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University of Southern California Dissertations and Theses
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Noxious Auditory Environment And Psychomotor Performance
(USC Thesis Other)
Noxious Auditory Environment And Psychomotor Performance
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Content
NOXIOUS AUDITORY ENVIRONMENT AND
PSYCHOMOTOR PERFORMANCE
by
W 0 A g ib T rem bly
A D i s s e r t a t i o n P r e s e n t e d t o t h e
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In P a r t i a l F u l f i l l m e n t o f t h e
R e q u ire m e n ts f o r t h e D e g re e
DOCTOR OF PHILOSOPHY
(P s y c h o lo g y )
J u n e 1959
This dissertation, written by
.................W. A.gib Trem bly.............
under the direction ofh.ls.Guidance Committee,
and approved by all its members, has been pre
sented to and accepted by the Faculty of the
Graduate School, in partial fulfillment of re
quirements for the degree of
D O C T O R O F P H I L O S O P H Y
Dean
D ate Jyne„.!9_5&
TABLE OF CONTENTS
CHAPTER
I . INTRODUCTION.................................................... . ........................
S ta te m e n t o f t h e problem .............................................
Im p o rta n c e o f th e p r o b l e m ...................... . . .
H e SELECTIVE REVIEW OF STUDIES PERTAINING TO THE
EFFECTS OF NOISE ON HUM AN PERFORMANCE. . , .
I I I . INSTRUMENTATION. ...........................
The n a t u r e o f th e a u d i t o r y m a t e r i a l s and
t h e i r mode o f p r e s e n t a t i o n ....................................
The apparatus. . . . . . . . . . . . . . . .
IV. EXPERIMENTAL DESIGN AND PROCEDURE. . . . . . .
s u b j e c t s . . . . . . . . . . . . . . . . . .
E x p e rim e n ta l d e s ig n and p r o c e d u re . . . . . «
S c o r in g . . . ........................................ . . . . . . .
V. ANALYSIS AND DISCUSSION OF RESULTS . . . . . .
P la n f o r s t a t i s t i c a l a n a l y s i s . . . . . . . .
A n a ly s is o f r e s u l t s . . . . . . .......................... .
D is c u s s io n and e v a l u a t i o n o f r e s u l t s . . . .
V I. SUMMARY AND CONCLUSIONS.................................... . . . .
Summary . . . . . . . . . . . . . . . . . .
PAGE
1
6
13
17
51
51
53
62
62
63
67
69
69
73
96
105
105
iv
CHAPTER PAGE
C o n c lu s io n s • . ........................................................................109
I m p l i c a t i o n s ...................................................... I l l
BIBLIOGRAPHY .................................... ...... . 1 1 3
APPEND 1^- 118
LIST OF TABLES
TABLE PAGE
I . C oding o f t h e In d e p e n d e n t V a r ia b le s .. .. . . 70
II® A n a ly s is o f E r r o r S c o r e s . ................................. 75
I I I . Mean E r r o r D if f e r e n c e S c o re s and S ta n d a rd
D e v i a t io n s ........................ 7&
IV. Mean Number o f E r r o r S c o re s f o r E ach V a r ia b le
A lon e .................... . . . . . . . . . . . . . . . ?8
V. A n a ly s is o f V a ria n c e o f E r r o r D i f f e r e n c e
S c o r e s . . . ..................... . . . . . . . . . . . . 79
V I. A n a ly s is o f Time S c o re s .............................. • 8k
V I I. Mean Time D if f e r e n c e S c o re s and S ta n d a rd
D e v ia tio n s ( S e l f - P a c i n g ) ......................... 86
V I I I . Mean Time S c o res f o r Each V a r ia b l e A lone
( S e lf - P a c in g ) . . . . . . . . . . . 87
IX. A n a ly s is o f V a ria n c e o f Time D i f f e r e n c e
S c o re s ( S e l f - P a c i n g ) . . . . . . . . . . . . . 88
X, Mean Time D if f e r e n c e S c o re s and S ta n d a rd
D e v ia tio n s ( E x t e r n a l - P a c i n g ) ...............................................91
X I. Mean Time S c o re s f o r Each V a r ia b le A lone
( E x te r n a l- P a c in g ) . . . . . . . . . . . . . . 92
X I I . A n a ly s is o f V a ria n c e o f Time D if f e r e n c e
S c o re s ( E x t e r n a l - P a c i n g ) ................................................. 93
LIST OF FIGURES
FIGURE
1 *
2,
PAGE
E x t e r n a l View o f t h e A p p a r a t u s .................................... %
View o f A p p a ra tu s Show ing th e Drum and Con
t r o l OhaSSiS * e a 4 * « < a 4 & » * s « e a e 57
CHAPTER I
INTRODUCTION
Th© s o c i e t y t h a t we l i v e i n to d a y i s r e l a t i v e l y
com plex i n c o m p a riso n t o t h a t o f o n ly a few s h o r t y e a r s
past® Man i s e v e r s e a r c h i n g f o r t h a t e l u s i v e " h i g h e r
s t a n d a r d o f l i v i n g 1 1 w h ich h e n e v e r seem s t o l o c a t e and
a d j u s t t o — t h a t i s , J u d g in g fro m h i s u n t i r i n g l a b o r s t o
p e r f e c t l a b o r - s a v i n g d e v i c e s , t o d i s c o v e r f a s t e r m odes o f
t r a n s p o r t a t i o n , a n d , among o t h e r t h i n g s , t o c o n s t r u c t
l a r g e r an d m ore p r o d u c t i v e d e v ic e s t o a i d him i n t h e e f f e c
t i v e e l i m i n a t i o n o f h i s f e l l o w men* A lo n g w i t h t h e r e a l i
z a t i o n o f many o f t h e s e v a r i e d p i e c e s o f a p p a r a t u s t h a t h e
h a s d e v i s e d t o make h i s l i f e e a s i e r (an d t o c o m p lic a te i t )
h a v e come c e r t a i n c h a r a c t e r i s t i c s o f t h i s e q u ip m en t t h a t
man f i n d s n o t q u i t e t o h i s lik in g ® One o f t h e s e n o c u o u s
c h a r a c t e r i s t i c s i s t h e p r o p e r t y o f many o f t h e s e m a c h in e s
t o c r e a t e c e r t a i n d i s t u r b a n c e s t o m an8s s e n s e o f w e l l - b e i n g ,
t o h i s c o m f o r t, an d t o h i s e q u a n im ity *
I t i s an u n f o r t u n a t e c ir c u m s ta n c e t h a t many o f m an 3 s
c r e a t i o n s , w h ile s e r v i n g a d m ir a b ly i n th© s e r v i c e f o r w hich
t h e y w ere d e s i g n e d , a l s o h a v e t h e a b i l i t y t o p ro d u c e noise®
W h e th e r a p a r t i c u l a r sound i s c o n s id e r e d a s n o i s e o r n o t
2
d e p e n d s upon t h e p e rs o n o r p e rs o n s who h e a r t h a t sound*
A g iv e n c o m b in a tio n o f sound may c o n s t i t u t e m u sic f o r one
i n d i v i d u a l , w h e re a s t o a n o t h e r i t may be condemned a s
n o i s e . The c a t e g o r y t o w h ic h i t i s r e l e g a t e d d e p e n d s t o a
g r e a t e x t e n t on t h e h e a r e r ' s a t t i t u d e i n te r m s o f r e j e c t i o n
o r a c c e p t a n c e o f t h a t s o u n d . The r e j e c t i o n o r a c c e p t a n c e
o f t h e sound i s o f t t i m e s a f u n c t i o n o f t h e a c t i v i t y o f t h e
i n d i v i d u a l a t t h e moment o f r e c e p t i o n o f th© so u n d . I t
may a l s o depend on th e d i r e c t i o n fro m w h ic h t h e sound
comes o r upon t h e h e a r e r ' s a b i l i t y t o i d e n t i f y i t o r upon
h i s a t t i t u d e to w a rd t h e s o u r c e o f t h e a c o u s t i c e n e r g y .
I t i s a p p a r e n t t h a t many d i v e r s e f a c t o r s e n t e r i n t o
t h e p i c t u r e o t h e r t h a n t h e s t r i c t l y p h y s i c a l c h a r a c t e r i s
t i c s o f t h e a c o u s t i c e n e rg y w h ich t h e h e a r e r p e r c e i v e s a s
s o u n d . L o o king a t t h e s i t u a t i o n i n t h i s l i g h t p r o v i d e s a
s im p le b u t c l e a r - c u t d e f i n i t i o n o f n o i s e . N o ise I s
u n w an ted s o u n d . J u s t how much t h e sound i s u n w an ted w i l l
m e d ia te t h e e x t e n t t o w h ich one w i l l go i n h i s e f f o r t s t o
c o n t r o l t h e a c o u s t i c e n e r g y b e in g t r a n s m i t t e d o r how much
h e w i l l s t r i v e t o rem ove t h e s o u r c e , o r i f d r i v e n f u r t h e r ,
w h e th e r h e w i l l a t t e m p t t o rem ove h i m s e l f from t h e f i e l d
o f r e c e p t i o n o f t h e n o i s e i t s e l f .
C o m m u n ities h a v e a r i s e n ©n m asse t o e x e r t p o s i t i v e ,
c o n c e r te d a c t i o n t o rem ove t h e s o u r c e o f some sound w hich
t h e m a j o r i t y o f i t s members f e e l i s d e l e t e r i o u s t o h e a l t h ,
p o t e n t i a l l y d e t r i m e n t a l t o i t s econom y, o r s im p ly a n n o y
i n g . O f f i c e m an a g ers a s w e l l a s i n d u s t r i a l c o n c e rn s a r e
c o n c e rn e d w i t h t h e e f f e c t s o f n o i s e upon t h e o u tp u t o r t h e
e f f i c i e n c y o f t h e i r a d m i n i s t r a t i v e o r p r o d u c t i o n p e r s o n n e l .
The v a r i o u s b r a n c h e s o f t h e m i l i t a r y s e r v i c e a r e v i t a l l y
i n t e r e s t e d i n i t s e f f e c t s upon t h e s a f e t y and e f f i c i e n c y
o f i n d i v i d u a l s i n t h e p e rfo rm a n c e o f t h o s e d u t i e s w here
any a d v e r s e e f f e c t o f n o i s e m ig h t be c o s t l y i n te rm s o f
l i v e s a s w e l l a s i n te rm s o f tim e and m oney.
W ith t h e a d v e n t o f m ore and m ore com plex o p e r a t i n g
e q u ip m e n t a lo n g w ith m ore and m ore com plex o p e r a t i o n s
s y s te m s , t h e p e rfo rm a n c e o f e a c h i n d i v i d u a l o p e r a t o r i n
h i s a p p o i n t e d t a s k becom es o f p a ra m o u n t im p o r ta n c e t o t h e
s u c c e s s f u l a c c o m p lis h m e n t o f t h e g o a l t h a t h a s b e e n s e t
f o r t h e w h o le . The i n d i v i d u a l may be a f f e c t e d by n o i s e
i n many and d i v e r s e w a y s. He may be i n t e r f e r r e d w ith i n
h i s e f f o r t s t o com m unicate w ith o t h e r s 5 h e may s u f f e r from
a l o s s o r a d e c re m e n t i n h e a r i n g 5 he may be th w a r te d i n
h i s d e s i r e t o c o m p le te some m e n ta l a n d / o r m o to r t a s k .
D i f f e r e n t A p p ro a c h e s t o I n v e s t i g a t i o n o f t h e E f f e c t s o f
N o ise on t h e I n d i v i d u a l
The p ro b lem o f t h e e f f e c t s o f n o i s e on t h e i n d i v i d
u a l h a s b e e n a p p ro a c h e d fro m s e v e r a l p o i n t s o f v ie w .
M e d ic a l s c i e n c e h a s made a c o n ti n u i n g and e x h a u s t i v e s e a r c h
i n t o t h e t r a u m a t i z i n g e f f e c t o f a c o u s t i c e n e rg y upon t h e
a u d i t o r y m echanism . The p h y s i c a l s c i e n c e s h a v e e n d e a v
o re d t o q u a l i f y and t o q u a n t i f y a c o u s t i c e n e rg y and t o
i n v e s t i g a t e i t s t r a n s m i s s i o n i n an e f f o r t t o d i s c o v e r
im p ro v ed m ethods o f c o n t r o l o r e l i m i n a t i o n o f unw anted
a u d i t o r y s t i m u l i . The f i e l d o f p s y c h o lo g y h a s o c c u p ie d
i t s e l f w i t h , among o t h e r t h i n g s , t h e s e n s a t i o n and p e rc e p
t i o n o f a c o u s t i c e n e r g y .
In d e e d , i t i s t h e s e n s a t i o n and p e r c e p t i o n o f
a c o u s t i c e n e rg y t h a t c o n s t i t u t e s t h e h e a r t o f m a n 's
i n t e r e s t i n w hat w ould o th e r w is e be o n ly a p h y s i c a l d i s
t u r b a n c e o f some e l a s t i c medium. S e n s a t io n and p e r c e p
t i o n o f sound can be s a i d t o h av e p e r s o n a l i z e d a c o u s t i c
e n e rg y f o r man. H is c o n c e rn w ith th© p ro b lem s c r e a t e d by
t h e a c t i o n o f t h i s a c o u s t i c e n e rg y upon h i s a u d i t o r y
m echanism a n d , i n t u r n , upon h i s b e h a v io r h a s l e d t o th e
b i r t h o f a r e l a t i v e l y new f i e l d stem m ing fro m th e u n io n
o f p s y c h o lo g y and p h y s i c s . T h is new f i e l d , w hich t r e a t s
w i t h t h e s e v e ry p ro b le m s , h a s b e e n c a l l e d P s y c h o a c o u s t ic s .
R e s e a rc h c o n c e rn in g th© e f f e c t s o f n o i s e upon
b e h a v i o r h a s o c c u p ie d a p ro m in e n t p la c e among th© a c t i v i
t i e s o f t h i s g ro u p . Some o f t h e o ld r e a c t i o n - t i m e s t u d i e s
f u r n i s h e d an Im p e tu s t o l a t e r i n v e s t i g a t i o n s on d i s t r a c
tion® Many o f t h e s e i n v e s t i g a t i o n s had t o do w ith t h e
e f f e c t o f d i s t r a c t i o n s upon t h e " m e n ta l p r o c e s s e s " su ch
a s a t t e n t i o n and r e a s o n i n g . C o u n tle s s s t u d i e s h a v e b een
5
m ade o f t h e e f f e c t s o f n o i s e on c e r t a i n p h y s i o l o g i c a l p r o
c e s s e s su c h a s m e ta b o lis m , h e a r t r a t e , b r e a t h i n g r a t e and
v o lu m e , b lo o d p r e s s u r e , and t e n s i o n i n t h e m u s c le s .
A p p e a rin g l a t e r on i n t h e s c e n e w e re s t u d i e s w h ich had t o
d o w ith t h e e f f e c t s o f n o i s e upon g e n e r a l e f f i c i e n c y and
p e rfo rm a n c e a lo n g w ith t h o s e t r e a t i n g w ith t h e a n n o y a n c e
v a lu e o f d i f f e r e n t n o i s e s .
A lth o u g h b e h a v i o r i s s u b j e c t t o s t u d y by an y o f
t h e s e a p p r o a c h e s , t h a t a p p ro a c h w h ich s e e k s t o a s c e r t a i n
t h e e f f e c t s o f e x p o s u r e t o n o i s e upon t h e p e rfo rm a n c e o f
some a s s i g n e d t a s k i s o f t e n m ore d i r e c t and m ore e a s i l y
m e a su re d t h a n i s t h e c a s e w ith o t h e r a t t e m p t s a t q u a n
t i f i c a t i o n o f t h e s e e f f e c t s . M easu rem en ts y i e l d e d by
t h e s e d i f f e r e n t a p p r o a c h e s a r e o f t e n n e g a t i v e l y c o r r e l a t e d
o r show l i t t l e p o s i t i v e c o r r e l a t i o n . I n t r o s p e c t i v e
r e p o r t s o f a n n o y a n c e f r e q u e n t l y show l i t t l e r e l a t i o n s h i p
w i t h o t h e r m ore o b j e c t i v e m e a su re m e n ts o f t h e s e e f f e c t s
u p o n an i n d i v i d u a l ' s p e rfo rm a n c e i n some " p u r e l y m e n ta l"
o r i n some p sy c h o m o to r t a s k . In o t h e r c a s e s , some
s t u d i e s h a v e shown v e ry s i g n i f i c a n t d i f f e r e n c e s i n th e
I n d i v i d u a l ' s p e rfo rm a n c e o f a t a s k w h i l e , a t th e same
t i m e , p h y s i o l o g i c a l m e a s u re s h a v e y i e l d e d no d i f f e r e n c e s
t o sp e a k o f , and v i c e v e r s a . I t i s a t o n ce a p p a r e n t
t h a t b e h a v i o r u n d e r o r a f t e r e x p o s u re t o n o i s e h a s many
f a c e t s and t h a t , i n t h e i n t e r e s t s o f b r e v i t y and a d e q u a te
t r e a tm e n t o f th e s u b j e c t , some o f th e s e f a c e t s s h o u ld be
l e f t f o r d i s c u s s i o n e ls e w h e r e . T h e r e f o r e , u n l e s s m easu res
i n t h e p h y s i o l o g i c a l s e n s e a p p e a r t o be v e ry c l o s e l y
r e l a t e d t o a s p e c t s o f t h e problem u n d e r c o n s i d e r a t i o n ,
t h e s e m ea su re s w i l l n o t be t r e a t e d f u r t h e r *
STATEMENT OF THE PROBLEM
I t was th e p u rp o se o f t h i s i n v e s t i g a t i o n t o a s c e r
t a i n f o r a sam ple o f 108 m ale s t u d e n t s a t th e U n i v e r s i ty
o f S o u th e rn C a l i f o r n i a t h e r e l a t i v e i n f l u e n c e o f d i f f e r
e n t ty p e s o f sound ( n o is e ) and o f d i f f e r e n t p a t t e r n s o f
i n t e r r u p t i o n o f t h e sound ( n o is e ) upon th e p e rfo rm a n c e o f
a p sy cho m otor t a s k when t h e t a s k i t s e l f was v a r i e d w ith
r e s p e c t t o w h e th e r th e s u b j e c t o r t h e e x p e r im e n te r d e t e r
m ined t h e r a t e o f t h e r e q u i r e d r e a c t i o n s . In th e c o u rs e
o f i n q u i r i n g i n t o t h e i n f l u e n c e o f each o f th e s e m ain
v a r i a b l e s ta k e n a l o n e , i t was in te n d e d t o i n v e s t i g a t e th©
p o s s i b l e i n f l u e n c e o f j o i n t e f f e c t s o f ty p e o f sound
( n o is e ) and p a t t e r n o f i n t e r r u p t i o n a lo n g w ith re s p o n s e
p a c in g ( i * e . , r e q u i r e d r a t e o f re s p o n s e ) upon psychom otor
p erfo rm an ce*
The problem may be clarified in terms of the
following questionss
1. To w hat e x t e n t i s th e p e rfo rm a n c e o f an i n d i v i d
u a l on a p sychom oto r t a s k r e l a t e d t o h i s e x p o su re t o
n o i s e s d i f f e r i n g i n t h e i r q u a l i t a t i v e a s p e c t s ?
2* To w hat e x t e n t i s th e p e rfo rm a n c e o f an
i n d i v i d u a l on a psych om otor t a s k r e l a t e d t o h i s e x p o su re
t o n o i s e s d i f f e r i n g i n t h e i r te m p o ra l p a t t e r n s o f i n t e r
r u p tio n ?
3* To w hat e x t e n t i s th e p e rfo rm a n c e o f a n
i n d i v i d u a l on a p sychom otor t a s k r e l a t e d t o h i s e x p o su re
t o v a r io u s k in d s o f n o i s e u n d e r two d i f f e r e n t modes o f
t a s k p r e s e n t a t i o n r e l a t i v e t o th e r e q u i r e d r a t e o f re sp o n se
a s d e te rm in e d by th e s u b j e c t h im s e lf o r a s s e t by t h e
e x p e rim e n te r?
* ■ { ■ , To what e x te n t i s th e p e rfo rm a n c e o f a n
i n d i v i d u a l on a psychom o tor t a s k r e l a t e d t o h i s e x p o su re
t o n o i s e i n te rm s o f th e v a r io u s c o m b in a tio n s o f ty p e o f
n o i s e , p a t t e r n o f te m p o ra l o n s e t o f t h e n o i s e , and p a c in g
o f h i s r e s p o n s e s t o t h e ta s k ?
R e s e a rc h H y p o th eses
T hese q u e s t io n s may be f u r t h e r c l a r i f i e d and posed
somewhat more s p e c i f i c a l l y by s t a t i n g them I n o p e r a t i o n a l
te rm s a s f o llo w s :
1. An in c re m e n t o r a d ecrem en t i n th e p e rfo rm a n c e
o f a n i n d i v i d u a l on a psych om otor t a s k i n te rm s o f th e
num ber o f e r r o r s made and th e t o t a l tim e i n seco n d s
r e q u i r e d to co m p lete th e t a s k I s a f u n c t i o n o f h i s expo
s u r e t o t h r e e d i f f e r e n t ty p e s o f n o i s e , i , e « , a p u re s i n e
wave to n e o f 210 c p s . , a p u re s i n e wave to n e o f 3000 c p s . ,
and b ro a d -b a n d w h ite n o i s e .
2. An in c re m e n t o r a d e crem e n t i n th e p erfo rm an c e
o f an i n d i v i d u a l on a psychom otor t a s k i n te rm s o f th e
num ber o f e r r o r s made and th e t o t a l tim e i n se co n d s
r e q u i r e d t o c o m p lete t h e t a s k i s a f u n c t i o n of h i s ex p o -
s u r e t o n o i s e p r e s e n te d a c c o rd in g t o t h r e e d i f f e r e n t
p a t t e r n s o f i n t e r r u p t i o n , i . e . , c o n tin u o u s , r e g u l a r l y
i n t e r r u p t e d by s i l e n c e a t a r a t e o f f i v e i n t e r r u p t i o n s
p e r s e c o n d , and i r r e g u l a r l y i n t e r r u p t e d by s i l e n c e i n a
m ore o r l e s s random f a s h i o n .
3 * An in c re m e n t o r a decrem en t i n th e p e rfo rm an c e
o f an i n d i v i d u a l on a p sy ch o m o to r t a s k i n te rm s o f th e
num ber o f e r r o r s made and th e t o t a l tim e i n se co n d s
r e q u i r e d t o c o m p lete t h e t a s k i s a f u n c t i o n o f h i s expo
s u r e to n o i s e u n d e r two d i f f e r e n t modes o f r e s p o n s e p a c
i n g , i . e . , r a t e o f re s p o n s e d e te rm in e d by t h e s u b j e c t
( c a l l e d s e l f - p a c i n g ) and r a t e o f r e s p o n s e d e te rm in e d by
t h e e x p e r im e n te r ( c a l l e d e x t e r n a l - p a c i n g ) .
An in c re m e n t o r a d ecrem en t i n t h e p e rfo rm a n c e
o f an i n d i v i d u a l on a p sycho m otor t a s k i s a f u n c t i o n o f
h i s e x p o su re t o th e v a r io u s c o m b in a tio n s o f ty p e o f n o i s e
(210 e p s . , 3000 c p s , , and b ro ad -b a n d w h ite n o i s e ) w ith
d i f f e r e n t p a t t e r n s o f i n t e r r u p t i o n ( c o n tin u o u s , r e g u l a r l y
i n t e r r u p t e d by s i l e n c e a t f i v e i n t e r r u p t i o n s p e r s e c o n d ,
9
and i r r e g u l a r l y i n t e r r u p t e d by s i l e n c e i n a random
f a s h i o n ) and 'w ith th e mode o f t a s k p r e s e n t a t i o n ( s e l f
p a c in g o r e x t e r n a l - p a c i n g ) .
D e s c r i p t i o n o f t h e V a r i a b l e s i n t h e I n v e s t i g a t i o n
I t h a s b een h y p o th e s iz e d t h a t th e d e c re m e n t o r t h e
in c r e m e n t i n t h e p sy c h o m o to r p e rfo rm a n c e o f an i n d i v i d u a l
i s a f u n c t i o n o f h i s e x p o s u re t o so u n d s v a ry in g n o t o n ly
i n t h e i r q u a l i t a t i v e a s p e c t s , b u t a l s o i n t h e i r m anner o f
i n t e r r u p t i o n o r rhythm,, I t was f u r t h e r h y p o th e s iz e d t h a t
t h e p e rfo rm a n c e o f a n i n d i v i d u a l was a f u n c t i o n o f h i s
e x p o s u re t o t h e so u n d s u n d e r two d i f f e r e n t ty p e s o f t a s k s
i n te rm s o f s u b j e c t - d e t e r m i n e d r a t e o f r e s p o n s e o r e x p e r i
m e n te r - d e te r m in e d r a t e o f r e s p o n s e . I t w ould be a d v an
ta g e o u s a t t h i s p o i n t t o d e l i n e a t e m ore c l o s e l y t h e
v a r i a b l e s in v o lv e d i n t e r n s o f t h e i r b e in g c h o sen a s
in d e p e n d e n t v a r i a b l e s , d e p e n d e n t v a r i a b l e s , and c o n t r o l
v a r i a b l e s .
In d e p e n d e n t V a r ia b l e s
v
1 . The so u n d s p r e s e n t e d v a r ie d i n t h a t p h y s i c a l
d im e n s io n known a s f r e q u e n c y . A p u re s i n e wave to n e o f
210 c y c le s p e r se co n d ( c p s . ) and a p u re s i n e wave to n e o f
3000 c p s 0 a lo n g w ith b ro a d -b a n d w h ite n o i s e w ere p r e s e n t e d .
2 . The p a t t e r n o f i n t e r r u p t i o n o f e a c h ty p e o f
sound was v a r i e d so t h a t t h e s u b j e c t r e c e i v e d i t i n
c o n tin u o u s f o r m , a t a r e g u l a r l y i n t e r r u p t e d r a t e , and a t
a n i r r e g u l a r l y i n t e r r u p t e d r a t e .
3 . The t a s k p r e s e n t e d t o t h e s u b j e c t was v a r i e d
s u c h t h a t u n d e r one mode o f p r e s e n t a t i o n t h e i n d i v i d u a l
p ro c e e d e d t o make r e s p o n s e s a t a r a t e d e te r m in e d s o l e l y
by h i s own c o r r e c t r e s p o n s e s w h ile u n d e r t h e o t h e r co n
f i g u r a t i o n h e was d i r e c t e d t o re s p o n d a t a r a t e d e t e r
m in ed by t h e e x p e r i m e n t e r .
D e p e n d e n t V a r ia b l e
P e rfo rm a n c e on t h e t a s k a s s i g n e d c o n s t i t u t e d t h e
d e p e n d e n t v a r i a b l e . The p sy c h o m o to r t a s k a s s i g n e d
r e q u i r e d t h e s u b j e c t t o i n s e r t a s t y l u s i n t o one o f a
num ber o f h o l e s a s t h e y moved p a s t a n a rr o w s l o t i n t h e
c a b i n e t w h ic h c o n ta in e d t h e a p p a r a t u s . The h o l e s , e a c h
o f w h ich c o u ld be i d e n t i f i e d by a s u r r o u n d in g sy m b o l,
w e re l o c a t e d on t h e s u r f a c e o f a drum w h ich r e v o lv e d con
t i n u o u s l y d u r i n g t h e p r o c e d u r e . The d e p e n d e n t v a r i a b l e
was q u a n t i f i e d b o th by r e c o r d i n g t h e num ber o f e r r o r s
made and t h e t o t a l tim e i n s e c o n d s r e q u i r e d t o c o m p le te
t h e a s s i g n e d t a s k .
C o n t r o l V a r i a b l e s
The i n t e n s i t y o f t h e sound p r e s e n t e d was h e l d con
s t a n t a t 95 d b . by a d ju s tm e n t o f t h e g a i n c o n t r o l o f t h e
p la y b a c k c i r c u i t o f t h e r e c o r d i n g m a c h in e .
11
The r e v o l v i n g r a t e o f t h e drum was h e l d c o n s t a n t
th r o u g h o u t t h e m ain experim ent® The r a t e h ad b e en a s c e r -
t a i n e d p r e v i o u s l y d u r in g a b r i e f p r e - t e s t s p e c i f i c a l l y
c a r r i e d o u t f o r t h e p u rp o s e o f d e te r m in in g t h e o p tim a l
sp e e d a t w h ich t o t u r n t h e drum® A t t h e r a t e w hich
f i n a l l y was c h o s e n , t h e tw e n ty -tw o s u b j e c t s , a l l o f whom
w ere o b t a i n e d from th e same s o u r c e a s t h o s e u se d i n t h e
m a in e x p e r im e n t, y i e l d e d a more o r l e s s r e c t a n g u l a r d i s
t r i b u t i o n i n te rm s o f t o t a l tim e t o c o m p lete th e t a s k
u n d e r c o n d i t i o n o f q u i e t .
The d i s t r a c t i n g e f f e c t o f e x tr a n e o u s n o i s e was
h e l d t o a minimum by c o n d u c tin g t h e e x p e rim e n t i n a s m a ll
room w h ic h , a lth o u g h n o t s o u n d - p r o o f e d , was f a i r l y w e ll
i s o l a t e d fro m s u r r o u n d in g q u a rte rs ® In a d d i t i o n , a l a r g e
e l e c t r i c f a n was o p e r a t e d c o n ti n u o u s l y d u r in g th e e x p e r i
m e n ta l p r o c e d u r e . T h is f a n , i n a d d i t i o n t o s e r v in g t o
make th e s u b j e c t m ore c o m f o r ta b le i n th e c lo s e q u a r t e r s ,
a l s o a c t e d t o m ask t o a c e r t a i n e x t e n t , t h e o u t s i d e n o i s e s
w h ich may o c c a s i o n a l l y h a v e m anaged t o f i l t e r th ro u g h th e
w a l l s o f t h e e x p e r i m e n t a l room.
An a tt e m p t was made t o c o n t r o l t h e e f f e c t s o f
s u g g e s t i o n upon th e p e rfo rm a n c e o f th e s u b j e c t by r e a d in g
a s e t o f s t a n d a r d i z e d i n s t r u c t i o n s b e f o r e t h e b e g in n in g
o f t h e e x p e r im e n ta l procedure® A copy o f th e i n s t r u c
t i o n s i s i n c l u d e d i n t h e A p p en d ix .
12
I t h a s b e e n p o in te d o u t t h a t t h e d e p e n d e n t v a r i
a b l e was q u a n t i f i e d i n two w a y s. The r e c o r d i n g b o th o f
t h e num ber o f e r r o r s made and o f t h e t o t a l tim e r e q u i r e d
t o c o m p le te t h e t a s k makes i t p o s s i b l e t o exam ine th e
d a t a i n tw o s e p a r a t e a n a l y s e s . I t m u st b e s p e c i f i c a l l y
u n d e r s to o d t h a t t h e h y p o th e s e s a s s t a t e d make n o r e f e r
e n ce t o a n y c o m p a ris o n b e tw e e n p e rfo rm a n c e c a r r i e d o u t i n
t h e p r e s e n c e o f n o i s e and t h a t a c c o m p lis h e d u n d e r c o n d i
t i o n s o f q u i e t . The i n t e n t o f t h i s s tu d y was t o exam ine
p e rfo rm a n c e o n ly a s i t d i f f e r e d w ith r e s p e c t t o t h e
s p e c i f i c c o n d i t i o n s o f n o i s e . Thus i t was p o s s i b l e t o
c o n d u c t t h e e x p e r im e n t w ith o u t r e s o r t i n g t o t h e u s e o f a
c o n t r o l g r o u p .
S i n c e no h y p o th e s e s w ere made i n te r m s o f th e
d i r e c t i o n a l e f f e c t o f e x p o s u re t o n o i s e i n te rm s o f i n c r e
m ent o r d e c re m e n t i n p e rfo rm a n c e , i t i s p o s s i b l e t o t r a n s
l a t e t h e o p e r a t i o n a l h y p o th e s e s i n t o one s e t o f s t a t i s t i
c a l h y p o th e s e s f o r b o th e r r o r s and t o t a l tim e a s f o l l o w s :
1 . T h ere i s no d i f f e r e n c e b e tw e e n th e mean num ber
o f e r r o r s made o r b e tw een t h e mean num ber o f se c o n d s
r e q u i r e d t o c o m p le te t h e t a s k u n d e r s t i m u l a t i o n by n o i s e s
v a ry in g i n t h e i r q u a l i t a t i v e a s p e c t s , i . e . , i n f r e q u e n c y .
2 . T h e re i s no d i f f e r e n c e b e tw e e n th e mean num ber
o f e r r o r s made o r b e tw ee n t h e mean n u m ber o f se c o n d s
13
r e q u i r e d t o c o m p lete th e t a s k u n d e r s t i m u l a t i o n by n o i s e s
v a r y in g i n t h e i r p a t t e r n s o f te m p o ra l o n s e t (mode o f
i n t e r r u p t i o n ) .
3» T h ere i s no d i f f e r e n c e b etw een th e mean num ber
o f e r r o r s made o r b e tw e e n th e m ean num ber o f se c o n d s
r e q u i r e d t o c o m p le te th e t a s k u n d e r s t i m u l a t i o n by n o i s e
u n d e r two d i f f e r e n t modes o f t a s k p r e s e n t a t i o n ( s e l f -
p a c in g and e x t e r n a l - p a c i n g ) .
T h ere i s no d i f f e r e n c e b etw een th e m ean num ber
o f e r r o r s made o r b e tw ee n th e mean num ber o f se c o n d s
r e q u i r e d t o c o m p le te th e t a s k u n d e r s t i m u l a t i o n by t h e
v a r i o u s c o m b in a tio n s o f ty p e o f n o i s e 9 p a t t e r n o f i n t e r
r u p t i o n , and mode o f t a s k p r e s e n t a ti o n ,,
importance; of th e problem
I n a d e q u a c ie s N oted i n a Review o f t h e L i t e r a t u r e
In C h a p te r I I t h e r e w i l l be a re v ie w o f p r e v io u s
s t u d i e s t h a t w ere c o n ce rn e d w ith th e pro b lem o f t h e
e f f e c t s o f n o i s e upon human b e h a v io r* A s u rv e y o f e a r l i e r
I n v e s t i g a t i o n s r e v e a l e d t h a t many o f them s u f f e r e d d e f i
c i e n c i e s i n d e s ig n o r p r o c e d u re o f one s o r t o r a n o th e r*
I t v/as n o te d t h a t th e r e s u l t s o b ta in e d and th e i n t e r p r e t a
t i o n p la c e d upon them o f t e n a p p e a re d e q u i v o c a l , i f n o t
d i a m e t r i c a l l y o pposed i n t h e i r i m p l i c a t i o n s * I t was f e l t
t h a t p o s s i b l y some o f t h e c o n fu s io n c o u ld h a v e b e e n due
14-
t o th e f a c t t h a t a g iv e n s tu d y had t o do "with one p a r t i c u
l a r f a c e t o f b e h a v io r a s a f u n c t i o n o f e x p o su re t o n o i s e
w h ile a n o th e r i n v e s t i g a t i o n was co n cern ed w ith a s t i l l
d i f f e r e n t one a l t o g e t h e r . I t was an e s p e c i a l l y n o te w o rth y
c h a r a c t e r i s t i c o f many o f t h o s e s t u d i e s t h a t th e y w ere
c a r r i e d o u t w ith v a r i a b l e s and u n d e r c o n d itio n s so
i n a d e q u a t e l y d e fin e d t h a t w e ll- b a s e d g e n e r a l i z a t i o n s w ere
a lm o s t i m p o s s ib le .
A s e a r c h o f t h e l i t e r a t u r e was e x c e e d in g ly u n f r u i t
f u l i n r e v e a l i n g th e e x i s t e n c e o f s t u d i e s t h a t w ere con
c e rn e d w ith t h e i n v e s t i g a t i o n o f t h e e f f e c t s o f n o i s e on
p e rfo rm a n c e i n term s o f th e s e v e r a l e x p e r im e n ta l v a r i a b l e s
ta k e n a lo n e and i n c o m b in a tio n w ith e a c h o t h e r . I t was
f e l t t h a t an a d e q u a te i n v e s t i g a t i o n o f t h e e f f e c t s o f
n o i s e on psychom o tor p e rfo rm a n c e r e q u i r e d an e x p e r im e n ta l
d e s ig n t h a t would p e rm it a th o ro u g h i n v e s t i g a t i o n o f
s e v e r a l o f th e more im p o r ta n t p a ra m e te rs o f th e n o is e
dom ain i n t e r n s o f t h e i r s im u lta n e o u s i n d i v i d u a l and com
b in e d e f f e c t s upon p sy ch o m o to r p e rfo rm a n c e .
I t was n o te d t h a t i n many o f th e i n v e s t i g a t i o n s
c i t e d i n th e l i t e r a t u r e , th e ty p e s o f n o i s e s used a s d i s
t r a c t o r s w ere q u i t e com plex ( e . g . , f a c t o r y n o i s e s o r
b e l l s ) • I t seems r e a s o n a b le t o assum e t h a t i f t h e a u d i
t o r y s t i m u l i a r e k e p t sim p le i n n a t u r e th e y can be more
e a s i l y m e a su re d . To a c e r t a i n d e g re e t h e e f f e c t s o f su ch
15
s im p le s t i m u l i have a p r e d i c t i v e v a lu e f o r th e e f f e c t s o f
m ore c o m p lic a te d a u d i t o r y s i t u a t i o n s .
I t was a l s o f e l t t h a t , i n an a r e a w hich i s a s v u l
n e r a b l e t o th e e f f e c t s o f i n d i v i d u a l d i f f e r e n c e s among
s u b j e c t s a s th e a r e a a t h a n d , s p e c i a l c o n s i d e r a t i o n s h o u ld
be g iv e n t o an e x p e r im e n ta l d e s ig n w hich would re d u c e t h i s
i n f l u e n c e t o a minimum o r p e rm it a n e s t i m a t e o f th e e x te n t
o f su ch a s o u r c e o f v a r i a b i l i t y upon th e r e s u l t s o b ta in e d .
Som e , P r a c t i c a l I m p li c a t io n s
iiiiium h i n i r ' i m i iir-*-1 — f -ia i i ^ ^ T . r ~ T T r » — t -mnrrm ~ra ~ —n m ~i»rmii —
An u n d e rs ta n d in g o f t h e e f f e c t s o f n o i s e upon
p sy ch o m o to r p e rfo rm a n c e i s n o t o n ly o f t h e o r e t i c a l v a lu e ,
b u t a l s o o f p r a c t i c a l im p o r ta n c e . P e o p le a r e o f t e n fa c e d
w ith t h e n e c e s s i t y o f c a r r y i n g o u t a t a s k r e q u i r i n g s k i l l
and p e r s o n a l s t a b i l i t y u n d e r c o n d it i o n s w hich a r e n o t
c o n d u c iv e t o th e e f f e c t i v e p e rfo rm an c e o f t h e t a s k . In
t h e I n t r o d u c t i o n , r e f e r e n c e was made t o th e i n t e r e s t shown
by v a r io u s o r g a n i z a t i o n s r e l a t i v e t o t h e e f f e c t i v e p e r
fo rm an c e o f an i n d i v i d u a l i n c a r r y in g o u t h i s a s s ig n e d
d u t i e s .
Knowledge c o n c e rn in g t h e many v a r i a b l e s w hich a c t
t o i n f l u e n c e an i n d i v i d u a l ’ s p e rfo rm a n c e can be o f i n e s t i
m able v a lu e i n e f f e c t i n g ch an g es i n th e a u d i t o r y e n v ir o n
m e n t, i n th e t a s k i t s e l f , o r i n bofch.^ In e v a l u a t i n g
t o o l s , e n v iro n m e n ta l c o n d i t i o n s , and m ethods o f w ork, t h e
human e n g in e e r can p u t to p r a c t i c a l u se su ch p e r t i n e n t
16
in fo rm a tio n , a s i s a v a i l a b l e . The d e s ig n o f equipm ent su c h
t h a t i t s o p e r a t i o n i s w e ll w i t h i n t h e c a p a b i l i t i e s o f t h e
a v e r a g e o p e r a t o r demands t h a t th e d e s i g n e r be s u p p lie d
w ith m a t e r i a l d e l i n e a t i n g t h e s e n s o ry and p e r c e p t u a l a b i l i
t i e s o f man and th e e x te n t t o w hich th e s e a b i l i t i e s a re
s u s c e p t i b l e t o d i s r u p t i o n by th e v a r io u s f a c t o r s o p e r a t in g
i n th e w orking e n v iro n m e n t.
CHAPTER II
SELECTIVE REVIEW OF STUDIES PERTAINING TO THE
EFFECTS OF NOISE ON HUMAN PERFORMANCE
In t h e c u r r e n t c h a p t e r a t t e n t i o n w i l l b e g iv e n t o
p a s t i n v e s t i g a t i o n s w h ich w ere c o n c e rn e d w i t h prob lem s
s i m i l a r t o t h e one a t h a n d . An e f f o r t w i l l b e made t o
p o i n t o u t t h o s e d e f i c i e n c i e s t h a t a r e a p p a r e n t . At t h e
same tim e , and where a p p r o p r i a t e , c e r t a i n o f t h e v a r i a b l e s
( c o n s i d e r e d o r n o t c o n s id e r e d i n t h e s t u d i e s c i t e d ) w i l l
b e d is c u s s e d r e l a t i v e t o t h e i r p o s s i b l e e f f e c t upon
e x p e r im e n ta l r e s u l t s .
I n t r o d u c t i o n
One c a n f e e l f a i r l y s e c u r e i n m aking t h e s ta te m e n t
t h a t man h a s b een c o n c e rn e d d u r i n g m ost o f h i s h i s t o r y
w i t h th e p ro b lem o f n o i s e . One c an f e e l e q u a l l y c e r t a i n
t h a t th e s e p ro b lem s h a v e b e e n m u l t i p l i e d a num ber o f
tim e s s i n c e men began t o g a t h e r i n communal g ro u p s f o r
s u c h d i v e r s e p u rp o s e s a s p r o t e c t i o n from w ild a n im a ls ,
en han cem en t o f t h e i r s o c i a l w e l f a r e , o r s im p ly th e
im provem ent o f t h e i r econom ic p o s i t i o n . T h ro u g h o u t t h e
c o u rs e o f h i s d a t e l e s s e n c o u n te r s w ith t h e s e p ro b lem s
18
man h a s p r o b a b ly s o u g h t w ays and m eans o f a p p r a i s i n g e x i s t
i n g c o n d i t i o n s and t a k i n g a p p r o p r i a t e a c t i o n t o a l l e v i a t e
a n y d i s t u r b i n g i n f l u e n c e s a f f e c t i n g h i s way o f l i f e . By
h i s v e ry i n g e n u i t y and i n v e n t i v e n e s s man h a s s u rro u n d e d
h i m s e l f w ith e v e r - i n c r e a s i n g num bers o f v a r i o u s k in d s o f
i n d u s t r i a l e q u ip m e n t a s w e l l a s o t h e r m a c h in e s and g a d g e ts
w h ic h s e r v e , m ore o r l e s s , o n ly t o make l i f e more e n jo y
a b l e . B ut i n d o in g so h e h a s i n a d v e r t e n t l y s u r ro u n d e d
h i m s e l f w i t h o t h e r p ro b le m s t h a t s e r v e t o d i s r u p t th e
r e a l i z a t i o n o f t h e v e ry e n d s t h a t h e s e e k s .
Man h a s u n d o u b te d ly made many im p ro v e m e n ts i n h i s
m eth o d s o f c o n d u c tin g r e s e a r c h c o n c e r n in g t h e e f f e c t s o f
n o i s e up on h i s s u b j e c t i v e f e e l i n g s o f w e l l b e in g and h i s
m ore r e a d i l y o b s e r v a b l e e f f o r t s . M any o f t h e e a r l y
s t u d i e s w ere c a r r i e d o u t u n d e r t h e a u s p i c e s o f i n d u s t r i a l
co m p an ies w h ich w ere p r i n c i p a l l y i n t e r e s t e d i n t h e w ork
o u t p u t o f t h e i r p e r s o n n e l a s a f u n c t i o n o f e x p o s u re t o
d i s t u r b i n g o r d i s t r a c t i n g s o u n d s . A g r e a t num ber o f t h e s e
i n v e s t i g a t i o n s w ere c o n d u c te d " i n t h e f i e l d , " i . e . , u n d e r
t h e a c t u a l c o n d i t i o n s fo u n d i n th e i n d u s t r i a l s i t u a t i o n .
S t u d i e s c a r r i e d o u t u n d e r t h e s e c o n d i t i o n s a r e l i k e l y t o
be p la g u e d w i t h num erous f a c t o r s w h ich a r e beyond e x p e r i
m e n ta l c o n t r o l . C o n d i ti o n s s u c h a s b reak d o w n o f p ro d u c
t i o n e q u ip m e n t, t u r n o v e r o f p e r s o n n e l , p o s s i b l e e f f e c t s
o f e x p e r i m e n t a t i o n upon em ployee m o t i v a t i o n , ch an g e s i n
q u a l i t y o f m a t e r i a l s u s e d , and a d m i n i s t r a t i v e a c t i o n on
t h e p a r t o f m anagem ent may o p e r a t e i n su c h a f a s h i o n a s t o
o b s c u r e an y m e a n in g fu l r e s u l t s w hich may h a v e come a b o u t
a s a c o n se q u e n c e o f ch an g es in tr o d u c e d i n t h e w o rk in g
e n v iro n m e n t* I t i s no w o n d er, t h e n , t h a t many o f t h e s e
s t u d i e s i n b e in g open t o m e th o d o lo g ic a l c r i t i c i s m a r e s u s
p e c t i n t h e i r c o n c lu s io n s *
Some Early Field Studies
One o f t h e f i r s t s t u d i e s w hich s e r v e d t o aw aken t h e
i n t e r e s t o f t h e g e n e r a l p u b l i c w ith t h e r e a l i z a t i o n t h a t
t h e o u tp u t o f th e w o rk e r m ig h t be a f f e c t e d by n o i s e was
t h e New Y ork N o ise S u rv ey o f 1930* R e p o r tin g on th e
r e s u l t s o f t h i s s u r v e y , D e n n is (15) p o i n te d o u t t h a t a
r e d u c t i o n o f n o i s e l e v e l from to 35 d b . was f o llo w e d
by a 12 p e r c e n t i n c r e a s e i n o u tp u t o f o f f i c e w o rk e rs
w h ile a s i m i l a r change i n n o i s e l e v e l i n a t e le p h o n e room
was a s s o c i a t e d w ith a h2 p e r c e n t r e d u c t i o n I n e r r o r s .
U n f o r t u n a t e l y , t h e “n o i s e * 1 was n o t a d e q u a te ly d e fin e d ?
n o r w ere o t h e r p e r t i n e n t d a t a a v a i l a b l e f o r c o n s i d e r a t i o n .
T h is p a r t i c u l a r s u rv e y c a n n o t be c o n s id e r e d a n y th in g m ore
t h a n i t s t i t l e s u g g e s t s — a s u r v e y l a r g e l y b a se d on phenom
e n a l o b s e r v a t i o n . N e v e r t h e l e s s , i t d i d a c c o m p lis h a v e r y
n e c e s s a r y and d e s i r a b l e e f f e c t o f a l e r t i n g t h e p u b l i c t o
t h e s i t u a t i o n a t hand a n d , a l s o , a c t i n g a s a n im p e tu s t o
f u r t h e r s tu d y o f t h e e f f e c t s o f n o i s e .
20
I l l u s t r a t i v e o f e a r l y s t u d i e s t h a t la c k e d much i n
th e way of c o n t r o l o f e x tr a n e o u s s o u rc e s o f v a r i a t i o n
w ere th o s e by Weston and Adams (*f6 , *+7) who i n v e s t i g a t e d
t h e e f f i c i e n c y o f v/eavers i n B r i t a i n o v e r a p e rio d of
t w e n t y - s i x w eeks« In a l l o f th e s e s t u d i e s , o f which t h e r e
w ere t h r e e , th e n o i s e produced was t h a t o f th e looms them
s e l v e s and was on t h e o r d e r o f 96 db. I n one e x p erim e n t
t h e s u b j e c t s c o n s i s t e d of t e n w eavers who wore e a r d e fe n d
e r s on a l t e r n a t e weeks f o r a p e rio d o f s i x m onths. The
e a r p l u g s a t t e n u a t e d t h e n o i s e from a l e v e l of 96 db , t o
81 db. In t h e f i r s t o f t h e s e e x p e rim e n ts (^7) o n ly one
group was u s e d . In t h i s i n v e s t i g a t i o n a l l o f t h e w orkers
u s in g e a r p lu g s showed a g a in i n o u tp u t even thoug h th e
g a in was o n ly 1 p e r c e n t 5 how ever, s i n c e th e p o s s i b l e g a in
was somewhat l i m i t e d by t h e speed of t h e loom s, th e
i n c r e a s e o f t h e w e a v e rs' speed a t making a d ju s tm e n ts which
w ere non-m achine c o n t r o l l e d seemed to o f f e r a more r e v e a l
i n g s t a t i s t i c . T h is s o r t o f c r i t e r i o n , w hich v/as con
t r o l l e d e n t i r e l y by th e o p e r a t o r , showed a g a in i n speed
am ounting t o 12 p e r c e n t . I n th e second and t h i r d of
t h e s e e x p e rim e n ts (**6 ) , two groups were em ployed, one o f
w hich used e a r d e fe n d e r s w h ile th e o t h e r used no n e.
T hese s t u d i e s y i e l d e d a 3 1 / 2 p e r c e n t Im provem ent i n
o u tp u t and a 13 1 /2 p e r c e n t g a in i n speed f o r o p e r a t o r s
w e arin g e a r d e f e n d e r s . The s i g n i f i c a n c e o f t h e s e s t u d i e s
21
r e s t s I n t h e i r a p p a r e n t d e m o n s tr a tio n o f th e s u b s t a n t i a l
i n c r e a s e i n w orking p e rfo rm an c e f o l lo w in g a r e d u c t i o n i n
n o i s e l e v e l e v en when t h e w o rk ers had lo n g b een accu sto m ed
t o w orking i n t h e n o is y environm ent* Even tho ugh m odern
s t a t i s t i c a l m ethods o f a s s e s s i n g th e s i g n i f i c a n c e o f a
d i f f e r e n c e betw een t r e a t m e n t s were n o t u s e d s t h e d a t a f o r
eac h o f th e w o rk ers in v o lv e d a p p e a re d t o s u p p o r t t h e con
c l u s i o n s re a c h e d r e g a r d i n g th e d e l e t e r i o u s e f f e c t o f t h e
n o i s y c o n d i t i o n s .
T hat t h e r e s u l t s o f t h e s e s t u d i e s can n o t w h o lly be
a c c e p t e d a t t h e i r f a c e v a lu e i s e v id e n t upon a more
s e a r c h i n g e x a m in a tio n o f th e m ethodology u s e d . In t h e
i n s t a n c e o f t h e second and t h i r d e x p e r i m e n t s , t h e r e s e a r c h
e r s n e g l e c t e d t o d e m o n s tr a te th e e q u a l i t y o f th e two
g ro u p s a t t h e v e ry b e g in n in g o f t h e e x p e r i m e n t s . The m ost
s e r i o u s c h a l le n g e xdiich can be posed a g a i n s t th e e v id e n c e
p r e s e n t e d I s t h a t o f p o i n t i n g t o th e f a i l u r e o f t h e
r e s e a r c h e r s t o ta k e c o g n iz a n c e of t h e i n f l u e n c e o f f a c t o r s
o t h e r th a n t h o s e o p e r a t i n g , more o r l e s s , on th e s u r f a c e .
In a d d i t i o n t o th e p o s s i b l e d i f f e r e n c e betw een th e tiro
g ro u p s i n te r m s o f i n i t i a l a b i l i t y , t h e r e co uld h av e
emerged a d i f f e r e n c e i n m o t i v a t i o n a s a r e s u l t of t h e i r
d i f f e r e n t i a l t r e a t m e n t .
I t h a s been d e m o n s tr a te d i n s t u d i e s such a s th o s e
made a t W estern E l e c t r i c (37) t h a t w henever some w o rk e rs
22
a r e s e p a r a t e d from o t h e r s and a r e s u b s e q u e n t ly a d m in is
t e r e d d i f f e r e n t t r e a t m e n t s , t h e p e o p le s e l e c t e d f o r th e
" t r e a t m e n t * 1 M ill assum e an a p p a r e n t l y d i f f e r e n t k in d and
l e v e l o f m o t i v a t i o n . The f a c t t h a t t h e y hav e been "chosen"
may a c t t o m o ti v a te t h o s e p a r t i c u l a r i n d i v i d u a l s t o work
h a r d e r o r o t h e r w is e e x h i b i t a b e h a v i o r f o r e i g n t o t h a t
e l i c i t e d by t h e change i n e n v iro n m e n ta l c o n d i t i o n s a l o n e .
The V /estern E l e c t r i c s tu d y d e m o n s tr a te d t h a t t h e o u tp u t o f
w o rk e rs can be m a t e r i a l l y i n c r e a s e d s im p ly a s a f u n c t i o n
o f t h e i r b e in g a c c o rd e d " s p e c i a l " t r e a t m e n t .
Such a r e s u l t can be a t t r i b u t e d t o a t l e a s t two
d i f f e r e n t modes o f o p e r a t i o n . The i n f l u e n c e o f s u g g e s t i o n
a s t o what i s e x p e c te d t o a c c r u e from t h e change i n con
d i t i o n s can s e r v e t o e s t a b l i s h an a t t i t u d e r e g a r d i n g t h e
outcome o f t h e a c t i o n t a k e n . M oreover, t h e v e ry f a c t t h a t
h i s em ployer i s show ing an i n t e r e s t i n h i s w e l f a r e may
s p u r t h e w orker t o i n c r e a s e h i s p r o d u c t i o n .
In t h e p r e v i o u s l y m e n tio n e d s t u d i e s o f W eston and
Adams (^ 6 , H-?) t h i s m o t i v a t i o n a l f a c t o r cou ld h av e
o p e r a t e d i n a c y c l i c a l m anner. In t h e t h i r d e x p e rim e n t
t h e p e rfo rm an ce l e v e l s o f t h e two g ro u p s d iv e r g e d more a t
t h e b e g in n in g o f t h e e x p e rim e n t t h a n t h e y d id a t th e end
o f t h e y e a r . T his c o n v e rg e n c e o f o u t p u t l e v e l s f o r th e
two groups c o u ld h av e been d u e , i n p a r t , t o t h e waning o f
t h e i n c r e a s e i n m o t i v a t i o n f o r th o s e s u b j e c t s w e arin g e a r
23
p l u g s or i t could h a v e come a b o u t b e c a u se of a d a p t a t i o n
t o th e n o i s e on th e p a r t o f t h o s e s u b j e c t s n o t w e arin g
t h e e a r p l u g s . The s im p le e x p e d ie n t o f s w it c h in g th e
t r e a t m e n t s f o r b o th g ro ups c o u ld have been o f c o n s i d e r a b le
a i d i n b a la n c i n g t h e s e e f f e c t s .
A p r a c t i c e o f t e n r e s o r t e d t o i n m e d ic a l r e s e a r c h
c o u ld a l s o h av e been u t i l i s e d i n an e f f o r t t o e l i m i n a t e
t h o s e e f f e c t s a s s o c i a t e d w i t h a change i n a t t i t u d e t h a t
w e re in d u ce d by b e in g a c c o rd e d s p e c i a l t r e a t m e n t . M e d ica l
r e s e a r c h e r s f r e q u e n t l y a d m i n i s t e r " p la c e b o s " o r dummy
t r e a t m e n t s i n an a tt e m p t t o e l i m i n a t e e f f e c t s due t o sug~
g e s t i o n . In th e c o n te x t of t h e Weston and Adams s t u d i e s ,
i n e f f i c i e n t o r dummy e a r p l u g s co uld hav e been is s u e d t o
o ne group f o r th e s p e c i f i c p u rp o se o f making i t s members
f e e l t h a t t h e y to o w ere b e in g a d m i n i s t e r e d " s p e c i a l
t r e a t m e n t . "
Some O ther N o tew orthy F i e l d S t u d i e s
In te rm s of t h e r e a l i s a t i o n o f c o n t r o l o v e r th e
v a r i a b l e s I n v o l v e d , one of t h e somewhat more a d e q u a te o f
t h e s o - c a l l e d " f i e l d " s t u d i e s was one c o n d u cted by th e
A e t n a L if e I n s u r a n c e Company 3 0 , 33) * Sound a b s o r p
t i o n m a t e r i a l was i n s t a l l e d on th e w a l l s and c e l l i n g o f
t h e g e n e r a l o f f i c e s u c h t h a t a r e d u c t i o n i n t h e n o i s e
l e v e l from a b o u t H-l t o 35 " s e n s a t i o n u n i t s " o c c u r r e d .
O b j e c t i v e i n f o r m a t i o n r e f l e c t i n g t h e e f f i c i e n c y o f
2h
employees f o r th e y e a r p r i o r t o th e i n s t a l l a t i o n was
a v a i l a b l e i n th e form of bonus f i g u r e s . In t h i s i n v e s t i
g a t i o n , e f f i c i e n c y was d e fin e d i n term s of th e tim e
a llo w ed f o r a g iven amount of work as d e term in ed by tim e
s t u d i e s , d iv id e d by t h e amount o f tim e a c t u a l l y r e q u ir e d
t o com plete t h a t amount o f work. The a v erag e d i f f e r e n c e
i n bonus f i g u r e s r e l a t i v e t o th e e f f i c i e n c y o f f i f t e e n
c l e r k s , c a l c u l a t e d on th e b a s i s o f bonus f i g u r e s ta k e n
f o r th e y e a r p r i o r t o and th© su c ce ed in g y e a r ta k e n a t
sem i-m onthly i n t e r v a l s , showed a 9©2 p e r cent r i s e i n
e f f i c i e n c y f o llo w in g th e I n s t a l l a t i o n of th e a c o u s t i c a l
m a t e r i a l . S i m i la r r e s u l t s were found i n th e case of
ty p in g e r r o r s (29 p e r c e n t re d u c tio n ) and c a l c u l a t i n g -
m achine e r r o r s (52 p e r c e n t r e d u c t i o n ) . Bonus f i g u r e s
ta k e n f o r t h e y e a r f o llo w in g i n s t a l l a t i o n alw ays rem ained
above th o s e ta k e n d u rin g th e y e a r p r i o r t o I n s t a l l a t i o n .
D uring th e tw o -y ea r p e rio d of th e t e s t no o t h e r changes
were made i n th e working en viron m ent. A f o llo w -u p t o
th e o r i g i n a l change was c a r r i e d out by c o v e rin g th e w a lls
w ith hard gypsum board which in c r e a s e d th e n o i s e l e v e l t o
t h e o r i g i n a l v a lu e , and r e s t o r e d th e r e v e r b e r a t i n g q u a l
i t y of th e sounds® E f f i c ie n c y prom ptly dropped but
w i t h in two months was back up t o a l e v e l i n te r m e d i a t e
betw een th e " n o is y ” and " q u i e t " c o n d it i o n s . U n f o r tu n a te ly
th© a v a i l a b l e d a ta y i e l d e d by t h i s stu d y were n o t
25
am enable to s t a t i s t i c a l t e s t s of th e d i f f e r e n c e s fo u n d , b u t
B e r r ie n (**), who h as made an e x te n s iv e review o f t h i s
i n v e s t i g a t i o n , m a in ta in s t h a t th e a d v an tag e n oted f o r th e
" q u i e t " c o n d itio n was n o t a m a t t e r of chance.
T h is stu d y , u n d e rta k e n by th e A etna L if e In su ra n ce
Company, l i k e th o se conducted by Weston and Adams, was
s u s c e p t i b l e to some o f th e e x tra n e o u s i n f l u e n c e s p r e
v io u s ly m entioned, i . e . , changes i n m o tiv a tio n and su g g e s
tio n * The f a c t t h a t e f f i c i e n c y was rew arded by a bonus
could have contam inated th e s i t u a t i o n when th e n o is y con
d i t i o n was r e s t o r e d . Employees could very w e ll have been
e x e r t in g an e x t r a e f f o r t i n an a tte m p t t o r e s t o r e t h e i r
bonus f i g u r e s to th e h i g h e r l e v e l . S in c e th e purpose of
th e stu d y could have become g e n e r a l l y known, a "su g g e s
t i o n " e f f e c t m ight have been c re a te d t h a t would in d u ce th e
employees t o e x e r t g r e a t e r e f f o r t . Thus Baker (2) h as
d e m o n stra te d e x p e rim e n ta lly t h a t such e f f e c t s a r e a p t t o
be e n co u n tere d . M oreover, th e r e s u l t s o f s t u d i e s c a r r i e d
o u t over a long p e rio d a r e l i k e l y t o be in f lu e n c e d by th e
e f f e c t s of l e a r n in g o f t h e t a s k .
On th e o t h e r h a n d , one may f i n d f i e l d s t u d i e s t h a t
b r in g f o r t h e v id en ce d e m o n s tra tin g t h a t a n o is y e n v iro n
ment a c t u a l l y f a c i l i t a t e s perform ance on some t a s k s .
K ornhauser (22) and B o u lin (6) , i n v e s t i g a t i n g th e e f f e c t
of n o is y o f f i c e c o n d itio n s upon th e o u tp u t o f t y p i s t s ,
26
found t h a t th e y produced more work under th e c o n d it i o n s
p r e s e n t i n a g e n e r a l o f f i c e a r e a th a n u n d e r c o n d itio n s o f
q u i e t . Sm ith (^3) a d m in is te r e d th e M innesota C l e r i c a l
T e s t and th e M innesota P a p e r Form Board T e s t und er c o n d i
t i o n s o f q u i e t and n o i s e . H is s tu d y a l s o showed an
i n c r e a s e i n p r o d u c t i v i t y u n d er n o i s y c o n d it i o n s a lth o u g h
a c c u ra c y of p erform ance on th e s e t a s k s s u f f e r e d .
An i n t e r p r e t a t i o n and e v a l u a t i o n o f i n v e s t i g a t i o n s
su c h a s t h e s e j a lth o u g h p r e s e n t i n g e v id e n c e p o i n ti n g t o
t h e d e l e t e r i o u s e f f e c t s o f n o i s e a s w e ll a s t o i t s f a c i l i
t a t i n g e f f e c t s , do n o t p r e s e n t such e v id e n c e i n a s u f f i
c i e n t l y c l e a r - c u t , u n q u a l i f i e d manner as t o le a d one t o
f e e l t h a t t h e s e e f f e c t s have been u n e q u iv o c a lly demon
s t r a t e d . The i m p l i c a t i o n s a r e , h ow ever, t h a t n o i s e can
and does e x e r t an e f f e c t on human p e rfo rm an c e .
The e f f e c t o f n o i s e o r q u i e t on p erfo rm an c e i s n o t
sim p ly a f u n c t i o n o f th e e n v iro n m e n ta l s t i m u l i a lo n e . I t
i s th e r e s u l t a n t of th e i n t e r a c t i o n o f t h e en vironm ent
w ith th e ty p e of t a s k and w ith th e i n d i v i d u a l who p e rfo rm s
t h e work. T here a r e s e v e r a l p l a u s i b l e e x p la n a t i o n s f o r
t h e a p p a r e n t f a c i l i t a t i n g e f f e c t s o f n o i s e s upon p e rfo rm
a n c e . These e x p la n a t i o n s a r e a s a p p l i c a b l e t o l a b o r a t o r y
i n v e s t i g a t i o n s a s th e y a r e to f i e l d s t u d i e s . On th o s e
t a s k s which a r e more d i f f i c u l t o r i n t r i n s i c a l l y more
i n t e r e s t i n g t o t h e s u b j e c t , h e may s im p ly i g n o r e t h e n o i s e
■while t h e e a s i e r t a s k s te n d t o become a u to m a t i z e d . T here
may be a v o l u n t a r y c o m p e n sa tio n on t h e s u b j e c t ' s p a r t i n
t h a t he works h a r d e r b e c a u se o f th e n o i s e o r t h e r e may be
a n i n v o l u n t a r y c o m p e n sa tio n i n t h a t th e s u b j e c t t e n d s t o
a d a p t t o t h e n o i s e t h a t s im p ly becomes a p a r t o f t h e
e n v iro n m e n t. I t h a s b een f o u n d s i n g e n e r a l , t h a t th©
more th e t a s k p u ts a demand on th e h i g h e r m e n ta l p r o c e s s e s ,
t h e more lik e lih o o d t h a t t h e n o is e w i l l e x e r t a d i s t u r b i n g
e f f e c t .
The n o i s e s t h a t a r e met w ith i n d a i l y l i f e a r e of
s u c h d i v e r s e and complex n a t u r e s t h a t i t i s a lm o s t im po s
s i b l e t o s tu d y them a l l . The ty p e s o f s t u d i e s t h a t h av e
b e e n r e f e r r e d t o p r e v i o u s l y a s f i e l d s t u d i e s have
a tte m p te d t o d i s c o v e r th e changes i n p e rfo rm a n c e concom i
t a n t w ith e x p o su re t o n o i s e . These s t u d i e s were m ean in g
f u l i n t h a t t h e y d e f in e d n o i s e as th e a u d i t o r y s t i m u l i
u s u a l l y foun d i n th e w orking e n v iro n m e n t. I n a d d i t i o n t o
t h e d i s a d v a n t a g e s a l r e a d y p o in te d o u t , t h e s e f i e l d s t u d i e s
s u f f e r t h e d i s a d v a n t a g e t h a t when t h e y u t i l i s e e x i s t i n g
sounds i n an e x i s t i n g s i t u a t i o n t h e s tu d y becomes h i g h l y
s p e c i f i c t o t h a t s i t u a t i o n i t s e l f . T h e r e f o r e , g e n e r a l i z a
t i o n s from t h a t p a r t i c u l a r c o n d i t i o n t o o t h e r c o n d i t i o n s
become e x tr e m e ly te n u o u s , I f n o t h a z a r d o u s . The l a c k o f
r i g i d c o n t r o l o v e r th e e n v iro n m en t i n f i e l d s t u d i e s
28
f r e q u e n t l y r e s u l t s i n a c o n fo u n d in g o f th e e f f e c t s o f
c hang es i n t h a t e n v iro n m e n t w ith and i n a d d i t i o n to t h o s e
i n t e n d e d by t h e e x p e r i m e n t e r . Many o f t h e s e s t u d i e s f a i l
t o t a k e n o te o f th e f a c t t h a t th e d i f f e r e n c e i n o u tp u t
c o u ld have come a b o u t b e c a u s e o f o t h e r f a c t o r s such a s
v e n t i l a t i o n , l i g h t i n g , o r s i m i l a r a l t e r a t i o n s i n th e
e n v ir o n m e n t.
Some Ad v an t a g e s o f t h e L a b o r a to r y A ppr o a c h
f p ^ e t i w i r n i ■U »"P
I n an e f f o r t t o e s c a p e from t h i s c o n fo u n d in g , many
r e s e a r c h e r s h a v e moved t h e l o c a l e o f t h e i r i n v e s t i g a t i o n s
i n t o t h e l a b o r a t o r y . I n a n a tm o sp h e re o f t h i s k in d t h e
e x p e r i m e n t e r h a s a f r e e r hand a t p ro d u c in g t h e e n v i r o n
m ent and c o n t r o l l i n g t h e r e l e v a n t f a c t o r s , a s w e l l a s
i r r e l e v a n t o n e s , w hich m ig h t p o s s i b l y e x e r t some I n f l u e n c e
upon h i s c h o sen d e p e n d e n t v a r i a b l e . T h a t i s t o s a y ,
s t i m u l i , b o t h I n te rm s o f t h e in d e p e n d e n t v a r i a b l e s and
t h e i n c i d e n t a l e n v ir o n m e n t a l v a r i a b l e s , a r e m ore a m en ab le
t o m a n i p u l a t i o n i n t h e m ore m anageable e n v ir o n m e n t.
A lth o u g h t h e s i t u a t i o n i s somewhat a r t i f i c i a l I n t h a t one
d o e s n o t e n c o u n t e r s o - c a l l e d " r e a l l i f e " c o n d i t i o n s , I t i s
r e a s o n a b l y s a f e t o c o n c lu d e t h a t i f one i s u n a b le t o demon
s t r a t e th e e f f e c t s o f n o i s e on b e h a v i o r i n t h e l a b o r a t o r y
s u c h e f f e c t s a t t r i b u t e d t o n o i s e i n t h e " f i e l d " could
p o s s i b l y h a v e been due t o o t h e r f a c t o r s .
29
S f f e c t s of H oise upon R e a c tio n Time i n L a b o r a to r y S t u d i e s
One o f th e f i r s t m ea su re s t o be d e v e lo p e d by
p s y c h o l o g i s t s was i n r e g a r d t o r e a c t i o n tim e . I t i s no
wonder t h e n t h a t , when th e a t t e n t i o n o f r e s e a r c h e r s was
t u r n e d t o i n v e s t i g a t i o n o f t h e e f f e c t s o f n o i s e upon
b e h a v i o r , t h i s f u n c t i o n was one o f t h e e a r l i e s t t o r e c e i v e
t h e i r c o n s i d e r a t i o n .
Using a hammer s t r i k i n g a n a n v i l a s t h e n o i s e ,
C a s s e l and D a lle n b a c h (12) i n v e s t i g a t e d i t s e f f e c t upon
th e tim e i t to o k a man t o move a f i n g e r i n re s p o n s e t o a
v i s u a l s i g n a l . T hese i n v e s t i g a t o r s found t h a t r e a c t i o n
tim e was le n g th e n e d somewhat b u t t h a t , a s f a r a s th e o v e rf
a l l e f f e c t was c o n c e rn e d , t h e a b i l i t y o f n o i s e t o s e r v e
a s a d i s t r a c t o r was e q u i v o c a l . In a s tu d y made by
M ile s ( 1 0 ) , s u b j e c t s were exp osed t o a j e t e n g in e b l a s t
w ith a n i n t e n s i t y l e v e l o f 130 d b . T h is group of f i v e
s u b j e c t s y i e l d e d a p e rfo rm a n c e showing a s l i g h t b u t i n s i g
n i f i c a n t im provem ent i n th e a b i l i t y to p r e s s one key i n
r e s p o n s e t o a s i n g l e s i g n a l w h ile th e y were b e in g su b
j e c t e d to t h e n o i s e . These two s t u d i e s s u p p o r t th e s t a n d
t h a t n o i s e h a s l i t t l e e f f e c t upon a r e l a t i v e l y e le m e n ta r y
o p e r a t i o n . S im ple r e a c t i o n t im e . I . e . , th e tim e r e q u i r e d
t o make a s i n g l e re s p o n s e t o a s i n g l e s i g n a l , I s f a i r l y
low on th e o r d e r o f psychom o tor f u n c t i o n s .
Yet e v id e n c e from o t h e r s t u d i e s h a s b een p r e s e n t e d
30
t o show t h a t even when t h e I n d i v i d u a l m ust make a p a r t i c u »
l a r ty p e of r e s p o n s e t o a g iv e n s i g n a l and a d i f f e r e n t
ty p e o f r e s p o n s e t o a n o th e r s o r t o f s i g n a l h i s p e rfo rm a n c e
s u f f e r s no d e c re m e n t. F o r exam ple, S te v e n s (M+) fo u n d no
d i f f e r e n c e i n s e r i a l d i s j u n c t i v e r e a c t i o n tim e a s a f u n c
t i o n o f e x p o s u re t o n o i s e s o f d i f f e r e n t i n t e n s i t y l e v e l s .
The n o i s e u sed i n t h i s s tu d y was s im u la te d a i r c r a f t n o i s e s
g e n e r a te d i n a t e s t cham ber. The i n t e n s i t y l e v e l s used i n
th e c o m p ariso n w ere 90 and 115 d b , r e . .0 0 0 2 dynes p e r
s q u a r e c e n t i m e t e r . F iv e s u b j e c t s worked c o n t i n u a l l y f o r
f o u r c o n s e c u tiv e d ay s o v e r a p e r io d o f f o u r w eeks. In
t h i s e x p e r im e n t, w hich a p p e a re d t o have b een p r o p e r l y
b a la n c e d and c o n t r o l l e d , s u b j e c t s e x h i b i t e d no s t a t i s t i
c a l l y s i g n i f i c a n t d i f f e r e n c e i n t h e i r p e rfo rm a n c e o f a
t a s k c o n s i s t i n g o f p r e s s i n g a key w ith e i t h e r t h e hand o r
th e f o o t d e p e n d in g upon w hich s i g n a l l i g h t came o n .
In a n o t h e r s tu d y o f r e l a t i v e c o m p le x ity , B ro u s s a rd
( 11) had s u b j e c t s w atch an i l l u m i n a t e d f i e l d i n o r d e r t o
d e t e c t a n e x t r a b r i g h t l i g h t w hich a p p e a re d w i t h i n i t .
The s u b j e c t r e p o r t e d th e p r e s e n c e o f th e l i g h t by p u l l i n g
a t r i g g e r . E x cep t f o r th e f a i n t e s t s t i m u l u s s u b j e c t s
w ere c o n s i s t e n t l y and s i g n i f i c a n t l y l o n g e r i n t h e i r
r e s p o n s e tim e s u n d e r e x p o su re t o r e c o r d e d t a n k n o i s e a t a
l e v e l o f 95 db . a s compared t o th o s e y i e l d e d u n d e r th e
n o i s e a t a l e v e l o f 95 d b . a s compared t o th o s e y i e l d e d
31
u n d e r t h e n o i s e a t an i n t e n s i t y l e v e l o f ^5 db* B ro ad b eat
( 9) found t h a t a g r e a t e r decrem ent r e s u l t e d when t h e r e a c
t i o n was a tw o -c h o ic e r a t h e r th a n a s i n g l e d e c i s i o n ,
a lth o u g h t h e d i f f e r e n c e was s m a ll i n amount.
T h us, i t a p p e a rs t h a t th e r e s u l t s produced by t h e s e
s t u d i e s o f f e r no c o n c lu s iv e e v id e n c e showing t h a t th e
s p e c i f i c p ro c e ss o f r e a c t i o n tim e a lo n e i s a f f e c t e d by
e x p o su re t o n o is e t o any g r e a t e x t e n t . However, t h e s e
s t u d i e s were concerned p r i m a r i l y w ith e f f e c t s o f n o is e on
t h i s p r o c e s s i n r e l a t i v e i s o l a t i o n . T h e r e f o r e , t h i s e v i
dence cannot le a d t o t h e c o n c lu s io n t h a t r e a c t i o n tim e i s
n o t a f f e c t e d when su c h a p r o c e s s i s a p a r t and p a r c e l o f a
more complex task * Many of t h e s t u d i e s y e t t o be r e f e r r e d
t o were concerned w ith p erform ance o f t a s k s i n which r e a c
t i o n tim e u n d o u b ted ly was h e a v i l y w e ig h te d i n term s o f th e
m ea su re s ta k e n . U n f o r tu n a te ly t h e s e p a r a t i o n o f t h i s
m o to r f u n c t i o n from t h e o t h e r components o f th e complex
t a s k o f which i t i s a p a r t i s f r a u g h t w ith numerous d i f f i
c u l t i e s .
E f f e c t o f N oise upon th e Perform ance o f R e l a t i v e l y Sim ple
V i s u a l T asks i n th e L a b o ra to ry
V i s u a l f u n c t i o n s have a l s o come i n f o r t h e i r s h a r e
o f a t t e n t i o n on th e p a r t o f p s y c h o l o g i s t s . L u ek iesh ( 32)
i n v e s t i g a t e d th e e f f e c t s o f n o i s e upon th e perform ance o f a
v i s u a l t a s k i n an atm osp here a p p ro a c h in g t h a t o f a " f i e l d
32
s t u d y ” a lth o u g h e n v iro n m e n ta l c o n d itio n s seem t o have been
a d e q u a te ly c o n tr o l le d as th e a c t u a l t e s t was accom plished
i n a s e p a r a t e b o o th . He found t h a t th e tim e r e q u i r e d t o
com plete th e G en eral E l e c t r i c 'D e m o n stra tio n V is u a l T e s t '
was i n f a v o r o f q u i e t c o n d itio n s over th o s e found i n a noisy
g e n e r a t o r room i n a f a c t o r y . The Gener-al E l e c t r i c t e s t
r e q u i r e d th e s u b j e c t t o a cc o m p lish th e jo b of l o c a t i n g
p a r t i c u l a r p a t t e r n s of l i n e s among o t h e r c o n fu sin g l i n e s .
This ty p e o f t a s k , to say th e l e a s t , can not be c o n sid e re d
a t e s t of v i s u a l f u n c t i o n s a lo n e ,
B roadbent (10) c i t e s a n o th e r stu d y d e a lin g w ith t h e
e f f e c t o f n o is e on a v i s u a l t a s k , s p e c i f i c a l l y , on the
a b i l i t y t o ju d g e d i s t a n c e s . The t a s k was c a r r i e d out i n a
n o i s e f i e l d of 115 db. and a l s o u n d e r t h e same n o i s e
a d ju s te d to an i n t e n s i t y l e v e l o f 90 db. S u b j e c t s ' a b i l i t y
t o m atch t h e d i s t a n c e s o f two w ire s s u f f e r e d no d i s c e r n i b l e
decrem ent when th e perform ance was compared under th e two
c o n d itio n s of n o i s e . The same stu d y was u n a b le t o produce
any s i g n i f i c a n t change i n s e n s i t i v i t y t o f a i n t i l l u m i n a t i o n
n o r i n d a rk a d a p t a t i o n .
On th e o t h e r han d , a r e p o r t by B ogoslovsky and
Kravkov, which was c i t e d by B e r r ie n ( 5 ) , s u g g e s ts t h a t su b
j e c t s exposed to n o is e l e v e l s a s h ig h a s 105 to 110 db. f o r
p e rio d s as long as tw enty t o t h i r t y m in u te s a c t u a l l y s u f f e r
a decrem ent i n t h e i r v i s u a l e f f i c i e n c y . However, s in c e th e
33
r e p o r t could be se en o n ly i n a b s t r a c t fo rm , i t was im p o s s i
b l e to e v a l u a t e i t . T hus, i n t h i s case a l s o , e v id e n c e
seems t o i n d i c a t e t h a t ex p o su re t o n o i s e d oes n o t n e c e s
s a r i l y y i e l d any a p p r e c i a b l e change i n a r e l a t i v e l y sim p le
f u n c t i o n such a s t h a t b ro u g h t i n t o o p e r a t i o n i n sim p le
v i s u a l t a s k s . T h is c o n c lu s io n , l i k e t h a t rea ch ed i n th e
case o f r e a c t i o n tim e , sho uld be tem pered by r e c o g n i t i o n
o f th e f a c t t h a t v i s u a l p r o c e s s e s , i n c o m b in atio n w ith
o t h e r p r o c e s s e s t o form more complex f u n c t i o n s , may o r may
n o t be a f f e c t e d by e x p o su re to n o i s e .
E f f e c t s o f N oise upon P e rfo rm an ce of Sim ple Motor T asks i n
a L a b o ra to ry S e t t i n g
In an i n v e s t i g a t i o n of t h e e f f e c t s o f n o i s e on th e
" s im p le ” p r o c e s s e s , a t t e n t i o n m ust be b ro u g h t t o b e a r upon
th o s e f u n c t i o n s c a r r i e d o u t by t h e m u s c le s , i . e . , m o to r
f u n c t i o n s . S te v en s (^5) found t h a t th e e f f e c t s o f n o i s e
on body sway and upon hand s t e a d i n e s s w ere n e g l i g i b l e .
P o lla c k and B a r t l e t t (39) produced r e s u l t s t h a t a r e d i f f i
c u l t t o i n t e r p r e t . The t a s k , w hich was one i n w hich th e
s u b j e c t had t o p ic k up and r e p l a c e pegs i n a moving peg-
b o a rd , p o se s some q u e s t i o n as t o w h e th e r i t could be
term ed a sim p le m otor t a s k . I t a p p e a rs t h a t t h e r e m ight
have been some eye-hand c o o r d i n a t i o n in v o lv e d i n th e ex ec u
t i o n o f such a t a s k , N e v e r t h e l e s s , th e p re s e n c e o f n o is e
was fo llo w e d by a d e c r e a s e In t h e q u a l i t y and q u a n t i t y o f
31 *
t h e responses., At l e a s t , su c h an i n i t i a l e f f e c t was
o b s e rv e d , a lth o u g h i t was follo w ed by a f a i r l y r a p id adap-
t a t i o n to th e c irc u m s ta n c e s. In t h i s s tu d y , th e d i s t r a c t
in g s t i m u l i c o n s is te d of t h e n o ise produced by such
s o u rc e s a s heavy p r i n t i n g p r e s s e s , phonograph r e c o r d s , o r
b e l l s . The r e p o r t n e g le c te d t o m ention th e i n t e n s i t y l e v e l
o f th e s e so un d s.
Using a somewhat s i m i l a r t a s k ( i n s e r t i n g a s t y l u s
i n t o h o le s i n a moving b e l t ) , L aird (28) produced compar
a b l e r e s u l t s ; however, t h i s study has been c r i t i c i s e d
b e c a u se of l i m i t a t i o n s i n th e s t a t i s t i c a l tr e a tm e n t th e
d a t a were g iv e n . B roadbent (10) r e f e r s t o a com parison of
th e a b i l i t y t o keep a s t y l u s on a s m a ll t a r g e t d i s k on a
r o t a t i n g phonograph t u r n t a b l e . Such a t a s k i s commonly
c o n sid e re d t o be one m ainly in v o lv in g a sim ple m otor
re sp o n se even though fe e d b a c k v ia th e se n se o rgans i s
u t i l i z e d i n keeping th e s t y l u s on th e t a r g e t . Be t h a t as
i t may, th e a b i l i t y t o perform th e t a s k showed no drop
when i t was perform ed under h ig h n o is e l e v e l c o n d itio n s as
compared t o t h a t y ie ld e d under low n o i s e l e v e l s .
E v a lu a tio n o f E xperim ents Regarding E f f e c t s of Noise f o r
R e l a t i v e l y Simple L ab o ra to ry Tasks
S urveying th e e v id en ce as a w h o le , one can come t o
t h e t e n t a t i v e c o n c lu sio n t h a t n e i t h e r r e a c t i o n tim e ,
s e n s o r y f u n c t i o n , n o r m otor f u n c t i o n s s u f f e r any g r e a t
decrem ent when th ey a r e observed i n r e l a t i v e i s o l a t i o n .
C a u tio n must be e x e rc is e d i n con clu d in g t h a t th e s e fu n c
t i o n s w i l l not be a d v e r s e ly a f f e c t e d i n ev eryday l i f e .
These f u n c t i o n s r a r e l y o p e r a te i n i s o l a t i o n i n th e perfo rm
ance o f th o se ta s k s o r d i n a r i l y e n co u n tere d i n th e workaday
w o rld . A r e a l i z a t i o n t h a t most of th e p r a c t i c a l , everyday
d u t i e s t h a t a re c a r r i e d out by most i n d i v i d u a l s a r e an
i n t e g r a t i o n (not a sum) o f th e more sim ple se n so ry and
m otor f u n c tio n s d i r e c t s one t o s e a rc h f o r i n v e s t i g a t i o n s
t h a t have been made p e r t a i n i n g t o th e more o r l e s s complex
t a s k s t h a t a re met d a i l y o r f o r th o s e s t u d i e s concerned
w ith re a s o n a b le s im u la tio n s of th o s e t a s k s .
Some R e p r e s e n ta tiv e E x p e rim e n ta l I n v e s t i g a t i o n s C oncerning
th e E f f e c t s of Noise upon P erform ance i n R e l a t i v e l y Complex
L a b o ra to ry Tasks
B e r rie n (5) and K ry te r (21 *) r e f e r t o s e v e r a l i n v e s
t i g a t i o n s conducted by S tevens i n which th e t a s k s a p p e a r to
be h i g h e r on th e la d d e r of com plexity th a n th o s e a lr e a d y
d is c u s s e d * These s t u d i e s showed t h a t n o is e p re s e n te d a t
two l e v e l s (115 and 90 d b . ) produced no d i f f e r e n t i a l
e f f e c t s on th e perform ance o f a t a s k c a l l e d c o o rd in a te d
s e r i a l p u r s u i t o r com pensatory t r a c k i n g i n which th e su b
j e c t was re q u ire d to a d j u s t , by means o f a i r p l a n e c o n t r o l s ,
th e p o s i t i o n of a sp o t on a c a th o d e -ra y o s c i l l o s c o p e and
t h e p o s i t i o n of a p o i n t e r on a m e te r. T here was no
36
d i s c e r n i b l e d i f f e r e n t i a l e f f e c t betw een th e two n o i s e con
d i t i o n s * On th e o t h e r h a n d , d u r in g t h e same s t u d i e s
S te v e n s found a s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e
b etw een t h e p e rfo rm an c e s u n d e r th e h i g h e r and lo w e r l e v e l s
i n th e a b i l i t y to d i r e c t a beam o f l i g h t a lo n g an opaque
pathw ay u s i n g th e same a i r p l a n e c o n tr o l s * B ro a d b en t (10)
s u g g e s t s t h a t t h i s d i f f e r e n t i a l e f f e c t p o s s i b l y was s p u r i
ous b e c a u se c lu e s m ig h t h av e b een g iv e n t o t h e s u b j e c t by
r e l a y s i n th e a p p a r a t u s . A s i m i l a r t r a c k i n g t a s k u se d i n
a s tu d y mad© a t T u f ts C o lle g e (10) a l s o f a i l e d t o s u f f e r
any c o n s i s t e n t d i s r u p t i o n when th e s u b j e c t s were exposed
t o n o i s e s h a v in g i n t e n s i t y l e v e l s up t o 120 and 130 d b .
R e s e a rc h c o n d u cted by B ro ad b en t (7) produ ced some
w hat more p o s i t i v e e v id e n c e t h a n t h a t found i n p r e v i o u s ly
c i t e d s t u d i e s * The o p e r a t i o n a c c o m p lish e d was a s o r t o f
s e r i a l r e a c t i o n ta s k * The s u b j e c t was r e q u i r e d t o to u c h a
s t y l u s t o a p a r t i c u l a r m e t a l c o n ta c t when a g iv e n l i g h t
a p p e a r e d . T here were f i v e c h o ic e s w i t h t h e p r e s e n t a t i o n
o f s t i m u l i b e in g paced by th e equipm ent i t s e l f * B ro a d b en t
found t h a t t h e number o f b lo c k s (an i n t e r v a l o f tim e i n
w hich no r e s p o n s e i s made) ten d e d t o i n c r e a s e w ith p r o
lo n g e d p e rfo rm a n c e b u t t h a t th e i n c r e a s e was n o t s i g n i f i
c a n t . B lo c k in g h a s been a t t r i b u t e d , i n p a r t , t o th e
p r e s e n c e o f an i n t e n s e com peting s t i m u l u s d u r in g a p e r io d
o f c o n tin u o u s p e rfo rm a n c e . I t s p r e s e n c e , d e p en d in g on th e
37
l i s t e n e r ' s a t t i t u d e , may s e r v e t o d i s t r a c t a t t e n t i o n from
t h e t a s k a t hand. In t h i s stu d y B roadbent used n o i s e a t a
c o n s t a n t i n t e n s i t y o f 100 db, b u t v a ry in g i n f re q u e n c y frcm
100-5000 c y c le s p e r se co n d . The d i s t r a c t i n g s tim u lu s w hich
was c o n tin u o u s i n n a t u r e p o ss e s se d no d i r e c t i o n a l c h a r a c
t e r i s t i c s . The i n c r e a s e i n t h e number o f e r r o r s under t h e
n o i s e c o n d it i o n s was s u b s t a n t i a l , a lth o u g h t h e number o f
r e s p o n s e s s u f f e r e d o n ly a s l i g h t d e c r e a s e .
In a n o th e r s tu d y ( 8) , t h e same e x p e r im e n te r found
t h a t s u b j e c t s had c o n s id e r a b ly more d i f f i c u l t y i n r e a d in g
steam gauges when th e y w ere s u b je c te d t o n o i s e l e v e l s up
t o 70 db. On t h e o t h e r h a n d , when th e t a s k c o n s i s t e d o f
m aking re s p o n s e s to i n d i c a t o r lam p s, s u b j e c t s showed no
e f f e c t s from t h e e x p o su re t o n o i s e . These s t u d i e s
r e f l e c t e d t h e u s u a l change i n perfo rm an ce i n t h a t th©
I n i t i a l s t a g e s s u f f e r e d more decrem ent t h a n l a t e r ones.
However, tow ard th e end o f t h e t a s k t h e r e was a te n d e n c y
f o r p e rfo rm an ce t o show a f i n a l d e c l i n e , B ro ad b en t h as
s u g g e s te d t h a t t h i s e f f e c t was due t o t h e s u b j e c t s making
a n e f f o r t d u rin g th e n o is e c o n d itio n s which th e y were
u n a b le t o m a i n t a i n .
I m p l i c a t i o n s of E x p e rim e n ta l F in d in g s C oncerning E f f e c t s
o f N oise upon Perform ance R e l a t i v e t o D u ra tio n o f Exposure
The e f f e c t j u s t r e f e r r e d t o p o in ts o u t th© d i f f e r
e n t i a l I n f l u e n c e o f n o i s e upon perform an ce a s a f u n c t i o n
o f th e l e n g t h o f ex p o su re t o th e c o n d i t i o n s . Most s t u d i e s
show t h a t t h e r e i s o f t e n an i n i t i a l d e c re m e n t i n p e rfo rm
ance d u r in g th e n o i s e c o n d it i o n s b u t t h a t t h e d e t r i m e n t a l
e f f e c t i s r a p i d l y r e d u c e d . T h is phenomenon s u g g e s t s t h a t
some sox*t o f a d a p t a t i o n i s t a k i n g p l a c e . O th e r s t u d i e s
( 8 , 11) o f f e r e v id e n c e show ing t h a t , w ith p r o lo n g e d expo
s u r e t o n o i s e , th e s u b j e c t w i l l c o n tin u e t o e x p e r ie n c e an
e v e r - i n c r e a s i n g d e t r i m e n t a l e f f e c t i n h i s p e rfo rm a n c e .
T h ere i s a l s o t h e p o s s i b i l i t y t h a t a n o v e r - a l l m easure o f
p e rfo rm an c e w i l l n o t show su c h a d e crem en t i n p e rfo rm an c e
b e ca u se o f t h e e x t r a e f f o r t t h a t a s u b j e c t m ig h t e x e r t
u n d e r t h e n o i s e c o n d i t i o n .
Even thou gh a d a p t a t i o n t o a sound i s p o s s i b l e t o
t h e e x t e n t t h a t an i n d i v i d u a l becomes unaw are o f i t ,
e n e rg y i s expended i n such a p r o c e s s . Under t h e s e c o n d i
t i o n s i t may be e x p e c te d t h a t p ro lo n g e d e x p o s u re t o n o i s e
w i l l g r a d u a l l y b r in g on f a t i g u e . By e x p en d in g more o r
l e s s e f f o r t , an i n d i v i d u a l may com pensate f o r changes i n
t h e e n v iro n m en t i n such a m anner t h a t h i s p e rfo rm a n c e i s
m a in ta in e d a t a f a i r l y c o n s t a n t v a l u e . T h is v a r i a t i o n i n
e f f o r t may a l s o s e rv e t c p ro duce f l u c t u a t i o n s i n p e rfo rm
an c e u n d e r r e l a t i v e l y c o n s t a n t c o n d i t i o n s o f t h e e n v ir o n
m ent.
S in c e p erfo rm an ce i s r e l a t e d t o e f f o r t a s w e ll a s
t o e n v iro n m e n ta l c o n d i t i o n s , one m ust ta k e i n t o
39
c o n s i d e r a t i o n th o s e e f f e c t s t h a t may he due t o t h e e x t r a
e f f o r t expended, I t i s e v id e n t t h a t many im p o r ta n t p ro b
lem s canno t be so lv e d u n t i l some p r a c t i c a l and v a li d
m ethods o f m easu rin g e f f o r t a r e a v a i l a b l e .
Some R e p r e s e n t a t i v e S tu d ie s Employing P h y s i o l o g i c a l
I n d i c e s f o r D e m o n stratio n o f E f f e c t s , o f P ro lo n g ed Exposure
t o N oise
S te p s have been t a k e n toward t h e s o l u t i o n of t h i s
p e r p l e x in g problem o f the con fo u n d in g i n f l u e n c e o f changes
i n i n d i v i d u a l e f f o r t and e n v iro n m e n ta l c o n d it i o n s upon
p e rfo rm a n c e by r e s o r t i n g t o c e r t a i n p h y s i o l o g i c a l m easu re
m e n ts, Harmon ( 2 0 ) , L aird ( 2 6 ) , and Morgan (35) p r e s e n t
e v id e n c e t h a t m e ta b o lic r a t e , b r e a t h in g r a t e , b r e a t h in g
volum e, and h e a r t r a t e i n c r e a s e u n d e r c o n d it i o n s of n o i s e .
O th e r s t u d i e s (13, 18, 29) have found s i m i l a r e f f e c t s b u t ,
i n a d d i t i o n , have shown t h a t th e p r o c e s s o f a d a p t a t i o n
shows up even i n t h e s e p h y s i o l o g i c a l p r o c e s s e s . Using
e l e c t r i c a l a c t i v i t y of th e m u scles a s a n i n d i c a t o r , Ryan
and o t h e r s (*+1), Freeman (18) , and D avis ( l 1 *) found e v i
den ce t h a t t h e p o t e n t i a l s te n d e d t o i n c r e a s e u n d e r n o is e
s t i m u l a t i o n . These m easures l ik e w i s e showed a d e c lin e as
a f u n c t i o n o f l e n g t h of e x p o su re t o t h e n o is y c o n d i t i o n s ,
Morgan (35) found t h a t s u b j e c t s e x e r t e d more m u sc u la r
e f f o r t i n m a n ip u la tin g th e e x p e r im e n ta l a p p a r a t u s . By an
in g e n io u s d e v ic e a tt a c h e d t o t y p e w r i t e r keys he d e te rm in e d
ko
t h a t s u b j e c t s s t r u c k th e keys w ith g r e a t e r f o r c e when th e y
w ere exposed t o n o i s e .
Some R e p r e s e n t a t i v e S t u d i e s C oncerning E f f e c t s of N o ise i n
Terms o f R a te o f R esponse R equired i n P erfo rm an ce o f a
l a s k
The p o in t sh o u ld be b ro u g h t o u t t h a t th e c o m p le x ity
o f a t a s k h a s a s p e c t s o t h e r th a n th o s e d e f i n i n g i t o n ly i n
term s o f t h e re s p o n s e s w hich th e s u b j e c t i s r e q u i r e d to
make* An im p o r ta n t d im e n sio n o f many complex t a s k s i s th e
sp e e d a t w hich th e s u b j e c t makes h i s responses® Some
t a s k s may be acc o m p lish e d a t a r a t e d e te rm in e d by th e su b
j e c t him self® In o t h e r w o rd s , w ith a c c u ra c y o f re s p o n se
a s th e prim e c o n s i d e r a t i o n } th e s u b j e c t may proceed a t a
r a t e commensurate w ith h i s a b i l i t y t o make such re s p o n s e s
a s a r e r e q u i r e d by th e ta sk * Such a d e s ig n may be
r e f e r r e d t o as s e l f - p a c i n g * O ther t a s k s ( f o r e x am p le,
t h e one r e f e r r e d t o i n a p r e v i o u s ly c i t e d stu d y by
B ro a d b en t [ ? ] ) » a r e o f su ch a n a t u r e t h a t th e r a t e a t
w hich r e s p o n s e s m ust be made i s d e te rm in e d by th e speed o f
t h e o p e r a t i o n of t h e apparatus® In such c a se s a momentary
p a u se u s u a l l y r e s u l t s I n a l o s s o f o p p o r t u n it y to make a
c o r r e c t r e s p o n s e — a l o s t o p p o r t u n it y f o r which th e s u b j e c t
i s u n a b le t o com pensate by i n c r e a s i n g h i s r a t e a t o t h e r
t i m e s . Such a t a s k may be r e f e r r e d t o a s one t h a t i s
e x t e r n a l l y paced*
Using w hite n o is e a t 110 db* as a d i s t r a c t o r ,
J e r i s o n (21) a s sig n e d s u b j e c t s a t a 3k in v o lv in g e x t e r n a l
p a cin g i n which th ey were r e q u ir e d t o keep t r a c k of a
s e r i e s o f c o n tin u in g e v e n ts . His r e s u l t s a l s o i n d i c a t e d
t h a t e r r o r s were s u b s t a n t i a l l y g r e a t e r on a t a s k t h a t
r e q u i r e s co n tin u o u s a t t e n t i o n and prompt a c t i o n by th e sub-*
j e c t , O b vio usly , i n d i v i d u a l d i f f e r e n c e s betw een s u b j e c t s
w i l l m e d ia te t o a g r e a t e x te n t j u s t itfhat s o r t of l a b e l a
t a s k shou ld be a s s ig n e d . The lo a d p la c e d upon th e o p e r a t o r
i s a f u n c t i o n of th e i n t e r a c t i o n betw een h i s own a b i l i t y t o
make re s p o n s e s and th e speed of the a p p a r a t u s . In g e n e r a l ,
how ever, i t i s c o n sid e re d t h a t an o p e r a t io n which i s
e x t e r n a l l y paced poses a more d i f f i c u l t t a s k f o r an
i n d i v i d u a l th a n one w ith r e s p e c t to which he can proceed
a t w ill*
Ryan and o th e r s (**.1) have d e m o n stra te d t h a t t a s k
d i f f i c u l t y i n term s of s e l f - p a c i n g o r e x t e r n a l p acing i s
even r e f l e c t e d i n p h y s i o l o g ic a l m easures* They showed
t h a t r a t e o f work d eterm in ed by th e o p e r a t io n of th e
a p p a r a tu s was a s s o c i a t e d w ith a more u n i v e r s a l i n c r e a s e i n
m uscle t e n s i o n th a n t h a t a s s o c i a t e d w ith s e l f - p a c e d ta s k s*
A.t any r a t e , e x p e rim e n ta l ev id e n ce seems t o su p p o rt th e
p o s i t i o n t h a t e x t e r n a l l y paced ta s k s a r e more s u s c e p t i b l e
t o d i s t r a c t i n g s t i m u l i th a n a r e t a s k s paced by th e s u b j e c t
h i m s e l f .
k-2
R e f le c t i n g th e im p o rtan c e o f a b i l i t y i n t a s k p e r
form ance, e x p e rim e n ta l e v id e n c e y ie ld e d i n s t u d i e s by
P o lla c k and B a r t l e t t (39) and by B a h ric k and o th e r s (1)
i n d ic a t e d t h a t th e i n f l u e n c e of d i s t r a c t i n g s t i m u l i was a
f u n c t i o n of th e amount o f p r a c t i c e on th e task® Those
t a s k s which were w e ll le a r n e d s u f f e r e d l e s s d e tr i m e n t a l
e f f e c t s th a n th o s e upon w hich th e s u b j e c t had had l e s s
p ra c tic e *
A c o n s i d e r a ti o n of th e l i t e r a t u r e review ed le a d s
one t o the t e n t a t i v e c o n c lu s io n t h a t th e e f f e c t s o f n o i s e
on b e h a v io r , whenever th e y do a p p e a r, a r e dependent upon
th e com plexity of th e t a s k , th e speed w ith which th e su b
j e c t must work, and th e i n h e r e n t p r o p e r t i e s of th e n o is e
i t s e l f ® Not o n ly i s th e i n t e n s i t y o f th e n o is e a d e t e r
m ining f a c t o r i n i t s e f f e c t s , b u t a l s o o t h e r dim ensions
such a s th e p i t c h and rhythm of th e sound e x e r t t h e i r
i n f l u e n c e . I t a p p e a rs t h a t th e s e a t t r i b u t e s have a g r e a t
d e a l to do w ith th e a b i l i t y o f n o i s e to a t t r a c t th e
h e a r e r ' s a tte n tio n ®
Some R e p r e s e n ta tiv e S tu d ie s Showing th e R e la ti o n s h ip of
P erform ance t o P i t c h and I n t e n s i t y o f Noise
L aird (27) has shown t h a t even such a sim ple
resp o n se as p r e s s u r e on a hand dynamometer v a rie d w ith
th e p i t c h o f th e a u d it o r y stimulus® L ikew ise h a n d w ritin g
made under th e i n f l u e n c e o f a ton e of low p i t c h was
* + 3
in c r e a s e d i n s i z e . In a n o th e r stu d y L aird ( 28) found t h a t
e r r o r s in c r e a s e d w ith a change i n the fre q u e n c y of to n e s
from 6U - to 512 c y c le s p e r second. He a l s o d eterm in ed t h a t
complex to n e s which were r i c h i n h ig h fre q u e n c y components
a f f e c t e d p ro d u c tio n more a d v e r s e ly th an pu re t o n e s . How
e v e r , th e d e s ig n o f t h i s stu d y i s open t o c r i t i c i s m
because th e e x p e rim e n te r p re s e n te d the h ig h l e v e l and h ig h
fre q u e n c y s t i m u l i f o r s e v e r a l days b e fo re n o tin g th e h ig h
e r r o r c o u n ts . These e f f e c t s could have r e s u l t e d , i n p a r t ,
from a drop i n th e m o tiv a tio n l e v e l of t h e weary s u b j e c t s .
B roadbent (10) h as shown t h a t , e s p e c i a l l y i n th e
case of h ig h i n t e n s i t y l e v e l s , th e mean number o f e r r o r s
i s s i g n i f i c a n t l y g r e a t e r under h ig h p itc h e d n o i s e th a n
under low p i tc h e d . In t h i s s tu d y , h ig h p itc h e d n o is e was
d e fin e d as m achinery n o is e hav in g a f l a t o c ta v e -b a n d s p e c
trum from 2000 t o 5000 c y c le s p e r second w h ile low p itc h e d
n o is e was from 50 t o 2000 c y c le s p e r second.
Some Representatlve Studies Indicating the Relationship of
Performance to Pattern of Sound (Continuous or Interrupted)
A p e r u s a l o f s e v e r a l s t u d i e s (3 > 21 * , 39) d i s c l o s e s
t h a t d is c o n tin u o u s sounds a r e more d i s t r a c t i n g th a n th o se
o f a co n tin u o u s n a t u r e . M oreover, i t a p p e a rs t h a t th o se
n o i s e s which a r e i n t e r r u p t e d i r r e g u l a r l y a r e more r e s i s t
a n t t o h a b i t u a t i o n th a n th o s e which a r e broken up more
e v e n ly . I t i s h ig h ly p ro b ab le t h a t th e i n t e r r u p t i n g of a
sound o p e r a t e s t o enhance i t s a t t e n t i o n - g e t t i n g q u a l i t i e s .
Some R e p r e s e n t a t i v e L a b o r a to ry S tu d ie s R egarding th e
Annoyance Value of N oise
A lth o u g h t h e r e i s n o t n e c e s s a r i l y a c o n n e c tio n
betw een an i n d i v i d u a l 1s r e p o r t on how he f e e l s tow ard a
p a r t i c u l a r sound and t h e e f f e c t t h a t such a sound h as on
h i s p e rfo rm a n c e , i t seems re a s o n a b le to supp ose t h a t th e r e
sh o u ld be some c o r r e l a t i o n betw een t h e s e two s e p a r a t e
m e a s u re s . The more o r l e s s d e t r i m e n t a l e f f e c t s of n o ise
upon psychom otor perform ance have been a s c r i b e d t o the
a b i l i t y o f n o i s e t o a c t as a d i s t r a c t o r r e l a t i v e t o th e
t a s k a t hand. Along t h e same l i n e s , i t seems r e a s o n a b le
t o supp ose t h a t th o se sounds which a r e c o n s id e re d t o be
more an n oyin g sh o u ld b e a r a c lo s e r e l a t i o n s h i p t o th o se
which r a t e h ig h as d i s t r a c t o r s or a t t e n t i o n - g e t t e r s . This
l i n e o f r e a s o n in g l e a d s one t o i n q u i r e i n t o t h e c h a ra c
t e r i s t i c s o f a u d i t o r y s t i m u l i t h a t peo p le f i n d m ost annoy
i n g .
The p a ra m e te rs o f i n t e n s i t y , f r e q u e n c y , and reg u
l a r i t y o r rhythm have s e rv e d as th e f o c a l p o i n t s f o r
i n v e s t i g a t i o n s mad© i n e f f o r t s to d e f i n e th e annoyance
a s p e c t o f n o i s e . L a b o ra to ry s t u d i e s o f th e annoyance
v a lu e o f n o is e r e s t upon t h e p r e s u p p o s i t io n t h a t an
i n d i v i d u a l can r e a c t i n a r e p e a t a b l e way t o n o is y e n v iro n
m e n ta l c o n d i t i o n s . In g e n e r a l , th e l i s t e n e r 13 asked to
^5
compare d i f f e r e n t sounds on t h e b a s i s o f t h e i r ann oyance
v a lu e . The p s y c h o m e tric m ethods o f p a ir e d c o m p a ris o n s,
r a t i n g s c a l e s , and ra n k o r d e r h a v e been employed as
m e a su rin g t o o l s t o a id i n e v a l u a t i n g th e v a r i a b l e s con
t r i b u t i n g t o th e annoyance v a lu e o f t h e e n v ir o n m e n ta l
a u d i t o r y s t i m u l i .
D re h e r (16) asked s u b j e c t s t o i n d i c a t e how an n o y in g
th e y w ould ju d g e a to n e t o be i f t h e y had t o l i s t e n t o i t
f o r f i v e hours* The s u b j e c t s ' e s t i m a t e s w ere q u a n t i f i e d
th r o u g h t h e use o f a m e a su rin g u n i t c a l l e d a " f r e t . "
T h is u n i t i s d e f i n e d a s "a n in c re m e n t o f an noy an ce i n a
s c a l e e x te n d in g fro m z e ro t o one h u n d re d , t h e low er
e x t r e m i t y r e p r e s e n t i n g co m p lete a b se n c e o f a n n o y a n c e , th e
u p p e r e x t r e m i t y r e p r e s e n t i n g maximum ann oyance*" T h is
s t u d y u t i l i z e d p u re to n e s and b ro a d -b a n d w h i t e n o i s e , th e
i n t e n s i t i e s of w hich were a d j u s t e d t o p ro d u c e a lo u d n e s s
o f 80 p h o n s . R e s u l t s from t h i s s tu d y i n d i c a t e d t h a t
annoyance i n c r e a s e s ( m o n o to n !c a lly ) w ith f r e q u e n c y from
50 to 7000 c y c le s p e r seco n d when t h e l o u d n e s s o f t h e pure
to n e i s h e ld c o n s t a n t a g a i n s t a q u i e t b a ck g ro u n d . I t i s
i n t e r e s t i n g to n o t e t h a t t h e annoyance v a l u e s g e n e r a te d
grouped th e m s e lv e s s t a t i s t i c a l l y i n t o t h r e e groups* 50-
200 c p s . , 300-3000 c p s * , and * * 000-7000 c p s . , w ith t h e
m id d le r e g i o n show ing th e g r e a t e s t d is a g r e e m e n t among
s u b j e c t s .
Such a f i n d i n g s u g g e s t s t h a t t h e u b i q u i t o u s p ro blem
o f i n d i v i d u a l d i f f e r e n c e s a r e r e f l e c t e d t o a g r e a t e r
e x t e n t i n t h a t ra n g e o f f r e q u e n c i e s . In th e same s tu d y
D r e h e r found t h a t slow r a t e s o f i n t e r r u p t i o n w ere more
a n n o y in g t h a n th e p r e s e n c e o f c o n tin u o u s n o i s e w ith t h e
p o i n t o f maximum annoyance c o rr e s p o n d in g t o an i n t e r r u p
t i o n r a t e o f f i v e i n t e r r u p t i o n s p e r s e c o n d . Mean annoy
a n c e ju d g m e n ts i n c r e a s e d ( m o n o to n ic a lly ) w ith o c ta v e ban ds
o f n o i s e o f i n c r e a s i n g f re q u e n c y from 50 t o M300 cps® when
t h e bands w ere p r e s e n t e d a t c o n s t a n t sound p r e s s u r e . S ub
j e c t s i n t h i s i n v e s t i g a t i o n i n d i c a t e d t h e maximum l e v e l
o f to n e s w hich th e y would be w i l l i n g t o t o l e r a t e f o r
s e v e r a l h o u r s . The h i g h e s t t o l e r a n c e v a lu e was s e t a t
77 d b . f o r 60 c p s . w h ile t h e lo w e s t was f o r 56 d b . a t
7000 c p s.
T h ese f i n d i n g s a r e b o rn e o u t by e v id e n c e p r e s e n t e d
i n a s tu d y by K r y te r ( 2*+ ) i n w hich he showed t h a t h i g h e r
p i t c h e d t o n e s a t a lo w e r i n t e n s i t y a r e e q u a l l y an n o y in g
t o lo w e r p i tc h e d to n e s a t a h i g h e r i n t e n s i t y . U sing a
p a i r e d co m p ariso n t e c h n i q u e ? L a ird and Coye (29) i n v e s t i
g a te d s e v e n o c ta v e s o f pu re to n e from 6* + t o 8192 cps*
They found t h a t a l l f r e q u e n c i e s were somewhat an n o y in g
b u t t h a t t h e h ig h f r e q u e n c i e s w ere ra n k e d h i g h e r a s a n n o y -
e r s . Yet t h e same s tu d y y i e l d e d a c u rv e of annoyance
v a lu e s t h a t r o s e s h a r p l y below 256 c p s .J T h ese
^7
i n v e s t i g a t o r s and o t h e r s (2 3 , 29, 3$» * + 0 ) p o i n t t o th e low
m id d le a c o u s t i c ra n g e ( 200-3000 cps*) a s b e in g t h e l e a s t
an n o y in g b o th i n th e case o f pure to n e s and bands o f n o i s e .
As f a r as th e rhythm of n o i s e i s c o n c e rn e d , t h e r e
i s s u b s t a n t i a l e v id e n c e t h a t i n t e r r u p t e d n o i s e i s more
a n n o y in g th a n c o n tin u o u s n o i s e (1 2 , 29, 3 8, 3 9 ) . M oreover,
M i l l e r (3V) and P o l l a c k and B a r t l e t t (39) have shown t h a t
a sound became even more an noy ing i f th e p e rio d o f i n t e r -
l'u p tio n was i r r e g u l a r .
T h ere a r e a s p e c t s o f n o i s e o t h e r t h a n th o s e
d e s c r i b e d o n ly by t h e i r p h y s i c a l m easurem ents which a c t
t o d e te rm in e i t s annoyance v a lu e . L a b o ra to ry s t u d i e s r e s t
upon t h e a ssu m p tio n t h a t a more o r l e s s " n e u t r a l a t t i t u d e '1
can be assumed by t h e s u b j e c t . The f a c t re m a in s , how ever,
t h a t p e o p le a r e seldom found w ith a t t i t u d e s which could
a p p r o p r i a t e l y be l a b e l e d " n e u t r a l . " Even u n d e r th e con
t r o l l e d c o n d it i o n s o f t h e l a b o r a t o r y , s u b j e c t s ’ a t t i t u d e s
w i l l v a ry a s a f u n c t i o n o f t h e i n t e r p r e t a t i o n th e i n d i v i d
u a l p l a c e s upon t h e i n s t r u c t i o n s g iv e n , upon h i s id e a o f
t h e p u rp o se o f th e e x p e r im e n t, upon prefo rm ed o p in io n s
c o n c e rn in g o t h e r f a c t o r s , a n d / o r e g o -in v o lv e m e n t.
D e p a r tu r e s from a " n e u t r a l " a t t i t u d e may be b ro u g h t a b o u t
by t h e u n e x p e c te d n e s s of t h e sound, by i t s I n a p p r o p r i a t e -
n e s s to t h e i n d i v i d u a l ’ s a c t i v i t y a t th e t im e , o r by h i s
a b i l i t y t o l o c a t e th e s o u r c e of t h e sound. The in d iv id u a l's
1 + 8
a t t i t u d e tow ard th e agency c r e a t i n g t h e d i s t u r b a n c e , a p a r t
from th e d i s t u r b a n c e i t s e l f , may d e te rm in e , to a g r e a t
e x t e n t , h i s “ a c c e p ta n c e 1 5 of t h a t sound.
Summary
I t i s a p p a r e n t from a review o f s t u d i e s p e r t a i n i n g
t o th e e f f e c t s of n o i s e on behavior- t h a t no c l e a r - c u t ,
u n q u a l i f i e d e v id e n c e i s a v a i l a b l e t o show t h a t n o i s e d o e s ,
o r does n o t , a f f e c t th e p erform an ce o f people*
R e l a t i v e t o t h e e f f e c t s o f n o is e on th o se f u n c t i o n s
w hich can be la b e le d “sim p le se n so ry " o r “sim ple m o to r , 1 5
i t can be s a i d t h a t t h e r e s u l t s a r e e q u iv o c a l. The d i s -
t r a c t o r may i n h i b i t and le n g th e n th e r e a c tio n } i t may
f a c i l i t a t e and s h o r t e n i t ; o r i t may become h a b i t u a l and
pro d u ce no e f f e c t a t a l l . On th e o t h e r h a n d , t h e r e i s
some i n d i c a t i o n t h a t , as t a s k s become more complex, t h e r e
a c c r u e s a decrem ent i n p erform ance a s a r e s u l t o f ex p o su re
t o n o is e a lth o u g h th e p ro c e s s of a d a p t a t i o n u s u a l l y a c t s
t o n u l l i f y th e e f f e c t s a f t e r a s h o r t tim e . The p ro c e s s of
a d a p t a t i o n i s e s p e c i a l l y e v id e n t i n th o s e t a s k s which can
be a u to m a tic iz e d and i n th o s e i n which t h e worker can p ro
ceed t o c a rry out t h e re s p o n s e s a t a r a t e w e ll w i th in h i s
a b i l i t y .
I t i s d i f f i c u l t to s p e c i f y th e c h a r a c t e r i s t i c s of
n o i s e t h a t a r e a s s o c i a t e d w ith a decrem ent i n p e rfo rm an ce.
Many s t u d i e s have found no such e f f e c t , and even i n th o s e
ij.9
which h av e, th e a u d it o r y s t i m u l i have been in a d e q u a te ly
d e s c r ib e d . This shortcom ing along w ith th e f a c t t h a t i n
many cases th e sounds used i n e x p erim en ts have been q u i t e
complex makes i t e x c e e d in g ly h azard o u s to p o in t t o s p e c i f i c
a r e a s o r c h a r a c t e r i s t i c s as being th o s e d e s c r i p t i v e o f
1 1 perform ance d i s r u p t i n g so u n d s . ,1 The p re s e n c e of i n d i v i d
u a l d i f f e r e n c e s among s u b j e c t s h as a l s o se rv e d to cloud
th e p i c t u r e . N e v e r th e le s s , t h e r e i s a s u g g e s tio n t h a t a
d e t r i m e n t a l e f f e c t i s l i k e l y t o be a s s o c i a t e d w ith h ig h
i n t e n s i t y , h ig h e r f r e q u e n c i e s , and w ith d is c o n tin u o u s
p a t t e r n s of sound.
As f a r as th e c h a r a c t e r i s t i c s of sound t h a t a r e
a s s o c i a t e d w ith annoyance a r e con cern ed , t h e r e i s much
g r e a t e r ag reem ent. In g e n e r a l , h i g h e r f r e q u e n c ie s seem to
be more annoying th a n th o s e i n th e m iddle range f o r b o th
pure to n e s and bands o f n o i s e . A sid e from f re q u e n c y ,
e x p e rim e n ta l e v id e n ce i s u n e q u iv o c a l i n showing t h a t loud
n o i s e s and d is c o n tin u o u s n o i s e s a r e more annoying th an
th o s e o f a low er i n t e n s i t y l e v e l and th o s e which a r e con
tin u o u s .
One le a v e s a rev ie w of th e l i t e r a t u r e w ith a vague
f e e l i n g t h a t many o f th e q u e s tio n s rem ain unansw ered. A
g r e a t number of th e i n v e s t i g a t i o n s c o n c e rn in g th e e f f e c t s
o f n o i s e have been d e f i c i e n t w ith r e s p e c t to th e d e s ig n
employed and w ith r e s p e c t t o the a d e q u a te d e f i n i t i o n of
50
t h e a u d it o r y s t i m u l i employed* These d e f i c i e n c i e s and th e
om nipresen t e f f e c t s due to i n d i v i d u a l d i f f e r e n c e s among
p e o p le make broad g e n e r a l i z a t i o n s e x c e e d in g ly h a z a rd o u s.
CHAPTER I I I
INSTRUMENTATION
THE NATURE OF THE AUDITORY MATERIALS
AND THEIR MODE OF PRESENTATION
The a u d it o r y s t i m u l i c o n s is te d of t h r e e q u a l i t a
t i v e l y d i f f e r e n t s i g n a l s . S p e c i f i c a l l y th e y were:
1, A pure s in e wave to n e a t 210 c y c le s per
second®
2, Broad-band w h ite n o is e .
3 , A pure s i n e wave to n e a t 3000 c y c le s per
seco n d .
Each o f th e s e q u a l i t a t i v e l y d i f f e r i n g s t i m u l i was
p r e s e n te d to s u b j e c t s under th r e e d i f f e r e n t p a t t e r n s of
te m p o ra l o n s e t 5 i . e . , th e p a t t e r n of i n t e r r u p t i o n was
v a rie d i n t h r e e ways as f o llo w s :
1, C on tin u o u s,
2, R e g u la rly i n t e r r u p t e d by p e rio d s of s i l e n c e a t
th e r a t e of f i v e i n t e r r u p t i o n s p e r second,
3 , I r r e g u l a r l y i n t e r r u p t e d w ith random p e rio d s of
sound v a ry in g i n le n g th b ein g s e p a ra te d by random p e rio d s
o f s i l e n c e v a ry in g i n l e n g t h .
The sound s t i m u l i were p re s e n te d t o th e s u b j e c t s
by means of tap e r e c o r d i n g s . The sounds , which were
g e n e ra te d by an A l l is o n R esearch A udiom eter Model 21B,
were re c o rd e d th ro u g h a d i r e c t c o n n e c tio n w ith a W ollensak
Tape R eco rd er Model T-1515* This same r e c o r d e r was sub
s e q u e n tly used t o rep ro d u c e th e sounds f o r p r e s e n t a t i o n to
t h e s u b j e c t s . From th e ta p e r e c o r d e r th e s i g n a l was fe d
t o a t r a n s d u c e r c o n s i s t i n g o f a p a i r of T e le p h o n ic TDH-39
headphones f i t t e d w ith MX-^-1/AR c u sh io n s. The headphones
w ere h e ld s e c u r e ly over b o th e a r s by a m e ta l headband.
The tr a n s d u c e r s were connected i n s e r i e s p r e s e n tin g an
im pedence of 20 ohms to th e o u tp u t l i n e of th e ta p e
r e c o r d e r . Sine© th e o u tp u t o f th e r e c o r d e r was on th e
o r d e r o f 8 ohms im pedence, t h i s r e s u l t e d i n a s l i g h t m is
m atch which i s deemed to be o f no consequence h e r e .
The a u d it o r y s t i m u l i were p r e s e n te d t o th e s u b j e c t s
a t a sound p r e s s u r e l e v e l o f 95 d e c i b e l s r e l a t i v e t o a
r e f e r e n c e p r e s s u re o f .0002 dynes p e r sq u a re c e n tim e te r
(.0 0 0 2 m ic r o b a r s ) . This sound p r e s s u r e l e v e l v/as
a c c u r a t e l y determ in ed f o r each o f th e sound s t i m u l i by
p la y in g th e rec o rd ed tape on th e W ollensak R eco rd er thro u g h
th e T elep h o n ic phones which were mounted on an A l l i s o n
A r t i f i c i a l Ear Model 300A. The g a in c o n t r o l ( p o p u la r ly
known as a volume c o n tr o l) o f th e r e c o r d e r was c a r e f u l l y
logged a t t h a t p o s i t i o n which produced a l e v e l o f 95
d e c i b e l s f o r th e c o n tin u o u s sound a t th e a r t i f i c i a l e a r .
The i n t e r r u p t e d s t i m u l i were p re s e n te d to th e s u b j e c t s a t
th e same s e t t i n g o f th e g a in c o n t r o l found t o y i e l d 95
d e c i b e l s f o r th e c o n tin u o u s sound of th e same fre q u e n c y .
THE APPARATUS
The e n t i r e a p p a r a tu s was e n c lo se d w i t h i n a b i r c h
c a b in e t a p p ro x im a te ly 26 in c h e s wide by 1^ in c h e s h ig h by
20 in c h e s d eep. On th e f a c e o f th e c a b i n e t , which was
i n c l i n e d a t an a n g le o f d e g r e e s , was an opening 13
in c h e s lo ng by 1 1 /2 in c h e s w id e. L ocated a t a d i s t a n c e
o f 7 in c h e s above t h i s op en in g i n th e f r o n t p a n el was a
sm a ll b la c k p l a s t i c p a n e l 6 in c h e s lon g by 2 in c h e s w ide.
T h is s m a ll p a n e l was c o n s t r u c t e d of th r e e l a y e r s o f
la m in a te d p l a s t i c . The to p l a y e r o f th e p a n e l was b la c k ;
th e m id d le l a y e r was w h ite w h ile th e bottom l a y e r was r e d .
Four sym bols ( t r i a n g l e , c i r c l e , s q u a r e , and half-m oon)
were e n g raved upon t h i s p a n e l w ith t h e en g raved d e p th
a d j u s t e d so a s t o cu t th ro u g h th e b la c k l a y e r and i n t o th e
w h ite l a y e r . With th e e n g ra v in g made i n t h i s m anner, a l l
o f th e symbols a p p e a re d c o n tin u o u s ly as w h ite f i g u r e s on
a b la c k b ackg ro und . However, whenever a s m a ll l i g h t came
on b eh in d any g iv en sym bol, t h a t symbol a p p e a re d a s a red
f i g u r e on th e b la c k b ack groun d. In t h i s m anner any p a r
t i c u l a r symbol could be made c l e a r l y t o s ta n d out a s th e
d e s ig n a te d t a r g e t . H e r e a f t e r t h i s s m a ll p a n e l w i l l be
9 +
r e f e r r e d t o a s th e s i g n a l p a n e l.
The d i s t a n c e betw een th e s i g n a l p a n e l and th e lo ng
s l o t below (7 in c h e s ) was s u f f i c i e n t to i n s u r e t h a t th e
s u b j e c t a c t u a l l y had to f i x a t e upon th e s i g n a l p a n e l i n
o r d e r to i d e n t i f y any p a r t i c u l a r symbol r a t h e r t h a n b e in g
a b l e to make t h i s o b s e r v a t i o n th ro u g h th e u se of p e r ip h e r a l
v i s i o n . W ith in th e l a r g e opening ( h e r e a f t e r r e f e r r e d to
a s th e t a r g e t f i e l d ) c o u ld be se en th e s u r f a c e o f a drum
upon which were engraved f o u r symbols I d e n t i c a l t o th o s e
a p p e a rin g on th e s i g n a l p a n e l. In a d d i t i o n to t h e s e
s y m b o ls ? t h e r e were f o u r o t h e r s eng raved upon th e s u r f a c e
o f th e drum. These s y m b o ls, which would n e v e r se rv e a s
t a r g e t s d e s ig n a te d by th e e x p e r im e n te r, were in te n d e d t o
a c t as p la c e b o s o r dummy t a r g e t s .
The o u t e r s u r f a c e o f th e drum was co v ered by co p p er
t u b in g w hich had been n i c k e l - p l a t e d b u t had been l e f t
u n p o lis h e d so a s to r e t a i n a d u l l o r f l a t f i n i s h . The
e n g ra v in g d e p th had been a d ju s te d so as to c u t th ro u g h
t h e n i c k e l p l a t i n g i n t o t h e copper m a t e r i a l making each
symbol a p p e a r as a b r i g h t copper image on a d u l l n i c k e l
back g ro u n d , A o n e - f o u r t h in c h round h o le was d r i l l e d
e x a c t l y i n th e c e n t e r of eac h f i g u r e .
A ll of t h e s e sy m b o ls, both r e g u l a r t a r g e t s and
p la c e b o s , were s y s t e m a t i c a l l y l o c a t e d on th e s u r f a c e of
th e drum so a s t o i n s u r e t h a t one o f each ty p e would be
55
v i s i b l e w ith in th e t a r g e t f i e l d a t any one time w h ile the
drum was r e v o l v i n g . The drum, w hich was 6 in c h e s i n
d i a m e t e r , was made to r e v o lv e c o n tin u o u s ly th ro u g h th e use
o f a s m a ll e l e c t r i c m otor which was g eared down and
d i r e c t l y connected to th e drum. P h o to g ra p h s o f th e
a p p a r a t u s a re shown i n F i g u r e s 1 and 2.
T hroughout th e e n t i r e p ro c e d u re th e drum re v o lv e d
c o n tin u o u s ly a t t h e r a t e o f 2 1 /2 r e v o l u t i o n s p e r m inute
so as t o p r e s e n t th e p r e v i o u s ly d e s c r ib e d symbols w ith in
t h e t a r g e t f i e l d b r i e f l y . T his speed had been d e te rm in e d
p r e v i o u s l y to be th e one w hich would p ro v id e a t a s k a t th e
o p tim a l d i f f i c u l t y . The s u b j e c t ’ s t a s k was to I n s e r t a
s t y l u s i n t o th e h o le i n t h e c e n t e r o f th e " c o r r e c t ’ -* symbol
d u r in g th e tim e t h a t i t was v i s i b l e w i t h in th e t a r g e t
f i e l d . The " c o r r e c t ” symbol was i n d i c a t e d t o th e s u b j e c t
by th e l i g h t i n g o f one o f th e f i g u r e s o r symbols a p p e a rin g
on th e s i g n a l p a n e l above th e t a r g e t f i e l d , i . e , , t h e sym
b o l a p p e a rin g i n red became h i s t a r g e t i n th e t a r g e t f i e l d
below . The drum and i t s a s s o c i a t e d equipm ent w ere so con
s t r u c t e d t h a t whenever t h e s u b j e c t p lac ed th e s t y l u s w ith in
th e " c o r r e c t ” h o l e an e l e c t r o m a g n e t i c c o u n te r would re c o rd
t h a t o p e r a t i o n . I f th e s u b j e c t to u ch ed anywhere e l s e on
th e drum, a c i r c u i t was com pleted so as to r e c o rd t h a t
a c t i o n a s an e r r o r on a s i m i l a r e le c t r o m a g n e ti c c o u n te r .
In a d d i t i o n to th e s e two c o u n te r s t h e r e was a n o t h e r one o f
56
FIGURE 1
EXTERNAL VIEW OF THE APPARATUS
FIGURE 2
VIEW OF APPARATUS SHOWING THE DRUM
AND CONTROL CHASSIS
58
a s i m i l a r ty p e which k ept a rec o rd o f th e number of stim u
l u s p r e s e n t a t i o n s made.
The s u b j e c t was r e q u ir e d to c a r r y out h i s t a s k
u n d e r two d i f f e r e n t c o n f i g u r a ti o n s of stim u lu s p r e s e n t a
t i o n . Under one c o n f i g u r a ti o n , c a l le d s e l f - p a c i n g , a new
t a r g e t a pp eared on th e s i g n a l p a n el im m ed iately a f t e r th e
s u b j e c t had made a c o r r e c t re s p o n s e , i . e . , touched th e
s t y l u s w i th in th e " c o r r e c t " h o le . In o t h e r words, th e sub
j e c t could proceed a t a r a t e of speed which was d e term in ed
s o l e l y by h i s own c o r r e c t re s p o n s e s on th e t a s k . Under
th e o th e r c o n f i g u r a t i o n , c a l l e d e x t e r n a l p a c in g , th e
s tim u lu s t a r g e t changed a b o u t every 1 1 /2 seconds w hether
t h e s u b j e c t made a c o r r e c t re s p o n s e , an e r r o r , or no
re s p o n se a t a l l . In o th e r w ords, th e s h i f t of t a r g e t s was
n o t determ in ed i n any manner by th e a c t i o n o f th e s u b j e c t .
The tim e i n t e r v a l s betw een t a r g e t changes were p u rp o se ly
made s l i g h t l y d i f f e r e n t i n le n g th f o r th e purpose of
b re a k in g up o r p re v e n tin g any rhythm ic p a cin g of t a r g e t
p r e s e n t a t i o n s »
The c o n tr o l c h a s s i s , l o c a te d w ith in th e c a b in e t and
mounted d i r e c t l y i n r e a r of th e drum, housed a l l the
o p e r a tin g c o n t r o l s , s tim u lu s s h i f t i n g a p p a r a tu s , and
r e c o r d in g equipm ent. The e n t i r e e le c tr o - m e c h a n ic a l
a rran g em en t o p e ra te d on a 12-V olt D ir e c t C u rre n t e l e c t r i
c a l system o b ta in e d from th e l i n e v o lta g e by means of a
step -d ow n tr a n s f o r m e r and a b r id g e - ty p e selen iu m r e c t i
f i e r . The a c t u a l s h i f t i n g o f s tim u lu s t a r g e t s was accom
p lis h e d th ro u g h th e a c t i o n o f an e le c tr o m a g n e tic s te p p in g -
s w itc h . T his s te p p in g - s w itc h was equipped w ith a r o t o r
w iping c o n ta c t which made tw enty -tw o s e p a r a t e p o s i t i o n s ,
each o f which was p ro v id e d w ith f i v e t e r m in a l s .
On each o c c a sio n o f th e s h i f t to a new s te p two
c i r c u i t s were com pleted. One of t h e c i r c u i t s f u r n is h e d
power t o th e l i g h t b u lb s behind th e symbols on th e s i g n a l
p a n e l. At th e same tim e a c i r c u i t was com pleted th ro u g h
a m u lt i - c o n d u c to r c a b le to a c o l l e c t o r r in g a tta c h e d t o
one end of th e drum. From th e w iping c o n ta c ts a t th e
c o l l e c t o r - r i n g th e w irin g was c a r r i e d to c o n n e c tio n s
which armed th e m e ta l c o n ta c t u n d er th e h o le i n th e
" c o r r e c t " symbols on th e drum s u r f a c e , i . e . , th e symbol
c o rre sp o n d in g t o th e one a p p e a rin g i n red on th e s i g n a l
p a n e l. O ther c o n n e c tio n s th ro u g h t h i s same system com
p le te d a c i r c u i t f o r th e re c o rd in g o f e r r o r s . This method
of l i g h t i n g th e p ro p e r symbol on th e s i g n a l p a n e l and of
arm ing th e co rre sp o n d in g symbols o f th e drum was common
t o both th e s e l f - p a c i n g and e x t e r n a l - p a c i n g c o n fig u ra
t i o n s 5 how ever, i n o th e r r e s p e c ts t h e two d i f f e r e d .
Under th e s e l f - p a c i n g c o n f i g u r a t i o n th e fo llo w in g
sequence of o p e ra tio n s occurred?
The s t y l u s , which was a t a p o s i t i v e p o t e n t i a l of
12-VDC, upon to u c h in g w i t h in th e 1 1 c o r r e c t '• h o l e , completed
a c i r c u i t th ro u g h th e m e ta l c o n ta c t p l a t e a t th e bottom of
t h a t h o le . Thence th e c u r r e n t co u rsed th ro u g h th e
c o l l e c t o r - r i n g t o one of th e te r m in a l s o f th e s t e p - s w i t c h
and on t o a te le p h o n e type ( th e c o r r e c t s ) s o le n o id r e l a y .
T h is te le p h o n e r e l a y , i n t u r n , com pleted two c i r c u i t s one
o f which caused th e " c o r r e c t " re sp o n se c o u n te r t o r e g i s t e r
w h ile th e o t h e r c i r c u i t caused th e s t e p - s w i t c h t o move t o
t h e n e x t p o s i t i o n . I f th e s t y l u s touched anywhere e l s e
o t h e r th a n w ith in th e " c o r r e c t " h o l e , a c i r c u i t was com
p l e t e d to a n o th e r te le p h o n e (th e e r r o r s ) r e l a y w hich, i n
t u r n , a c t u a t e d only th e e r r o r s c o u n te r . S w itch in g
a rra n g e m e n ts were a l s o made whereby an e r r o r resp o n se
could t r i p th e s t e p - s w i t c h a lth o u g h t h i s arrangem ent was
n o t u t i l i z e d d u rin g th e p r e s e n t i n v e s t i g a t i o n .
Under th e e x t e r n a l - p a c i n g c o n f i g u r a t i o n th e f o llo w
in g sequence of o p e r a tio n s to o k places
The c u r r e n t went from th e s t y l u s down t o th e
" c o r r e c t s " te le p h o n e r e l a y w hich, i n t u r n , a c t u a t e d th e
" c o r r e c t s " c o u n te r . However, u n d er t h i s c o n f i g u r a ti o n ,
t h e l i n e from th e te le p h o n e r e l a y t o th e s t e p - s w i t c h was
b ro k en so t h a t i t was n o t a c t u a t e d by a " c o r r e c t " re s p o n s e .
The " e r r o r s " c i r c u i t r y rem ained th e same a s i t was un der
s e l f - p a c i n g . The change of t a r g e t s t i m u l i was a f f e c t e d
by th e s t e p - s w i t c h ; how ever, i n t h i s c a s e , th e s t e p - s w i t c h
6 1
s o le n o id was a c tu a te d by a m ic ro sw itc h b e in g cammed t o th e
ON p o s i t i o n by round head machine screw s on one end of th e
r e v o lv in g drum* In t h i s manner th e change o f s tim u lu s was
governed s o l e l y by th e o p e r a t io n of th e r e v o lv in g drum and
had n o th in g w hatever t o do w ith th e s u b j e c t ’s re s p o n s e .
The drum and s t e p - s w i t c h were sy n c h ro n ize d i n such a
manner t h a t j u s t as th e s i g n a l p a n e l p r e s e n te d a new sym
bol t h e c o rre sp o n d in g symbol would b e g in to a p p e a r a t th e
to p edge of th e t a r g e t f i e l d . A p ie c e o f b la c k e l a s t i c
was s t r e t c h e d a lo n g th e bottom of th e t a r g e t f i e l d f o r
th e pu rp o se o f p r o t e c t i n g th e equipm ent from p o s s ib le
damage t h a t m ight a r i s e from th e s t y l u s b e in g caught i n
th e r e v o lv in g p a r t s of th e ap p aratu s*
The o p e r a tin g c h a s s i s was equipped a u to m a t i c a ll y to
s to p th e e n t i r e a p p a r a tu s a f t e r a c e r t a i n number of
re s p o n s e s had been com pleted. Manual s w itc h e s were a l s o
a v a i l a b l e to a c t u a t e t h e s t e p - s w i t c h a s w e ll as to t u r n
o f f t h e equipment a t t h e w i l l of th e o p e r a t o r .
CHAPTER TV
EXPERIMENTAL DESIGN AND PROCEDURE
SUBJECTS
The s u b j e c t s c o n s is te d of 10 fi male s t u d e n ts from
u n d e rg ra d u a te psychology c l a s s e s a t th e U n iv e r s ity of
S o u th e rn C a lif o r n ia * I t was s p e c i f i e d t h a t on ly th o se
s t u d e n ts betw een th e age l i m i t s o f e ig h te e n and t h i r t y
would be e l i g i b l e t o p a r t i c i p a t e i n th e e x p erim e n t.
P r o s p e c t iv e s u b j e c t s were re a d a s h o r t (b u t n o t to o
in f o r m a tiv e ) d e s c r i p t i o n o f th e s tu d y f o r th e s p e c i f i c
pu rpo se o f m o tiv a tin g them to v o lu n te e r t o s e rv e a s sub-
j e c t s * However, i t was q u i t e p ro b ab le t h a t th e g r e a t e s t
m o tiv a tin g s tim u lu s t o v o l u n te e r was p ro v id ed by th e
i n s t r u c t o r ' s o f f e r of f i v e p o in ts c r e d i t toward th e s t u
d e n t ' s se m e s te r g rad e i n th e course i f he a g re e d t o p a r t i
i p a t e i n t h e i n v e s t i g a t i o n .
A ll s u b j e c t s were g iv e n a s c re e n in g t e s t on a
B e llto n e Model 9A A ud iom eter i n o rd e r t o e li m in a te any
v o l u n te e r who had d e f e c t i v e h e a r in g . No one was a c c e p te d
a s a p a r t i c i p a n t i f he s u f f e r e d more th a n a 20 d e c i b e l
h e a r in g l o s s . A ll s u b j e c t s were t e s t e d on th e a u d io m ete r
a t t h r e e f r e q u e n c ie s ! 250, 1000, and 3000 c y c le s p er
63
se c o n d .
A t o t a l number of 108 s u b j e c t s was o b ta in e d i n
t h i s m anner. Each s u b j e c t was s u b s e q u e n tly a s s ig n e d t o
one o f t h r e e groups a c c o rd in g to a t a b l e o f random num bers,
EXPERIMENTAL DESIGN AND PROCEDURE
I t i s g e n e r a l l y conceded t h a t i n many p s y c h o l o g ic a l
e x p e rim e n ts t h e d i f f e r e n c e among i n d i v i d u a l s c o n s t i t u t e s a
m ajo r so u rc e o f v a r i a t i o n . I f a f a c t o r i a l d e s ig n i s so
p lan n ed t h a t some of th e tr e a tm e n t c o m b in atio n s a r e admin
i s t e r e d t o some of t h e s u b j e c t s and o t h e r t r e a tm e n t com
b i n a t i o n s a r e a d m in is te re d to o t h e r s u b j e c t s , i t may be
p o s s i b l e t o c o n t r o l i n d i v i d u a l d i f f e r e n c e s i n some b u t n o t
a l l o f th e tr e a tm e n t e f f e c t s . In an e f f o r t t o a cc o m p lish
t h i s aim , t h e e x p e r im e n ta l d e s ig n of t h i s i n v e s t i g a t i o n
was s e t up so a s to y i e l d th e more p r e c i s e com parisons i n
t h o s e t r e a tm e n t com parisons which w ere c o n s id e re d t o be
more im p o r t a n t . L in d q u is t (31) h a s p r e s e n t e d a th o ro u g h
and e x h a u s tiv e tr e a tm e n t of some of t h e s e s o - c a l l e d mixed
d e s ig n s i n w hich some of th e t r e a tm e n t com parisons a r e
i n t e r - s u b j e c t and some a r e i n t r a - s u b j e c t .
The p a r t i c u l a r d e s ig n u t i l i z e d i n t h i s i n v e s t i g a
t i o n in v o lv e d a th re e -w a y f a c t o r i a l t y p e . In one of th e
d im e n sio n s ( c a l l e d th e A dim ension) th e a u d i t o r y s t i m u l i
were g iv e n i n t h r e e q u a l i t a t i v e l y d i f f e r e n t l e v e l s as
e x p la in e d i n t h e s e c t i o n on A u d ito ry M a te r ia ls * In th e
second d im e n sio n ( c a l l e d t h e B dim ension) each of t h e
a u d i t o r y s t i m u l i was o f f e r e d a c c o rd in g t o t h r e e d i f f e r e n t
p a t t e r n s o f i n t e r r u p t i o n o f th e sound. The t h i r d dim en
s i o n ( c a l l e d t h e C dim ensio n) d e a l t w ith t h e two d i f f e r e n t
t a s k c o n f i g u r a t i o n s , i . e , ? s e l f - p a c i n g and e x t e r n a l p a c in g .
The 108 s u b j e c t s were d iv id e d a t random i n t o groups w ith
each group c o n s i s t i n g of t h i r t y - s i x i n d i v i d u a l s . Each of
t h e s e t h r e e groups i s a d m in is te r e d a c o f a l l th e p o s s i b l e
abc t r e a t m e n t - c o m b i n a t i o n s ; h o w ev ers th e i n d i v i d u a l s i n
any g iv en group to o k n o t more th a n one tr e a tm e n t i n any a
c a te g o ry n o r more th a n one t r e a tm e n t i n any B c a te g o r y .
A l l i n d i v i d u a l s c a r r i e d o u t th e t a s k under each of t h e
t r e a tm e n ts i n c a te g o ry C. I t can be seen t h a t each s u b je c t
was in v o lv e d i n s i x s e p a r a t e and d i s t i n c t t r e a t m e n t -
c o m b in a tio n s. For ex am p le9 th e s u b j e c t s a s s ig n e d t o
group 1 were a d m in is te r e d tr e a tm e n t- c o m b in a tio n s
A2B2CX> A3B3C1s A1B1C2j A2B2C2* A3B3C2‘
A l l s u b j e c t s were a llo w e d one and o n e - h a l f h o u rs to
com plete th e e n t i r e e x p e r im e n ta l p ro c e d u re a lth o u g h th e
t o t a l amount o f tim e a c t u a l l y r e q u i r e d t o a c c o m p lish th e
t a s k ran g e d from f o r t y - f i v e m in u te s t o one h o u r and f i f
t e e n m in u te s depending on th e re s p o n se tim e s of t h e
i n d i v i d u a l h i m s e l f . Upon r e p o r t i n g f o r th e exp erim ent*
each s u b j e c t was g iv en a h e a r i n g t e s t on t h e B eItone
6 5
A udiom eter, S u b je c ts were n o t a d m in is te re d th e com plete
a u d io m e te r t e s t b u t were checked only on th r e e f r e q u e n
c i e s , i . e . , 250, 1000, and 3000 c y cles p e r second, A
l o s s of 20 d e c i b e l s had been p re v io u s ly d e s ig n a te d as th e
maximum h e a r in g l o s s t h a t would be t o l e r a t e d . A f t e r th e
h e a r in g t e s t each s u b j e c t was s e a te d f a c i n g th e t e s t
a p p a r a tu s which had been p lac ed i n a p o s i t i o n on a sm all
t a b l e so a s t o p e rm it i t to be a t a c o n v en ien t h e i g h t .
Each s u b j e c t was th e n read th e i n s t r u c t i o n s and g iv en a
s h o r t d e m o n s tra tio n a s t o how th e s e l f - p a c i n g and e x t e r n a l -
pacin g c o n f i g u r a ti o n s o p e ra te d and d i f f e r e d i n t h e i r p r e
s e n t a t i o n s of th e t a s k . Each s u b j e c t was re q u e s te d to
po stp one any q u e s tio n s he m ight have con cern in g th e p u r
pose of th e stu d y u n t i l a f t e r he had com pleted th e e n t i r e
ex p erim en t a t which tim e th e e x p e rim e n te r would endeavor
t o s a t i s f y a l l q u e r i e s .
A f te r th e s u b j e c t was c o m p letely s a t i s f i e d t h a t he
u n d e rsto o d th e t a s k he was t o acco m p lish he was allow ed
s i x p r a c t i c e t r i a l s . However, th e s u b j e c t was n o t a d v ise d
t h a t any of th e s e t r i a l s were t o be c o n sid ere d as p r a c t i c e
t r i a l s n o r was he t o l d t h a t th e l a s t two o f th e s i x t r i a l s
would be ta k e n as c r i t e r i o n t r i a l s . The s i x p r a c t i c e
t r i a l s were g iv en i n th e o rd e r SP, XP, SP, XP, SP, and XP
(where SP s ta n d s f o r s e l f - p a c i n g and XP r e p r e s e n ts
e x te r n a l- p a c in g ) f o r a l l s u b j e c t s . On each t r i a l th e
s u b j e c t was r e q u ir e d t o c o n tin u e w orking a t th e ta s k u n t i l
he had e x ecu ted f o r ty - tw o c o r r e c t r e s p o n s e s . At no tim e
was th e s u b je c t e v er e n lig h te n e d as t o j u s t how many c o r
r e c t re s p o n se s c o n s t i t u t e d a t r i a l . Each s u b j e c t was
allow ed a tw o-m inute r e s t p e rio d betw een each o f the t r i a l s
c o n s t i t u t i n g th e p r a c t i c e p e rio d . D uring t h i s i n t e r v a l he
rem ained i n a sm all room a d ja c e n t t o t h e t e s t i n g room
w hile th e e x p e rim e n te r r e s e t th e a p p a ra tu s i n p r e p a r a t i o n
f o r th e su c ce ed in g t r i a l . A fte r th e s i x p r a c t i c e t r i a l s
were concluded th e s u b j e c t was a d v ise d t h a t he v/ould be
allo w ed fo u r m in u te s d u r in g which tim e he m ight have a
c i g a r e t t e j ta k e a w alk, 01* r e l a x a p p r o p r i a t e l y . During
t h i s fo u r-m in u te p e rio d t h e e x p e rim e n te r proceeded to s e t
up th e t e s t a p p a r a tu s and sound equipm ent i n p r e p a r a t i o n
f o r th e t e s t t r i a l s which were to f o llo w .
At th e c o n c lu s io n o f t h i s fo u r-m in u te r e s t p e rio d
th e s u b j e c t was r e c a l l e d t o th e t e s t i n g room and ad v ised
t h a t he was now t o perform e x a c tly t h e same t a s k a g a in ;
how ever, w hile he was p u rsu in g h is t a s k on t h e s e t r i a l s he
would be exposed to some sounds by means of th e headphones
p ro v id e d . I t was s p e c i f i c a l l y s t a t e d t h a t th e I n t e n s i t y
o f t h e s e sounds was so a d ju s te d t h a t no damage t o the
s u b j e c t ' s h e a r in g would r e s u l t from exposure t o them. In
o rd e r t o redu ce f u r t h e r any a n x ie ty t h a t the s u b j e c t m ig h t
have co n cernin g h i s h e a r in g a f t e r th e c o n c lu sio n of th e
6 7
e x p e r im e n t, th e e x p e r im e n te r e x p la in e d to him t h a t p o s s i b l y
f o r an h o ur o r two a f t e r th e e x p erim e n t h i s h e a r in g
t h r e s h o l d would be s l i g h t l y h i g h e r but t h a t i t would
r e t u r n t o i t s norm al v a lu e s h o r t l y t h e r e a f t e r (see i n s t r u c
t i o n s t o s u b j e c t s ) . The s u b j e c t th e n went th ro u g h th e
i d e n t i c a l t a s k w h ile a t th e same tim e b e in g exposed t o th e
a u d i t o r y s t i m u l i p r e v io u s ly a s s ig n e d t o th e group i n which
he was a member* The o r d e r of each tr e a tm e n t- c o m b in a tio n
a d m in is te re d t o a l l s u b j e c t s w i t h in a p a r t i c u l a r group was
c o u n te rb a la n c e d to e q u a liz e th e e f f e c t s due to l e a r n in g
a s w e ll as th o se a t t r i b u t a b l e to f a t i g u e . The exp erim en
t a l s e s s i o n was concluded by d e v o tin g some tim e t o an sw er
in g q u e s tio n s p u t f o r t h by th e s u b j e c t .
SCORING
F o r each s u b j e c t e v e ry t r i a l y ie ld e d two ty p e s o f
s c o r e s . C o n c u rre n tly w ith th e s t a r t i n g of th e t e s t
a p p a r a tu s a synchronous m otor c lo c k was a u to m a t i c a ll y
s t a r t e d . The tim in g c lo c k was a u t o m a t i c a l l y sto p p ed when
th e f o r ty - s e c o n d c o r r e c t re s p o n se had been made. T his
p ro ce d u re y ie ld e d a s c o re i n term s o f th e t o t a l le n g th of
tim e i n seconds r e q u ir e d to com plete one t r i a l . A
s e p a r a t e sc o re was p ro v id ed i n term s of th e number o f
e r r o r s made d u r in g th e p ro c e s s o f a c c o m p lish in g th e f o r t y -
two c o r r e c t r e s p o n s e s . These e r r o r s were a u to m a t i c a ll y
68
re c o rd e d by means o f th e e le c tro m a g n e tic c o u n te r p re
v i o u s l y d e s c r ib e d . A re c o rd was m a in ta in e d i n term s o f
t h e s e two s e p a r a t e s c o r in g system s f o r a l l s u b j e c t s d u rin g
a l l p r a c t i c e t r i a l s as w e ll as d u rin g a l l t e s t t r i a l s .
CHAPTER V
ANALYSIS AND DISCUSSION OF RESULTS
PU N FOR STATISTICAL ANALYSIS
D e s c r i p t i o n s of N o ta tio n s t o be Employed i n Defining; th e
Independent V a ria b le s
For th e sake of c l a r i t y it- v /ill be a d v is a b l e to
r e p e a t th e d e s c r i p t i o n o f th e in d e p e n d e n t v a r i a b l e s and to
a s s i g n each of them a code l e t t e r . Code l e t t e r s a r e
a s s ig n e d to each of th e v a r i a b l e s i n o r d e r t o e l i m i n a t e
u nw ieldy d e s c r i p t i o n s on each o c c a sio n to which r e f e r e n c e
i s made to them . The in d e p e n d e n t v a r i a b l e s a re shown, i n
T able I a lo n g w ith t h e i r a ssig n e d code l e t t e r s and a s h o r t
v e r b a l d e s c r i p t i o n . S ince th e s e v a r i a b l e s have been
d e s c r ib e d e x te n s i v e l y i n e a r l i e r s e c t i o n s o f t h i s r e p o r t }
th e y a r e d e s c rib e d m in im ally i n Table I t o p e rm it a
d e f i n i t e i d e n t i f i c a t i o n o f each p a r t i c u l a r code l e t t e r
w ith a p a r t i c u l a r e x p e rim e n ta l c o n d itio n .
The com plete d e s c r i p t i o n o f th e c o n d itio n s i n c i d e n t
t o any e x p e rim e n ta l tr e a tm e n t ( i . e . 5 th e sim u lta n e o u s
p re s e n c e o f a g iv e n l e v e l o r q u a l i t y i n each of th e th r e e
in d e p e n d e n t v a r i a b l e s ) i s given by th e co m b ination o f code
l e t t e r s d e s c r i b i n g t h e component v a r i a b l e s which combine
70
TABLE I
CODING OP THE INDEPENDENT VARIABLES
V a r ia b le Code L e t t e r s and D e s c r ip t i o n s
Type
r
1® B road-band w h ite n o is e
of A
2® P ure s i n e wave to n e -3 0 0 0 e p s.
N o ise
3 . Pure s i n e wave to n e -210 c p s .
Typ© 1 . C o n tin u o u s sound
o f B 2o R e g u la r ly i n t e r r u p t e d
I n t e r r u p t i o n 3 . I r r e g u l a r l y i n t e r r u p t e d
Type
1 . S e l f - p a c i n g
of C
2® E x t e r n a l p a c in g
Task
. .. .. _ .
71
t o produce th e a u d i t o r y environm ent ( ty p e of n o i s e and
p a t t e r n o f i n t e r r u p t i o n ) as w e l l a s t h e t a s k c o n d it i o n s
( s e l f - p a c i n g o r e x t e r n a l p a cin g )* F o r exam ple, an e x p e r i
m e n ta l t r e a tm e n t c o n s i s t i n g o f ex p o su re t o w h ite n o is e
(A-jP p r e s e n t e d c o n tin u o u s ly (B-j_) d u rin g th e e x e c u tio n o f
th e a s s ig n e d t a s k u n d e r s e l f - o a c i n g (C^) I n s t r u c t i o n s can
be d e s ig n a te d by th e code c o m b in atio n ApBqC].
S c o re s Used i n S i g n i f i c a n c e T e s ts o f S t a t i s t i c a l H ypotheses
In th e s ta te m e n t o f t h e h y p o th e s e s i t was i n d i c a t e d
t h a t two s e t s of m easu res on th e d e p en d e n t v a r i a b l e were
re c o rd e d a s th e number o f e r r o r s made i n e x e c u tin g th e
t a s k and t h e t o t a l tim e i n se co n d s r e q u i r e d to com plete
th e task®
F o r p u rp o se s o f th e s t a t i s t i c a l a n a l y s i s o f r e s u l t s
d i f f e r e n c e s c o r e s were used i n th e a n a l y s i s o f v a r i a n c e .
A d i f f e r e n c e s c o r e was o b ta in e d by s u b t r a c t i n g th e i n d i v i d
u a l ’s p erform ance s c o re und er c o n d it i o n s of q u i e t from th e
s c o r e t h a t he y i e l d e d under th e one t r i a l f o r each p a r t i c u
l a r e x p e rim e n ta l c o n d it i o n . The s u b j e c t ' s s c o r e s u n d er
c o n d it i o n s of q u i e t b o th f o r s e l f - p a c i n g and e x t e r n a l
p a c in g were y i e l d e d by h i s p erfo rm an ce on th e l a s t two
t r i a l s o f th e s i x t r i a l s c o n s t i t u t i n g t h e t r a i n i n g p e r i o d .
D if f e r e n c e s c o r e s were o b ta in e d f o r e a c h i n d i v i d u a l i n
term s o f e r r o r s a s w e ll a s th e number o f seconds r e q u i r e d
f o r t a s k c o m p le tio n . The d i f f e r e n c e s c o r e s w e re , i n t u r n ,
72
summed f o r e a c h t r e a tm e n t gro up so a s t o y i e l d a mean
d i f f e r e n c e s c o r e f o r t h a t p a r t i c u l a r e x p e r im e n ta l c o n d i-
t i o n . I t was assumed t h a t t h e d e g re e of r e l i a b i l i t y o f
t h e d i f f e r e n c e s c o r e s was s u f f i c i e n t l y h igh t o a llo w f o r
a m e a n in g fu l s t a t i s t i c a l e v a l u a t i o n .
Overview o f S t a t i s t i c a l P ro c e d u re s Follow ed
C o n s e q u e n tly , s t a t i s t i c a l t e s t s of th e v a rio u s
h y p o th e s e s in v o lv e d p ro c e d u re s d i r e c t e d a t d e te rm in in g
w h e th e r t h e s e mean d i f f e r e n c e s among th e t r e a t m e n t gro u p s
s i g n i f i e d g e n u in e p o p u l a t i o n d i f f e r e n c e s ( a f t e r tr e a tm e n t)
o r w h ether th e y r e p r e s e n te d m erely chance v a r i a t i o n s such
a s could be e x p e c te d among s e v e r a l random sam ples from
t h e same p o p u l a t i o n , F o r t h e p u rp o ses of t h i s s t u d y , i t
was d e cid ed t o r e j e c t th e n u l l h y p o th e s is i f th e a n a l y s i s
o f v a r ia n c e y i e l d e d a v alue f o r which th e a s s o c i a t e d
p r o b a b i l i t y o f o c c u rre n c e was e q u al t o or l e s s th a n , 0 5 *
I t was deemed a d v i s a b l e } i n t h e I n t e r e s t s of c l a r
i t y and s i m p l i f i c a t i o n , t o t e s t th e n u l l h y p o th e s e s i n
two s e p a r a t e and d i s t i n c t a n a ly s e s o f v a r i a n c e , i . e . , i n
te rm s o f e r r o r s and a l s o i n term s o f t o t a l tim e r e q u i r e d
t o com plete t h e t a s k .
The q u e s t i o n s posed i n th e s ta te m e n t o f th e problem
w i l l se rv e a s th e fram ework w i t h in which th e a n a l y s i s and
e v a l u a t i o n o f r e s u l t s w i l l be e f f e c t e d . D i s c u s s io n o f th e
q u e s t i o n s po sed i n th e s ta te m e n t of t h e problem w i l l be
73
made i n th e o r d e r of t h e i r a p p e a ra n c e i n t h a t s e c t i o n .
ANALYSIS OF RESULTS
A n a ly s is o f E r r o r S co res
T ra n s fo r m a tio n of s c o r e s . An i n s p e c t i o n of th e
d i s t r i b u t i o n s o f th e raw s c o r e s f o r t h e e ig h te e n tr e a tm e n t
g rou ps i n d i c a t e d t h a t th e d i s t r i b u t i o n s of th e s c o r e s i n
raw form could n o t be c o n sid e re d as b e in g norm al. T his
i n s p e c t i o n a l s o d i s c l o s e d a s i g n i f i c a n t d e p a r t u r e from
h o m og en eity o f v ariance,, S in c e hom ogeneity o f v a r ia n c e
and n o r m a l it y of d i s t r i b u t i o n a r e assumed t o e x i s t i n
u t i l i z i n g th e a n a l y s i s o f v a r ia n c e t e c h n iq u e , i t was
d e c id e d t o tr a n s fo r m th e m easures o f t h e d ep en d e n t v a r i a
b l e i n t o a form t h a t would y i e l d v a r ia n c e s which were
more n e a r l y homogeneous and d i s t r i b u t i o n s o f s c o r e s which
more c l o s e l y a p p ro x im ated n o r m a l it y .
Edwards ( 1 7 ) , G u ilfo rd ( 1 9 ) s and L in d q u is t (31)
have recommended t h a t a t r a n s f o r m a t i o n t o a l o g a r i th m i c
s c a l e be made when th e s ta n d a r d d e v i a t i o n o f th e o b s e r v a
t i o n s i n th e v a r io u s groups te n d to be p r o p o r t i o n a l t o
t h e c o rre sp o n d in g means. T h e r e fo r e , th e o r i g i n a l d a ta
w ere tra n s fo rm e d t o a s c a l e c o rre sp o n d in g t o log^Q (X * 1 0 ).
The amount 10 was added to eac h o r i g i n a l s c o r e X i n o r d e r
t o e l i m i n a t e n e g a t iv e v a lu e s . An i n s p e c t i o n o f th e t r a n s
form ed d i s t r i b u t i o n s and v a r ia n c e s i n d i c a t e d no s i g n i f i c a n t
7 ^
d e g re e o f d e p a r t u r e from h om o g en eity of v a r i a n c e o r n o r
m a l i t y of d i s t r i b u t i o n . (F o r a d d i t i o n a l i n f o r m a t i o n
r e g a r d i n g t h e e f f e c t s upon a n a l y s i s o f v a r i a n c e o f d e p a r
t u r e s from i d e a l c o n d i t i o n s th e r e a d e r i s r e f e r r e d t o
L in d q u i s t [3 1 ]* )
The A n a ly s is o f V a ria n c e o f E r r o r S c o re s
The t o t a l sura o f s q u a r e s o f th e tr a n s f o r m e d s c o r e s
was th e n f r a c t i o n a t e d i n t o i t s component p a r t s and a n a
l y z e d a c c o r d in g t o th e p l a n sh o rn i n T ab le I I . R e l a t i v e
t o t h e a n a l y s i s of v a r i a n c e c a r r i e d o u t , t h i s e x p e r i m e n t a l
d e s i g n conform s t o th e g e n e r a l s p e c i f i c a t i o n s o f one
d e s c r i b e d by L in d q u i s t (3 1 )• The t o t a l sum of s q u a r e s
i n t h i s ty p e o f d e s i g n i s composed o f what i s c a l l e d
b etw een s u b j e c t s and w i t h i n s u b j e c t s v a r i a n c e com ponents.
The components a r e in d e p e n d e n t o f each o t h e r , and may be
a n a ly z e d s e p a r a t e l y . Each i s composed o f i t s c o n s t i t u e n t
v a r i a n c e s . S in c e t h e r e a r e s e v e r a l s e t s o f w i t h i n su b
j e c t s v a r i a n c e s , t h e s e m ust be a n a ly z e d s e p a r a t e l y w ith
t h e i r c o rr e s p o n d in g sums o f s q u a r e s , mean s q u a r e s , and
d e g r e e s o f freed o m . F o r t h i s ty p e o f a n a l y s i s , th e v a r i
ous t e s t s o f s i g n i f i c a n c e a r e a s f o l l o w s : A, B, and AB(w)
a g a i n s t e rro r]_ (w ); AC, BC, and AB(yj)C a g a i n s t e rro r^ C ^ )*
C and AB(b)C a g a i n s t e r r o r ^ ( w ) ; AB(b) a g a i n s t e r r o r ( b ) .
D a ta p e r t i n e n t t o t h e q u e s t io n s posed i n th e s t a t e
m ent o f th e problem a r e shown i n T able I I I which c o n t a i n s
75
TABLE I I
ANALYSIS OF ERROR SCORES
V a ria n ce Components
Source df Sums of S q uares
Between S u b je c ts
AB(b)
e r r o r ( b )
an -1
a -1
a ( n - 1)
s s 3
S3AB(b)S SSG
SSe r r o r ( b ) s SoS"SSAB(b)
W ith in S u b je c ts a n ( a c - l )
s s w8s SV SSS
A S'"!
ssA
B a -1
s s B
C c-1
SSC
AB(w) ( a - 1) ( a - 2)
SSAB('w)S SSAB” SSAB(b)
AC (a = -l)(c - 1)
SSAC
BC ( a - 1) ( c - 1)
SSBC
AB(b)C ( a - l ) ( c - l )
SSAB(b)CS SSGC
AB(w)C (a-1 ) (a-2)X
( c - 1)
SSAB(v/)CS SSABC"SSAB(b)C
e rro r(w ) a ( a c - l ) ( n - 1) s s
e r r o r (y j)
e r r o r j (w) a ( a - l ) ( n - 1)
qc
‘ e r r o r i ( W )
e r r o r ^ (v/) a ( c - 1) ( n - 1)
s s e r r o r 2(w)
e rro r^ (w ) a ( a - 1 ) ( c - l ) X
( n - 1)
s s
e r r o r 3(w)
T o ta l a^cn -1
1
SSrji
76
TABLE I I I
MEAN ERROR DIFFERENCE SCORES AND STANDARD DEVIATIONS
E x p e rim e n ta l
T rea tm en t
Group
Mean S ta n d a rd
D e v ia tio n
A1B1C1
. 967^4 .025726
A1B2C1
*9325^
o053508
a1B3C1
. 9^534-
.028916
A2B1C1
, 986^0
.023571
A~B„Cn
Cm 4^ « ►
.96611
.03^909
A2B3C1
.96613
.053231
A3B1C1
1.00053
.0507lM )
A3B2C1
.95208
.025377
A3B3C1
.95383 , 03^760
A1B1C2
.96778
.108507
A1B2C2
.95^92
.079633
A1B3G2
1.00260 .050762
A2B1C2
.93018
.QJ K>003
a 2b 2c 2 . 976^8 .076270
A2B3G2
.98915
.0930^8
A3B1C2
1.03 ^32 .075920
ii3B2C2
1*03 22^5- .036250
A3B3°2
1.0587^ .057817
77
t h e mean d i f f e r e n c e s c o r e s and s ta n d a rd d e v i a t i o n s f o r
each e x p e r im e n ta l t r e a tm e n t g ro u p and i n T able IV which
c o n ta in s mean e r r o r s c o r e s f o r each e x p e r im e n ta l v a r i a b l e
t a k e n a l o n e . The a n a l y s i s o f v a r ia n c e i n term s o f mean
d i f f e r e n c e e r r o r s c o r e s i s shown i n T a b le V.
E v id en ce C oncerning t h e T e n a b i l i t y o f t h e S t a t i s t i c a l
H ypo theses Along w ith C o rresp o n d in g I n f e r e n c e s R egardin g
t h e P l a u s i b i l i t y o f t h e R e se arch H y p o th e se s.
R e fe re n c e I s made to T a b le V i n p r o v id in g in fo rm a
t i o n f o r a c c e p ta n c e o r r e j e c t i o n of th e s t a t i s t i c a l
h y p o th e s e s posed r e l a t i v e to t h e r e s e a r c h h y p o th e s e s t h a t
w ere d e v elo p ed w i t h in th e s ta te m e n t o f t h e problem .
K v p o th e sis 1 . T here i s no d i f f e r e n c e betw een th e
mean number of e r r o r s made o r betw een t h e mean number o f
second s r e q u ir e d t o com plete t h e t a s k u n d e r s t i m u l a t i o n by
n o i s e s v a ry in g i n t h e i r q u a l i t a t i v e a s p e c t s , i . e . , i n
f r e q u e n c y .
As shown i n T a b le V, th e F t e s t r e l a t i v e t o v a r i a
b l e A was s i g n i f i c a n t beyond t h e 9001 l e v e l . S in c e t h i s
p r o b a b i l i t y was s m a l l e r th an t h e l e v e l o f s i g n i f i c a n c e
chosen ( . 0 5 ) j th e d e c i s i o n was made t o r e j e c t th e n u l l
h y p o t h e s is and to i n f e r t h a t t h e r e were v e ry p ro b a b ly r e a l
d i f f e r e n c e s among means and t h e r e f o r e d i f f e r e n t i a l e f f e c t s
a s s o c i a t e d w ith v a r i o u s ty p e s o f n o is e upon psychom otor
78
TABLE IV
MEAN NUMBER OF ERROR SCORES FOR EACH VARIABLE ALONE
E x p e rim e n ta l V a r ia b le Mean
Type of n o is e i r r e s p e c t i v e
o f mode o f i n t e r r u p t i o n and
ty p e of resp o n se pacing
A1
1.9237
Ao
ci
1.9381
2.0106
Mode o f i n t e r r u p t i o n i r r e
s p e c t i v e of ty p e of n o is e
and ty pe of respon se pac
in g
B1
1.962**
b2 1.9381
B3
1.9719
Type of resp o n se pacing
i r r e s p e c t i v e of type of
n o i s e and mode of i n t e r
r u p t i o n
c i
.963^
° 2
,99*+0
79
table v
ANALYSIS OF VARIANCE OF ERROR DIFFERENCE SCORES
S ource df Sums of S qu ares M S F
Between
Subj e c t s 107 10.0127
AB(b) 2 .005*+ .0027
_ —
error- (b)
105 10.0073 .0953
W ithin
Subj e c t s 54-0 24-. 864-3
A 2 .2340 .1170
* A
12.1 9
B 2 .0328 .0164-
1 .7 1
C 1
.1517 .1517
4-. 1 + 6
AB (w) 2 .0353
.0179
1 .8 6
AC 2
.1767
,0884-
-------
BC 2
.1337
.0668
AB(b)C 2
.004*9 .0025
•M B r t W *
AB(w)C 2 .0036 .0018
mm Ok» a x
e r r o r (w)
525 2*+. 0 9 U
e rro r^ (w ) 210 2,0164- .0096
error^Cw) 105 14-. 827 .14-12
e r r o r ^ (w) 210 7 . 14-74- .034-0
T o ta l
61+7 34-. 8770
S i g n i f i c a n t a t th e p - .05 l e v e l
S i g n i f i c a n t a t th e p r .001 l e v e l
80
p e rfo rm a n c e . An i n s p e c t i o n o f T able IV d i s c l o s e d t h a t th e
l a r g e s t d e crem e n t i n p e rfo rm an c e was a s s o c i a t e d w ith ex p o -
s u r e t o a pure s i n e wave to n e o f 210 c p s . A t t h e same
tim e i t was a p p a r e n t t h a t a p ure s i n e wave to n e o f
3000 c p s. rank ed second as a d i s t r a c t o r w h ile w h ite n o is e
was a s s o c i a t e d w ith t h e l e a s t d ecrem en t i n perform ance*
H y p o th e s is 2 . T h ere i s no d i f f e r e n c e betw een th e
mean number of e r r o r s made o r betw een t h e mean number o f
s e c o n d s r e q u i r e d t o co m p lete th e t a s k u n d e r s t i m u l a t i o n by
n o i s e s v a ry in g i n t h e i r p a t t e r n s o f te m p o r a l o n s e t (mode
o f i n t e r r u p t i o n ) ,
The F t e s t r e l a t i v e t o v a r i a b l e B f a i l e d t o a t t a i n
a l e v e l o f s i g n i f i c a n c e s u f f i c i e n t f o r r e j e c t i o n o f th e
n u l l h y p o t h e s i s . T h e r e f o r e 9 i t was co n clu d ed t h a t , ju d g in g
from t h e d a t a o b ta in e d i n t h i s e x p e r im e n t, t h e r e was no
d i f f e r e n t i a l e f f e c t upon psychom otor p e rfo rm an c e a s s o c i a t e d
w ith e x p o s u re t o n o i s e s d i f f e r i n g i n t h e i r p a t t e r n s of
i n t e r r u p t i o n . I t sh o u ld be p o in te d o u t , h ow ever, t h a t t h e
te n d e n c y was f o r t h e p a t t e r n o f I r r e g u l a r i n t e r r u p t i o n t o
be a s s o c i a t e d w ith t h e g r e a t e s t d e crem e n t even th o u g h t h e
d i f f e r e n c e s were n o 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 . I t was
i n t e r e s t i n g t o n o t e t h a t a te n d e n c y a l s o e x i s t e d f o r th e
p re s e n c e o f c o n tin u o u s n o i s e t o be a s s o c i a t e d w ith a
g r e a t e r d e t e r i o r a t i o n i n p erfo rm an c e th a n t h a t o f th e
r e g u l a r l y i n t e r r u p t e d n o i s e .
81
H y p o th e s is 3 . T h ere i s no d i f f e r e n c e b etw een th e
mean num ber o f e r r o r s made o r betw een t h e mean num ber o f
s e c o n d s r e q u i r e d t o c o m p le te t h e t a s k u n d e r s t i m u l a t i o n by
n o i s e u n d e r two d i f f e r e n t modes o f t a s k p r e s e n t a t i o n ( s e l f -
p a c in g and e x t e r n a l p a c i n g ) •
The F t e s t p e r t a i n i n g t o v a r i a b l e C was s i g n i f i c a n t
beyond t h e ,0 5 l e v e l . S in c e t h i s p r o b a b i l i t y was s m a l l e r
t h a n t h e l e v e l o f s i g n i f i c a n c e p r e v i o u s l y c h o se n , t h e
d e c i s i o n was made t o r e j e c t t h e n u l l h y p o t h e s i s and t o
i n f e r t h a t d i f f e r e n t i a l e f f e c t s a r o s e i n c o n j u n c t i o n w ith
t h e two modes o f p a c in g upon t h e p sy c h o m o to r p e rf o r m a n c e .
An i n s p e c t i o n o f t h e d a t a i n T ab le IV r e v e a l e d t h a t t h e
e x t e r n a l p a c in g o f s u b j e c t s ' r e s p o n s e s was a s s o c i a t e d w ith
t h e l a r g e r d e c re m e n t i n p e rf o rm a n c e . I t was a l s o a p p a r e n t
t h a t v a r i a b i l i t y i n p e rfo rm a n c e was s l i g h t l y g r e a t e r u n d e r
t h e e x t e r n a l p a c in g c o n d i t i o n th a n u n d e r t h e s e l f - p a c i n g
o n e .
H y p o th e s is *fa T h e re i s no d i f f e r e n c e betw een t h e
mean num ber o f e r r o r s made o r b etw een t h e mean number o f
s e c o n d s r e q u i r e d t o co m p lete t h e t a s k u n d e r s t i m u l a t i o n
by t h e v a r i o u s c o m b in a tio n s o f t y p e s o f n o i s e , p a t t e r n of
i n t e r r u p t i o n , and mode o f t a s k p r e s e n t a t i o n .
None o f t h e i n t e r a c t i o n s b etw een th e d i f f e r e n t
v a r i a b l e s a t t a i n e d t h e chosen l e v e l o f s i g n i f i c a n c e a c c o r d
in g t o t h e F t e s t . T h e r e f o r e , i t was i n f e r r e d t h a t no
82
d i f f e r e n t i a l e f f e c t s upon psychom otor perform ance could be
a s s o c i a t e d w ith th e p a r t i c u l a r com bination of any two of
th e v a r i a b l e s ta k e n t o g e t h e r o r w ith a t h i r d v a r i a b l e .
A n a ly s is o f R e s u lts i n Terms of Time t o Complete th e Task
T ra n sfo rm a tio n of s c o r e s . An i n s p e c t i o n of th e
d i s t r i b u t i o n s and s ta n d a rd d e v ia ti o n s o f raw tim e sc o re s
f o r th e e ig h te e n tre a tm e n t groups i n d i c a t e d t h a t th e d i s
t r i b u t i o n s of th e sc o re s were non-norm al and t h a t t h e
v a r ia n c e s were q u i t e h e te ro g e n e o u s . Hence, th e raw s c o re s
were tra n sfo rm e d t o a l o g a r i th m i c s c a l e . The amount 10Q
was added to each raw d i f f e r e n c e sc o re and th e lo g a rith m
t o th e b a se 10 was d e term in ed f o r th e sum. An i n s p e c t i o n
o f th e d i s t r i b u t i o n s a f t e r t r a n s f o r m a ti o n of th e s c o re s
r e v e a le d t h a t th e y had been improved c o n s id e r a b ly i n terms
o f n o r m a lity . However, i t was a p p a re n t t h a t th e v a r ia n c e s
v/ere homogeneous o n ly w ith in each type o f t a s k p r e s e n t a
t i o n . In o th e r w ords, i n term s o f th e dim ension C, th e
v a r ia n c e s were homogeneous w i t h in th e c o n d itio n C-^ ( s e l f -
pacin g) and w i th in C2 ( e x t e r n a l pacing) but n o t w ith in the
C d im en sio n as a whole.
N e c e s s ity f o r Two S e p a ra te A nalyses o f V a ria n ce of Time
S c o res R e la ti v e to Mode o f P acing
I t was th e o r i g i n a l i n t e n t to a n a ly z e th e d a ta in
term s of tim e d i f f e r e n c e s c o re s a c c o rd in g to th e same
83
d e s ig n t h a t was employed w ith e r r o r s c o r e s . However, th e
f a c t t h a t th e v a ria n c e s of th e e ig h te e n t r e a tm e n t groups
could n o t be c o n sid e re d homogeneous p re c lu d e d th e use of
t h a t d e s ig n . Hence i t was d e cid ed to a n a ly z e th e d a ta
s e p a r a t e l y in term s of s e l f - p a c i n g (C^) and e x t e r n a l p acing
(C2) s i n c e th e d i s t r i b u t i o n s were n e a r l y norm al and th e
v a ria n c e s were r e l a t i v e l y homogeneous w i t h in th e s e two
gro u p s.
A d d i t io n a l ev id e n ce re g a r d in g th e f a c t t h a t th e
two s e t s of d a ta (c o rre sp o n d in g t o s e l f - and e x t e r n a l -
p acin g c o n d itio n s ) a ro s e from d i f f e r e n t p o p u la tio n s w ith
r e s p e c t to c e n t r a l ten dency v a lu e was f u r n i s h e d by a s i g
n i f i c a n c e t e s t d i s c lo s e d by Walsh and r e p o r te d i n S i e g e l
(i+2). T his t e s t r e q u i r e s o n ly t h a t th e e x p e rim e n te r assume
t h a t th e d i f f e r e n c e s c o re s he o b se rv es i n two r e l a t e d
sam ples a re drawn from sy m m etrical p o p u la tio n s*
The p la n of th e d e s ig n and the p a r t i t i o n i n g o f th e
t o t a l v a ria n c e i n t o i t s c o n s t i t u e n t v a r ia n c e s i s shown in
T able VI. The q u e s tio n s posed i n th e s ta te m e n t of th e
problem w i l l be used a s a p a t t e r n i n the a n a l y s i s o f
r e s u l t s i n each of th e two s e p a r a t e a n a ly s e s to f o llo w .
E v iden ce C oncerning th e T e n a b l l i t v o f th e S t a t i s t i c a l
H ypotheses Along w ith C o rresp o n d in g I n f e r e n c e s R egarding
t h e P l a u s i b i l i t y of R ese arch H ypotheses ( f o r S e lf- P a c in g )
D ata p e r t i n e n t t o th e answ ering of th e q u e s tio n s
8*+
TABLE VI
ANALYSIS OF TIME SCORES
V a ria n c e Components
Source df Sums of Squares
Between
S u b je c ts a n ~ l SSg
AB(b) a -1
SSAB(b)s SSG
e r r o r (b) a ( n - 1)
^ e r r o r ( b ) ” SSq-SS q
W ithin
S u b j e c t s a n ( a - l )
SSv;s” s s r ”s s s
A a -1 SSA
B a -1 SSB
AB(w) ( a - 1) ( a - 2)
SSAB(w)® SSAB"SSG
e rro r(w ) a ( a - 1) ( n - 1)
S^ e r r o r ( w ) " s ^wS”" ^ A ”
SSB-SSAB(W )
T o ta l a ^ n -1 s s T
8 5
posed a r e shown i n T ab les V II , V I I I , and IX. T able V II
c o n ta in s in f o r m a tio n r e l a t i v e t o th e mean d i f f e r e n c e
s c o r e s and th e v a ria n c e s of th e n in e t r e a tm e n t g ro u p s,
w h ile Table V I I I c o n ta in s th e mean tim e s c o re s f o r each
v a r i a b l e ta k e n a lo n e . Table IX c o n ta in s in f o r m a tio n con
c e rn in g t h e a n a l y s i s o f v a r ia n c e .
H y p o th e sis 1 . There i s no d i f f e r e n c e between the
mean number of e r r o r s made o r between th e mean number of
seconds r e q u ir e d t o com plete th e t a s k under s t i m u l a t i o n
by n o is e s v a ry in g i n t h e i r q u a l i t a t i v e a s p e c t s , i . e . , i n
fre q u e n c y .
The F t e s t r e l a t i v e to v a r i a b l e A was s i g n i f i c a n t
beyond t h e .05 l e v e l . Since t h i s p r o b a b i l i t y was s m a lle r
th a n th e l e v e l of s i g n i f i c a n c e chosen ( . 0 5) j the d e c i s i o n
was ta k e n t o r e j e c t th e n u l l h y p o th e s is and to i n f e r t h a t
v e ry p ro b a b ly genuine d i f f e r e n c e s e x is te d among th e e f f e c t s
f o r v a rio u s ty p e s o f n o i s e upon psychom eter perform ance.
An i n s p e c t i o n of th e d a t a shown i n Table V I I I r e v e a le d
t h a t th e l a r g e s t decrem ent i n perform ance was a s s o c i a t e d
w ith e x p o su re t o a pure s in e wave to n e o f 210 cps. White
n o is e ranked second as a d i s t r a c t o r w h ile a pure s in e wave
to ne of 3000 cp s. correspo nded to th e s m a ll e s t decrem ent
on psychom otor perform ance.
H y p o th e sis 2 . There i s no d i f f e r e n c e between th e
86
TABLE VII
MEAN TIME DIFFERENCE SCORES AND STANDARD DEVIATIONS
( S e lf -P a c in g [Cx ])
E x p erim en tal
T reatm ent
Group
Mean S ta n d ard
D e v ia tio n
A1B1
1,9727
0 00*+1
A1B2
1,9568 ,0056
A1B3
1,9623 .0057
A2B1
1.9357
0OO65
A2B2
1.9638 ,0028
A2B3
1,9606 .0063
A3B1
1,9526
.0055
A3B2
1,9550 .0069
3 3
1 a 98^+2 .0052
87
TABLE VIII
MEAN TIME SCORES FOR EACH VARIABLE ALOME
( S e lf -P a c in g )
E x p e rim e n ta l V a ria b le Mean
Type o f n o is e i r r e
s p e c t i v e o f mod© of
i n t e r r u p t i o n
A1
1*9639
a 2
1*953**
a 3
1.96*40
Mode o f i n t e r r u p t i o n
i r r e s p e c t i v e o f type
o f n o i s e
B1
1*9537
b 2
1.9586
1.9691
8 8
TABLE IX
ANALYSIS OF VARIANCE OF TIME DIFFERENCE SCORES
( S e lf -P a c in g )
S ource
1
df Sums o f Squares M S F
Betw een
S u b j e c t s 107 1.511^-
AB(b) 2 .0297
. 01*5-8
i . o 5
e r r o r ( b ) 105
.H-817 «01*4-1
V /ith in
S u b j e c t s 216 . 270*5-
A 2 .0081 .00*4-1 3 . 68*
B 2 .0133 .0067 6.05**
AB(w) .0009 .000*4-5
M
e r r o r ( w ) 210 . 2*f8l ,0011
T o t a l
323
1.7817
sff .
S i g n i f i c a n t a t th e p = .0 5 l e v e l
S i g n i f i c a n t a t t h e p = .0 1 l e v e l
89
mean number o f e r r o r s mad© o r betw een th e mean number of
second s r e q u i r e d to co m p lete t h e t a s k u nd er s t i m u l a t i o n by-
n o i s e s v a ry in g i n t h e i r p a t t e r n s o f te m p o ra l o n s e t (mode
o f i n t e r r u p t i o n ) .
S in c e th e F t e s t p e r t a i n i n g to v a r i a b l e B was s i g
n i f i c a n t beyond th e #01 l e v e l , th e n u l l h y p o t h e s is was
r e j e c t e d * T h e r e f o r e , i t was con cluded t h a t th e e f f e c t s on
psychom otor p e rfo rm an ce a s s o c i a t e d w ith ex p o su re t o n o i s e s
d i f f e r e i n g i n t h e i r p a t t e r n s o f i n t e r r u p t i o n were very
l i k e l y r e a l . An i n s p e c t i o n o f th e d a ta shown i n T able ¥111
i n d i c a t e d t h a t t h e c o n d i t i o n o f i r r e g u l a r i n t e r r u p t i o n of
th e n o i s e was a s s o c i a t e d w ith th e l a r g e s t decrem ent izi p e r
form ance w ith r e g u l a r i n t e r r u p t i o n and c o n tin u o u s n o is e
f o llo w in g i n t h a t o r d e r .
H y p o th e s is 8. T h e re i s no d i f f e r e n c e betw een th e
mean number o f e r r o r s made o r betw een th e mean number of
second s r e q u i r e d t o com plete th e t a s k u n d e r s t i m u l a t i o n by
n o i s e u n d er two d i f f e r e n t modes of t a s k p r e s e n t a t i o n ( s e l f
p a c in g and e x t e r n a l - p a c i n g ) .
I t has been p o in te d o u t t h a t t h e te c h n iq u e of
a n a l y s i s of v a r i a n c e could n o t be used I n a n a ly z in g th e
e f f e c t s upon psychom otor p e rfo rm an c e a s s o c i a t e d w ith the
two d i f f e r e n t ty p e s of t a s k p r e s e n t a t i o n . The a ssu m p tio n
o f hom ogeneity of v a r i a n c e was n o t met i n t h i s c a s e . How
e v e r , as was i n d i c a t e d p r e v i o u s l y , th e a p p l i c a t i o n of th e
90
Walsh t e s t serv ed t o r e j e c t th e n u l l h y p o t h e s is and t o
p e rm it th e i n f e r e n c e t h a t th e psychom otor p erform ance
r e f l e c t e d th e d i f f e r e n t i a l e f f e c t s of n o i s e under t h e two
c o n d it i o n s o f p a c in g .
H y p o th e sis *+. T here i s no d i f f e r e n c e betw een th e
mean number of e r r o r s made o r bet\*jeen th e mean number of
seconds r e q u i r e d to com plete th e t a s k u nder s t i m u l a t i o n
by th e v a r io u s co m b in atio n s of ty p e s o f n o i s e , p a t t e r n of
i n t e r r u p t i o n , and mode of t a s k p r e s e n t a t i o n .
The F t e s t s r e l a t i v e to th e i n t e r a c t i o n s among th e
in d e p e n d e n t v a r i a b l e s f a i l e d t o a t t a i n s i g n i f i c a n c e
a c c o rd in g to th e l e v e l choseru T h e r e f o r e , th e d e c i s i o n
was made t o a c c e p t th e n u l l h y p o t h e s is and t o conclude
t h a t t h e r e were no d i f f e r e n t i a l e f f e c t s upon psychom otor
p e rfo rm an c e u n d er t h e v a r io u s c o m b in atio n s o f c o n d it i o n s
o f ty p e s o f n o is e and p a t t e r n s o f i n t e r r u p t i o n .
E v iden ce C on cernin g th e T e n a b i l i t y o f t h e S t a t i s t i c a l
H y poth eses Along w ith C o rre sp o n d in g I n f e r e n c e s R egarding
th e P l a u s i b i l i t y o f R e se arch H ypoth eses ( f o r E x t e r n a l
P acing)
D ata p e r t i n e n t t o th e a c c e p ta n c e o r r e j e c t i o n o f
t h e n u l l h y p o th e s e s a s p r e s e n te d i n th e s ta te m e n t o f th e
problem a r e c o n ta in e d i n T a b le s X, X I, and X I I.
H y p o th e sis 1 . T here i s no d i f f e r e n c e betw een th e
91
TABLE X
MEM TIME DIFFERENCE SCORES AND STANDARD DEVIATIONS
E x t e r n a l P a c in g (C2)
E x p e rim e n ta l
T reatm en t
Group
Mean S ta n d a rd
D e v ia tio n
Ai Bi
2*0733
.0380
A1B2
1 . 9 ^ 1
„0l>00
A^B^
2.0276
.065^
A2B1.
1 .9897 .0 3 3 ^
a 2b 2 2.0002 .0303
A2B3
1 .952 2 .0357
A3B1
2.0212
.02*4-9
A3B2
2.0710
.0325
A-jB-.
3 3
2.1062 , 023*f
92
TABLE XI
MEAN TIME SCORES FOR EACH VARIABLE ALONE
E x te r n a l- P a c in g
E x p erim e n tal V a ria b le Mean
Type o f n o is e i r r e
s p e c t i v e of mode of
i n t e r r u p t i o n
A1
2.0150
A2
1.9807
a 3
2.0662
Mode o f i n t e r r u p t i o n
i r r e s p e c t i v e of type
of n o is e
Bi
2.0281
b 2
2.0051
b3
2.0287
93
TABLE X II
ANALYSIS OF VARIANCE OF TIME DIFFERENCE SCORES
E x te r n a l Pacing
Source d f Sums o f Squares M S F
Between
Subj e c ts 107 11.^563
AB(b) 2 . V2^6 .2123
e r r o r ( b )
105 11.0317 . I.05I
W ithin
S u b je c ts 216 1. 06^3
A 2 .3990
.1995
* **
7 1 .2 5
B 2 .0382 .0191 6 . 82**
AB(w) 2
.0237
,0118
k. 21*
e rro r(w ) 210
. 603^
.0028
T o ta l
323
12,5206
S i g n i f i c a n t a t th e p s .001 l e v e l
^ S i g n i f i c a n t a t th e p = .01 l e v e l
S i g n i f i c a n t a t th e p " .05 l e v e l
9 * +
mean number of e r r o r s made o r betw een th e mean number o f
seconds r e q u ir e d t o com plete th e t a s k under s t i m u l a t i o n by
n o i s e s v a ry in g i n t h e i r q u a l i t a t i v e a s p e c t s , i . e . , i n f r e
quency.
The F t e s t r e l a t i v e to v a r i a b l e A was s i g n i f i c a n t
beyond th e ,001 l e v e l . S in c e th e n u l l h y p o th e s is was
t h e r e f o r e u n te n a b le , i t was i n f e r r e d t h a t a genuine d i f f e r
e n t i a l e f f e c t of v a rio u s ty p e s of n o is e upon psychom otor
perform ance e x i s t e d . An i n s p e c t i o n of T able XI d i s c lo s e d
t h a t th e l a r g e s t decrem ent in perform ance corresp ond ed to
an ex p osure to a pure s in e v/ave o f 210 cp s. White n o is e
was ranked second and a pure s in e wave to ne o f 3000 cps.
was ranked t h i r d .
H y p o th esis 2 . T here i s no d i f f e r e n c e betw een th e
mean number of e r r o r s made o r betw een th e mean number of
seconds re q u ire d to com plete th e t a s k under s t i m u l a t i o n by
n o i s e s v a ry in g i n t h e i r p a t t e r n s of tem p o ral o n se t (mode
o f i n t e r r u p t i o n ) .
In t h i s case th e n u l l h y p o th e s is was re g a rd e d as
u n te n a b le s in c e th e l e v e l of s i g n i f i c a n c e reach ed i n th e
F t e s t was s m a lle r th a n ,0 1 . On t h i s b a s i s th e d e c i s i o n
was made t o i n f e r t h a t t h e r e were very l i k e l y r e a l d i f f e r
e n t i a l e f f e c t s on psyehom otor perform ance a s s o c i a t e d w ith
th e d i f f e r e n t p a t t e r n s o f n o i s e i n t e r r u p t i o n . An i n s p e c
t i o n o f T able XI re v e a le d t h a t an i r r e g u l a r p a t t e r n o f
95
i n t e r r u p t i o n , co n tin u o u s n o i s e , and r e g u l a r l y i n t e r r u p t e d
n o i s e corresp ond ed ■with th e l a r g e s t to s m a ll e s t decrem ent
i n perform ance i n t h a t o r d e r .
H y p o th esis 3 . S in c e t h i s item h as been d is c u s s e d
i n th e p re v io u s s e c t i o n , i t would be red u n d a n t t o in c lu d e
su c h a d i s c u s s i o n h e r e .
H y p o th e sis T here i s no d i f f e r e n c e between th e
mean number of e r r o r s made o r betw een th e mean number of
seconds r e q u ir e d t o com plete th e t a s k under s t i m u l a t i o n by
th e v a rio u s co m binations of ty p e s of n o i s e , p a t t e r n of
i n t e r r u p t i o n , and mode o f t a s k p r e s e n t a t i o n .
The F t e s t r e l a t i v e to th e i n t e r a c t i o n s among the
v a rio u s independent- v a r i a b l e s prov ided a b a s i s f o r r e j e c
t i o n of th e n u l l h y p o t h e s is . I t was, t h e r e f o r e , i n f e r r e d
t h a t very p ro b a b ly a r e a l d i f f e r e n t i a l e f f e c t e x i s t e d i n
term s of perform ance on a psychom otor t a s k under d i f f e r e n t
co m b in atio n s of ty p e of n o i s e and p a t t e r n of i n t e r r u p t i o n
of th e n o i s e . I n s p e c t i o n o f Table XI r e v e a le d t h a t th e
l a r g e s t decrem ent was a s s o c i a t e d w ith an i r r e g u l a r l y
i n t e r r u p t e d tone of 210 c p s. I t was a l s o e v id e n t t h a t
t h i s typ e o f n o i s e , when p re s e n te d c o n tin u o u s ly , c o r r e s
ponded w ith a s m a lle r decrem ent i n perform ance th a n w hite
n o is e p r e s e n te d c o n tin u o u s ly . On. th e o t h e r hand, a
3000 cp s, to n e p re s e n te d i n a r e g u l a r l y i n t e r r u p t e d
96
p a t t e r n was a s s o c i a t e d w i t h a g r e a t e r d ecrem e n t th a n r e g u
l a r l y i n t e r r u p t e d v/hite n o i s e . T his was a r e v e r s a l o f th e
r e l a t i v e p o s i t i o n s of t h e s e two ty p e s o f n o i s e u nder con
d i t i o n s o f c o n tin u o u s p r e s e n t a t i o n . The r e l a t i v e e f f e c t s
o f o t h e r c o m b in a tio n s o f th e v a rio u s in d e p e n d e n t v a r i a b l e s
a r e r e a d i l y o b se rv ed by r e f e r e n c e t o t h e d a ta shown i n
T a b le X i r .
DISCUSSION AND EVALUATION OF RESULTS
The d i s c u s s i o n o f r e s u l t s , as e x p la in e d e a r l i e r i n
t h i s r e p o r t , w i l l be made w i t h i n th e fram ew ork o f q u e s
t i o n s posed i n t h e s ta te m e n t of t h e pro b lem , These q u e s
t i o n s v / i l l be c o n s id e r e d i n th e o r d e r o f t h e i r a p p e a ra n c e
i n t h a t s e c t i o n .
1. To w hat e x te n t i s t h e p erfo rm an c e o f an
i n d i v i d u a l on a psychom otor t a s k r e l a t e d t o h i s e x p o su re
t o n o i s e s d i f f e r i n g i n t h e i r q u a l i t a t i v e a s p e c t s ?
An i n s p e c t i o n o f t h e t h r e e s e p a r a t e a n a l y s e s o f
r e s u l t s r e v e a l e d t h a t a l l t h r e e of them ( i n te rm s of
e r r o r s , tim e s c o r e s u n d e r s e l f - p a c i n g , and tim e s c o r e s
u n d e r e x t e r n a l p acing) were i n a c c o rd i n p r e s e n t i n g e v i
d e n c e t o show t h a t t h e r e were v e ry l i k e l y r e a l d i f f e r e n
t i a l e f f e c t s upon psyehom otor p e rfo rm an c e a s s o c i a t e d w ith
ex p o su re t o n o i s e s d i f f e r i n g i n t h e i r q u a l i t a t i v e a s p e c t s ,
i . e . , d i f f e r e n t ty p e s o f n o i s e . M oreover, a l l t h r e e
9 7
a n a ly s e s were i n agreem ent i n p o in tin g to a pure s in e wave
to n e of 210 cp s, as th e one a s s o c i a t e d w ith t h e g r e a t e r
decrem ent i n perform ance. On th e o th e r hand, r e s u l t s were
somewhat e q u iv o c a l i n th e c ase of th e o th e r two ty p e s of
n o i s e . According to th e a n a l y s i s of r e s u l t s i n term s of
e r r o r s c o r e s , broad band v/hite n o ise corresponded to th e
l e a s t decrem ent i n perform ance of th e t a s k w h ile a pure
s i n e wave to n e of 3000 cps, occupied an in te r m e d i a t e p o s i
t i o n , However, when th e d a ta were a n aly zed i n term s of
tim e t o com plete the t a s k , i n th e i n s t a n c e of b o th s e l f
pacing and e x t e r n a l pacing c o n d it i o n s , a pure s in e v/ave
to n e of 3000 cps, v/as a s s o c i a t e d w ith th e l e a s t decrem ent
i n p erform an ce.
I t i s i n t e r e s t i n g to n o te t h a t th e s e r e s u l t s
u n e q u iv o c a lly p o in t t o th e low er fre q u e n c y n o is e s as
th o s e r e l a t e d to a low er l e v e l of perfo rm an ce. Such a
r e s u l t i s somewhat c o n t r a d i c t o r y t o th e r e s u l t s re v e a le d
i n c e r t a i n o t h e r i n v e s t i g a t i o n s (10, 28) i n which a
g r e a t e r decrem ent i n perform ance v/as found t o correspon d
t o expo sure to th e h ig h freq u e n cy so un d s. On th e o th e r
han d , i t may be r e c a l l e d t h a t ev id e n ce p re s e n te d i n
a n o th e r stu d y (27) r e v e a le d t h a t h a n d w ritin g made under
t h e i n f lu e n c e of a to n e of low p i t c h (low freq u e n cy ) v/as
in c r e a s e d i n s i z e . The tend en cy f o r r e l a t i v e l y sm all
p r e c i s e movements, such as a r e u t i l i z e d i n h a n d w r itin g ,
98
t o s u f f e r i n term s o f p r e c i s i o n and p o s s i b l y i n c o o r d in a
t i o n may have m a n ife s te d i t s e l f i n th e m otor re s p o n s e s and
i n th e eye-hand c o o r d i n a t i o n t h a t were r e q u i r e d i n th e
p e rfo rm an ce of th e t a s k a s s ig n e d i n t h i s i n v e s t i g a t i o n *
T here i s a l s o th e p o s s i b i l i t y t h a t some e x t r a -
a u d i t o r y s e n s a t i o n may have been e x p e rie n c e d by th e su b
j e c t s i n t h i s stu d y upon t h e i r b e in g exposed t o th e low
fre q u e n c y to n e . D uring t h e course o f th e i n v e s t i g a t i o n ,
numerous s u b j e c t s b ro u g h t t o th e a t t e n t i o n o f th e e x p e r i
m e n te r t h e f a c t t h a t th e y f e l t some d is c o m f o r t upon b e in g
exposed t o th e 210 c p s , to n e . I t i s p o s s i b l e t h a t some
r e s o n a n t fre q u e n c y of one o r more o f th e components of
th e h e a r i n g mechanism was a t o r n e a r 210 c p s. In t h i s
c a s e , t h e p r e s e n t a t i o n o f th e 210 c p s, to n e a t an i n t e n
s i t y a s h ig h as 95 db, co uld v ery w e l l have caused extrem e
d i s c o m f o r t .
In any e v e n t , t h i s f i n d in g i s s u g g e s t i v e of some
p r a c t i c a l i m p l i c a t i o n s . I t a p p e a rs t h a t i t m ig h t be
p r o f i t a b l e to e x p lo re ways and means of r e d u c in g th e v e ry
low f re q u e n c y components o f th e a u d i t o r y environment® I t
would be even more p r o f i t a b l e to d i s c o v e r means whereby
th e low fre q u e n c y sounds co u ld be e l i m in a te d e n t i r e l y
p ro v id e d th e y a re n o t n e c e s s a r y i n a c c o m p lis h in g th e t a s k
a t hand ( i n t h i s c a se t h e y would n o t be c o n s id e re d as
n o is e ) b e ca u se i t h a s been found t h a t th e p r o c e s s of
99
a c h ie v in g a d e q u a te i n s u l a t i o n a g a i n s t low fre q u e n c y sounds
i s very d i f f i c u l t and e x p e n s iv e . D e sig n e rs of m achinery
and o t h e r ty p e s o f a p p a r a t u s m ight w e l l p u t t h i s knowledge
t o good use i n t h e i r e f f o r t s to f u r n i s h o p e r a t in g p e rs o n
n e l w ith equipm ent th e o p e r a t in g c h a r a c t e r i s t i c s of which
a r e conducive to o p tim a l perform ance o f t h e t a s k .
2, To what e x te n t i s th e p e rfo rm an c e of an i n d i v i d
u a l on a psychom otor t a s k r e l a t e d t o h i s ex p o su re t o
n o i s e s d i f f e r i n g i n t h e i r te m p o ra l p a t t e r n o f i n t e r r u p
t i o n ?
The t h r e e a n a ly s e s ( i . e . , i n term s of e r r o r s , tim e
r e q u i r e d f o r c o m p letio n o f th e t a s k u n d e r s e l f - p a c i n g , and
tim e f o r c o m p letio n o f th e t a s k u n d e r e x t e r n a l p acin g ) a l l
p o in te d t o i r r e g u l a r l y i n t e r r u p t e d n o i s e as th e c o n d it i o n
c o rre s p o n d in g t o t h e g r e a t e s t d e t e r i o r a t i o n i n p e rfo rm
a n c e . I t must be m e n tio n e d , how ever, t h a t i n th e i n s t a n c e
o f th e a n a l y s i s i n term s o f e r r o r s c o r e s , th e d i f f e r e n t i a l
e f f e c t s d id n o t a t t a 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 . Yet th e
e v id e n c e d id show a te n d e n c y f o r I r r e g u l a r n o i s e t o be
a s s o c i a t e d w ith th e l a r g e s t decrem ent i n p e rfo rm an c e .
E q u i v o c a l i t y was a l s o e v id e n t i n t h i s d im e n sio n ( p a t t e r n
o f n o is e i n t e r r u p t i o n ) . Under s e l f - p a c i n g c o n d itio n s
c o n tin u o u s n o is e was a s s o c i a t e d w ith th e l e a s t decrem ent
w h ile u n d e r th e c o n d it i o n o f e x t e r n a l p a c in g r e g u l a r l y
i n t e r r u p t e d n o is e o ccu p ied th e c o rre s p o n d in g p o s i t i o n .
100
Even though th e d i f f e r e n t i a l e f f e c t o f d i f f e r e n t p a t t e r n s
o f n o ise i n t e r r u p t i o n was n o 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
i n th e a n a l y s i s r e l a t i v e to e r r o r s c o r e s , th e ten d en cy
e x h ib i t e d by th e d i f f e r e n t p a t t e r n s was i n acco rd w ith th e
i n f e r e n c e s a r r i v e d a t i n th e case of e x t e r n a l pacing con
d i t i o n .
There seems to be no q u e s tio n b ut t h a t th e b u lk of
th e e v id e n c e produced by t h i s stu d y was w holly i n accord
w ith t h a t o f e a r l i e r i n v e s t i g a t i o n s of th e e f f e c t s of
n o i s e i n t e r r u p t i o n i n i n d i c a t i n g t h a t i r r e g u l a r l y i n t e r
ru p te d n o is e as compared w ith r e g u l a r l y i n t e r r u p t e d n o i s e
and c o n tin u o u s ly p r e s e n te d n o is e was a s s o c i a t e d w ith th e
g r e a t e s t decrem ent i n psychom otor p erfo rm an ce. F in d in g s
such as th e s e could p o s s ib l y have been due to t h e phenom
enon o f a d a p t a t i o n e x e r t in g i t s i n f lu e n c e on th e e f f e c t s .
I t I s re a s o n a b le to suppose t h a t a sound t h a t i s p re s e n te d
a c c o rd in g t o a r e g u l a r p a t t e r n o f i n t e r r u p t i o n would be
more r e a d i l y adapted to th a n one i n which th e p a t t e r n was
o f such a n a tu r e t h a t i t s o n s e t and d is a p p e a ra n c e v/as
more o r l e s s u n p r e d i c ta b l e .
These f i n d in g s p o in t t o p r a c t i c a l im p l i c a ti o n s
s i m i l a r to th o s e m entioned i n re g a rd to th e e f f e c t s of
n o i s e s d i f f e r i n g I n t h e i r q u a l i t a t i v e a s p e c t s . Human
e n g in e e r s and o th e r d e s i g n e r s , armed w ith knowledge of
th e d i f f e r e n t i a l e f f e c t s o f p a t t e r n s of n o is e i n t e r r u p t i o n
1 01
upon psychom otor p e rfo rm an c e , can ta k e s t e p s to e f f e c t th e
p r o d u c tio n of equipm ent, th e n o i s e c h a r a c t e r i s t i c s o f
which a r e n o t o f a d i s c o n tin u o u s n a t u r e . S u p e rv is o r y p e r
s o n n e l, c o g n iz a n t o f t h e s e e f f e c t s , may have an o p p o rtu n
i t y t o a l t e r th e w orking environm ent o r to change i t s
l o c a t i o n a l t o g e t h e r i n o r d e r t o a c h ie v e and m a in ta in o p t i
m al e f f i c i e n c y on th e p a r t o f t h e i r o p e r a t in g p e rs o n n e l,
3 . To what e x te n t i s th e perfo rm an ce of an i n d i v i d
u a l on a psyehom otor t a s k r e l a t e d t o h i s ex posu re t o v a r i
ous k in d s o f n o is e (embodying b o th th e n a t u r e o f n o i s e i n
term s of i t s fre q u e n c y and t h e p a t t e r n o f i n t e r r u p t i o n )
u n d e r two d i f f e r e n t modes o f t a s k p r e s e n t a t i o n r e l a t i v e to
th e r e q u i r e d r a t e of r e s p o n s e s as d e te rm in e d by th e s u b
j e c t h im s e lf o r as s e t by th e e x p e rim e n te r?
S t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s w ere e v id e n t
r e l a t i v e t o t h e e f f e c t o f n o is e upon psyehom otor p e rfo rm
a n c e u n d e r th e two d i f f e r e n t ty p e s of r e s p o n s e p a c in g .
Such d i f f e r e n t i a l e f f e c t s were d e m o n s tra te d b o th i n term s
o f e r r o r s made and i n term s o f t o t a l tim e r e q u ir e d t o
com plete th e t a s k . A ccording t o b o th o f t h e s e c r i t e r i o n
m easures th e g r e a t e r d ecrem ent i n perfo rm an ce c o rre sp o n d e d
t o th e c o n d it i o n o f e x t e r n a l p a c in g .
I t v/as a l s o e v id e n t t h a t th e v a r i a b i l i t y of
r e s p o n s e s ten d ed to be g r e a t e r u nder th e c o n d it i o n of
e x t e r n a l p acin g as compared t o s e l f - p a c i n g . However, th e
v a r i a b i l i t i e s were deemed to be d e s c r i p t i v e of two
102
d i f f e r e n t p o p u la tio n s o nly i n th e a n a l y s i s of tim e s c o r e s .
I t i s re a s o n a b le to assume t h a t t h e h ig h e r th e
l e v e l of d i f f i c u l t y of a g iv en t a s k (as r e f l e c t e d by th e
e x is te n c e o f a c o n d itio n of e x t e r n a l p acin g as compared
w ith one o f s e l f - p a c i n g ) th e h ig h e r th e l e v e l of s t r e s s
p lac ed upon th e s u b j e c t . I t i s l i k e l y t h a t th e f a c t o r of
m o tiv a tio n d e te rm in e s , t o a g r e a t d e g re e , th e b e h a v io r of
th e s u b j e c t under v a rio u s k in d s of en v iro n m en ta l or t a s k
c o n d it i o n s . I t i s p o s s ib l e t h a t , i n some c a s e s , th e l e v e l
o f m o tiv a tio n may become so g r e a t as t o cause a d i s r u p t i o n
o f perform ance thro u g h a n x i e t i e s c re a te d by th e s i t u a t i o n .
E x c e ssiv e a n x ie ty can, i n t h i s way, a c t a s an added d i s
t r a c t i o n o r may even cause th e s u b je c t t o giv e up o r to
le a v e th e f i e l d p s y c h o lo g ic a lly . On th e o t h e r han d, some
s u b j e c t s may improve t h e i r perform ance becau se of in c r e a s e d
m o ti v a ti o n . Thus i n d i v i d u a l d i f f e r e n c e s i n th e kind and
l e v e l of m o tiv a tio n can o p e ra te t o i n c r e a s e th e v a r i a b i l i t y
of th e group.
An e f f o r t v/as made n o t to c r e a te any i n i t i a l b ia s e s
o r s e t s w i t h in th e i n d i v i d u a l s u b j e c t s a t th e b e g in n in g of
th e e x p erim e n t, Even though t h i s method was more o r l e s s
s u c c e s s f u l , t h e r e rem ained no way of c o n t r o l l i n g th e
a t t i t u d e s o r l e v e l s of m o tiv a tio n of th e i n d i v i d u a l sub
j e c t d u rin g h i s perform ance of th e ta s k e i t h e r w ith
r e s p e c t t o th e t a s k or i n re g a rd t o th e n o i s e . Of c o u rs e ,
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t h e l e v e l o f d i f f i c u l t y of th e t a s k i t s e l f remained con-
s t a n t und er th e c o n d itio n s o f both q u i e t and n o is e . There
i s s t i l l th e p o s s i b i l i t y , however, t h a t th e s t r e s s added
by th e n o i s e c o n d itio n may have had a d i f f e r e n t i a l e f f e c t
upon th e kind and l e v e l of m o tiv a tio n p r e s e n t under th e
two t a s k c o n d it i o n s . E f f e c t s of changes i n m o tiv a tio n
p o s s ib ly could have produced the d i f f e r e n c e i n c e n t r a l
ten d e n cy a s w e ll as i n v a r i a b i l i t y betw een th e two c o n d i
t i o n s o f re sp o n se p a cin g .
To what e x te n t i s the perform ance o f an i n d i
v id u a l on a psyehomotor t a s k r e l a t e d t o h i s exposure t o
n o i s e i n term s of th e v a rio u s com binations o f ty p e of
n o i s e , p a t t e r n of tem p o ral o n se t of th e n o i s e , and pacing
o f h i s re s p o n se s t o th e ta s k ?
A p p aren tly under th e c o n d itio n of e x t e r n a l p acing
t h e r e was a d i f f e r e n t i a l re s p o n s e , i n term s of tim e
r e q u ir e d to complete th e t a s k , to th e d i f f e r e n t modes o f
i n t e r r u p t i o n of th e n o i s e . On th e o th e r h an d, t h i s
d i f f e r e n t i a l e f f e c t d id n o t re v e a l i t s e l f i n th e amount
o f tim e t o com plete th e t a s k when th e i n d i v i d u a l governed
h i s r a t e o f re s p o n se . N e ith e r d id th e e f f e c t o p e ra te t o
a s i g n i f i c a n t d eg ree in term s of th e e r r o r s made by the
i n d i v i d u a l i n c a r r y in g o u t th e a ssig n e d t a s k .
The e v id e n c e , viewed as a w hole, was somewhat
e q u iv o c a l. However, t h e r e was a s u g g e s tio n t h a t the
e f f e c t s of v a rio u s co m b inatio ns o f ty p es o f n o is e "with
v a rio u s p a t t e r n s of i n t e r r u p t i o n of th e n o i s e did n o t
o p e r a te d i f f e r e n t i a l l y t o any g r e a t d e g re e upon th e per
form ance of th e s u b j e c t s in v o lv e d in t h i s stu d y .
CHAPTER V I
SUMMARY AND CONCLUSIONS
SUMMARY
I t was th e pu rp o se o f t h i s i n v e s t i g a t i o n t o a s c e r -
t a i n f o r a sample o f 108 male s t u d e n t s a t th e U n i v e r s i t y
o f S o u th e rn C a l i f o r n i a th e r e l a t i v e i n f l u e n c e of d i f f e r e n t
ty p o s o f sound ( n o is e ) and of d i f f e r e n t p a t t e r n s of i n t e r
r u p t i o n o f th e sound ( n o is e ) upon t h e p erform ance o f a
psyehom otor t a s k when th e t a s k i t s e l f was v a r ie d w ith
r e s p e c t to w h e th er th e s u b j e c t o r th e e x p e rim e n te r d e t e r -
mined th e r a t e o f th e r e q u i r e d r e a c t i o n s . In th e co u rse
o f i n q u i r i n g i n t o th e I n f l u e n c e o f each o f t h e s e main
v a r i a b l e s ta k e n a l o n e , i t was in te n d e d to i n v e s t i g a t e th e
p o s s i b l e i n f l u e n c e o f j o i n t e f f e c t s o f ty p e o f sound
( n o i s e ) and p a t t e r n o f i n t e r r u p t i o n a lo n g w ith re s p o n se
p a c in g ( i . e . , r e q u i r e d r a t e o f re s p o n se ) upon psyehom otor
p e rfo rrn a n ce .
The problem may be c l a r i f i e d i n term s o f th e
f o llo w in g q u e s t i o n s ;
1. To what e x t e n t i s th e p erform ance o f an
i n d i v i d u a l on a psyehom otor t a s k r e l a t e d t o h i s expo sure
1 0 6
t o n o i s e s d i f f e r i n g i n t h e i r q u a l i t a t i v e a s p e c ts ?
2. To what e x te n t i s th e p erform ance of an
i n d i v i d u a l on a psyehom otor t a s k r e l a t e d to h i s exposure
t o n o is e s d i f f e r i n g i n t h e i r te m p o ra l p a t t e r n s o f i n t e r
r u p tio n ?
3. To what e x te n t i s th e perform ance of an
i n d i v i d u a l on a psyehom otor t a s k r e l a t e d t o h i s exposure
t o v a r io u s k in d s o f n o is e (embodying b o th th e n a tu r e of
n o i s e i n term s o f i t s fre q u e n c y and th e p a t t e r n of i n t e r
r u p t io n ) under two d i f f e r e n t modes o f t a s k p r e s e n t a t i o n
r e l a t i v e to th e r e q u ir e d r a t e o f re s p o n s e as d e term in ed
by th e s u b j e c t h im s e lf ( s e l f - p a c i n g ) o r as s e t by t h e
e x p e r im e n te r ( e x t e r n a l - p a c i n g ) ?
To what e x te n t i s th e perform ance of an
i n d i v i d u a l on a psyehom otor t a s k r e l a t e d to h i s exposure
t o n o i s e i n term s of th e v a rio u s c o m b in atio n s o f ty p e of
n o i s e , p a t t e r n o f te m p o ra l o n se t of th e n o i s e , and p acing
o f h i s re s p o n se s to th e ta s k ?
In o rd e r t o a s c e r t a i n th e e f f e c t s upon psyehom otor
perfo rm an ce a s s o c i a t e d w ith exp osu re t o n o i s e under th e
a fo re m e n tio n e d e n v iro n m e n ta l and t a s k c o n d i t i o n s , a
l a b o r a t o r y stu d y was d e sig n e d and e x e c u te d . S u b je c ts
were r e q u i r e d to a cco m p lish an a s s ig n e d t a s k d u rin g which
th e in d e p e n d e n t v a r i a b l e s ( i . e . , ty p e o f n o i s e , mode of
i n t e r r u p t i o n , and ty p e o f t a s k p r e s e n t a t i o n ) were m anipu
l a t e d by th e e x p e r im e n te r as f o llo w s :
107
1. The sounds p r e s e n t e d v a r i e d i n t h a t p h y s i c a l
d im e n sio n known as f r e q u e n c y , A p u re s i n e wave to n e of
210 c p s, and a p ure s i n e v/ave to n e o f 3000 c p s, a lo n g
w ith b ro a d -h a n d w h ite n o i s e w ere p r e s e n t e d .
2. The p a t t e r n o f i n t e r r u p t i o n o f each ty p e o f
sound was v a r i e d so t h a t t h e s u b j e c t r e c e i v e d i t i n con
t in u o u s form., a t a r e g u l a r l y i n t e r r u p t e d r a t e , and a t a n
I r r e g u l a r l y i n t e r r u p t e d r a t e ,
3* The t a s k p r e s e n t e d to t h e s u b j e c t was v a r i e d
su ch t h a t u n d e r one mode o f p r e s e n t a t i o n th e i n d i v i d u a l
p ro ceed ed to make r e s p o n s e s a t a r a t e d e te rm in e d s o l e l y
by h i s ov/n c o r r e c t r e s p o n s e s w h ile u n d e r th e o t h e r con
f i g u r a t i o n h e was d i r e c t e d t o resp o n d a t a r a t e d e t e r
mined by t h e e x p e r im e n te r .
P erfo rm a n ce on th e t a s k a s s ig n e d c o n s t i t u t e d th e
d e p e n d e n t v a r i a b l e . The psyehom otor t a s k a s s ig n e d r e q u ire d
th e s u b j e c t t o i n s e r t a s t y l u s i n t o one o f a number o f
h o l e s as th e y moved p a s t a n a rro w s l o t i n th e c a b i n e t
w hich c o n ta in e d th e a p p a r a t u s . The h o l e s , each o f w hich
c o u ld be i d e n t i f i e d by a s u r r o u n d in g sym bol, were l o c a t e d
on t h e s u r f a c e o f a drum which r e v o lv e d c o n ti n u o u s l y d u r
in g t h e p ro c e d u r e . The d e p en d e n t v a r i a b l e v/as q u a n t i f i e d
b o th by r e c o r d i n g th e number o f e r r o r s made and th e t o t a l
tim e i n se c o n d s r e q u i r e d t o co m plete th e t a s k .
The v a r io u s t r e a t m e n t c o m b in a tio n s o f ty p e s of
l o 8
sound and p a t t e r n s of I n t e r r u p t i o n were p r e s e n te d t o th e
s u b j e c t s a t a c o n s t a n t sound p r e s s u r e l e v e l o f 95 d b . r e .
.0002 dynes p e r sq u a re c e n t im e te r th ro u g h th e use o f a
W ollensak ta p e r e c o r d e r and T e le p h o n ic TDH-39 h ead pho nes.
S in ce t h i s i n v e s t i g a t i o n was n o t concerned w ith any
com parisons betw een p erform ance c a r r i e d o u t i n th e p resence
o f n o is e and t h a t accom plished u nder c o n d it i o n s o f q u i e t s
i t was p o s s i b l e t o conduct th e e x p erim e n t w ith o u t th e u se
o f a c o n tr o l g ro u p . The 108 s u b j e c t s w ere random ly
a s s ig n e d to t h r e e groups each of which c a r r i e d out th e
t a s k under t h r e e d i f f e r e n t treatm ent- c o m b in atio n s o u t of
n i n e p o s s ib le t r e a tm e n t c o m b in atio n s a r i s i n g from t h r e e
ty p e s o f n o is e and t h r e e p a t t e r n s of i n t e r r u p t i o n such
t h a t no group was exposed to t h e same c o m b in atio n a s any
o t h e r group. A ll s u b j e c t s perform ed th e t a s k u n d er s e l f -
p a c in g and e x t e r n a l p acin g c o n d i t i o n s . Each s u b j e c t a l s o
e x e c u te d th e t a s k u n d er q u i e t c o n d it i o n s u n d e r b o th s e l f -
p a c in g and e x t e r n a l p a cin g of r e s p o n s e s . D if f e r e n c e
s c o r e s were t h e n o b ta in e d by s u b t r a c t i n g th e s c o r e s
y i e l d e d under q u i e t c o n d itio n s from each o f th e s i x s c o r e s
y ie ld e d under t h e v a r io u s c o n d itio n s of n o i s e .
The te c h n iq u e o f a n a l y s i s of v a r i a n c e was u t i l i z e d
i n exam ining th e d a ta a f t e r s c o r e s had b een tra n s fo rm e d
i n t o a l o g a r i t h m i c s c a l e i n o r d e r t o im prove t h e i r c h a r a c
t e r i s t i c s r e l a t i v e to n o r m a l it y o f d i s t r i b u t i o n and
109
hom ogeneity o f v a r ia n c e . T hree s e p a r a te a n a ly s e s o f d a ta
were perform ed; (1) in term s of e r r o r s made, (2) i n terms
o f tim e r e q u i r e d f o r com p letio n of th e t a s k under s e l f
p a c in g , and (3) i n term s o f tim e r e q u ire d f o r com pletion
o f th e t a s k under e x t e r n a l p acin g of r e s p o n s e s . The two
s e p a r a t e a n a ly s e s r e l a t i v e to tim e d i f f e r e n c e s c o re s were
n e c e s s a r y because o f f a i l u r e of th e d a ta ( c o n s id e r in g
s e l f - p a c i n g and e x t e r n a l p a cin g to g e th e r ) to meet th e
assu m p tio n s of th e te c h n iq u e of a n a l y s i s o f v a r i a n c e ,
a lth o u g h th e d a ta under each o f th e d i f f e r e n t t a s k c o n d i
t i o n s a d e q u a te ly f u l f i l l e d t h e re q u ire m e n ts .
CONCLUSIONS
1. There a re very l i k e l y g enuine d i f f e r e n t i a l
e f f e c t s upon psyehom otor perform ance a s s o c i a t e d w ith expo
s u r e to n o i s e s d i f f e r i n g i n t h e i r q u a l i t a t i v e a s p e c t s ,
i . e . , ty p e s of n o i s e . E v id e n ce i s u n e q u iv o c a l I n p o in tin g
t o a tone o f 210 cps. as b e in g a s s o c i a t e d w ith a g r e a t e r
decrem ent i n perform ance th a n e i t h e r w h ite n o is e o r a
3000 cps® to n e . T here i s some q u e s tio n co n ce rn in g th e
r e l a t i v e e f f e c t s of w hite n o i s e and. th e 3000 cps. to n e .
I t a p p e a rs t h a t a to n e of 3000 cps. i s a s s o c i a t e d w ith a
g r e a t e r number of e r r o r s w h ile w hite n o is e c o rre sp o n d s to
a lo n g e r p e rio d of tim e r e q u ir e d to com plete th e t a s k .
2. I t a p p e a rs t h a t , i n term s o f tim e to complete
110
th e t a s k , an i r r e g u l a r l y i n t e r r u p t e d n o i s e compared w ith a
r e g u l a r l y i n t e r r u p t e d or c o n tin u o u s ly p re s e n te d n o is e
corresp o n d s t o th e g r e a t e s t decrem ent in perform ance under
both s e l f - p a c i n g and e x t e r n a l pacin g . Under s e l f - p a c i n g of
re s p o n se s a r e g u l a r mode of i n t e r r u p t i o n i s a s s o c i a t e d w ith
a g r e a t e r decrem ent th a n continuous n o is e w hile under
e x t e r n a l p acing c o n d itio n s th e two p a t t e r n s of i n t e r r u p
t i o n a re r e v e rs e d r e l a t i v e t o t h e i r a s s o c i a t i o n w ith th e
l a r g e r decrement* The d i f f e r e n t i a l e f f e c t s between the
v a rie d p a t t e r n s of i n t e r r u p t i o n in term s of e r r o r s made
a re n o t of s u f f i c i e n t m agnitude to be c o n sid ere d s i g n i f i
c an t .
3* I t was d em o n stra te d t h a t v ery p robably r e a l
d i f f e r e n t i a l e f f e c t s of exposure to n o is e d i f f e r i n g in
fre q u e n c y and i n p a t t e r n of i n t e r r u p t i o n upon psyehom otor
perform ance e x i s t under s e l f - p a c i n g and e x t e r n a l p acin g o f
resp onses* E x te r n a l pacing of re sp o n se s co rresp o n d s to
th e g r e a t e r decrem ent i n term s of e r r o r s as w ell a s i n
tim e re q u ir e d t o com plete th e t a s k . I t i s a l s o l i k e l y
t h a t , e s p e c i a l l y in th e case of tim e r e q u i r e d , a g r e a t e r
v a r i a b i l i t y I s a s s o c i a t e d w ith th e c o n d itio n of e x t e r n a l
pacing*
lf, I t does n o t a p p e a r t h a t t h e r e a r e im p o rta n t
d i f f e r e n t i a l e f f e c t s upon perform ance r e l a t i v e to exposure
t o th e v a rio u s com bination s of ty p e of n o i s e , p a t t e r n of
I l l
n o i s e i n t e r r u p t i o n , and th e p acing of respon ses* There i s
th e s u g g e s tio n , however, t h a t such e f f e c t s may be encoun
te r e d under e x t e r n a l pacing o f re sp o n se s when th e c r i t e r i o n
i s th e amount of time r e q u ir e d to com plete th e t a s k ,
IMPLICATIONS
An i n t e g r a t e d and com prehensive t h e o r e t i c a l p i c t u r e
co n cernin g th e e f f e c t s of n o is e upon psyehomotor* p erfo rm
ance should ta k e i n t o c o n s i d e r a ti o n th e e f f e c t s of d i f f e r
e n t k in d s and amounts of n o i s e , the f in d in g o f im pairm ent
as w e ll as improvement i n p erfo rm ance, and above a l l , th e
o m nipresent problem of i n d i v i d u a l d if f e r e n c e s *
The a b i l i t y to p r e d i c t which peo p le w i l l be e f f e c t e d
by exposure to n o is e as w e ll as th e e x te n t and d i r e c t i o n
of th e e f f e c t s of such exposure could be a most u s e f u l t o o l
i n s c re e n in g p e rs o n n e l f o r d u ty in both m i l i t a r y and
c i v i l i a n p u rs u its *
I t is th e e x p lo r a ti o n of th e s e f a c e t s of b e h a v io r
t h a t w i l l a id in moving th e working environm ent from an
a re a c h a r a c t e r i z e d by chance and s p e c u l a t i o n to one In
which i n t e l l i g e n t p r e - p la n n in g and c o n s t r u c t i v e change i s
th e o r d e r of th e day.
B I B L I O G R A P H Y
BIBLIOGRAPHY
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i n g , and a f t e r a p e rio d of n o i s e s t i m u l a t i o n .
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I k . D a v is, R. C. R esponse to 'm e a n i n g f u l' and ’ m ea n in g
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e n erg y e x p e n d i tu r e d u r in g a d a p t a t i o n to ’d i s t r a c
t i n g ’ s t i m u l i . Amer. J . of P s y c h o l . , 1 9 3 9 , 2 ,
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and E d u c a ti o n . New York: M cGraw-Hill Book
Company, I n c , , 1956.
20. Harmon, F, L. E f f e c t s of n o i s e upon c e r t a i n p sycho
l o g i c a l and p h y s i o l o g i c a l p r o c e s s e s . A rch,
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25* L a i r d , D. A. The m easurem ent o f th e e f f e c t s o f n o i s e
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1927, 2 , >*31.
26. L a i r d , D. A. E x p erim e n ts o f th e p s y c h o l o g i c a l c o s t
of n o i s e . J . N a t, Ind. P s y c h o l . , 1929? 251“
253.
27. L a i r d , D. A. E f f e c t s of n o i s e . J . A c o u st. Soc. Amer.,
1930, 1, 256 -262.
23, L a i r d , D. A. The i n f l u e n c e o f n o is e on p r o d u c tio n
and f a t i g u e , as r e l a t e d t o p i t c h , s e n s a t i o n
l e v e l , and s t e a d i n e s s o f n o i s e , J , A pnl.
P s y c h o l , , 1933? ! Z j 1 58-163.
29® L a i r d , D. A. and K. Coye. P s y c h o l o g i c a l m ea su re s o f
annoyance as r e l a t e d t o p i t c h and l o u d n e s s .
J . A c o u st. Soc. Amer., 1929, 1 , 1 58-162.
30. L i n d a h l , R. N o ise I n I n d u s t r y . I n d u s t r i a l M e d ic in e ,
1938, Zs 66I+-669.
31. L i n d q u i s t , E. F. D e sig n and A n a l y s i s o f E x p e rim e n ts
i n P sy c h o lo g y and E d u c a t i o n . San F r a n c i s c o :
Ho ughton-M i f f 1i n , 19 53 •
32. L u c k ie s h , M. V i s u a l e f f i c i e n c y i n q u i e t and n o i s y
w o rk p la c e s . E l e c t . W orld, 1931, Z8 , 1 +72-l+73•
33. McCord, C. P . , E. E. T e a l, and W. N. W ith e r id g e .
Noise and i t s e f f e c t on human b e in g s . J . o f Am.
Med. A s s . , 19 38. 110, 1553®
31 *. M i l l e r , G, A. The m asking o f s p e e c h . P s y c h o l, B u l l . .
19^7, M±, 1Q5 ®
35. M organ, J . J 9 B. The overcom ing o f d i s t r a c t i o n and
o t h e r r e s i s t a n c e s . A rch, P s y c h o l . , 1916, No, 35®
36. O b a ta , J . , S. M o r i t a , K. H i r o s e , and H. M atsum oto,
The e f f e c t s o f n o i s e on human e f f i c i e n c y .
J . A co u st. Soc, A m er,, 1930, £ , 1.
37* P e n n o c k , G. A. I n d u s t r i a l r e s e a r c h a t H aw th o rn e.
P e r s o n n e l J , , 1 9 3 1 *, 13., 3) +~38,
38, P o l l a c k , I . C o m fo rta b le l i s t e n i n g l e v e l s f o r pure
to n e s i n q u i e t and n o i s e , J . A c o u st. S o c . A m er.,
1952, 2 ^ , 2.
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39 . P o l l a c k , K. G ., and F* C. B a r t l e t t . Two s t u d i e s I n
p s y c h o l o g ic a l e f f e c t s o f n o ise * P a r t 1.
P s y c h o l o g i c a l e x p e rim e n ts on th e e f f e c t s of
n o i s e . R e p t. I n d u s t r . H e a lth R es. B d ., London,
1932, R e p t. Ho, 65.
5-0. R e e se , T. W., and K. D. K r y te r , The r e l a t i v e annoy
ance produced by v a r io u s bands o f n o i s e . Psycho-
A c o u s tic s L a b ., H arvard U n iv .. Mar. 17, 1955- =
P . B. No„ 27306.
5-1. Ryan, T. A ., C, L. C o t t r e l l , and M. E, B itte r m a n .
M uscu lar t e n s i o n a s an in d e x o f e f f o r t : th e
e f f e c t o f g l a r e and o t h e r d i s t u r b a n c e s on v i s u a l
work. Am, J . o f P s y c h o l . , 1950 , 63., 3-17®
5-2, S i e g e l , S id n e y . N o n p a ra m e tric S t a t i s t i c s f o r th e
B e b a v io r a l S c i e n c e s . New York: M cGraw-Hill
Book Company, I n c . , 1956.
*+3. S m ith , K. R. I n t e r m i t t e n t lo ud n o i s e and m e n ta l
perform ance* S c ie n c e , 195-1, 115-, 132.
5-5-. S te v e n s , S. S, The e f f e c t s o f n o i s e and v i b r a t i o n
on p sy c h o -m o to r e f f i c i e n c y . P s y c h o - a c o u s ti c
L a b ., H arvard U n iv ., Mar. 3-1 j 195-1. OSRD R e p t.
No. 32.
55. S t e v e n s , S. S . , e t a l * P a r t 1. The e f f e c t s o f n o i s e
on p sy c h o -m o to r e f f i c i e n c y . P a r t 2. N o ise
r e d u c t i o n i n a i r c r a f t as r e l a t e d t o communica
t i o n , an n o y an c e, and a u r a l i n j u r y , H arvard
U niv. P s y c h o l o g i c a l L a b o r a to r y , OSRD R e p t. 275-,
Dec* 1 , 195-1.
5-6, 'Weston, H. C. and S. Adams. The p e rfo rm an c e of
w eavers u n d er v a r y in g c o n d i t i o n s of n o i s e ,
B r i t . M. R e s e a rc h Bd. R e p t, 70. H is M a je sty * s
S t a t i o n e r y O f f i c e , London, 1935-
5-7. W eston, H. C. and S . Adams. The e f f e c t s o f n o is e on
t h e p erfo rm an ce o f w eav e rs, I n d u s t r . H e a lth
Res* B d ., 1932, Rept* 6 5.
A P P E N D IX
APPENDIX
INSTRUCTIONS TO THE SUBJECT
"You w i l l n o t i c e t h a t on th e f r o n t p an el of the
a p p a r a tu s t h e r e i s a lo n g , narrow s l o t . V i s i b l e j u s t
behind t h i s s l o t i s th e s u r f a c e of a drum upon which
a p p e a r numerous symbols w ith sm a ll h o le s i n t h e i r c e n t e r s .
Your t a s k w i l l be to i n s e r t t h i s s t y l u s [ s t y l u s i s shown
t o s u b j e c t ] I n t o th e 'c o rrec t® h o le w h ile th e drum i s
r e v o lv in g . The ' c o r r e c t ' h o le w i l l be i n d ic a t e d by the
l i g h t i n g of one of th e symbols shorn on th e sm all b la c k
p a n e l above th e long s l o t [ t h e s e symbols a re shown t o sub-
j e c t ] . You must d e te rm in e y o u r t a r g e t by lo o k in g a t t h i s
p a n e l, th e n l o c a t e your t a r g e t on th e re v o lv in g drum, and
th e n i n s e r t th e s t y l u s i n t o th e h o le b e fo re i t d is a p p e a r s
b e n e a th the b la c k e l a s t i c band a t th e low er edge of th e
s l o t . I t i s n ot n e c e s s a r y t o push th e s t y l u s i n t o th e h o le
w ith a g r e a t amount o f f o r c e . A l i g h t to u ch and a q u ic k
w ith d ra w a l w i l l be s u f f i c i e n t . Make c e r t a i n t h a t you
alw ays w ithdraw th e s t y l u s i n tim e t o p re v e n t i t s g e t t i n g
caught in the equipm ent [d e m o n s tra te t o th e s u b j e c t how th e
s t y l u s can be caught i n the moving p a r t s ] . You w i l l be
allow ed o n ly one ’to u c h ' w hile th e s t y l u s i s w i th in th e
h o l e . In o t h e r w ords, do n o t make m u lt i p le ' j a b s ’ w hile
you have th e s t y l u s i n th e p ro p e r h o le . Are t h e r e any
q u e s tio n s ?
" I t w i l l be your jo b t o accom plish t h i s t a s k under
two c o n f i g u r a t i o n s . I w i l l e x p la in th e d i f f e r e n c e between
th e two to you now. The a p p a r a tu s i s now s e t up so t h a t a
new t a r g e t w i l l ap p ea r whenever you p lac e the s t y l u s w ith in
th e 'c o r r e c t* h o le . A g iv en symbol w i l l c o n tin u e to be
your t a r g e t u n t i l you do make th e c o r r e c t re s p o n s e .
N othing e l s e c o n tr o ls th e change of t a r g e t s . That i s , you
may c o n tr o l th e r a t e of change o f th e t a r g e t s by your own
c o r r e c t r e s p o n s e s . I w i l l show you how t h i s works [demon
s t r a t e t o s u b j e c t ] . You w i l l be sco red on the le n g th of
time t h a t you tak e t o make a g iv en number of c o r r e c t
r e s p o n s e s . You w i l l a l s o be sco red on th e number of e r r o r s
t h a t you make. An e r r o r w i l l be rec o rd ed whenever you
to uch th e s t y l u s anywhere o t h e r th a n w ith in th e ’ c o r r e c t ’
h o le .
"Under th e o th e r c o n f i g u r a ti o n th e a p p a ra tu s w i l l
119
be s e t up so t h a t th e t a r g e t s change e v e r so o f te n w h ether
you make th e c o r r e c t re sp o n se or n o t. Even i f you do
n o th in g a t a l l th e t a r g e t w i l l s t i l l change. In o th e r
w ordsj y ou r re s p o n s e s have n o th in g t o do w ith th e r a t e a t
which you can proceed w ith th e t a s k as th e r a t e of p r e s e n
t a t i o n o f t a r g e t s i s c o n tr o l le d e n t i r e l y by th e a p p a r a tu s .
Only d u rin g th e tim e t h a t a given t a r g e t i s in d ic a te d on
t h e sm all b la c k p a n e l w i l l i t be your t a r g e t on th e drum.
As soon as th e l i g h t goes on behind a n o th e r symbol a touch
w i t h in th e h o le a s s o c i a t e d w ith th e p re v io u s symbol w i l l
n o t be re c o rd e d as a c o r r e c t re s p o n se . Even though a
c o r r e c t re s p o n se w i l l n o t cause a change of t a r g e t , th ey
w ill be rec o rd ed as w i l l a l s o th e e r r o r s t h a t you make.
"You may ta k e a p o s i t i o n d i r e c t l y i n f r o n t of th e
a p p a r a tu s . Hold, th e s t y l u s i n your fav o re d hand and p la c e
y o u r o th e r hand on y our l a p . Do n o t r e s t any p a r t o f your
body on or a g a i n s t th e c a b i n e t . I w i l l i n d i c a t e to you
b e fo re each t r i a l w hether i t i s th e type where the s i g n a l s
change upon your c o r r e c t resp o n se o r the type where th ey
change a u t o m a t i c a l l y . At th e b e g in n in g of each t r i a l I
w i l l say: 'A ll s e t - r e a d y — -go. ' At the word *go! you may
s t a r t im m e d ia te ly . Are t h e r e any q u e s t i o n s ? ”
J u s t b e fo re b e in g exposed t o th e v a r io u s n o is e con
d i t i o n s th e s u b j e c t was g iv en the fo llo w in g i n s t r u c t i o n s :
" I am now going t o a sk you t o a cco m p lish th e same
t a s k s t h a t you have j u s t com pleted, how ever, w hile you a re
doing them t h i s tim e I am going t o expose you to some
sounds by means of t h i s h e a d s e t [show s u b j e c t to h e a d s e t ] .
The i n t e n s i t y of t h e s e sounds has been a d ju s te d so t h a t
you w i l l n o t s u f f e r any permanent h e a r in g damage a lth o u g h
you w i l l p ro b a b ly n o t h e a r a s w e ll f o r an hour or two.
A f t e r t h a t tim e you w i l l be a b le to h e a r j u s t as w e ll as
you do n o rm a lly . I w i l l a d v is e you a t th e b e g in n in g of
each t r i a l j u s t how th e s i g n a l s w i l l be changed, i . e . , by
your c o r r e c t re sp o n se o r a u to m a t i c a ll y . P le a s e a d j u s t th e
h e a d s e t so t h a t i t f i t s c o m fo rtab ly and sn u g ly on y our
head [ a s s i s t s u b j e c t in a d j u s t i n g th e h e a d s e t ] . ”
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Trembly, W. Agib
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Core Title
Noxious Auditory Environment And Psychomotor Performance
Degree
Doctor of Philosophy
Degree Program
Psychology
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Digitized by ProQuest
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Warren, Neil D. (
committee chair
), Grings, William W. (
committee member
), Michael, William B. (
committee member
), Ruch, Floyd L. (
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