6
o f s u c c e s s iv e
k»9
s t i m u l i
1 .6 " 5 .5 5 .2
B . Mean R e c o g n itio n S c o re s
Tima b e tw e e n o n s e t 1 .0 " 8*3 9*1
o f s u c c e s s iv e
s t i m u l i
1 .6 * 9 .6 9 -3
175
TABLE 19
EXPERIMENT I I
ANALYSIS OP VARIANCE SUM M ARY
S o u ro e d f S3 M S p
A* R e c a l l
Tiiba b e tw e e n
s u c c e s s iv e
I n t e r p o l a t e d
tim e
( C e l l s )
I n t e r a c t i o n
W ith in
o n s e t o f
s t i m u l i
a c t i v i t y
1
1
(3 )
1
36
3 .6 0 0
0*000
(14-500)
0*900
l+ i.lio o
3 .6 0 0
0*900
1 .1 5 0
3 .1 3
T o ta l
39
145.900
B . R e c o g n itio n
Time b e tw e e n o n s e t o f
s u c c e s s iv e s t i m u l i
I n t e r p o l a t e d a c t i v i t y
tim e
( C e l l s )
I n t e r a c t i o n
W ith in s u b j e c t
1
1
(3 )
1
36
7 .2 2 5
1 .2 2 5
( 1 0 4 7 5 )
2 .0 2 5
6 3 .9 0 0
7 .2 2 5
1 .2 2 5
2 .0 2 5
1 .7 7 5
l4 .0 7 a
T o t a l
39 7*4.375
a
An F o f 4 * 1 1 I s n e c e s s a r y f o r s i g n i f i c a n c e
a t th e *05 l e v e l*
176
th e n p e rh a p s 20 s e c o n d s d o e s n o t a llo w t h e t r a c e t o d e c a y
t o th e e x t e n t t h a t i t I s b elo w th e t h r e s h o l d f o r r e c a l l *
C o n s e q u e n tly , i t w as d e c id e d t o p e rfo rm a n o th e r e x p e rim e n t
e x te n d in g th e d u r a t i o n o f i n t e r p o l a t e d a c t i v i t y t o tw o
m in u te s . The sem e p ro c e d u re a s t h a t u s e d i n E x p e rim e n t
I I was fo llo w e d i n t h i s e x p e rim e n t e x c e p t f o r th e u s e o f
o n ly th e s h o r t e r e x p o s u re t i m e . I n t e r p o l a t e d a c t i v i t y
tim e s w ere lj.0, 6 0 , and 120 s e c o n d s . T w e n ty -fo u r p r e v i o u s
l y u n t e s t e d s u b j e c t s w ere ra n d o m ly a s s ig n e d t o t h e t h r e e
tr e a tm e n t g ro u p s so t h e r e w ere e i g h t s u b j e c t s p e r g ro u p *
R e s u l t s *— The r e s u l t s o f t h i s e x p e rim e n t s t i l l do
n o t i n d i c a t e an y d e c a y o f a memory t r a c e . As t h e d u r a
t i o n o f i n t e r p o l a t e d a c t i v i t y i n c r e a s e d , r e c a l l s c o r e s o f
1^*75, If*75* an d 1+.375 w e re o b ta in e d w h ile r e c o g n i t i o n
s c o r e s o f 8 .7 5 * 9*00 and 9 .1 2 5 w ere r e v e a l e d . (S e e T a b le
2 0 .) An a n a l y s i s o f v a r i a n c e was p e rfo rm e d b u t a n on
s i g n i f i c a n t r e s u l t was a g a in o b t a i n e d . (S ee T a b le 21*)
E x p e rim e n t IV
The r a t e o f s t i m u l i was l i m i t e d i n E x p e rim e n t I I
by th e u s e o f a s l i d e p r o j e c t o r . I t i s p o s s i b l e t h a t th e
h y p o th e s is t e s t e d i n t h a t e x p e r im e n t, i . e . , t h a t th e o c
c u r r e n c e o f d e c a y i s l i m i t e d t o s h o r t e r s tim u lu s ex p o
s u r e s , w ould h a v e b e e n s u p p o r te d i f a n e v e n s h o r t e r
s tim u lu s d u r a t i o n h a d b e e n u s e d . E x p e rim e n t IV w as d e
s ig n e d t o t e s t t h i s *
TABLE 20
EXPERIMENT I I I
M EAN SCORES
R B a a a a d B n a a n t a a n H E e a a n a a n B B n B a B n H M M H H H i
D u r a tio n o f I n t e r p o l a t e d A c t i v i t y
1 + 0 60 120
R e c a l l 1+.75 1+.75 l|-.38
R e c o g n itio n 8 ,7 5 9*00 9*12
TABLE 21
EXPERIMENT I I I
ANALYSIS OP VARIANCE SUM M ARY
S o u ro e d f SS M S P
A . R e c a ll
B etw een 2 0 .7 6 8 0.381+
0.11+7
W ith in 21
5 M 5 7
2 .6 1 2
T o ta l 23 £ £ . 62£
B. R e c o g n itio n
B etw een 2
0 .5 8 3
0 .2 9 2 0 .1 2 2
W ith in 21
5 0 .3 7 5 2 .3 9 9
T o ta l 23 £0.958
173
M ethod . — The w ords fro m th e e le v e n -w o rd L i s t A
w ere r e c o r d e d on ta p e a t two s p e e d s , one w ord e v e r y seco n d
o r t h r e e w ords e v e r y s e c o n d . The e x p e r im e n te r p r a c t i c e d
a t r e a d in g e v e n ly an d w ith o u t e m p h a sis b e f o r e th e t e s t
ta p e w as r e c o r d e d . The sam e t h r e e - d i g i t num ber u s e d f o r
a l l o f th e v i s u a l d i s p l a y s was r e c o r d e d im m e d ia te ly f o l
lo w in g th e l a s t w ord i n th e s e r i e s . Thus* th e a u d ito r y
t a s k was e n t i r e l y a n a lo g o u s t o th e v i s u a l t a s k u s e d i n
t h e p r e v io u s e x p e r im e n ts .
The d u r a t i o n o f t h e I n t e r p o l a t e d a c t i v i t y was
e i t h e r 0* 2 0 , o r 60 s e c o n d s . A ra n d o m iz e d g ro u p d e s ig n
was u s e d w ith n in e s u b j e c t s b e in g a s s ig n e d t o e a c h o f th e
s i x o e l l s .
A f t e r th e s u b j e c t s h a d b e e n t e s t e d f o r t h e i r r e
c a l l * th e s l i d e p r o j e c t o r was u s e d to d i s p l a y th e r e c o g n i
t i o n l i s t and s u b j e c t s w ere r e q u e s te d t o w r i t e down th e
w ords fro m t h i s l i s t t h a t w ere o r i g i n a l l y p r e s e n t e d
a u r a l l y . I n a l l o t h e r r e s p e c t s * th e p ro c e d u re f o llo w e d
t h a t u se d i n th e p r e v io u s e x p e r im e n ts .
R e s u lts .- - W h e n th e w ords w ere a u r a l l y p r e s e n te d
t h e r e was a c h a n c e o f some m i s i n t e r p r e t a t i o n o r m is u n d e r
s t a n d i n g . F o r exam ple* th e w ord " g n a t* m ig h t be h e a r d as
"N a t" o r " n e t . * C o n s e q u e n tly s u b j e c t s w ere i n s t r u c t e d to
s p e l l th e w ords p h o n e t i c a l l y i f t h e r e was any d o u b t. A ll
w ords t h a t w ere s p e l l e d so upon p r o n o u n c ia tio n th e y
179
so u n d ed l i k e th e l i s t - w o r d w ere s c o r e d c o r r e c t *
Two s u b j e c t s d id n o t a p p e a r t o p a r t i c i p a t e I n th e
e x p e r im e n t. T hus tw o g ro u p s h ad o n ly e i g h t s u b j e c t s I n
s te a d o f n i n e . The m ean r e c a l l and r e c o g n i t i o n s c o r e s
a re l i s t e d I n T a b le 2 2 . F o r t h i s e x p e rim e n t b o th th e
s tim u lu s r a t e and I n t e r p o l a t e d a c t i v i t y r e s u l t e d i n s i g
n i f i c a n t d i f f e r e n c e s f o r th e r e c a l l ta s k * I t a p p e a rs as
th o u g h t h e t r a c e d e c a y th e o r y h a s f i n a l l y r e c e i v e d some
s u p p o rt* The s u p p o r t i s n o t u n e q u iv o c a l, h o w e v e r, s in c e
when th e d e p e n d e n t m e a su re was r e c o g n i t i o n , o n ly th e
s tim u lu s r a t e was s i g n i f i c a n t . (S e e T a b le 23*) T h ere i s
some e v id e n c e , h o w e v e r, t h a t w ith a l a r g e enough s a m p le ,
a s i g n i f i c a n t i n t e r a c t i o n m ig h t o c c u r f o r th e r e c o g n i t i o n
t a s k . A t l e a s t th e F - v a lu e f o r i n t e r a c t i o n was much
g r e a t e r f o r th e r e c o g n i t i o n t a s k . M o re o v er, f o r th e
f a s t e r r a t e t h e t r e n d i s i n th e d i r e c t i o n f a v o r i n g d e c a y
w h ile no t r e n d i s a p p a r e n t f o r th e s lo w e r r a t e *
X80
TABLE 22
EXPERIMENT IV
MEAN SCORES
S tim u lu s R a te
D u r a tio n o f I n t e r p o l a t e d A c t i v i t y
o» 2 0 * * 6 o*
A« R e c a l l
3 w o r d s /s e c *
if.3 3 3 .6 7 3 .1 1
1 w o rd /s e c * 5 . 1 2 lf . 6 2 If. 1 1
B . R e c o g n itio n
3 w o rd s /a e o * 6 • 1 + 4
5 .5 5
$ .k k
X w o rd /s e c * 8 , 0 0 8 .5 0 7 . 2 2
181
TABLE 23
EXPERIMENT IV
ANALYSIS OF VARIANCE SUM M ARY
S o u rc e d f SS M S F
A* R e c a l l
R a te
I n t e r p o l a t e d a c t i v i t y
( C e l l s )
I n t e r a c t i o n
W ith in
1 1 0 * 4 2 8
2 1 0 4 8 6
(S ) ( 2 1 .5 3 0 )
2 0 . 6 1 6
4 6 5^— 5>28
10.1^28
5.21*3
0 . 3 0 8
1 .1 8 5
8 .7 9 7 *
4 4 2 3 *
T o ta l 5 2 7 6 . 0 ^ 8
B . R e c o g n itio n
R a te
I n t e r p o l a t e d a c t i v i t y
( C e l l s )
I n t e r a c t i o n
W ith in
1 s i:ig
(5 ) (6 7 .8 5 3 )
2 5*827
I4-6 1 2 6 . 2 2 3
# . 3 6 2
3 .3 3 2
2.91b-
2.71*4
2 0 . 1 7 6 °
1 .2 1 4
T o ta l 52 1914..076
Sp
•01
*P .0 2 5
°P •001
CHAPTER V
DISCUSSION AND CONCLUSIONS
T h re e T ypes o f L e a rn in g In v o lv e d
i n Memory S p a n
T h ere a r e a c t u a l l y t h r e e ty p e s o f l e a r n i n g I n
v o lv e d I n m e a s u rin g t h e s p a n o f Im m e d ia te m em ory. The
s u b j e c t m u st f i r s t h a v e l e a r n e d t h e p o o l o f sy m b o ls fro m
w h io h t h e Ite m s d is p la y e d w ere s e l e c te d * E xam ples o f
t h i s l e a r n i n g a re th e k n o w led g e o f th e a lp h a b e t* w ords*
d i g i t s * e tc * * w ith o u t w h ic h nam es c o u ld n o t be a tt a c h e d
and no v e r b a l t r a n s m i s s i o n c o u ld ta k e p la c e * T h is l e a r n
in g s t a r t s e a r l y I n l i f e and c o n tin u e s th r o u g h o u t l i f e *
T h e re I s l i t t l e d o u b t t h a t t h i s l e a r n i n g I s i n f l u e n t i a l
I n h e l p i n g to d e te rm in e th e memory sp an * Im a g in e a
se q u e n c e o f sym bols fro m A ra b ic o r A rm enian a f t e r e a c h
one w as e x p o se d f o r one se c o n d i n a s e r i e s * how many
c o u ld b e r e p r o d u c e d f C e r t a i n l y n o t v e ry many* S u ch
l e a r n i n g may b e an exam ple o f r e c o d in g a p e r c e p t u a l l y
com plex d i s p l a y I n t o a r e l a t i v e l y s im p le v e r b a l co d e*
A t any r a t e * I n f o r m a tio n o f t h i s ty p e may be named " c l a s s
In f o r m a tio n * "
A se c o n d ty p e o f l e a r n i n g I s t h a t o f th e s p e c i f i c
Ite m s s e l e c t e d fro m t h e e n t i r e c l a s s w h lo h a c t u a l l y w ere
182
1 8 }
d i s p l a y e d . I n th e o r i g i n a l e x p e r im e n ts r e p o r t e d e a r l i e r ,
th e e l e v e n s p e c i f i c w ords o u t o f th e h u n d re d s o f th o u s a n d s
o f w ords i n t h e E n g lis h d i c t i o n a r y a r e r e p r e s e n t a t i v e o f
t h i s ty p e o f le a r n in g * T h ese a r e th e " t o h e rem em bered"
i te m s , an d t h i s ty p e o f in f o r m a ti o n may b e c a l l e d
" c o n t e n t" o r " ite m " in f o r m a tio n *
The t h i r d ty p e o f in f o r m a tio n t h a t m u st be l e a r n e d
i s t h e p a r t i c u l a r o r d e r i n w h ich t h e ite m s w ere d is p la y e d *
T h is i s w h at h a s b e e n o a l l e d th r o u g h o u t t h e p r e s e n t w o rk ,
th e " o r d e r in f o r m a tio n * "
As n o te d e a r l i e r , u n d e r s ta n d in g t h e u n d e r ly in g
memory p r o c e s s h a s b a f f l e d s c i e n t i s t s f o r y e a r s and we
seem no c l o s e r t o su c h an u n d e r s ta n d in g to d a y th a n we
w ere y e a r s ago* The s u g g e s tio n t h a t t h e r e may be m ore
th a n one ty p e o f memory m echanism may le a d t o g r e a t e r
u n d e r s ta n d in g o f t h e e n t i r e memory p r o c e s s *
T h ere i s l i t t l e d o u b t t h a t lo n g - te r m memory may
I n f lu e n c e t a s k s w h ich h a v e b e e n I n c lu d e d i n th e s h o r t
te rm memory c l a s s i f i c a t i o n * A num ber o f s t u d i e s h a v e
show n t h a t t h e c l o s e r a s e r i e s o f w o rd s a p p ro x im a te s
E n g l i s h , th e m ore w ords t h a t c a n be rem em bered*
A tte m p ts h a v e b e e n made a t r e d u c in g t h e i n f lu e n c e
o f t h i s lo n g - te r m le a r n in g * B ut i n a tt e m p t in g t o re d u c e
th e I n f l u e n c e o f la n g u a g e s , o t h e r w e l l - l e a r n e d ite m s h a v e
b e e n u s e d su c h as n o n s e n s e s y l l a b l e s o r g e o m e tric fo rm a ,
1 8 1 + .
b o th o f w h ic h p r o v id e o p p o r t u n i t i e s f o r v e r b a l m e d ia tio n ;
th e f o r m e r , i f n o t by a s s o c i a t i o n , th e n by p ro n o u n c e -
a b i l i t y i n t h e c a s e o f CVC s y l l a b l e s . F o r CCC s y l l a b l e s
w here a s s o c i a t i o n s do n o t o c c u r , t h e n o n ly d ig ra m o r
t r i g r a m f r e q u e n c y o r p e rh a p s th e i n f lu e n c e due t o C h u n k
in g * p r e v e n ts them fro m b e in g t h r e e u n i t s r a t h e r th a n
one*
F o r th e g e o m e tr ic sy m b o ls, w e l l l e a r n e d v e r b a l
m e d ia tio n s a r e p r o b a b ly a v a i la b l e * The u s e o f su c h
te rm s a s " t r i a n g l e " o r " c i r c l e - s l a s h " may i n f l u e n c e th e
memory o f t h i s ty p e o f m a t e r i a l .
I f th e I n f l u e n c e o f lo n g - te r m memory on th e memory
s p a n i s t o b e m e a su re d , a s e t o f sym bols h o l d in g t o a
minimum th e I n f lu e n c e o f p r e v io u s l e a r n i n g i s n e e d e d . I t
i s known t h a t memory s p a n i n c r e a s e s w ith age* I t i s t h i s
f a c t t h a t k e p t p s y c h o l o g i s t s I n t e r e s t e d i n memory sp a n
f o r m any y e a r s and th e r e a s o n t h a t th e t a s k w as in c lu d e d
i n i n t e l l i g e n c e t e s t s * C o u ld i t n o t be t h a t t h e r e a s o n
memory s p a n in c r e a s e d w ith age w as due t o a d d i t i o n a l
f a m i l i a r i t y w ith th e sy m b o ls? (A n o th e r p o s s i b i l i t y i s
a d d i t i o n a l p r a c t i c e a t r o t e l e a r n i n g . )
The p o i n t o f view b e in g p r e s e n te d h e r e i s t h a t t h e
t r a d i t i o n a l memory s p a n e x p e rim e n ts c o n fo u n d e d a l l t h r e e
ty p e s o f in f o r m a tio n * A c l a r i f i c a t i o n o f memory p r o c e s s e s
may r e s u l t w hen th e I n f l u e n c e s o f th e d i f f e r e n t ty p e s o f
185
l e a r n i n g a r e s e g r e g a t e d . An i n i t i a l a tte m p t h a s h e e n
made a t p a r t i t i o n i n g t h e s e i n f l u e n c e s i n th e r e s e a r c h
t h a t was r e p o r t e d i n C h a p te r I I I . The n e x t s e c t i o n w i l l
ta k e a c l o s e r lo o k a t th e i m p l i c a t i o n s o f t h i s e x p e rim e n t
f o r memory th e o r y * a s w e l l a s th e i m p l i c a t i o n s o f th e
f o llo w - u p e x p e rim e n ts r e p o r t e d i n C h a p te r IV .
E x p e r im e n ta l C o n c lu s io n s
E x p e rim e n t I . — O rd e r i n f o r m a tio n d o e s n o t seem to
i n h i b i t th e s t o r a g e o f ite m in f o r m a ti o n . T h is c o n c lu s io n
i s s u p p o r te d by s e v e r a l e x p e rim e n ts c i t e d i n C h a p te r I I
w hich* a lth o u g h n o t s p e c i f i c a l l y t e s t i n g o rd e r* fo u n d
t h a t ite m s w ere r e o a l l e d i n th e o r d e r o f p r e s e n t a t i o n
e v e n th o u g h f r e e r e c a l l w as e n c o u ra g e d . I t a p p e a rs t h a t *
f o r s h o r t - t e r m memory ta s k s * a s e p a r a t e m ech an ism may be
In v o lv e d o r t h a t o r d e r i n f o r m a tio n i s a c o n c o m ita n t o f
th e ite m i n f o r m a ti o n . One f e a s i b l e e x p la n a t i o n m ig h t be
t h a t m a t e r i a l t h a t h a s b e e n le a r n e d p r e v i o u s l y and th u s
i s a lr e a d y p r e s e n t i n th e lo n g - te r m s t o r e i s m a in ta in e d
by some lo n g - te r m p r o c e s s . O rd e r in f o r m a tio n * o n th e
o t h e r hand* i s m a in ta in e d o n ly a s lo n g as t h e r e i s a t
l e a s t one j u s t n o t i c e a b l e d i f f e r e n c e i n th e n e u r a l
s t r e n g t h s o f th e d e c a y in g t r a c e s o f th e s e p a r a t e s tim u li* .
S p e c i f i c o r d e r in f o r m a tio n i s l o s t v e ry q u ic k ly *
T h is i s s u g g e s te d by th e low num ber o f ite m s p la c e d c o r
r e c t l y w hen t h e "num ber c o r r e c t and i n o r d e r " c r i t e r i o n
186
was u se d * I t I s p o s s i b l e t h a t t h i s o r d e r i n f o r m a t i o n may
be m a in ta in e d by r e h e a r s a l and t h a t w hen th e l i s t l e n g t h
e x c e e d s a c e r t a i n am o u n t, c o m p le te r e h e a r s a l b ecom es im
p o s s i b l e w i t h i n th e r e q u i r e d tim e f a c t o r * A b o u t a s many
w ords w ere c o r r e c t l y p la c e d f o r th e se v e n -w o rd l i s t a s
f o r th e e le v e n -w o rd l i s t a lth o u g h many m ore w o rd s w ere
r e c a l l e d fro m t h e l a t t e r * T h is i n d i c a t e s a l i m i t e d " c h a n
n e l c a p a c i t y " f o r o r d e r in f o r m a tio n *
R e h e a r s a l may e s t a b l i s h some s e r i a l o r d e r d e p e n d
e n c i e s d u r in g th e tim e ite m s a r e b e in g d is p la y e d * A
g r e a t d e a l m ore " o r d e r " e x i s t e d i n th e r e s u l t s t h a n w as
I n d i c a t e d by th e p o s i t i o n c r i t e r i o n t h a t was u se d * A
s im p le r e v e r s a l o f two w o rd s d id n o t c o n t r i b u t e t o th e
o r i t e r i o n s c o r e a lth o u g h th e w o rd s w e re c o r r e c t l y p l a c e d
i n th e f i r s t , m id d le o r en d o f t h e l i s t * M o re o v e r, i f
one w ord w as f o r g o t t e n t h e n a l l o f t h e w o rd s a f t e r t h a t
w o u ld b e c o u n te d w rong a lth o u g h i n th e c o r r e c t o r d e r * I f
o r d e r i s to b e t r e a t e d a s a v a r i a b l e some m e a s u rin g t e c h
n iq u e a c c o u n tin g f o r t h e s e r e v e r s a l s an d t r a n s p o s i t i o n s
m u st be d e v e lo p e d i f a n e x a c t m e a su re o f t h e am ount o f
o r d e r i n f o r m a ti o n t h a t i s t r a n s m i t t e d i s t o be ta k e n *
Some ite m in f o r m a ti o n i s p la c e d v e ry q u i c k l y i n t o
th e lo n g - te r m s t o r e * The am ount t h a t i s s t o r e d d e p e n d s
u p o n th e s p e e d w ith w h ic h t h e i n f o r m a ti o n m u st b e p r o c
e s s e d a s w e ll a s o t h e r f a o t o r s *
187
W hat l a p la o e d I n th e lo n g - te r m s t o r e l a m a in ta in e d
f o r lo n g p e r i o d s o f tim e * W ith o u t b e in g fo re w a rn e d f i v e
s u b j e c t s w ere t e s t e d o n th e r e c o g n i t i o n t a s k tw o d a y s
a f t e r th e y had p a r t i c i p a t e d i n th e e x p e r im e n t. T h a t i s ,
th e l i s t o f c a t e g o r i e s w ith f o u r w ords p e r c a te g o r y was
show n t o t h e s u b j e c t s and th e y w ere a sk e d t o p i c k o u t
th o s e w ords t h a t th e y h ad s e e n tw o d a y s e a r l i e r * The
a v e ra g e s c o r e s f o r t h e s e s u b j e c t s w ere 5*0 and 6.1|. w ords
f o r th e s e v e n and e le v e n -w o rd l i s t s r e s p e c t i v e l y . When
th e s e r e s u l t s w ere s c o re d i n te rm s o f how many o f th e
w ords p ic k e d w e re o r i g i n a l l y o n e i t h e r th e s e v e n o r
e le v e n -w o rd l i s t s , m ean s o o r e s im p ro v e d t o 6 .2 and 7 *6
w ords r e s p e c t i v e l y . ( O r i g i n a l m ean s c o r e s f o r t h e s e f i v e
s u b j e c t s o n th e r e c o g n i t i o n t a s k w ere 7*0 and 8 . 2 . ) T h is
i n d i c a t e s t h a t th e s u b j e c t s n o t o n ly rem em bered q u i t e
w e ll w h a t th e y h a d s e e n tw o d a y s e a r l i e r , b u t w ere a b le
w ith some s u c c e s s t o s e p a r a t e s i m i l a r w ard s t h a t h a d b e e n
d is p la y e d o n ly a l i t t l e m ore th a n f i v e m in u te s a p a r t* Of
c o u r s e , th e o la lm i s n o t b e in g made t h a t t h i s w as p o s s i b l e
a f t e r o n ly one b r i e f e x p o s u r e . Otoe s u b j e c t s w ere a b le t o
s a y th e w o rd s , r e c a l l th em , and th e n I d e n t i f y th e m , b u t
t h i s w as s t i l l o n th e b a s i s o f th e f i r s t e x p o s u re and th e
t o t a l tim e s p e n t p e r w ord was p r o b a b ly q u i t e b r i e f *
The above i n d i c a t e s t h a t a lth o u g h s p e c i f i c o r d e r
I n f o r m a tio n may b e l o s t , g e n e r a l o r d e r in f o r m a ti o n i s
188
m a in ta in e d e x c e p t i o n a l l y w e ll*
S u p p o rt f o r t h e p erm an en ce o f I n f o r m a tio n p la c e d
i n th e lo n g - te r m s t o r e h a s b e e n p r o v id e d by Blum ( I 9 6 I ) •
U nder h y p n o s is a s u b j e c t w as show n a c a r to o n and t o l d t o
s tu d y i t c a r e f u l l y f o r a b o u t 30 s e c o n d s . A p r e - a r r a n g e d
s i g n a l w as u s e d t o b r i n g th e s u b j e c t i n and o u t o f h y p
n o s i s . D i f f e r e n t i n s t r u c t i o n s b e tw e e n s u c c e s s iv e h y p n o tic
s t a t e s r e v e a l e d am azin g c h a n g e s i n th e am ount r e c a l l e d .
The p o i n t t h a t i s r e l e v a n t h e r e , h o w e v e r, i s t h a t u n d e r
c e r t a i n i n s t r u c t i o n s t h e s u b j e c t was a b le t o r e c a l l m in u te
d e t a i l s e v e r a l m in u te s a f t e r he h ad b e e n e x p o se d t o th e
c a r t o o n . I t m ig h t b e h y p o th e s iz e d t h a t th e c r i t i c a l
f e a t u r e o f th e h y p n o tic s t a t e w as e i t h e r th e l a c k o f
i n t e r f e r e n c e o r t h e m ore c o n c e r te d e f f o r t p o s s i b l e u n d e r
h y p n o s is *
A n o th e r, n o t e n t i r e l y new , c o n c lu s io n t h a t may be
draw n i s t h a t t h e r e a r e s e p a r a t e t h r e s h o l d s f o r r e c a l l
and r e c o g n i t i o n . M a t e r i a l t h a t c a n n o t be r e c a l l e d may be
i n th e lo n g - te r m s t o r e . Much h i g h e r s c o r e s w ere o b ta in e d
fro m t h e r e c o g n i t i o n t a s k th a n fro m r e c a l l , e v e n th o u g h
th e r e c o g n i t i o n t r i a l s t a r t e d a t l e a s t l . £ m in u te s a f t e r
th e r e c a l l t r i a l s t a r t e d . I t i s p o s s i b l e t h a t t h e c o n d i
t i o n s o f t h i s e x p e rim e n t d id n o t t a x s u b j e c t s on th e
r e c o g n i t i o n ta s k * A lth o u g h th e m ean s c o r e f o r r e c o g n i t i o n
w as n o t p e r f e c t f o r th e e le v e n -w o rd l i s t , n e i t h e r w as i t
189
p e r f e c t f o r th e s h o r t e r , se v e n -w o rd l i s t . The m is s in g
w ords may n o t h a v e b e e n p la o e d i n t h e lo n g - te r m s t o r e due
t o a d i v e r s i o n o f a t t e n t i o n o r c o n f l i c t b e tw e e n w h e th e r
t o r e h e a r s e t h e p r e s e n t l y d is p la y e d w ord o r w ords t h a t h ad
o c c u r r e d p r e v i o u s l y . The f o r g o t t e n w ords may n e v e r h a v e
g o t t e n p a s t th e s h o r t - t e r m s t o r e *
E x p e rim e n t I I . — The g e n e r a l aim o f th e f o llo w - u p
e x p e r im e n ts w as t o d e m o n s tra te th e o c c u r r e n c e o f a t r a c e
d e c a y f o r ite m i n f o r m a ti o n . A lth o u g h E x p e rim e n t I I d id
n o t do t h i s i t d id g iv e some b o r d e r l i n e s u p p o r t t o th e
p o s i t i o n t h a t i n c r e a s e d s tim u lu s tim e a llo w e d m ore ite m s
t o b e s t o r e d i n t h e lo n g - te r m m em ory. A lth o u g h th e r e c a l l
d a t a do n o t s u p p o r t su c h a c o n c l u s i o n , th e d a t a o b ta in e d
fro m th e r e c o g n i t i o n t a s k a lm o s t r e a c h e s th e *0£ l e v e l o f
c o n f id e n c e . Of c o u r s e , i t m u st b e assum ed t h a t th e
d i f f e r e n c e s o b ta in e d i n s t a t i s t i c a l s i g n i f i c a n c e a re r e
s u l t s o f th e i n c r e a s e d s e n s i t i v i t y o f th e r e c o g n i t i o n
ta s k *
N e i th e r d id E x p e rim e n t I I I s u p p o r t th e h y p o th e s is
o f ite m d e c a y . I t d i d , h o w e v e r, p r o v id e e v id e n c e t h a t
m a t e r i a l p l a c e d i n t h e lo n g - te r m s t o r e was r e l a t i v e l y
im p e rv io u s t o d i s s i m i l a r I n t e r p o l a t e d a c t i v i t y m a in ta in e d
f o r p e r i o d s u p t o two m in u te s . The m eans o b ta in e d i n t h i s
e x p e rim e n t a g re e d q u i t e w e l l w ith th o s e e s t a b l i s h e d f o r
s h o r t e r p e r i o d s o f tim e i n E x p e rim e n t I I w hen th e tim e
190
b e tw e e n th e o n a e t o f s u c c e s s iv e s t i m u l i was th e sam e.
S in c e th e num ber o f w ords c o r r e c t l y r e c a l l e d d id
d e c r e a s e a s th e tim e d e v o te d t o i n t e r p o l a t e d a c t i v i t y
i n c r e a s e d i n E x p e rim e n t IV , t h i s e x p e rim e n t d id s u p p o r t
th e e x i s t e n c e o f a d e c a y in g t r a c e f o r ite m in f o r m a ti o n .
I t d id n o t d e te rm in e w h e th e r t h i s d e c a y i s d e p e n d e n t up on
th e r a t e o f p r e s e n t a t i o n o f th e s t i m u l i o r w h e th e r t h e r e
i s some i n t r i n s i c d i f f e r e n c e b e tw e e n v i s u a l and a u d it o r y
p r o c e s s in g * The r e c a l l d a t a p r o v id e s e v id e n c e t h a t th e
d e c a y o c c u rs f o r t h e r a t e t h a t was u s e d i n th e v i s u a l
e x p e rim e n ts and i n w h ic h no d e ca y was f o u n d , as w e l l a s
f o r th e f a s t e r r a t e * ( I n c i d e n t l y , t h i s e x p e rim e n t a ls o
g iv e s m ore p o s i t i v e s u p p o r t t o t h e I n f lu e n c e o f r a t e on
th e am ount p la c e d i n t h e lo n g - te r m s t o r e * ) The i n t e r
a c t i o n n e c e s s a r y to d e m o n s tra te th e i n f l u e n c e o f r a t e o f
p r e s e n t a t i o n o n d e ca y was n o t s i g n i f i c a n t , how ever*
F o r th e r e c o g n i t i o n d a t a , s i g n i f i c a n c e was n o t ob
t a i n e d f o r i n t e r p o l a t e d a c t i v i t y and t h i s m ig h t be i n t e r
p r e t e d a s c a s t i n g some d o u b t o n th e d e c a y p o s i t i o n * The
I n t e r a c t i o n f o r t h e s e d a t a was s t i l l n o t s i g n i f i c a n t b u t
i t d id i n c r e a s e s u b s t a n t i a l l y i n s iz e * I n f a c t , th e m ean
num ber r e c a l l e d f o r th e f a s t e r r a t e d o es d e c r e a s e a s th e
l e n g t h o f i n t e r p o l a t e d a c t i v i t y in c r e a s e * T h u s, a lth o u g h
n o t s i g n i f i c a n t , t h e t r e n d i s i n th e r i g h t d i r e c t i o n t o
s u g g e s t t h a t r a t e i s th e c r i t i c a l v a r i a b l e i n o b t a i n i n g
191
e v id e n c e f o r a d e c a y in g t r a c e th e o r y *
I t I s p r o b a b le t h a t a u d i t o r y p r o c e s s i n g r e q u i r e s
m ore tim e th a n v i s u a l , a t l e a s t f o r th e p r e s e n t t a s k , and
t h a t a lo n g e r i n t e r v a l b e tw e e n t h e o n s e t o f s u c c e s s iv e
s t i m u l i w ould a g a i n f i n d i n t e r p o l a t e d a c t i v i t y I n e f f e c t
i v e . A l a r g e r sam p le a t th e f a s t e r r a t e may a ls o demon
s t r a t e a s i g n i f i c a n t i n t e r a c t i o n . B u t f u r t h e r e x p e r i
m e n ta tio n i s n e c e s s a r y t o e s t a b l i s h c o n c l u s i v e l y t h e p o s i -
t l o n t h a t r a t e o f s tim u lu s p r e s e n t a t i o n i s t h e c r i t i c a l
v a r i a b l e .
G e n e ra l C o n c lu s io n s
I t a p p e a rs t h a t th e t r a d i t i o n a l memory s p a n e x p e r i
m e n ts p r i m a r i l y m e a su re th e s t o r a g e o f o r d e r i n f o r m a t i o n .
I t i s p r o b a b le t h a t t h i s s p a n i s n o t e n t i r e l y d e p e n d e n t
u p o n th e d e o ay o f t r a c e s b u t t h a t some r e c o d in g o r c h u n k
i n g o f th e i n f o r m a ti o n t a k e s p l a c e . The f a c i l i t a t i o n due
to g r o u p in g may o c c u r i n p a r t b e c a u s e t h e " f i l t e r * i s
a b le t o h a n d le two ite m s o f i n f o r m a ti o n a s one c h u n k . As
n o te d by B row n (1 9 5 9 ) * one p ro b le m i n i n v e s t i g a t i n g t h e
i n f l u e n c e o f o r d e r in f o r m a ti o n o n r e t e n t i o n i s t h a t some
o f th e o r d e r in f o r m a ti o n may b e r e c o d e d a s ite m in fo rm a
t i o n th r o u g h su c h d e v ic e s a s c h u n k in g . One s u b j e c t who
p a r t i c i p a t e d i n E x p e rim e n t I , f o r e x a m p le , re c o d e d f i v e
o f t h e s e v e n w o rd s i n t o a s e n te n c e w h ic h e f f e c t i v e l y u s e d
m e a n in g f u ln e s s and re d u n d a n c y t o p u t th e ite m s i n t o a
s t a b l e s e q u e n c e . The I te m s , i n o r d e r , w ere " s l i n g , l y r e ,
g o r g e , h o g , g l e n , s k i f f , and w r i s t . " The s e n te n c e th e
s u b j e c t u s e d a s a m nem onic was " s l i n g a l y r e o y e r th e
g o r g e , a h o g i s i n th e g l e n , " and th e n s im p ly fd d e d on
s k i f f and w r i s t . The f a c t t h a t sh e c o u ld o r i g i n a t e t h i s
m nem onic w h ile th e w o rd s w ere b e in g d i s p l a y e d ( a c t u a l l y
o n ly 1 1 .2 s e c o n d s e la p s e d w h ile t h e l i s t w as b e in g d i s
p la y e d ) i s q u i t e a te s tim o n y t o h e r i n g e n u i t y . She w as
n o t a b le t o d u p l i c a t e t h i s f e a t f o r t h e e le v e n -w o rd l i s t .
B u t i t i s q u i t e p o s s i b l e t h a t s u b j e o t s w e re a b le t o p u t
two o r m ore w o rd s t o g e t h e r i n s u b g ro u p s and e a s e t h e lo a d
on t h e i r m e m o rie s. T h is ty p e o f a c t i v i t y may be a p a r t
o f th e e x p l a n a t i o n o f why th e s u b j e c t s t e s t e d s e v e r a l d a y s
l a t e r w ere a b l e t o s e g r e g a t e th o s e w o rd s a p p e a r in g on th e
two l i s t s so w e l l .
T y p i c a l l y , s u b j e c t s w ould r e p e a t t h e w o rd s t o th em
s e l v e s s e v e r a l tim e s u n t i l t h e n e x t s t i m u l u s a p p e a r e d .
T hey w ould t h e n a tte m p t t o s a y t h i s a c o u p le o f t i m e s ,
t h e n r e p e a t t h e s t i m u l i i n o r d e r . A f t e r t h r e e o r f o u r
w o rd s h a d a p p e a r e d , h o w e v e r, t h i s becam e im p o s s ib le and
t h e i r s t r a t e g y h a d t o c h a n g e . T h is may a c c o u n t f o r some
o f th e d i f f i c u l t y e n c o u n te r e d w ith o r d e r a s w e l l a s i t e m s .
A c h a n g e fro m one ty p e o f s t r a t e g y to a n o th e r may c h an g e
th e s t r e n g t h s o f th e r e s p e c t i v e n e u r a l t r a c e s , and t h u s ,
i f o r d e r memory i s a t l e a s t p a r t l y b a s e d on t h e s e d e c a y in g
193
t r a c e s , c o n fu s e t h e o r d e r* Ite m memory c o u ld b e d i s
r u p t e d b e c a u s e f u l l a t t e n t i o n may n o t be d e v o te d t o some
ite m s a s th e y a p p e a r w hen s u b j e c t s a r e s im u lta n e o u s ly
t r y i n g t o r e h e a r s e e a r l i e r m a t e r i a l *
I t m ig h t b e p o s s i b l e t o t e s t w h e th e r o r n o t o r d e r
memory i s d e p e n d e n t u p o n th e r e l a t i v e s t r e n g t h o f th e
n e u r a l t r a c e s by h a v in g one g ro u p o f s u b j e c t s e x p o se d t o
s t i m u l i w h ic h v a ry i n I n t e n s i t y i n a random f a s h i o n w h ile
a se c o n d g ro u p i s e x p o s e d t o s t i m u l i w h ic h a re a l l o f th e
sam e i n t e n s i t y * I f th e s t r e n g t h o f n e u r a l a c t i v i t y i s
th e k e y t o e s t a b l i s h i n g o r d e r , t h e p r e d i c t i o n m ig h t b e
made t h a t th e l a t t e r g ro u p w o u ld h a v e a h i g h e r s c o r e f o r
th e num ber o f ite m s c o r r e c t l y p la c e d *
I t i s i n t e r e s t i n g t o n o te t h a t G u i l f o r d 's
" S t r u c t u r e o f I n t e l l e c t M odel" ( i 9 6 0 ) w ould p r e d i c t t h a t
o r d e r and ite m i n f o r m a ti o n w ould n o t I n f l u e n c e one
a n o th e r* T hey a re v ie w e d a s s e p a r a t e a b i l i t i e s w ith a n
h y p o th e s iz e d c o r r e l a t i o n o f z e ro * I f th e y d id I n t e r a c t
i n t h e d i r e c t i o n p r e d i c t e d b y i n f o r m a ti o n t h e o r y , one
m ig h t assum e a n e g a t i v e c o r r e l a t i o n *
I n c o n c l u s i o n , t h e e v id e n c e fro m t h e s e e x p e r im e n ts
s u g g e s t s t h a t an i n t e r f e r e n c e t h e o r y o f f o r g e t t i n g i s
m ore a p p r o p r i a t e f o r ite m in f o r m a tio n * O rd e r i n f o r m a t i o n ,
h o w e v e r, may b e b a s e d o n a d e c a y in g t r a c e o f n e u ro n s
r e c e n t l y a c t i v a t e d b y th e e x p o s u re o f a n ite m * I t i s
... *
1 9 U -
p o s s i b l e t h a t ite m I n f o r m a tio n i s n e v e r f o r g o t t e n . A
l a s t i n g r e c o r d o f e a c h memory may b e s t o r e d som ew here i n
th e o rg a n is m . The p e rfo rm a n c e d e c re m e n t t h a t t y p i c a l l y
o c c u rs w ith t h e p a s s a g e o f tim e may be a r e s u l t o f a
f a u l t y r e t r i e v a l s y s te m . The a n a lo g y o f a f i l i n g c l e r k
may be a s u i t a b l e o n e . The f u n c t i o n o f r e h e a r s a l , i s o l a
t i o n , g r o u p in g , e t c e t e r a , may be t o make m a t e r i a l e a s i e r
t o l o c a t e b y t h e " s c a n n e r * 1 i n th e s to r a g e m ech an ism . V ery
few s t u d i e s h a v e b e e n r e p o r t e d i n v e s t i g a t i n g r e t e n t i o n
o v e r lo n g p e r i o d s o f tim e . One s tu d y o f i n t e r e s t , p e r
fo rm ed b y H ilg a r d and C am p b ell (193& )» m e a su re d c o n d i
tio n e d e y e l i d r e s p o n s e s o v e r I n t e r v a l s fro m 1 t o 28 w e e k s .
S i z e a b le r e t e n t i o n w ith v e r y slo w d im in u tio n w as i n d i c a t e d .
I t i s d i f f i c u l t t o d e te rm in e j u s t how t h i s r e l a t e s t o
v e r b a l l e a r n i n g b u t i t i s s u g g e s t i v e . C e r t a i n l y , l e a r n i n g
o f t h i s ty p e i s d i f f e r e n t fro m v e r b a l l e a r n i n g i n r e s p e c t
t o t h e am ount o f i n t e r f e r e n o e t o w hioh i t i s s u b j e c t e d .
T h e o r e t i c a l C o n c lu s io n s
B r o a d b e n t's m odel ( 1957b , 1958) seem s t o be a
r e a s o n a b ly a c c u r a te d e s c r i p t i o n o f th e f u n c t i o n a l p r o p e r
t i e s o f s h o r t - t e r m m em ory. I t d o e s , h o w e v e r, n eed some
e l a b o r a t i o n . A lth o u g h o r d e r in f o r m a tio n d o e s n o t a p p e a r
to l i m i t t h e am ount o f ite m in f o r m a tio n t h a t c a n b e
p r o c e s s e d , i t i s a u s e f u l d i s t i n c t i o n . I t w ould a p p e a r
t h a t o r d e r in f o r m a ti o n i s s u b j e c t to r a p i d d e c a y a t any
195
r a t a o f t r a n s m i s s i o n , a lth o u g h Ite m i n f o r m a t i o n , on ce
th r o u g h th e " f i l t e r , 1 1 h a s v e ry good p e rm a n e n c y . E v i d e n t
l y , i f th e r a t e o f t r a n s m i s s i o n i s r e a s o n a b l y slo w (o n e
s e c o n d p e r i t e m o r s l o w e r ) , ite m in f o r m a ti o n i s t r a n s
f e r r e d w i t h l i t t l e l o s s . A t f a s t r a t e s , h o w e v e r, some o f
th e ite m i n f o r m a ti o n d o e s n o t g e t th r o u g h th e f i l t e r and
s t a y s i n t h e s h o r t - t e r m s t o r e w here i t i s s u b j e c t t o
d e c a y .
The p e rm a n en c y o f ite m I n f o r m a tio n i s i n d i c a t e d by
t h e a lm o s t p e r f e c t r e c o g n i t i o n s c o r e s . The r e a s o n t h a t
th e w ord " a lm o s t" i s r e q u i r e d may b e due t o t h e i n a b i l i t y
o f some ite m s t o g e t i n t o t h e lo n g - te r m s t o r e . T h is may
be a r e s u l t o f m om entary I n a t t e n t i o n o r c o n f l i c t b e tw e e n
r e h e a r s a l o r t r a n s m i s s i o n o f th e p a r t i c u l a r i te m , e t
c e t e r a . The s t r a t e g y o f t h e s u b j e c t i s v a r i a b l e . He
may h o ld one ite m i n th e s h o r t - t e r m s t o r e w h ile r e h e a r s i n g
a p r e v i o u s i te m . B ut a t th e tim e he i n te n d e d t o p r o c e s s
t h e s e c o n d i t e m , a t h i r d h a s a p p e a r e d , and h e may p r o c e s s
t h a t i n s t e a d . T h u s, t h e ite m h e ld i n th e s h o r t - t e r m
s t o r e d e c a y s .
O rd e r i n f o r m a ti o n may be t r a n s m i t t e d th r o u g h th e
f i l t e r . B u t t h e lo n g - te r m l e a r n i n g , o r " c l a s s " in f o r m a
t i o n i s n o t a v a i l a b l e to f a c i l i t a t e i t s r e t r i e v a l . I n
B ro w n 's t e r m s , t h e r e i s no r e d u n d a n c y . T h a t o r d e r i n
f o r m a tio n may h a v e a n e f f e c t i n th e l o n g - te r m memory i s
196
s u g g e s te d b y th e e x p e rim e n t r e p o r t e d b y Hebb t h a t was
m e n tio n e d e a r l i e r * B u t t h i s I n f o r m a tio n r e m a in s belo w
th e r e t r i e v a l t h r e s h o ld * I t i s o n ly w ith r e p e t i t i o n t h a t
th e t h r e s h o l d i s lo w e re d en o u g h f o r r e t r i e v a l *
Blum*a " F a c i l i t a t i o n o f A s s o c i a t i v e R e c a l l W ith o u t
A w a re n e ss" (1 9 6 1 ) may b e in v o k e d t o e x p l a i n t h e a b i l i t y
o f t h e s u b j e c t s t e s t e d tw o d a y s l a t e r to s e g r e g a t e t h e
w ords a p p e a r in g o n th e tw o d i f f e r e n t l i s t s , w h ic h was
c e r t a i n l y lo n g - te r m s t o r a g e o r o r d e r i n f o r m a t i o n . U s in g
h y p n o s i s , Blum e s t a b l i s h e d t h a t l e t t e r s c o u ld be a s s o
c i a t e d v e ry q u i c k l y e v e n th o u g h th e s u b j e c t d id n o t know
why* T h is may a l s o a c c o u n t f o r th e o c c u r r e n c e o f m ore
o r d e r th a n th e c r i t e r i o n i n d i c a t e s i n th e a n sw e rs* One
o f th e g r e a t d i f f i c u l t i e s i n w o rk in g w i t h o r d e r in f o r m a
t i o n fro m a t h e o r e t i c a l s t a n d p o in t i s t h a t s u c h in f o r m a
t i o n may be c h a n g e d i n t o ite m i n f o r m a t i o n th r o u g h r e c o d
i n g , c h u n k in g , e to *
P r a c t i c a l I m p l i c a t i o n s
The I n t r o d u c t i o n s t r e s s e d t h e n e e d f o r k n o w led g e
a b o u t t h e s h o r t - t e r m s t o r e i n t h e d e s i g n in g o f m an -m ach in e
sy s te m s* V ery l i t t l e h a s b e e n s a i d i n th e s u c c e e d in g
p a g e s t h a t c o u ld b e a p p lie d d i r e c t l y to s u c h s y s te m s*
T h e o r e t i c a l i m p l i c a t i o n s h a v e p la y e d th e d o m in a n t r o l e *
The b e s t way t o b e t t e r a p p l i c a t i o n s i n e v e r y a r e a i s
p r o b a b ly th r o u g h th e d e v e lo p m e n t o f c o m p re h e n s iv e ,
197
i n c l u s i v e c o n c e p ts le a d in g t o a n a c c u r a te th e o ry * None
t h e l e s s , c u r r e n t d e s ig n s c a n n o t w a it f o r t h i s , e s p e c i a l l y
i
s in c e th e o r y d e v elo p m e n t i n p s y c h o lo g y i s s u b j e c t t o so
many d i f f i c u l t i e s * T h e r e f o r e , i t seem s a p p r o p r i a te to
p r e s e n t a fe w , r e a s o n a b ly c o n c r e te s u g g e s tio n s f o r th e
Im provem ent o f t h i s s h o r t - t e r m memory c a p a c ity *
1* P r e s e n t th e in f o r m a ti o n i n s u c h a way s o t h a t
" c h u n k in g " i s f a c i l i t a t e d * F o r e x a m p le , i f l e t t e r s a r e
to b e u s e d , d e s ig n th e code so t h a t th e l e t t e r s may be
p r e s e n te d a s CVC s y l l a b l e s * T h is w i l l f a c i l i t a t e p r o -
n o u n c e a b l l i t y and m ore i n f o r m a tio n w i l l b e c a r r i e d i n th e
same num ber o f chunks*
2 . U se p r i n c i p l e s o f o r g a n i z a t i o n ; g ro u p sy m b o ls*
3 * U se d i s t i n c t c a t e g o r i e s , i f p o s s i b l e , to
l e s s e n i n t e r f e r e n c e *
lj.* S im u lta n e o u s p r e s e n t a t i o n i s p r o b a b ly b e t t e r
th a n s e q u e n t i a l , s in c e th e o p e r a t o r s may be a b le t o fo rm
t h e i r own m nem onic d e v ic e s and u s e t h e i r own r a t e o f
p r o c e s s in g * T h e re i s p r o b a b ly a l i m i t o n th e num ber o f
ite m s t h a t s h o u ld b e shown a t once* M o re o v e r, t h i s may
h a v e t o b e te m p e re d by th e n e e d f o r d i s c r l m l n a b l l i t y f o r
some d is p la y s *
5* P ro v id e t r a i n i n g i n th e code and p e rh a p s i n
th e d i f f e r e n t p o s s i b i l i t i e s f o r m nem onics*
6 * I f p o s s i b l e , k e e p th e num ber o f ite m s t h a t a r e
1 9 8
changing at a minimum. I f the item s must change, slow
the p resen ta tio n ra te to allow reh ea rsa l*
7* I f o r d e r in f o r m a tio n i s i m p o r t a n t , t r y t o code
i t i n t o ite m in f o r m a tio n *
8 * C h u n k in g i s f a c i l i t a t e d b y o r g a n i z a t i o n , p r o
n o u n ce a b i l i t y , c l u s t e r i n g , a s s o c i a t i o n , and p e rh a p s
s i m i l a r i t y * The u s e o f some o f t h e s e d e v ic e s may le a d t o
i n t e r f e r e n c e * The t r a d e - o f f f o r a s p e c i f i c t a s k w i l l
p r o b a b ly h a v e t o be d e te rm in e d e m p i r ic a ll y *
9* Add m ore d im e n sio n s t o th e d is p la y * T h is w i l l
p r o b a b ly l e s s e n i n t e r f e r e n c e b u t a d d i t i o n a l s t u d i e s a re
n e c e s s a r y t o v e r i f y t h i s * A lth o u g h A n d e rso n and F i t t s
d e te rm in e d t h a t m ore I n f o r m a tio n was t r a n s m i t t e d w ith i n
c r e a s e d d i m e n s i o n a l i t y , kn o w led g e i s n e e d e d c o n c e rn in g
th e e f f e c t s o f d e l a y , e t c * , f o r m a t e r i a l o f t h i s ty p e *
10* Make s u re i n f o r m a tio n g e t s i n t o th e lo n g - te r m
s t o r e * Have t h e o p e r a t o r s r e p o r t i t v e r b a l l y , o r c h e c k
i t o f f o n a c h e c k - l i s t *
1 1 * U se th e p r i n c i p l e s o f I s o l a t i o n o r s e q u e n t i a l
s t r u c t u r e t o overcom e s e r i a l o r d e r e f f e c t s *
A g r e a t d e a l m ore kn o w led g e i s n eed ed * I t i s im
p o r t a n t t h a t th o s e r e s p o n s i b l e f o r t h e d e s i g n o f sy ste m s
r e c o g n iz e th e n e ed f o r e m p i r ic a l s t u d i e s to p r o v id e t h i s
know ledge* M ost o f th e s t u d i e s w i l l , o f c o u r s e , be r e
l a t e d t o s p e c i f i c p ro b le m s i n s p e c i f i c sy ste m s* B ut th e
r e s e a r c h e r who i s a l e r t f o r th e I m p l i c a t i o n s c a n d e s ig n
h i s s t u d i e s n o t o n ly to o b t a i n th e n e ed e d s p e c i f i c i n
f o r m a t io n , b u t a l s o p r o v id e a n o p p o r t u n it y f o r th e o r y
t e s t i n g a n d /o r d e v e lo p m e n t*
CHAPTER V I
SU M M A R Y
I n t r o d u c t i o n
F o r m any y e a r s I n t e r e s t I n s h o r t - t e r m memory was
r e s t r i c t e d p r i m a r i l y to I t s u s e I n I n t e l l i g e n c e t e s t s *
D u rin g th e p a s t t e n y e a r s o r so* I n c r e a s e d I n t e r e s t h a s
b e e n g e n e r a te d w h ic h h a s f o llo w e d new d i r e c t i o n s * T h is
I n t e r e s t h a s b e e n g e n e r a t e d b y : The d e v e lo p m e n t o f com
p u t e r s iftilc h h a v e a " b u f f e r " s t o r a g e s y s te m ; t h e a p p l i c a
t i o n o f I n f o r m a t io n T h e o ry a s a m o d el f o r hum an In fo rm a
t i o n p r o c e s s i n g ; and t h e d e v e lo p m e n t o f l a r g e s c a l e m an-
m ach in e s y s te m s w h ic h Im p o se new dem ands o n m a n 's c a p a c i t y
f o r s h o r t - t e r m memory t a s k s *
R eview o f t h e L i t e r a t u r e
An e x te n s i v e r e v ie w o f many e x p e r im e n ta l s t u d i e s
w as in c lu d e d * T h ese e x p e r im e n ts w e re g ro u p e d i n te rm s o f
th e m a jo r in d e p e n d e n t v a r i a b l e * T h is I s th e f i r s t com pre
h e n s iv e r e v ie w o f t h e a r e a t h a t h a s b e e n m ade a v a i l a b l e
s in c e 193d* Many o f t h e s e s t u d i e s seem t o s u p p o r t a d e c a y
th e o r y o f s h o r t - t e r m memory* O th e rs * how ever* seem t o
s u g g e s t a n i n t e r f e r e n c e ty p e o f th e o r y * E v id e n c e s u p p o r t
i n g t h e s e p o s i t i o n s was g ro u p e d a t th e c o n c l u s i o n o f th e
2 0 0
2 0 1
c h a p te r a s w as some o t h e r e m p i r ic a l e v id e n c e . Two m o d els
o f I n f o r m a tio n p r o c e s s in g h a v e b e e n p ro p o s e d i n r e c e n t
y e a r s . The f i r s t by Brown u s e s in f o r m a tio n th e o r y to
d e v e lo p c o n c e p ts w h ic h , I t was s u g g e s te d , may d e s c r i b e
th e memory p r o c e s s . The se co n d m o d e l, by B ro a d b e n t, h a s
u s e d e m p ir ic a l e v id e n c e t o d e v e lo p a m e c h a n ic a l m o d e l.
The b a s i c t e n e t s o f t h e s e tw o t h e o r i e s w ere o u t l i n e d .
E x p e rim e n t I
The f i r s t e x p e rim e n t was d e s ig n e d t o t e s t c e r t a i n
p r e d i c t i o n s fro m Brown* s m o d e l. S p e c i f i c a l l y , Brown
s t a t e s t h a t o r d e r I n f o r m a tio n may Im pose a b u rd e n o n th e
s h o r t - t e r m memory w h ic h l i m i t s th e am ount o f ite m i n f o r
m a tio n t h a t c a n be s t o r e d . W ords fro m s p e c i f i c c a t e g o r i e s
w ere p r e s e n te d t o th e s u b j e c t s . F o r e x a m p le , th e w ords
" s k i f f , Tim , c a b , • • • " w ere s e l e c t e d fro m th e c a t e
g o r i e s " b o a t , nam e, v e h i c l e , . . . " L i s t s o f s u c h w o rd s ,
e i t h e r s e v e n o r e le v e n w o rd s lo n g , w ere p r e s e n t e d t o th e
s u b j e c t s s e q u e n t i a l l y u s in g a s l i d e p r o j e c t o r . One g ro u p
o f s u b j e c t s u se d a n sw e r fo rm s w h ic h l i s t e d th e o a te g o r y
nam es i n t h e o r d e r i n w h ich th e w o rd s w ere p r e s e n t e d . A
se c o n d g ro u p r e o e iv e d b la n k f o rm s . A t h i r d g ro u p r e c e i v e d
a fo rm l i s t i n g th e c a te g o r y nam es i n a l p h a b e t i c a l o r d e r .
T h is l a s t g ro u p c o n t r o l l e d f o r th e p o s s i b i l i t y t h a t s e e in g
th e c a te g o r y nam es m ig h t f a c i l i t a t e r e c a l l . A l l l i s t s
w ere t o be r e c a l l e d i n as c lo s e to th e c o r r e c t o r d e r a s
2 0 2
p o s s ib l e * I t w as p o in te d o u t t o th e s u b j e c t s i n th e f i r s t
g ro u p t h a t th e y c o u ld d e v o te a l l o f t h e i r e f f o r t t o memo
r i z i n g th e ite m s*
The d u r a t i o n o f i n t e r p o l a t e d a c t i v i t y w as a l s o
v a r i e d b e tw e e n z e ro * f iv e * o r tw e n ty se c o n d s* T he t a s k
was t o c o u n t baokw ards* by th r e e s * fro m a t h r e e - d i g i t
num ber d is p la y e d a f t e r th e l a s t w ord i n t h e se q u e n c e *
The s u b j e c t s w ere a llo w e d a s e t tim e t o w r i t e t h e i r
r e c o l l e c t i o n o f t h e w ords o n th e an sw er fo rm . A f t e r t u r n
in g t h i s fo rm o v e r th e y w ere t e s t e d f o r r e c o g n i t i o n * The
a n sw e rs w ere s c o re d f o r th e num ber o f c o r r e c t w o rd s i r
r e s p e c t i v e o f o r d e r a s w e l l a s th e num ber o f w o rd s p la c e d
i n th e c o r r e c t p o s i t i o n i n th e seq u en ce*
A lth o u g h th e g ro u p t h a t w as p r o v id e d o r d e r in fo rm a
t i o n d id s i g n i f i c a n t l y b e t t e r w hen t h e m e a su re w as th e
"num ber c o r r e c t and i n o r d e r , " no im p ro v em en t o c c u r r e d i n
th e t o t a l num ber o f ite m s c o r r e c t l y r e c a l l e d I r r e s p e c t i v e
o f o rd e r* T h is was i n t e r p r e t e d a s r e f u t i n g th e h y p o th e
s i s t h a t o r d e r i n f o r m a tio n Im poses a n a d d i t i o n a l lo a d on
th e s h o r t - t e r m memory*
The f a c t t h a t l i s t le n g th h a d a s i g n i f i c a n t e f f e c t
f o r th e num ber c o r r e c t l y r e c a l l e d b u t n o t w hen o r d e r was
c o n s id e re d * i n d i c a t e d a l i m i t e d c h a n n e l c a p a c i t y f o r
o r d e r in f o r m a tio n *
I n t e r p o l a t e d a c t i v i t y d id n o t h a v e any s i g n i f i c a n t
203
e f f e c t .
Follow-Up Experim ents
The f a c t t h a t i n t e r p o l a t e d a c t i v i t y d id n o t h a v e a
s i g n i f i c a n t e f f e c t w as b e l i e v e d t o b e w o rth y o f f u r t h e r
e x p e r i m e n t a t io n s i n c e i t h a d b e e n fo u n d t o b e q u i t e im
p o r t a n t i n o t h e r s i t u a t i o n s * S e v e r a l p o s s i b i l i t i e s
seem ed t o e x i s t * Brown s u g g e s te d t h a t o r d e r i n f o r m a ti o n
i s s u b j e c t t o r a p i d d e c a y b u t h e d o u b ts w h e th e r o n ly t h i s
ty p e o f in f o r m a ti o n d e c a y s . I t c o u ld b e t h a t h e w as
w rong and i te m in f o r m a ti o n i s n o t s u b j e c t t o d ecay *
A n o th e r p o s s i b i l i t y w as t h a t t h e r a t e o f d e c a y f o r d i f
f e r e n t ty p e s o f m a t e r i a l i s d i f f e r e n t . S t i l l a n o th e r
p o s s i b i l i t y was t h a t d e c a y o c c u r s o n ly i f m a t e r i a l i s i n
th e s h o r t - t e r m s t o r e * A s e r i e s o f e x p e r im e n ts w as p e r
fo rm ed i n v e s t i g a t i n g t h e s e p o s s i b i l i t i e s *
E x p e rim e n t I I u s e d t h e same s ti m u l u s m a t e r i a l and
p r o c e d u r e a s t h e f i r s t e x p e r im e n t b u t d id n o t v a ry l i s t
l e n g t h o r o r d e r in f o r m a tio n * S u b j e c t s saw th e e le v e n
w o rd s and e i t h e r p a r t i c i p a t e d i n I n t e r p o l a t e d a c t i v i t y
f o r e i t h e r z e r o o r 2 0 se c o n d s * A ls o v a r i e d w as t h e tim e
b e tw e e n th e o n s e t o f s u c c e s s iv e s t i m u l i w h ic h was e i t h e r
1*6 s e c o n d s , t h e v a lu e u s e d i n th e f i r s t e x p e r im e n t, o r
1*0 s e c o n d s , th e l i m i t i n g v a lu e f o r th e a p p a r a tu s u se d *
The s tim u lu s r a t e n e a r l y o b ta in e d s i g n i f i c a n c e , b u t i n t e r
p o l a t e d a c t i v i t y s t i l l h a d n o s i g n i f i c a n t e f f e c t *
2 O l|.
E x p e rim e n t I I I u s e d th e f a s t e r r a t e and v a r i e d th e
d u r a t i o n o f i n t e r p o l a t e d a c t i v i t y among lf.0 9 6 0 , and 120
s e c o n d s . T h e re w as no s i g n i f i c a n t d i f f e r e n c e b e tw e e n
t h e s e t h r e e g ro u p s *
E x p e rim e n t IV u s e d a t a p e r e c o r d e r t o p r e s e n t th e
s t i m u l i i n o r d e r t o o b t a i n f a s t e r p r e s e n t a t i o n s p e e d s .
The e le v e n w o rd s w ere d i s p l a y e d a t th e r a t e o f t h r e e
w o rd s p e r s e c o n d o r one w ord p e r s e c o n d . I n t e r p o l a t e d
a c t i v i t y w as m a in ta in e d f o r z e r o , 2 0 , o r 60 s e c o n d s .
U n d er t h e s e c o n d i t i o n s , f o r r e c a l l b o th r a t e and i n t e r -
p o l a t e d a c t i v i t y h a d s i g n i f i c a n t e f f e c t s b u t f o r th e
r e c o g n i t i o n m e a su re a g a i n o n ly r a t e w as s i g n i f i c a n t .
T h is w as I n t e r p r e t e d a s m o st p r o b a b ly s u p p o r t i n g a n ite m
d e c a y p o s i t i o n w ith a slo w e d r a t e o f p r o c e s s i n g f o r a u d i
t i o n u n d e r t h e s e c o n d i t i o n s a lth o u g h t h i s i s n o t c o n c lu
s i v e . A p o s s i b i l i t y e x i s t s t h a t d e c a y o c c u rs o n ly i n th e
a u d i t o r y m o d e.
D i s c u s s io n
W h ile B ro a d b e n t* s m o d el i s v ie w e d a s e s s e n t i a l l y
c o r r e c t i n i t s d e s c r i p t i o n o f t h e f u n c t i o n a l p r o p e r t i e s
o f s h o r t - t e r m m em ory, some o f t h e c o n c e p ts s u g g e s te d by
Brown c l a r i f y th e s i t u a t i o n . E s p e c i a l l y v a lu a b le i s th e
s e p a r a t i o n o f th e c o n o e p t o f o r d e r memory fro m ite m
m em ory. O rd e r memory i s e x tr e m e ly s u s c e p t i b l e t o d e c a y
o r l o s s a t an y r a t e o f p r e s e n t a t i o n . Ite m memory d e c a y s
205
o n ly a t r a t e s w h ic h e x c e e d t h e c a p a c i t y o f t h e n e rv o u s
s y s te m .
I t I s s u g g e s te d t h a t o r d e r I n f o r m a tio n I s l o s t
p r i m a r i l y b e c a u s e lo n g - te r m l e a r n i n g h a s n o t b u i l t up
"re d u n d a n c y * i n t h e lo n g - te r m s t o r e . T h u s, th o u g h o r d e r
I n f o r m a tio n may h a v e a n I n f lu e n c e o n th e lo n g - te r m
s t o r e s , i t re m a in s below t h e r e c a l l t h r e s h o l d .
Some s u g g e s tio n s f o r im p ro v in g th e d e s ig n o f m an-
m ach in e s y s te m s i n r e g a r d t o m an1 s memory f u n c t i o n s b r i n g
th e c h a p t e r t o a c l o s e .
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S h e p a rd , R . N ., and T e g h ts o o n ia n , M. R e t e n t i o n o f i n
f o r m a tio n u n d e r c o n d i t i o n s a p p ro a c h in g a s te a d y
s t a t e , j . e x p . P s y c h o l. . I 9 6 I , 6 2 , 3 0 2 -3 0 9 *
S i e g a l , p . S . S t r u c t u r e e f f e c t s w i t h i n a memory s e r i e s .
J . e x p . P s y c h o l . , 1914-3# 22# 3 1 1 -3 1 6 .
S p e r l i n g , G. The I n f o r m a tio n a v a i l a b l e i n b r i e f v i s u a l
e x p o s u r e s . P s y c h o l . M onogr. , i 9 6 0 , 7 ^ , # 1 1 , 1 -2 9 *
S t e l l a r , E . P h y s i o l o g i c a l p s y c h o lo g y . A nn, r e v .
P s y c h o l . , 1957# 8 , I4 .i 5 -I4 .3 6 .
2 1 6
T e ic h n e r , W * H ., R e i l l y , R . , and S a d l e r , E . E f f e c t s o f
d e n s i t y on I d e n t i f i c a t i o n and d i s c r i m i n a t i o n i n
v i s u a l sym bol p e r c e p tio n * J . exp* P s y c h o l* , 1 9 6 1 ,
6 1 , i4.9I4.-50O*
T e ic h n e r , W * H ., and S a d l e r , E* E f f e c t s o f e x p o s u re tim e
and d e n s i t y on v i s u a l sym bol i d e n t i f i c a t i o n * J*
exp* P s y o h o l*, 1 9 6 2 , 6£ , 37 6 -3 8 0 *
Thom as, G* T . N e u ro p h y s io lo g y o f le a r n in g * i n F a r n s
w o r th . P* R . ( e d * ) , Ann* re v * P s y c h o l . , 1 9 6 2 , 1 3 ,
71-106.
T h o rn d ik e , E* L * , and L o rg e , I* T e a c h e r* a w ord book o f
3 0 ,0 0 0 w o rd s . New Y o rk : C o lu m b ia 'dniv. T e a c h e r* a
C o lle g e , 1 9 l|4 .
T u lv ln g , E * , and P a tk a n , J . E . C o n c u rre n t e f f e c t s o f
c o n t e x t u a l c o n s t r a i n t and w ord f r e q u e n c y o n im
m e d ia te r e c a l l and l e a r n i n g o f v e r b a l m a t e r i a l *
C an ad . j . P s y c h o l* , 1 9 6 2 , 1 6 , 8 3 - 9 £ .
U nderw ood, B . J * , and S o h u ls , R . W. M e a n in g fu ln e s s and
v e r b a l l e a r n i n g * New Y o rk : L l p p l h c o t t , 19bO*
W augh, N. C* S e r i a l p o s i t i o n and memory sp a n * Amer* J*
P s y c h o l* . 1 9 5 0 , 72* 6 8 -7 9 .
W augh, N* C* F re e v e r s u s s e r i a l r e c a l l * J . exp*
P sy o h o l *, I 9 6 I , 6 2 , I 4 .9 6 - 5 0 2 .
Y ntem a, D* B *, and M u e se r, G. E* R em em bering th e p r e s e n t
s t a t e o f a num ber o f v a r i a b l e s * J* exp* P s y c h o l* ,
i 9 6 0 , 6 0 , 18- 2 2 .
Y ntem a, D* B *, and M e u se r, C* E« K e e p in g t r a c k o f
v a r i a b l e s t h a t h a v e few o r many s t a t e s . J* exp*
P s y c h o l ., 1962, 6 2 , 391- 3 9 5 *
Z a n g w ill, 0* L* A n o te on im m e d ia te memory* Q u a r t, j*
exp* P s y c h o l*, 1 9 £ 6 , Q$ llfO— 114-3*
APPENDICES
APPENDIX A
CALL FOR SUBJECTS
V o lu n te e r s a r e n e e d e d t o p a r t i c i p a t e i n a p s y c h o
l o g i c a l e x p e rim e n t c o n c e rn in g th e i n f l u e n c e o f c e r t a i n
v a r i a b l e s on w h a t may b e te rm e d Ns h o r t - t e r m m em ory."
A lth o u g h s p e c i f i c d e t a i l s o f th e e x p e rim e n t c a n n o t b e
g iv e n a t t h i s t im e , th e p ro c e d u r e i n g e n e r a l c a l l s f o r
th e memory f o r m a t e r i a l show n o n ly o n ce o r f o r a b r i e f
p e r io d o f t im e . S h o r t l y a f t e r th e m a t e r i a l h a s b e e n d i s
p l a y e d , th e s u b j e c t i s a sk e d t o r e c a l l th e m a t e r i a l*
M odern m an-m achine s y s te m s a r e p l a c i n g new dem ands
o n m a n 's c a p a c i ty to p e rfo rm t h i s ty p e o f ta s k * The r e
s e a r c h e r s r e s p o n s i b l e f o r t h i s r e s e a r c h h a v e r e c e i v e d a
g r a n t fro m t h e Navy t o d is c o v e r p r i n c i p l e s to f a c i l i t a t e
memory o f t h i s t y p e . The e x p e rim e n t i s n o t d i r e o t e d a t
t e s t i n g a p e r s o n 's a b i l i t y b u t r a t h e r e i t h e r w hat i s
shown o r how i t i s o rg a n is e d * P a r t i c i p a n t s w i l l n o t be
e m b a rra s s e d i n an y way*
L e s s t h a n t e n (1 0 ) m in u te s w i l l b e r e q u i r e d o f e a c h
v o l u n t e e r . A " s ig n - u p s h e e t" f o r e a c h day o f t h i s w eek i s
in c lu d e d i n t h i s f o l d e r . P le a s e f i l l y o u r name i n n e x t to
a tim e c o n v e n ie n t f o r y o u . (O r m aybe e v e n a t a tim e n o t
so c o n v e n ie n t* ) You w i l l be in fo rm e d c o n c e rn in g th e
219
2 2 0
l o c a t i o n o f t h e e x p e r im e n t, w h ic h w i l l be h e re on cam pus.
Thank you*
R ic h a rd P* G a b r ie l
INSTRUCTIONS
r * > *
GROUP 1A
The e x p e rim e n t f o r w h ic h you h a v e v o l u n te e r e d I s
c o n c e rn e d w ith s h o r t - t e r m memory* S p e c i f i c a l l y , I n a few
m in u te s a s e r i e s o f w ords w i l l be d is p la y e d o n th e s c r e e n
one a t a tim e . You a re t o o b se rv e th e w ords a n d , a s so o n
a s th e s e r i e s I s c o m p le te d , t o w r ite down th e w o rd s o n
th e a n sw e r fo rm I n th e same o r d e r as th e y a p p e a re d on th e
s c re e n * I f y o u c a n rem em ber m ore w o rd s th a n y o u c a n c o r
r e c t l y o r d e r , p u t a l l o f them down I n a s c lo s e t o th e
c o r r e c t o r d e r as y o u can*
A f t e r one m in u te th e e x p e rim e n te r w i l l a s k y o u to
t u r n th e an sw er fo rm o v e r . A l i s t o f w ords w i l l th e n ap
p e a r on th e s c re e n * A l l o f th e w ords o f th e o r i g i n a l
s e r i e s w i l l b e in c lu d e d i n t h i s l i s t a lo n g w i t h many
o th e r s * Now, w ith th e h e lp o f t h i s l i s t , t r y t o w r i t e
down a l l o f th e w ords o f th e o r i g i n a l l i s t , a g a in i n th e
o r d e r i n w h ic h th e y o c c u r r e d , b u t f a l l i n g t h i s , I n an y
o r d e r a t a l l *
T h is w i l l c o n c lu d e th e f i r s t p a r t o f th e e x p e r i
m e n t. A f t e r a s h o r t b r e a k , th e same p ro c e d u re w i l l be
f o llo w e d w ith a new , lo n g e r l i s t * I f you h a v e any q u e s
t i o n s p l e a s e a s k them now*
2 2 1
INSTRUCTIONS
GROUPS IB AND 1C
The e x p e rim e n t f o r w h ich y ou h a v e v o lu n te e r e d i s
c o n c e rn e d w ith s h o r t - t e r m memory* S p e c i f i c a l l y * i n a few
m in u te s a s e r i e s o f w ords w i l l be d is p la y e d on th e s c r e e n
one a t a tim e * You a re t o o b s e rv e th e w ords and th e
t h r e e - d i g i t num ber t h a t w i l l a p p e a r a f t e r th e l a s t word*
As so o n a s y ou s e e t h e number* s t a r t c o u n tin g b a ck w a rd s
by t h r e e s ( v o c a l l y so t h e e x p e r im e n te r c a n h e a r y o u ) a s
f a s t a s y o u c a n u n t i l y ou a re sto p p e d * T h a t i s * th e l a s t
s l i d e may be "3 8 5 * B When you s e e t h i s y ou w ould say *
"382* 379* e tc * * " a s f a s t a s y o u can* As so o n a s th e
e x p e r im e n te r s a y s " S to p ,* t r y t o w r i t e down th e w o rd s on
th e an sw er fo rm i n th e same o r d e r as th e y a p p e a re d o n th e
s c r e e n . I f y ou c a n rem em ber m ore w ords th a n you o an
o o r r e c t l y o rd e r* p u t a l l o f them down i n as c lo s e t o th e
c o r r e c t o r d e r as y ou can*
A f t e r one m in u te t h e e x p e r im e n te r w i l l a s k y o u t o
t u r n t h e an sw er fo rm o v e r . A l i s t o f w ords w i l l t h e n
a p p e a r on th e s c re e n * A l l o f th e w ords o f th e o r i g i n a l
s e r i e s w i l l b e in c lu d e d i n t h i s l i s t a lo n g w ith many
o th e r s * Now, w ith th e h e lp o f t h i s l i s t , t r y t o w r i t e
down a l l o f th e w ords o f th e o r i g i n a l s e r i e s * a g a in i n
2 2 2
223
th e o r d e r i n w h ich th e y o c c u r r e d ) b u t i f y ou a r e u n a b le
t o do t h i s * i n any o r d e r a t a l l *
T h is w i l l c o n c lu d e t h e f i r s t p a r t o f th e e x p e r i
m e n t. A f t e r a s h o r t b r e a k , th e same p r o c e d u r e w i l l be
fo llo w e d w ith a new , lo n g e r l i s t . I f y ou h a r e any q u e s
t i o n , p l e a s e ask them now*
I N S T R U C T I O N S
GROUP 2A
T h e e x p e r i m e n t f o r w h i c h y o u h a v e v o l u n t e e r e d l a
c o n c e r n e d w i t h s h o r t - t e r m m e m o ry . S p e c i f i c a l l y , i n a f e w
m i n u t e s a s e r i e s o f w o r d s w i l l b e d i s p l a y e d o n t h e s c r e e n
o n e a t a t i m e . Y o u a r e t o o b s e r v e t h e w o r d s a n d a s s o o n
a s t h e s e r i e s i s c o m p l e t e d , t o w r i t e d o w n t h e w o r d s o n
t h e a n s w e r f o r m I n t h e sa m e o r d e r a s t h e y a p p e a r e d o n t h e
s c r e e n . T o a s s i s t y o u , y o u w i l l f i n d o n t h e a n s w e r f o r m
a l i s t o f c a t e g o r y n a m e s I n a l p h a b e t i c a l o r d e r . F o r
e x a m p l e , t h e f i r s t w o rd d i s p l a y e d m i g h t b e " F o r d . " T h i s
w o rd w o u ld h a v e b e e n s e l e c t e d f r o m t h e c a t e g o r y " A u t o
m o b i l e M a n u f a c t u r e r s . * ( T h e s e s p e c i f i c i t e m s w i l l n o t
a p p e a r b u t a r e f o r d e m o n s t r a t i v e p u r p o s e s o n l y . ) T h u s ,
w h e n y o u s e e o n t h e a n s w e r f o r m " A u t o m o b i l e M a n u f a c t u r e r , *
y o u r m em o ry f o r " F o r d " m ay b e f a c i l i t a t e d . R e m e m b e r, t r y
t o w r i t e t h e w o r d s i n t h e sa m e o r d e r a s t h e y a p p e a r e d
o r i g i n a l l y i r r e s p e c t i v e o f t h e c a t e g o r y o r d e r o n t h e
a n s w e r f o r m . B u t , I f y o u c a n 11 d o t h i s , p u t d o w n a l l
o f t h e w o r d s t h a t y o u r e m e m b e r i n a s c l o s e t o t h e o r i g i n a l
o r d e r a s y o u c a n .
A f t e r o n e m i n u t e , t h e e x p e r i m e n t e r w i l l a s k y o u t o
t u r n t h e a n s w e r f o r m o v e r . T h e n a l i s t o f w o r d s w i l l
a p p e a r on th e s c re e n * A ll o f th e w ords o f th e o r i g i n a l
s e r i e s w i l l a p p e a r I n t h i s l i s t a lo n g w ith m any o th e r s *
Now, w ith th e h e lp o f t h i s l i s t , t r y t o w r i t e down th e
w ords t h a t o c c u r r e d I n th e o r i g i n a l l i s t , a g a in i n th e
o r d e r i n w h ic h th e y o c c u r r e d , b u t i f y o u a r e u n a b le t o do
t h i s , i n any o r d e r a t a l l *
T h is w i l l c o n c lu d e th e f i r s t p a r t o f t h e e x p e r i
m ent* A f t e r a s h o r t b r e a k , th e same p ro c e d u r e w i l l be
fo llo w e d w ith a new , lo n g e r l i s t * I f y ou h a v e any q u e s
t i o n s , p l e a s e a s k them now*
INSTRUCTIONS
GROUPS 2B AND 2C
The e x p e rim e n t f o r w h ic h y o u h a v e v o lu n te e r e d i s
c o n c e rn e d w ith s h o r t - t e r m m em ory. S p e c i f i c a l l y , i n a few ;
m in u te s a s e r i e s o f w o rd s w i l l b e d is p la y e d o n th e s c r e e n ,!
one a t a t im e . Y ou a r e t o o b s e r v e th e w ords and th e
t h r e e - d i g i t num ber t h a t w i l l a p p e a r a f t e r th e l a s t w o rd .
As so o n a s y ou s e e th e n u m b er, s t a r t c o u n tin g b a ck w a rd s by
t h r e e s a s f a s t a s y o u c a n . ( V o c a lly , so th e e x p e r im e n te r
can h e a r y o u .) T h a t i s , th e l a s t s l i d e may be *38*5.*
Hlhen y o u s e e t h i s y o u w o u ld s a y , ” 3 8 2 , 379>* ® t c ., a s
f a s t a s you c a n . As s o o n a s th e e x p e r im e n te r s a y s " s t o p ,*
t r y t o w r i t e down th e w o rd s on th e answ er fo rm i n th e
same o r d e r t h a t th e y a p p e a re d on t h e s c r e e n . To a s s i s t
y o u , y o u w i l l f i n d o n th e an sw er fo rm a l i s t o f c a te g o r y
nam es i n a l p h a b e t i c a l o r d e r . F o r e x a m p le , th e f i r s t
w ord d is p la y e d m ig h t b e " F o r d ." T h is w ord w ould h a v e b e e n
s e l e c t e d fro m t h e c a te g o r y "A u to m o b ile M a n u f a c tu r e r s ."
(T h e se s p e c i f i c ite m s w i l l n o t a p p e a r b u t a re f o r demon
s t r a t i v e p u r p o s e s o n l y .) T h u s, when y o u s e e on th e
an sw er fo rm "A u to m o b ile M a n u fa c tu re r" y o u r memory f o r
"F o rd * may be f a c i l i t a t e d . Rem em ber, t r y t o w r i t e th e
w o rd s i n t h e same o r d e r a s th e y o r i g i n a l l y a p p e a re d i r -
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r e s p e c t i v e o f th e c a te g o r y o r d e r on th e an sw er fo rm .
B u t, i f y ou c a n 1t do t h i s , p u t down a l l o f th e w ords
t h a t y o u c an rem em ber i n a s c lo s e t o th e c o r r e c t o r d e r
a s y o u can*
A f t e r one m in u te , t h e e x p e r im e n te r w i l l a sk y o u to
t u r n y o u r an sw e r fo rm o v e r . T hen a l i s t o f w o rd s w i l l
a p p e a r on t h e s c r e e n . A l l o f th e w ords o f th e o r i g i n a l
s e r i e s w i l l a p p e a r i n t h i s l i s t a lo n g w ith many o t h e r s .
Now, w ith t h e h e lp o f t h i s l i s t , t r y t o w r i t e down th e
w o rd s t h a t o c c u r r e d i n th e o r i g i n a l l i s t , a g a in i n th e
o r d e r i n w h ic h th e y o c c u r r e d , b u t i f y o u a r e u n a b le t o do
t h i s , i n any o r d e r a t a l l .
T h is w i l l c o n c lu d e t h e f i r s t p a r t o f t h e e x p e r i
m e n t. A f t e r a s h o r t b r e a k , th e same p r o c e d u r e w i l l be
fo llo w e d w ith a new , lo n g e r l i s t . I f y ou h a v e any q u e s
t i o n s , p l e a s e a s k them now .
INSTRUCTIONS
GROUP 3A
The e x p e rim e n t f o r w h ic h y o u h a v e v o l u n te e r e d i s
c o n c e rn e d w ith s h o r t - t e r m memory* S p e c i f i c a l l y , I n a
few m in u te s , a s e r i e s o f w ords w i l l be d is p la y e d o n th e
s c r e e n , one a t a t i m e . Y ou a re t o o b s e rv e th e w o rd s and
a s so o n a s t h e s e r i e s I s c o m p le te d , t o w r i t e down th e
w ords o n th e a n sw e r fo rm I n t h e same o r d e r a s th e y ap
p e a r e d o n th e s c r e e n . To a s s i s t y o u , y o u w i l l f i n d on
th e a n sw e r fo rm a l i s t o f c a t e g o r y n a m e s. The s e r i e s o f
w o rd s t h a t y o u w i l l s e e w ere p ic k e d t o c o n fo rm t o t h e s e
c a t e g o r i e s , one p e r c a t e g o r y , and w i l l b e d i s p l a y e d i n
th e same o r d e r t h a t t h e c a t e g o r i e s a r e a r r a n g e d o n th e
form * F o r e x a m p le , th e f i r s t w ord d i s p l a y e d m ig h t be
" F o rd * " T h is w ould h a v e b e e n s e l e c t e d fro m th e c a te g o r y
"A u to m o b ile M a n u fa c tu re rs * " (T h e s e s p e c i f i c Ite m s w i l l
n o t a p p e a r b u t a re f o r d e m o n s tr a tiv e p u r p o s e s o n l y ,)
T h u s, w hen y o u s e e o n t h e an sw er fo rm "A u to m o b ile Manu
f a c t u r e r " y o u r memory f o r " F o rd " may b e f a c i l i t a t e d *
Rem em ber, s i n c e th e c a t e g o r i e s on th e a n sw e r fo rm a re
a rra n g e d i n t h e same o r d e r a s t h e w o rd s t h a t w i l l be
d is p la y e d j u s t w r i t e th e w o rd s I n t h e same o r d e r a s th e
c a t e g o r i e s * T h is a l s o m eans t h a t y o u c a n d e v o te a l l
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229
y o u r e f f o r t t o m em o riz in g th e s p e c i f i c lte m a and d o n * t
h a v e to w o rry a b o u t t h e o r d e r .
A f t e r one m in u te th e e x p e r im e n te r w i l l aak y o u to
t u r n th e an sw er fo rm o v e r . T hen a l i s t o f w ords w i l l
a p p e a r o n t h e s c r e e n . A l l o f th e w ords o f th e o r i g i n a l
s e r i e s w i l l a p p e a r i n t h i s l i s t a lo n g w ith many o t h e r s .
Now, w ith t h e h e lp o f t h i s l i s t , t r y t o w r i t e down th e
w o rd s t h a t a p p e a re d on t h e o r i g i n a l l i s t .
T h is w i l l c o n c lu d e t h e f i r s t p a r t o f th e e x p e r i
m e n t. A f t e r a s h o r t b re a k th e same p ro c e d u re w i l l be
fo llo w e d w ith a new , lo n g e r l i s t . I f you hav e any q u e s
t i o n s p l e a s e a s k them now .
INSTRUCTIONS
GROUPS 3B AND 3C
The e x p e r im e n t f o r w h ic h y o u h a v e v o l u n te e r e d I s
c o n c e rn e d w i t h s h o r t - t e r m memory* S p e c i f i c a l l y , y o u w i l l
be show n a s e r i e s o f w o rd s , one a t a t im e . You a r e t o
o b s e rv e t h e w o rd s an d th e t h r e e - d i g i t num ber t h a t w i l l
a p p e a r a f t e r th e l a s t w o rd . As so o n a s y o u s e e th e
n u m b e r, s t a r t c o u n tin g b a c k w a rd s by t h r e e s a s f a s t a s
y o u can * ( V o c a lly so t h e e x p e r im e n te r c a n h e a r y o u * )
T h a t i s , th e l a s t s l i d e may b e *385*" When y o u s e e t h i s ,
y o u w o u ld s a y * 3 8 2 , 379** e t c . , a s f a s t a s y o u c a n . As
so o n a s th e e x p e r im e n te r s a y s " S to p * " t r y to w r i t e t h e
w o rd s on th e a n sw e r fo rm i n th e same o r d e r as th e y ap
p e a r e d on t h e s c r e e n . To a s s i s t y o u , y o u w i l l f i n d on
th e a n sw e r fo rm a l i s t o f c a te g o r y n am es. The s e r i e s
o f w ords t h a t y o u w i l l s e e w ere p ic k e d t o c o n fo rm t o
t h e s e c a t e g o r i e s , one p e r c a t e g o r y , and w i l l be d is p la y e d
i n th e same o r d e r t h a t th e c a t e g o r i e s a re a r r a n g e d o n th e
fo r m . F o r e x a m p le , t h e f i r s t w ord d i s p l a y e d m ig h t be
" F o r d .* T h is w ould h a v e b e e n s e l e c t e d fro m t h e c a te g o r y
* A u to m o b lle M a n u fa c tu re rs * * (T h e se s p e c i f i c ite m s w i l l
n o t a p p e a r b u t a r e f o r d e m o n s tr a tiv e p u r p o s e s o n l y .)
T h u s , w hen y o u s e e on th e a n sw e r fo rm " A u to m o b ile M anu-
231
fa c tu re rs * * y o u r memory f a r “F o rd " may b e f a c i l i t a t e d .
Rem em ber, s in c e t h e c a t e g o r i e s on th e a n sw e r fo rm a r e
a rr a n g e d i n th e same o r d e r a s th e w o rd s t h a t w i l l b e d i s
p l a y e d , y o u may s im p ly w r i t e th e w o rd s i n t h e same o r d e r
a s th e c a t e g o r i e s . T h is a l s o m eans t h a t y o u c a n d e v o te
a l l o f y o u r e f f o r t to m em o riz in g t h e s p e c i f i c ite m s and
d o n 't h a v e t o w o rry a b o u t th e o r d e r .
A f t e r one m in u te th e e x p e r im e n te r w i l l a s k y o u t o
t u r n t h e a n sw e r fo rm o v e r . T hen a l i s t o f w ords w i l l
a p p e a r on t h e s c r e e n . A l l o f th e w ords o f th e o r i g i n a l
l i s t w i l l b e in c lu d e d i n t h i s l i s t a lo n g w ith many o t h e r s .
Now, w ith th e a id o f t h i s l i s t , t r y t o w r i t e down th e
w ords t h a t a p p e a re d i n th e o r i g i n a l s e r i e s .
T h is w i l l c o n o lu d e th e f i r s t p a r t o f th e e x p e r i
m e n t. A f t e r a s h o r t b r e a k th e same p r o c e d u r e w i l l b e
fo llo w e d w ith a new , lo n g e r l i s t .
APPENDIX B
ANSWER FORM
(No o r d e r in f o r m a tio n )
I n s t r u c t o r ^ Name _______
(F ro m w hose c l a s s y o u v o l u n t e e r s d j
Y o u r Name ______________________________
E x p e r i m e n t a l G roup __
S c o r e ( T o t a l C o r r e c t )
S c o r e ( I n O rd e r) _____
I * F r e e R e c a l l
A n sw ers 3
1 . _________________________
2.
3 . _________________________
k * ______________________________
_
6.
7 . _________________________
2 3 2
N ote: In th e o r ig in a l the fo llo w in g m a teria l was
on th e rev erse s id e o f each answer form , id e n tic a l fo r
a l l task s*
A N SW E R F O R M
(A ll Groups)
II* R ecogn ition
Answers:
ANSWER FORM
(No C a te g o ry I n f o r m a tio n )
I n s tr u c to r * s Name
(From w hose c l a s s you v o lu n te e r e d )
Y o u r Name ______________________________
E x p e r im e n ta l C roup __
S c o re ( T o t a l C o r r e c t)
S c o re ( I n O rd e r) ____
I . F r e e R e c a ll
A nsw ers 3
1 . __________________________
2. ______________
3 .
I* . _______________________________
5 . __________________________
6. _______________
7 . __________ _ _____________
8. ______________
9 . ____________ ; _____________
1 0. ___
11. _________
235
ANSW ER FO RM
(A lp h a b e tiz e d C a te g o r ie s )
I n s tr u c to r 's Name
(From whose c la s s you volu n teered )
Your Name ___________________________
E xperim ental Group __________
Score (T o ta l C orrect) ______
Score (I n Order) ____________
I . Free R e c a ll
A* C ategories* B. Answers: (In the order
in which you saw them)
1 . Animal 1.
2 . Boat 2 .
3 .
Body P art
3 .
h.
G eo lo g ica l
Formation
Ki
5 .
M usical
Instrum ent
5 .
6 . Name 6 .
7*
Weapon
7 .
236
ANSWER FORM
( A lp h a b e tiz e d C a te g o r ie s )
I n s t r u c t o r 's Name
(From w hose c l a s s y o u v o l u n te e r e d )
Y our Name
I . F r e e R e e a l l
A . C a t e g o r i e s 3
1 • A nim al
2 . B o at
3 • Body P a r t
Ij.. C lo th in g
5* F u r n i t u r e
6* G e o lo g ic a l
F o rm a tio n
7 . I n s e c t
8 , M u s ic a l
I n s tr u m e n t
9* Name
1 0 . V e h ic le
11* W eapon
E x p e r im e n ta l G roup
S c o re ( T o t a l C o r r e c t)
S c o re ( I n O rd e r)______
B . A nsw ers 3
1 . ______
2. __
3 . ________
________
5 . _______
6 .
7 .
8.
9 .
10.
1 1 .
237
ANSWER FORM
(O rd e re d C a te g o r ie s )
A
I n s t r u e to r* s Name
(From w hose c l a s s y o u v o lu n te e r e d )
Y o u r Name
I* F r e e R e c a ll
A* C a t e g o r i e s :
1« Name
2« Body P a r t
3 . A nim al
I*. M u s ic a l
I n s tr u m e n t
5* W eapon
6* B o a t
G e o lo g ic a l
F o rm a tio n
E x p e r im e n ta l G roup
S c o re ( T o t a l C o r r e c t ^
S c o re ( i n O r d e r)______
B . A n sw e rs:
1 . ______
2. ___
3 . ______
k . ________
5 .
6.
7 .
238
ANSWER FORM
(O rd e re d C a te g o r ie s )
B
I n s t r u c t o r ’ s Name
(From w hose c l a s s y o u v o lu n te e r e d )
Y our Name _________________ ____
I* F r e e R e c a ll
A* C a te g o r ie s :
1. Boat
2. Body P art
3 .
Animal
k.
Weapon
5 .
G eological
Formation
6 . Musical
In s tr u m e n t
7* Name
E x p e r im e n ta l G roup
S c o re ( T o ta l C o r r e c t)
S c o re ( i n O rd e r)______
B . A nsw ers:
1 . ____________________
2. _________
3 . _________________
____________________
5 . _________________
6. ____________
7 . ________________
239
ANSWER FORM
(O rd e re d C a te g o r ie s )
C
I n s t r u c t o r 1s Name
(From w hose c l a s s y ou v o lu n te e r e d }
Your Name
I* F r e e R e c a ll
A* C a te g o r ie s :
1 . Body P a r t
2 . W eapon
3« Name
i|.« M u s ic a l
Instrument
£ • G e o lo g ic a l
F o rm a tio n
6* B o at
7 • A nim al
Experim ental Group
S c o re ( T o ta l C o r r e c t)
S c o re ( I n O rd e r)______
B. Answers:
1 . ______
2. _ _
3 . ______
k * _______
6.
7 .
2I 4 . O
A N SW E R F O R M
(Ordered C ategories)
D
I n s t r u c t o r 's Name
(From w hose c l a s s you v o lu n te e r e d )
Your Name
Experim ental Group
Score (T otal C orrect)
Score (I n Order)
I* Free R e c a ll
A* C a teg o ries: B. Answerst
1 . Weapon 1*
2 . M usical
Instrument
2 .
3 .
G eo lo g ica l
Formation
3 .
k*
Animal
k-
Name
5 .
6 . Boat 6 .
7 .
Body Part
7 .
2l*.l
ANSWER FORM
(O rd e re d C a te g o r ie s )
E
I n s t r u c t o r 's Name
(From w hose c l a s s y o u v o lu n te e r e d )
Y our Name
I • F re e R e c a ll
A« C a te g o r ie s *
1 . W eapon
2* Body p a r t
3 . A nim al
Ij.. M u s ic a l
I n s tr u m e n t
5>, Name
6* G e o lo g ic a l'
F o rm a tio n
E x p e r im e n ta l G roup
S c o re ( T o t a l C o r r e c t )
S c o re ( I n O r d e r ) ______
B, A n sw e rs:
1 . ______
2. ___
3 . ______
k . _______
5 .
6.
B o a t
7 .
2 1 + 2
ANSWER FORM
(O rd e ra d C a te g o r ie s )
A
I n s t r u e t o r * s Name________
(From w hose c l a s s y o u v o lu n te e r e d )
Y o u r Name
E x p e r im e n ta l G roup
S c o re ( T o t a l C o r r e c t)
S c o re ( I n O rd e r)
I* F re e R e c a ll
A . C a t e g o r i c s 2 B . A n sw e rs:
1*
B o a t 1 .
2 . F u r n i t u r e 2 .
3 .
I n s e c t
3 .
k .
G e o lo g ic a l
F o rm a tio n
k*
5 .
Name
6* C lo th in g 6.
7 .
Body P a r t
7 .
8. W eapon 8 .
9 .
V e h ic le
9 .
1 0 . A nim al 1 0 .
1 1 . M u s ic a l
I n s tr u m e n t
1 1 .
2 1 4 .3
A N SW E R F O R M
(Ordered C a teg o ries)
B
In stru cto r* s Name
(From whose c la s s you volu n teered )
Your Name____________________________
Experim ental Group
Score (T o ta l C orrect)
Score ( i n Order)
I* Free R e c a ll
A* C a teg o ries: B . Answers:
1 . Name 1 .
2 . M usical
Instrum ent
2 .
3 .
Boat 3 .
k.
Animal
$.
Weapon
S .
6 . Body Part 6 .
7 .
C loth in g
7 .
8 . G eo lo g ica l
Formation
8 .
9 .
Vehic le
9 .
1 0 . F urniture 1 0 .
1 1 . In se c t 1 1 .
2 1 *
A N SW E R F O R M
(Ordered C ateg o ries)
C
In stru c to r* s Name________
(From whose c la s s you volu n teered )
• >
Your Name
Experim ental Group___
Score (T o ta l C orrect)
Score (In Order)
I* Free R ec a ll
A. C a teg o ries: B. Answers:
1 . Body Part 1 .
2 . Weapon 2 .
3 .
V eh icle
3 .
1*.
M usical
Instrum ent
k.
5 .
Name
5 .
6 . I n s e c t 6 .
7 .
F urniture
7 .
8 . C lothin g 8 .
9 .
Animal
9 -
10 . G eo lo g ica l
Formation
10.
11. Boat 11.
2 k $
A N SW E R F O R M
(Ordered C a te g o rie s)
D
I n s tr u c to r 's Name
(From whose c la s s you v olu n teered )
Your Name
E xperim ental Group
Score (T o ta l C orrect)
Score ( i n Order)_____
I* Free R e c a ll
A* C a teg o ries: B. Answers:
1 . C loth in g 1 .
2 . I n s e c t 2 ,
3 .
Boat 3 .
Animal
k.
Name
5 .
6 . Weapon 6 .
7 .
Body Part
7 .
8 . G eo lo g ica l
Form ation
8 .
9 .
Vehlc le
9 .
10, F urniture 10.
11. M usical
Instrum ent
11.
2 1 * 6
A N SW E R F O R M
(Ordered C ateg o ries)
E
In stru ctor* a Name________ _
(From whose c la s s you volu n teered )
Your Name
Experim ental Group
Score (T o ta l C orrect)
Score (In Order)_____
I . Free R e c a ll
A. C a teg o ries: B. Answers:
1 . In se c t 1 .
2 . Name
2 .
3 .
F u rn itu re
3 .
k.
M usical Instrum ent
k-
S .
V eh icle
6 . Boat 6 .
7 .
Animal
7 .
8 . C lothin g 8 .
9 .
Weapon
9 .
10. G eo lo g ica l
Formation
10.
11. Body p art 11.
APPENDIX C
MURDOCK'S DISTINCTION BETWEEN
LEARNING AND M EM O RY
An e m p i r i c a l l y d e r iv e d r e l a t i o n s h i p d e te rm in e d by
M urdock w as a m e a su re o f a r a t e o f l e a r n i n g c o n s t a n t ,
" b , " He s t a t e s t h a t i n f r e e r e c a l l v e r b a l l e a r n i n g , th e
d a t a a s i n g l e s u b j e c t 's l e a r n i n g s i n g l e l i s t s i s a d e q u a te
ly d e s c r ib e d by
R = c (1 - e “ b n )
w here
R 8 th e num ber o f ite m s r e c a l l e d a f t e r
e a c h p r e s e n t a t i o n
C = a n u p p e r l i m i t o r a sy m p to te
b ■ th e r a t e c o n s t a n t o r s lo p e o f a
c u rv e i n s e m i- lo g p l o t , and
n = th e num ber o f p r e s e n t a t i o n s .
M urdock s u g g e s ts t h a t l e a r n i n g be c o n s id e r e d th e
s lo p e o f th e c u rv e sh o w in g R a s a f u n c t i o n o f n . T hus
l e a r n i n g i s t h e f i r s t d e r i v a t i v e o f R w ith r e s p e c t t o n
o r d n . S uch a d i s t i n c t i o n b e tw e e n l e a r n i n g and r e t e n
t i o n i s a n a lo g o u s t o t h e d i s t i n c t i o n b e tw e e n p o s i t i o n and
v e l o c i t y i n m e c h a n ic s . J u s t a s v e l o c i t y i s th e r a t e o f
ohange o f p o s i t i o n w ith r e s p e c t t o tim e , s o l e a r n i n g i s
th e r a t e o f ohange o f r e t e n t i o n w ith r e s p e c t t o th e
21#
250
number o f p r e se n ta tio n s. This i s c o n s is te n t w ith the
id e a th a t lea rn in g i s in d ica te d by an improvement in
performance*
The fa c t th a t R « f ( n ) , i s ex p o n en tia l, according
to Murdock, means th a t the slo p e of th e lin e (lea rn in g )
i s p ro p o rtio n a l to th e number of item s y e t to be r e
ca lle d * Thus, ^ /d n * b (C -R ). The le a rn in g becomes
slow er w ith each su c c e ssiv e p resen ta tio n * The obvious
measure of lea rn in g from t h is p o in t o f view i s b - the
slo p e of the s tr a ig h t lin e obtained by p lo ttin g In
(c -R )/c ) as a fu n ctio n o f n* The ra te con stant "b" r e
p la c e s such tr a d itio n a l measures o f lea rn in g as " t r ia ls
to c r ite r io n " or number of co r r e c t responses*
I t i s assumed by Murdock th a t the ex p o n en tia l
eq u ation d escrib es th e r e s u lts of a l l su b jec ts in tree-
r e c a ll verbal le a r n in g . In d iv id u a l d iffe r e n c e s are
assumed to be m anifested in d iffe r in g num erical v a lu es
of the param eters b and/or C*
APPENDIX D
B R O W N * S INFORM ATION T H E O R Y FO R M U L A S A N D
T H E .DERIVATION O F T H E A M O U N T O F
O R D E R INFORM ATION TRANSM ITTED
n Io g 2 N ■ " s e l e c t i v e " i n f o r m a ti o n
lo g 2 N I : o r d e r i n f o r m a ti o n w here N = th e num ber o f
* 11*2 - lo g 2 1 2 ,9 6 0
s 22 - lo g 1 2 ,9 6 0 ^ q x (C onversion fa c to r to g e t to lo g 2 )
S 22 - 1^.1127 x 3*32
= 22 - 13. 6&
T h u s, o r d e r i n f o r m a tio n i s a b o u t 62# o f t o t a l I n f o r m a tio n
t r a n s m i t te d *
I f yo u c o n s i d e r th e num ber o f ite m s p e r c a te g o r y
to be 3 2 , t h e n th e f o llo w in g w ould be th e r e l a t i v e am ount
o f o r d e r and ite m in f o r m a tio n *
n lo g g N - lo g 2 n I
s 11* lo g 2 32 - lo g 2 11 &
Item i n f o ■ n l o g 2 N - lo g 2n l
ite m s p e r c a te g o r y
and n = " s p a n s i z e "
l o g 10 12960 a I4 . . I I 27
o r i n t h i s c a s e
11 lo g 2 Ij. - lo g 2 111
8 * 3 1* 6
* 11 x £ - 1 3 .6 &
* $5 - 1 3 . 6&
= lvl.3^6
252
2S3
O rd e r I n f o r m a tio n I s s t i l l a p p ro x im a te ly 2$% o f th e t o t a l
I n f o r m a tio n p r e s e n te d *
And I f t h e t o t a l num ber o f Ite m s I n e a c h c a te g o r y
w ere 6I 4 ., t h e n 20% o f th e t o t a l I n f o r m a tio n I s o r d e r I n
fo rm a tio n *
0

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Creator Gabriel, Richard Flynn (author)

Core Title The Influence Of Order Information And Stimulus Display Time On Short-Term Retention

Degree Doctor of Philosophy

Degree Program Psychology

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag OAI-PMH Harvest,psychology, experimental

Language English

Contributor Digitized by ProQuest (provenance)

Advisor Mayzner, Mark S. (committee chair), Guilford, Joy P. (committee member), Wolbers, Harry L. (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c18-321269

Unique identifier UC11358821

Identifier 6406239.pdf (filename),usctheses-c18-321269 (legacy record id)

Legacy Identifier 6406239.pdf

Dmrecord 321269

Document Type Dissertation

Rights Gabriel, Richard Flynn

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA