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The Effects Of Transverse Accelerations And Exponential Time-Lag Constants On Compensatory Tracking Performance

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The Effects Of Transverse Accelerations And Exponential Time-Lag Constants On Compensatory Tracking Performance

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Content This dissertation
has been microfilmed
exactly as received
Mic 60-4464
KAEHLER, Richard Charles, THE EFFECTS
OF TRANSVERSE ACCELERATIONS AND
EXPONENTIAL TIME-LAG CONSTANTS ON
COMPENSATORY TRACKING PERFORMANCE.
University of Southern California
Ph. D ., 1960
Psychology, experimental
University M icrofilm s, In c., Ann Arbor, Michigan
THE EFFECTS OF TRANSVERSE ACCELERATIONS AND
EXPONENTIAL TIME-LAG CONSTANTS ON
COMP ENSATORY TR AC KING P ERFO RMANC S
by
R ic h a rd C h a rle s K a e h le r
A D i s s e r t a t i o n P r e s e n te d to 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 equ irem en ts f o r t h e Degree
DOCTOR OF PHILOSOPHY
(P sy ch o lo g y )
June I 960
UNIVERSITY OF SOUTHERN CALIFORNIA
GRADUATE SCHOOL
UNIVERSITY PARK
LOS ANGELES 7. CALIFORNIA
/
This dissertation, written by
.............R i c h a r d . C h a r l e s... Ka g h i e r ...............
under the direction of h±s....Dissertation Com
mittee, and approved by all its members, has
been presented to and accepted by the Graduate
School, in partial fulfillment of requirements
for the degree of
D O C T O R OF P H I L O S O P H Y
Dean
Date.
/
ISSPR.TAT/TGN COMMITTEE
Chairman
A C K N O W LED G M EN TS
T h is stu d y was co n d u cted under U. S . A ir F orce
C o n tr a c t 3 3 (3 1 6 ) - 54-07 betw een th e A erom edical L a b o r a to r y ,
W right A ir D evelopm ent C e n te r , O h io , and t h e Departm ent o f
P h y s io lo g y , U n i v e r s i t y o f S ou th ern C a l i f o r n i a , w ith Dr.
John P. Meehan s e r v in g a s R e s p o n s ib le I n v e s t i g a t o r .
The a u th o r w is h e s t o e x p r e s s h i s s i n c e r e g r a t i t u d e
t o P r o f e s s o r s N e i l D. W arren, F lo y d L . Ruch, and W illia m
W. G rin g s, Department o f P sy c h o lo g y , f o r t h e i r e n c o u r a g e
m ent, su p p o r t, a s s i s t a n c e , and a d v ic e w h ile s e r v in g a s
members o f th e a u t h o r ’ s Q u a lify in g and D i s s e r t a t i o n
C om m ittees.
G r a te fu l acknow ledgm ents a r e e x te n d ed t o : Mr.
W illia m S illim a n , N orth American A v ia t io n , I n c . , f o r
s e r v in g as a n a lo g com puter o p e r a to r ; Mr. P aul T o b ia s ,
Departm ent o f P h y s io lo g y , f o r s e r v in g as c e n t r i f u g e
o p e r a to r ; Mr. W illia m Monzon, Radio C o r p o r a tio n o f A m erica,
f o r p r e p a r in g t h e s c h e m a tic s and f i g u r e s p r e s e n te d in t h i s
D i s s e r t a t io n ; and th e Management o f North Am erican
A v ia t io n , I n c . , f o r p r o v id in g th e a n a lo g com puter and
t e c h n i c a l p e r so n n e l n e c e s s a r y f o r c o n d u c tin g t h i s s tu d y .
S p e c ia l acknowledgm ent i s made t o Mr. C a rl L a f o r s ,
E l e c t r i c a l E n g in e e r , f o r th e e n g in e e r in g d e s ig n and
i i
f a b r i c a t i o n o f t h e c o n tr o l system h o u sin g and a s s o c i a t e d
equipm ent f o r t h i s s tu d y , a s w e ll a s , e x c e l l e n t e n g in e e r
in g support in o t h e r s t u d i e s condu cted by t h i s a u th o r.
F i n a l l y , to Dr. John P. Meehan, A s s o c ia t e P r o f e s s o r
o f P h y s io lo g y , whose t e c h n i c a l a s s i s t a n c e , a d m in is t r a t iv e
su p p o r t, g e n e r o s i t y , and u n d e r sta n d in g has made t h i s
D i s s e r t a t io n p o s s i b l e , th e au th or o f f e r s h i s d e e p e st
t h a n k s .
TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS....................................................................................... i i
LIST OF TABLES........................................................................................... v i
LIST OF ILLUSTRATIONS....................................................................... v i i
SECTION ONE. INTRODUCTION
C h a p te r
I . ORGANIZATION o f t h e d i s s e r t a t i o n and
o r i e n t a t i o n in t h e f i e l d o f
a c c e l e r a t i o n ................................................................... 2
O r g a n iz a t i o n o f t h e D i s s e r t a t i o n
O r i e n t a t i o n in th e F i e l d o f
A c c e l e r a ti o n
I I . statement and importance OF THE
PROBLEM.................................................................................. 13
S ta te m e n t o f th e Problem
Im p o rta n c e o f t h e Problem
section two. background of the study
I I I . A HISTORY OF THE HUM AN as a CONTROLLER . . 22
The C om plexity o f th e Problem
C o n tro l System Dynamics
Human Dynamics
Man-Machine Dynamics
IV. A HISTORY OF THE HUM AN AS A CONTROLLER
IN THE ACCELERATION ENVIRONMENT ..................... 49
R e a c tio n Time
P e r c e p tu a l- M o to r P erform ance
C o g n itiv e P r o c e s s e s
C o n tin u o u s C o n tro l Perform ance
i v
C h a p te r Page
SECTION THREE. PROCEDURE
V. APPARATUS AND SUBJECT GROUP ........................................ 63
A p p a ratu s
S u b je c t Group
VI. PROCEDURE AND DESIGN OF THE EXPERIMENT . . . go
P ro c e d u re
D esign o f t h e E xperim ent
SECTION FOUR. RESULTS AND DISCUSSION
V I I. RESULTS AND DISCUSSION..................................................... £6
P i t c h Mode
R o ll Mode
Some I n t e r p r e t a t i o n s o f t h e R e s u l t s
SECTION FIVE. SUMMARY aND CONCLUSIONS
V I I I . SUMMARY and CONCLUSIONS ................ . . . . . 115
Summary
C o n c lu s io n s
Recommendations f o r F u tu r e R ese arch
APPENDIX A. MEANS AND STANDARD DEVIATIONS OF
PITCH AND ROLL MEASUREMENTS
OBTAINED ON THE FIRST AND SECOND
d a y s .................................................................... 123
APPENDIX B. ANALOG MECHANIZATION AND PRODUCTION
OF EXPONENTIAL TIME-LAG CONSTANTS . . 123
APPENDIX C. DERIVATION OF EQUATION FOR
CALCULATING RPM REQUIREMENTS FOR
PRODUCING VARIOUS ACCELERATION
LEVELS ON THE U. S. C. HUM AN
CENTRIFUGE.................................................... 134
APPENDIX D. SOME COMMENTS ON THE STATISTICAL
ANALYSIS......................................................... 137
BIBLIOGRAPHY
141
LIST OF TABLES
T ab le Page
1 . Mean P i t c h I n t e g r a t e d E r r o r , i n V o l t s ,
O b ta in e d f o r t h e V a rio u s A c c e l e r a t i o n
L e v e ls and Time-Lag C o n s ta n ts .................................... 90
2. A n a ly s is o f V a ria n c e R e s u l t s f o r P i t c h
E r r o r S c o r e s ........................................................ 94
3. Product-M om ent C o r r e l a t i o n C o e f f i c i e n t s
f o r P i t c h M easurem ents O b ta in e d f o r t h e
V a rio u s C o m b in atio n s o f E x p e rim e n ta l
C o n d itio n s and Time-Lag C o n s ta n ts ......................... 97
4. Mean R o ll I n t e g r a t e d E r r o r , i n V o l t s ,
O b ta in e d f o r t h e V a rio u s A c c e l e r a ti o n
L e v e ls and Time-Lag C o n s ta n ts .................................... 100
5. A n a ly s is o f V a ria n c e R e s u lts f o r R o ll
E r ro r S c o r e s ...................................................................................104
6 . Product-M om ent C o r r e l a t i o n C o e f f i c i e n t s
f o r R o ll M easurem ents O b ta in e d f o r t h e
V a rio u s C o m b in atio n s o f E x p e rim e n ta l
C o n d itio n s and Time-Lag C o n s ta n ts ......................... 107
LIST OF ILLUSTRATIONS
F i g u r e Page
1 . T hree D im en sio n a l Model o f t h e G e n e ra l
H y p o t h e s e s .................................................................................... 15
2.. V a rio u s Types o f I n p u t S t i m u l i , A f t e r
S ly , Bowen and O r la n s k y ( 4 2 ) ..................................... 25
3. R esponse t o S te p I n p u t w ith T hree
D i f f e r e n t ICinds o f L ag . A f t e r S ly ,
Bo\*fen and O r la n s k y (42) 26
4 . A Sim ple S tim u lu s -R e s p o n s e Model
f o r a Human C o n t r o l S y s t e m ............................................ 30
5. The S u b j e c t a s Viewed b y t h e C e n t r i f u g e
O p e r a t o r P o s i t i o n e d i n t h e C o n t r o l Booth . . 66
6 . Block D iagram Showing t h e I n t e r a c t i o n o f
t h e S u b j e c t and A p p a r a t u s .......................................... 67
7. The C u r v e -F o llo w e r s and th e A nalog
C om puter i n t h e C o n t r o l R o o m ..................................... 70
S. The A i r c r a f t R e p r e s e n t a t i o n on t h e
O s c i l l o s c o o e Showing a R o l l E r r o r
But no P i t c h E r r o r ............................................... 71
9. The R e l a t i v e P o s i t i o n o f t h e S u b j e c t ,
The C o n t r o l S t i c k , and t h e O s c il.lo s c o p e
on t h e Human C e n t r i f u g e ............................... 73
1 0 . A C lose-U p o f t h e R ig h t Hand S id e C o n t r o l
S t i c k .............................................................................................. 74
1 1 . The S u b j e c t S e a te d i n P o s i t i o n t o
E x p e rie n c e F ro n t-T o -B a c k A c c e l e r a t i o n
on t h e Human C e n t r i f u g e ............................................... 75
1 2 . The A nalog Com puter O p e r a t o r N o tin g
I n f o r m a t i o n on t h e R e c o rd e r D uring
a C e n t r i f u g e R u n .................................................................... 77
v i i
v i i i
F ig u re Page
1 3 . A T y p ic a l Record Showing t h e Use o f
E ig h t C h an n els f o r Data R e c o rd in g
and R e d u c t i o n ........................................................................
1 4 . Mean P i t c h E r r o r V a lu es a s a F u n c tio n
o f P r a c t i c e T r i a l s Conducted Over a
Two Day P e r i o d ........................................................................ $7
15. Mean P i t c h E r ro r a s a F u n c tio n o f
V a rio u s Time-Lag C o n s ta n ts and
A c c e l e r a t i o n L e v e ls ......................................................... 91
16. Mean P i t c h E r ro r as a F u n c tio n o f
I n c r e a s e d A c c e l e r a ti o n and V a rio u s
Time-Lag C o n s ta n ts ............................................................. 92
17. Three D im ensional P r e s e n t a t i o n o f
E x p e rim e n ta l R e s u l t s in th e P i t c h
M o d e ................................................................................................. 93
1$. Mean R o ll E rro r V alu es a s a F u n c tio n
o f P r a c t i c e T r i a l s C onducted Over
a Two Day P e r i o d ................................................................... 9&
19. Mean R o ll I n t e g r a t e d E r r o r as a F u n c tio n
o f V a rio u s Time-Lag C o n s ta n ts and
A c c e l e r a ti o n L e v e ls ........................................................ 101
20. Mean R o ll E r ro r as a F u n c tio n o f
I n c r e a s e d A c c e l e r a ti o n and V a rio u s
Time-Lag C o n s ta n ts ............................................................. 102
21. Three D im ensional P r e s e n t a t i o n o f
E x p e rim e n ta l R e s u lts in t h e R o ll Mode . . . 103
SECTION ONE
INTRODUCTION
CHAPTER I
ORGANIZATION OF THE DISSERTATION AND
ORIENTATION IN THE FIELD
OF ACCELERATION
With r e c e n t and a n t i c ip a t e d t e c h n i c a l d evelop m en ts
in th e f i e l d o f r o c k e t p r o p u ls io n , a g r e a t d e a l o f c o n s id
e r a t io n i s b e in g g iv e n to t h e many problem s o f s u c c e s s f u l l y
p la c in g a human in t o o r b i t and r e tu r n in g him s a f e l y to th e
e a r t h f s s u r f a c e . One o f t h e problem s en c o u n te re d in th e
developm ent o f manned sp ace v e h i c l e s i s th e e v a lu a tio n o f
human c o n t r o l c a p a b i l i t i e s w h ile exp osed t o r e l a t i v e l y
h ig h -m agn itu d e lo n g - d u r a tio n a c c e l e r a t i o n s d u rin g th e
c r i t i c a l b o o s t and r e - e n t r y p h a se s o f t h e m is s io n . I t i s
w ith t h i s q u e s t io n t h a t t h i s d i s s e r t a t i o n i s co n cern ed .
A. ORGANIZATION OF THE DISSERTATION
The d i s s e r t a t i o n i s o r g a n iz e d in f i v e s e c t i o n s .
S e c tio n I , c o n s i s t i n g o f two c h a p t e r s , i s d e v o ted to
in tr o d u c to r y m a t e r i a l. Chapter I d i s c u s s e s t h e p h y s ic a l
and p h y s i o l o g ic a l a s p e c t s o f th e t o p i c o f a c c e l e r a t i o n .
C hapter I I p r e s e n t s t h e sta te m e n t o f t h e p rob lem , in c lu d in g
a g e n e r a liz e d model o f th e e x p e r im e n ta l h y p o t h e s e s , and th e
im p ortan ce o f th e problem .
3
S e c tio n I I o f th e d i s s e r t a t i o n i s concerned w ith
th e d is c u s s io n o f r e le v a n t background m a t e r ia l. I t
c o n ta in s two c h a p te r s . Chapter I I I d is c u s s e s th e h i s t o r y
o f th e human o p e r a to r a s a c o n t r o l l e r in v a r io u s machine
sy stem s. Chapter IV d is c u s s e s ex p erim en ta l d ata reg a rd in g
m a ^ s c a p a b i l i t i e s and l i m i t a t i o n s as a c o n t r o l l e r in th e
a c c e le r a t io n environm ent.
S e c tio n I I I d e s c r ib e s th e v a r io u s p roced u res
in co rp o ra ted in co n d u ctin g th e exp erim en t. Chapter V i s
a p r e s e n ta tio n o f th e apparatus and th e s u b je c t group.
Chapter VI p r e s e n ts th e exp erim en tal procedure and th e
exp erim en tal d e sig n .
S e c tio n IV c o n s i s t s o f one ch a p ter c o v e r in g th e
r e s u l t s and d is c u s s io n . Chapter VII d e t a i l s in fo r m a tio n
on th e p it c h and r o l l modes and i n t e r p r e t a t io n o f th e
experim ent in l i g h t o f in fo rm a tio n th e o r y .
S e c tio n V i s th e f i n a l ch a p ter o f th e d i s s e r t a t i o n
and p r e s e n ts a summary o f th e ex p erim en t, some g e n e ra l
c o n c lu s io n s , and recom m endations fo r fu tu r e r e s e a r c h .
B. ORIENTATION IN THE FIELD
OF ACCELERATION
The purpose o f t h i s s e c t io n o f th e ch a p ter i s to
r ev iew th e p h y s ic a l and p h y s io lo g ic a l a s p e c ts o f th e t o p ic
o f a c c e le r a t io n in order th a t th e s e r e le v a n t c o n s id e r a tio n s
may be p r e se n te d t o th e rea d er who i s n ot f a m ilia r w ith
t h e g en era l a r ea .
P h y s ic a l c o n s id e r a tio n s
The f i r s t p o in t which i s o f t e n c o n fu s in g to th e
average read er i s t h a t v e l o c i t y , as su ch , does n ot c r e a te
a fo r c e environm ent which i s d e tr im e n ta l to th e human
body. In th e c a se o f v e l o c i t y , t h e r e i s no e f f e c t i v e
fo r c e a c tin g on th e o b je c t in q u e s tio n . T h is f a c t i s
dem onstrated by Newton’ s F ir s t Law o f M otion which
s t a t e s (1 0 0 ): ’’When a body i s a t r e s t or moving w ith
c o n sta n t speed in a s t r a ig h t l i n e , th e r e s u lt a n t o f a l l
f o r c e s e x e r te d on th e body i s z e r o .”
The d ir e c t im p lic a tio n from t h i s sta tem en t i s t h a t
o b j e c t s can t r a v e l a t any c o n sta n t speed in a s t r a ig h t
l i n e w ith o u t produ cin g d e tr im e n ta l e f f e c t s u s u a lly
a s s o c ia t e d w ith high speed m otion . I f , how ever, th e
speed or d ir e c t io n o f m otion i s changed, th e r a te o f
change i s termed th e ”a c c e le r a t io n ” (1 0 4 ). Newton’ s
Second Law o f M otion s t a t e s (1 0 0 ):
The a c c e le r a t io n o f a body i s p r o p o r tio n a l to
th e r e s u lt a n t fo r c e e x e r te d on th e body, i s in v e r s e ly
p r o p o r tio n a l t o th e mass o f th e body, and i s in th e
same d ir e c t io n as th e r e s u lt a n t f o r c e .
The g e n e ra l m athem atical sta tem en t o f t h i s law i s
th e f a m ilia r e q u a tio n :
F = MA (Equation l )
where F i s th e f o r c e , M i s th e mass o f th e o b j e c t and
A i s th e a c c e le r a t i o n . T his e q u a tio n i s , how ever,
a p p lic a b le in i t s p r e se n t form t o v e l o c i t y changes in a
s t r a i g h t l i n e o r l i n e a r m o ti o n .
I f t h e e q u a t i o n w ere t o b e w r i t t e n i n th e g r a v i t a
t i o n a l fo rm , m ass i s c o n v e r t e d t o w e ig h t a s f o l l o w s ( 5 4 ) :
M = ( E q u a tio n 2)
w
w here M i s t h e m ass o f t h e o b j e c t , 'W i s t h e w e i g h t o f
t h e o b j e c t and g i s t h e e a r t h ' s g r a v i t a t i o n a l c o n s t a n t
w ith a n u m e r ic a l v a lu e o f a p p r o x i m a t e l y 3 2 .2 f t / s e c ^ .
By s u b s t i t u t i o n , e q u a t io n 1 becom es:
F = • A ( E o u a tio n 3)
9
I f , t h e n , we w ere t o c o n s i d e r a man w e ig h in g
180 l b s . i n a v e h i c l e w h ich i s a c c e l e r a t i n g a t 9 6 .6
f t / s e c , we n o te from e q u a t i o n s 4 and 5 t h a t t h e f o r c e
a c t i n g on t h e man i s t h r e e t i m e s h i s own w e i g h t . I n t h i s
c a s e , i t i s u s u a l l y s a i d t h a t t h e man i s e x p e r i e n c i n g 3
g ' s s i n c e , in g r a v i t a t i o n a l u n i t s , 9 6 .6 f t / s e c ^ i s t h r e e
tim e s t h e m a g n itu d e o f 1 g. F u r t h e r , from e q u a t i o n 6, i t
becom es e v i d e n t t h a t t h e t o t a l a c c e l e r a t i v e f o r c e h a s a
m a g n itu d e o f 540 l b s . :
F = ^ ^ - * 9 6 . 6 (E q u a tio n 4)
F = 1 8 0 * 3 (Equation 5)
F = 5 4 0 lbs
(E q u a tio n 6)
The above d i s c u s s i o n w a s, o f c o u r s e , r e s t r i c t e d t o
l i n e a r a c c e l e r a t i o n . A nother ty p e o f a c c e l e r a t i o n i s
r a d i a l a c c e l e r a t i o n . Lombard (8 2 ) s t a t e s t h a t t h i s o c c u r s
when a mass m oving a t u n iform v e l o c i t y in a s t r a i g h t l i n e
i s ca u sed to d ep art from t h a t l i n e and t o move in a c u r v e ,
or c i r c u l a r p ath h a v in g a g iv e n r a d iu s from t h e a x i s o f
r o t a t i o n , i t e x e r t s an outw ard ( c e n t r i f u g a l ) f o r c e
e x p r e s s e d by th e e q u a tio n :
\ T 1
F = M - j r (E q u a tio n 7)
where F i s th e f o r c e , M . i s th e m a ss, V i s t h e v e l o c i t y
and 1* i s th e r a d iu s . N ote t h a t t h e same w e i g h t - t r a n s -
fo rm a tio n can be made by a lg e b r a ic s o l u t i o n o f th e u n i t s
in v o lv e d .
A t h i r d form o f a c c e l e r a t i o n , a n g u l a r , may be
added t o t h e two p r e v i o u s l y d i s c u s s e d , w hich i s a m easure
o f t h e r a t e o f change o f a n g u la r v e l o c i t y . A d e t a i l e d
d e s c r i p t i o n o f t h e e q u a t i o n s used f o r c a l c u l a t i n g t h e g
l e v e l s on t h e human c e n t r i f u g e i s p r e s e n t e d i n A ppendix C.
P h y s i o l o g i c a l c o n s i d e r a t i o n s
K a eh le r, Meehan, and Freedman (75) s t a t e t h a t
t h e r e a r e two human c a p a b i l i t i e s w hich must be c o n s id e r e d
w ith r e g a r d t o th e a c c e l e r a t i o n problem : (a ) t h e p s y c h o
l o g i c a l c a p a b i l i t y o f t h e crew w hich i n c lu d e s p rop er
p erform ance o f such d u t i e s a s d a ta p r o c e s s in g , n a v i g a t i o n ,
7
com m unication, c o n tr o l fu n c tio n s and th e like; (b) th e
p h y s io lo g ic a l a s p e c ts o f to le r a n c e to th e p r e d ic te d
a c c e le r a t io n f o r c e s .
For th e pu rp oses o f t h i s d i s s e r t a t i o n , each w i l l
be d is c u sse d s e p a r a te ly ; th e p h y s io lo g ic a l a s p e c ts in t h i s
s e c t io n ; th e p s y c h o lo g ic a l a s p e c t s in Chapter IV. Each
o f th e s e p aram eters, however, must be c o n sid e r e d in term s
o f (a) d i r e c t io n , (b) m agnitude, (c) d u r a tio n , and (d) r a te
o f o n s e t, o f th e a c c e le r a t iv e f o r c e .
In g e n e r a l, th e r e are fou r major ty p e s o f a c c e le r a
t i o n o f concern in th e stu d y o f human c a p a b i l i t i e s ; (a)
p o s i t i v e , (b) n e g a t iv e , (c ) n e g a tiv e t r a n s v e r s e , and
(d) p o s i t i v e t r a n s v e r s e . Each one i s d is c u s s e d below .
For a more d e t a ile d treatm en t se e Gauer (54).
P o s i t iv e a c c e l e r a t i o n . - - I n th e f i r s t o f t h e s e ty p e s
o f a c c e le r a t io n , th e fo r c e a c t s a lo n g th e lo n g a x is o f th e
human body in a h e a d -t o - s e a t d ir e c t io n and i s termed
" p o s itiv e " a c c e le r a t io n . T his i s th e most commonly known
typ e o f a c c e le r a t io n because i t i s th e typ e which ca u se s a
s t a t e o f " b la c k -o u t." I t o c c u r s , fo r exam ple, in a f l i g h t
s i t u a t i o n where th e a i r c r a f t " p u lls out" o f a d iv e . I t
i s a ls o o fte n r e fe r r e d to as "normal" a c c e le r a t io n .
In g e n e r a l, exposure t o p o s i t i v e a c c e le r a t io n
r e s u l t s in a narrow ing and a dimming o f th e v i s u a l f i e l d .
The f i r s t sig n o f a t o le r a n c e l i m i t i s th e l o s s o f p e r ip h
e r a l v i s i o n , known as " grayou t." T his o c c u r s fo r th e
average s u b je c t a t a p p rox im a tely 3 -4 g , u n p r o te c te d . I f
th e m agnitude o f th e g f o r c e i s in c r e a s e d , th e s u b je c t
l o s e s th e a b i l i t y to se e v is u a l s t i m u l i . T his v i s i o n l e s s
s t a t e i s c a ll e d ’'b la ck o u t” and occu rs fo r th e average
su b je c t a t ap p roxim ately 5-6 g. I f th e m agnitude o f th e
fo r c e i s fu r th e r in c r e a s e d , th e s u b je c t w i l l become
u n co n sc io u s. The rep o rted r eco v ery tim e from u n c o n sc io u s
n e ss i s between 15 seconds and 1 m inute (62). During th e
blackou t s t a t e , however, th e s u b je c t i s ca p a b le o f
resp ond ing to a u d ito ry s t im u li even a f t e r v is u a l s e n s i
t i v i t y i s l o s t (16).
These symptoms are c o n sid er ed to be due to th e
in c re a se d w eigh t o f th e b lood and d ecrea sed venous r etu r n
ren d erin g th e h ea rt in ca p a b le o f m a in ta in in g adequate
blood su p p ly to th e head a r ea . The reduced r e t i n a l blood
supply r e s u l t s in r e t i n a l f a i l u r e and b la ck o u t o c c u r s . A
standard G -su it w i l l in c r e a s e a l l o f th e above t o le r a n c e
l i m i t s by a p p roxim ately 1 g.
In r e c e n t work conducted a t t h e U. S. Naval
A c c e le r a tio n M edical L ab oratory, Webb and Gray (75)
conducted a stu d y in which th r e e human s u b j e c t s , submerged
in water w h ile in a s i t t i n g p o s i t i o n , were exposed to
p o s i t i v e g l e v e l s up t o 16 g. There was no l o s s o f
p e r ip h e r a l v i s i o n or a p p r e c ia b le f a t ig u e e f f e c t s as a
r e s u l t o f th e s e high p o s i t i v e g e x p o su r e s.
N e g a tiv e a c c e le r a t i o n . — In th e second major typ e
o f a c c e l e r a t i o n , t h e f o r c e a c t s a lo n g t h e l o n g a x i s o f t h e
human body i n a s e a t - t o - h e a d d i r e c t i o n . T h is ty p e o f
a c c e l e r a t i o n i s f a i r l y w e l l known s i n c e e x c e s s i v e e x p o su r e
t o i t p r o d u c e s a v i s u a l symptom c a l l e d " r e d - o u t ." I t may
o c c u r in such f l i g h t c o n d i t i o n s a s " p u s h - o v e r s ." I t i s
g e n e r a l l y c o n s id e r e d t o be e x tr e m e ly h a z a r d o u s . V a r io u s
r e p o r t s show t h a t r e t i n a l and c e r e b r a l h em orrh ages o c c u r
above 3 g (54). N e e d le s s t o s a y , l i t t l e e x p e r im e n ta l work
h as b een done w ith human s u b j e c t s e x p o se d t o t h i s ty p e o f
a c c e l e r a t i o n .
N e g a t iv e t r a n s v e r s e a c c e l e r a t i o n . - - I n th e t h i r d
m ajor ty p e o f a c c e l e r a t i o n th e d i r e c t i o n o f th e f o r c e i s
p e r p e n d ic u la r t o t h e l o n g a x i s o f t h e human body and a c t i n g
in a b a c k - t o - f r o n t d i r e c t i o n . T h is ty p e o f a c c e l e r a t i o n
w ould be e n c o u n te r e d when a v e h i c l e i s d e c e l e r a t i n g a s a
r e s u l t o f u s i n g r e t r o - r o c k e t s , d i v e - b r a k e s , e tc .
The m ajor p h y s i o l o g i c a l d i f f i c u l t y i s t h e " p o o lin g "
o f b lo o d in t h e e x t r e m i t i e s c a u s in g p r e s s u r e an d , f i n a l l y ,
s e v e r e p a in s e n s a t i o n s . C u r r e n t ly , t h e u n p r o t e c t e d human
can t o l e r a t e a p p r o x im a te ly 5 n e g a t i v e t r a n s v e r s e g f o r 15
s e c o n d s . W ith e s p e c i a l l y d e s ig n e d s u i t s and r e s t r a i n t
g e a r , human s u b j e c t s have t o l e r a t e d 1 0 g f o r b r i e f
d u r a t io n s (35). Gray and Webb (75) have r e p o r t e d t h a t
when s u b j e c t s a re subm erged i n w a te r t h e y a r e a b le to
t o l e r a t e 9 g .
P o s i t i v e t r a n s v e r s e a c c e l e r a t i o n . — The f o u r t h
10
m ajor t y p e o f a c c e l e r a t i o n i s d e f i n e d by t h e a c c e l e r a t i v e
f o r c e a c t i n g p e r p e n d ic u la r t o t h e l o n g a x i s o f t h e body in
a f r o n t - t o - b a c k d i r e c t i o n . T h is t y p e o f a c c e l e r a t i o n
w ould b e e n c o u n te r e d a s a r e s u l t o f h ig h t h r u s t f o r c e s
a c t i n g l o n g i t u d i n a l l y th r o u g h t h e v e h i c l e . T h is , o f
c o u r s e , i s t h e ty p e e n c o u n te r e d in t h e la u n c h p h a se o f an
o r b i t a l v e h i c l e and i s o f prim e c o n c e r n in t h i s d i s s e r t a
t i o n .
P a s t e x p e r im e n ta l work h a s d e m o n str a te d t h a t human
s u b j e c t s can w it h s t a n d 1 2 - 1 4 g f o r p e r io d s up t o ISO
s e c o n d s (54). R e ce n t t e s t s a t t h e U n i v e r s i t y o f S o u th ern
C a l i f o r n i a have r e p r o d u c e d t h e m ajor p o r t i o n s o f t h e s e
e a r l i e r f i n d i n g s . The m ajor o b s e r v e d p h y s i o l o g i c a l e f f e c t
i s b r e a t h in g d i f f i c u l t i e s o c c u r in g ab o ve S g .
One m ethod o f r e d u c in g b r e a t h in g d i f f i c u l t i e s ,
w h ich i s b e in g th o r o u g h ly i n v e s t i g a t e d by s e v e r a l a g e n c ie s
a t th e p r e s e n t t im e , i s by o r i e n t i n g t h e s u b j e c t s h ead and
upper t o r s o s l i g h t l y fo rw a rd i n t o t h e a c c e l e r a t i v e f o r c e
so t h a t t h e r e i s a p o s i t i v e com ponent a c t i n g on him a s
w e l l a s t h e m ajor t r a n s v e r s e com p on en t. The o b s e r v e d
e f f e c t in t h i s s i t u a t i o n i s t h e r e l i e f o f t h e b r e a t h in g
problem a lth o u g h some o f t h e l e s s d e s i r a b l e a s p e c t s o f
p o s i t i v e a c c e l e r a t i o n (g r a y o u t and b la c k o u t ) a r e in c lu d e d
i n t h i s com prom ise p o s i t i o n .
C o l l i n s , C r o s b ie , and Gray (75) have d e m o n str a te d
s u c c e s s f u l c e n t r i f u g e e x p o s u r e s up t o 20 g w ith no r e p o r t e d
11
p h y s i o l o g i c a l d i f f i c u l t i e s . T hese t e s t s w ere c o n d u cted
u s in g an e x p e r im e n ta l c o n to u r couch w h ich o r ie n t e d th e
s u b j e c t 17 d e g r e e s in t o th e l i n e o f th e a c c e l e r a t i v e
f o r c e . S im ila r r e s u l t s from t h i s comprom ise o r i e n t a t i o n
have been o b ta in e d by o th e r c e n t r i f u g e f a c i l i t i e s .
For t h e p u rp ose o f t h i s d i s s e r t a t i o n , p o s i t i v e
t r a n s v e r s e a c c e l e r a t i o n w i l l be r e f e r r e d t o a s " f r o n t - t o -
b ack ” a c c e l e r a t i o n , s i n c e i t i s f e l t t h a t t h i s te r m in o lo g y
i s more d e s c r i p t i v e .
P r e l i m i n a r y d e f i n i t i o n s
S in c e th e sta te m e n t o f th e problem i n c lu d e s a
number o f term s from t h e a r e a o f m an-machine d yn am ics,
s e v e r a l r e l e v a n t d e f i n i t i o n s are p r e s e n te d h e r e . More
d e t a i l e d d e f i n i t i o n s may be found in C hapter I I I .
E x p o n e n tia l t i m e - l a g c o n s t a n t . — The tim e i n t e r v a l
betw een t h e o p e r a t o r s r e s p o n s e and when 63% o f th e c o n t r o l
movement i s p r e s e n te d back t o th e o p e r a to r on th e v i s u a l
d i s p l a y . The fee d b a ck in fo r m a tio n i s , t h e r e f o r e , p r e s e n te d
a s an e x p o n e n t ia l f u n c t io n o f tim e and r e p r e s e n t s a p a r t i a l
l o s s o f in fo r m a tio n t o th e s u b j e c t on t h e r e s u l t s o f h i s
c o n t r o l movement.
Com pensatory t r a c k in g t a s k . —A t r a c k in g t a s k in
which th e s u b j e c t i s r e q u ir e d t o m a in ta in th e t a r g e t in
t h e zero p o s i t i o n . The s u b j e c t d o es n o t s e e t h e s t im u lu s
s e p a r a t e l y from h i s r e s p o n s e but r a t h e r , s e e s o n ly th e
12
e r r o r from t h e z ero p o s i t i o n .
U - h y p o t h e s i s . - - S t a t e d by H elson ( 6 2 ) , human
p e rfo rm a n c e w i l l t e n d to be o p tim a l a s ju d g ed by a c c u r a c y ,
e f f i c i e n c y , and c o m f o rt, o v e r a more o r l e s s b ro ad band o f
v a lu e s f o r a g iv e n s t i m u l u s - v a r i a b l e o u t s i d e o f which i t
becomes n o t i c e a b l y p o o r e r . When p e rfo rm a n c e i s p l o t t e d i n
te r m s o f e r r o r o r t h e r e c i p r o c a l o f a c c u r a c y , t h e r e s u l t a n t
c u rv e i s r o u g h ly U -sh a p e d .
P r i n c i p l e o f g e n e r a l i t y . - -H e ls o n (62) p o i n t s o u t
t h a t s t i m u l u s - v a l u e s i n th e o p tim a l band te n d to s t a y
o p tim a l when a c c e s s o r y c o n d i t i o n s a re ch an ged.
E r r o r . - - F o r th e p u rp o se o f t h i s s tu d y , e r r o r i s
d e fin e d as t h e i n t e g r a t i o n o f t h e a b s o l u t e d i f f e r e n c e
betw een t h e s t im u lu s ( i n p u t o f a com plex wave form ) and
t h e s u b j e c t ’ s r e s p o n s e ( d is p la c e m e n t o f t h e c o n t r o l s t i c k ) ,
as a f u n c t i o n o f tim e .
CHAPTER I I
STATEMENT AND IMPORTANCE OF THE PROBLEM
A. STATEMENT OF THE PROBLEM
The p u rp ose o f t h i s stu d y i s t o d e ter m in e th e
e f f e c t s o f in c r e a s e d f r o n t - t o - b a c k t r a n s v e r s e a c c e l e r a t i o n
and v a r io u s e x p o n e n t ia l t i m e - l a g c o n s t a n t s on human
c o n t r o l perform an ce in a com p en satory t r a c k in g t a s k .
The e x p e r im e n ta l h y p o th e s e s t o be t e s t e d , s t a t e d
a t t h e g e n e r a l l e v e l , a r e a s f o l l o w s :
1 . C om pensatory t r a c k in g e r r o r w i l l be d i f f e r e n
t i a l l y a f f e c t e d by in c r e a s e d e x p o n e n tia l t i m e - l a g c o n s t a n t s
r e s u l t i n g in a U -sh ap ed c u r v e . T h is e x p e r im e n ta l
h y p o t h e s is f o l lo w s H e ls o n 's U -H y p o th e sis fo r human
perform ance (62).
2. C om pensatory t r a c k in g e r r o r w i l l be s i g n i f i
c a n t ly in c r e a s e d w ith in c r e a s e d m a g n itu d es o f f r o n t - t o - b a c k
t r a n s v e r s e a c c e l e r a t i o n s . The l o c u s o f a c c e l e r a t i o n and
e r r o r p o i n t s w i l l d e s c r ib e a p o s i t i v e l y a c c e le r a t e d
f i m c t i o n .
3 . Com pensatory t r a c k in g e r r o r a t each o f v a r io u s
a c c e l e r a t i o n l e v e l s w i l l f o l lo w a U -shaped cu rve when
p l o t t e d a s a f u n c t io n o f e x p o n e n t ia l t i m e - l a g c o n s t a n t s .
13
14
T h is f o l l o w s H e ls o n ’ s P r i n c i p l e o f G e n e r a lit y (62).
F ig u r e 1 i s a t h r e e d im e n sio n a l m odel r e p r e s e n t in g
t h e s e t h r e e g e n e r a l e x p e r im e n ta l h y p o th e s e s in g r a p h ic
form . I t may be n o te d t h a t th e f r o n t f a c e o f th e m odel
d e m o n stra te s H y p o th e sis 1 , n am ely, a U -shap ed f u n c t io n
betw een e x p o n e n t ia l t i m e - l a g c o n s t a n t s and t r a c k in g e r r o r .
H y p o th e sis 2 i s r e p r e s e n t e d by sh ow ing t r a c k in g e r r o r to
be a p o s i t i v e l y a c c e le r a t e d f u n c t io n o f in c r e a s e d a c c e l e r
a t i o n . H y p o th e sis 3 , l a b e le d as t h e P r i n c ip l e o f
G e n e r a lit y , i s shown a s a c o n tin u e d U - fu n c tio n o f e x p o
n e n t i a l t i m e - l a g c o n s t a n t s and t r a c k in g e r r o r as
a c c e l e r a t i o n i s in c r e a s e d . The e x p e r im e n ta l r e s u l t s a r e
a l s o p r e s e n te d in t h r e e d im e n sio n a l form in C hapter VII
in o rd er t h a t th e y may be compared d i r e c t l y w ith th e
g e n e r a l m od el.
B. IMPORTANCE OF THE PROBLEM
The t i t l e o f t h e d i s s e r t a t i o n i s s u f f i c i e n t l y
e x p l i c i t to p la c e i t in t h e f i e l d o f e n g in e e r in g p s y c h o lo g y
o r , i f we w is h , in th e f i e l d o f human f a c t o r s e n g in e e r in g .
There a r e , how ever, d e f i n i t e c o n t r i b u t i o n s t o g e n e r a l
p s y c h o lo g y w hich must be c o n s id e r e d .
On t h e one hand, th e d a ta r e p o r te d from t h i s stu d y
sh o u ld have s i g n i f i c a n t a p p l i c a t i o n in th e d e s ig n o f h ig h
p erform ance o r manned sp a c e v e h i c l e s . The ty p e o f c o n t r o l
system u t i l i z e d , th e in t r o d u c t io n o f t i m e - l a g s , th e
15
_ 4~
T1ME-LA0 CONSTANTS
FIG. I - THREE DIMENSIONAL MODEL OF THE
GENERAL HYPOTHESES.
16
e x p o su re o f s u b j e c t s t o f r o n t - t o - b a c k a c c e l e r a t i o n , a r e
a l l a s p e c t s o f th e sp a c e f l i g h t p ro b le m . I n p a r t i c u l a r ,
t h i s i s t h e f i r s t p u b l is h e d s tu d y o f c o n tin u o u s human
c o n t r o l p e rfo rm an c e w here b o th c o n t r o l system p a ra m e te r s
and a c c e l e r a t i o n a re s y s t e m a t i c a l l y v a r i e d .
I n s u p p o rt f o r d e f i n i n g t h i s s tu d y in th e f i e l d o f
e n g in e e r in g p sy c h o lo g y , F i t t s (45) s t a t e s t h a t :
Man h a s p r o g r e s s e d i n th e a r t o f c o n t r o l from a
s t a t e i n w hich he u se d h a n d -h e ld t o o l s t o f a s h io n
t h e p r o d u c ts o f c i v i l i z a t i o n to a s t a g e i n w hich, by
a d j u s t i n g d e l i c a t e c o n t r o l d e v i c e s , he d i r e c t s
complex m achine p r o c e s s e s and g o v e rn s t h e flo w o f
e n erg y t o d i s t a n t p l a c e s . Man’ s r o l e in a t e c h n o
l o g i c a l s o c i e t y i s t h u s becom ing more and more one
o f g u id in g and d i r e c t i n g . A lthough t h e t o o l s and
sim p le m achines employed by c ra fts m e n can p r o b a b ly
be somewhat im proved, e n g in e e r i n g p sy c h o lo g y to d a y
sh o u ld c o n ce rn i t s e l f in l a r g e m easure w ith th e
d e s ig n o f d e v ic e s t h a t p e rm it i n d i v i d u a l s to
e x e r c i s e p r e c i s e c o n t r o l o v e r l a r g e so u rc e s o f
e n e r g y .
On t h e o t h e r h an d , how ever, S e n d e r s ’ (102) view on
t r a c k i n g s t u d i e s would show g r e a t a p p l i c a t i o n in th e
g e n e ra l f i e l d o f p sy c h o lo g y . He s t a t e s t h a t : ’’T ra c k in g
b e h a v io r i s such a u n i v e r s a l a s p e c t o f b i o l o g i c a l
f u n c t i o n i n g , t h a t i t i s r e a l l y t h e u n d e r l y i n g p r i n c i p l e
o f a l l b e h a v io r a l r e s e a r c h . ” He c o n tin u e s by p o i n t i n g o u t
t h a t :
The v a r i o u s e le m e n ts in t h e t r a c k i n g system
i n t e r a c t i n complex w ays. The d i s p l a y t h a t i s
optimum w ith one c o n t r o l l e d e lem en t may be p oor
w ith a n o th e r . . . t h u s , e v e ry t r a c k i n g s tu d y sho uld
i d e a l l y be a p a r a m e tr ic s tu d y i n w hich s e v e r a l o r
many v a r i a b l e s a r e m a n ip u la te d s i m u lt a n e o u s ly . . . .
S p e c i f i c i t y , r a t h e r th a n broad a n p l i c a b i l i t y i s
o f t e n c h a r a c t e r i s t i c o f t r a c k i n g s t u d i e s .
17
G arvey (52) s u p p o r t s t h e s e n o t i o n s and s t a t e s t h a t
what i s n eed ed i s a b e t t e r u n d e r s ta n d in g o f :
1 . t h e in f o r m a t io n p r o c e s s i n g r e q u ir e m e n t s o f th e
o p e r a t o r in d i f f e r e n t s y s te m s ,
2 . how men d i f f e r in t h e i r a b i l i t y t o m eet t h e s e
r e q u ir e m e n t s ,
3 . how t r a i n i n g e n h a n ce s human in f o r m a t io n
p r o c e s s i n g ,
4 . how d i f f e r e n t t y p e s o f s t r e s s a c t t o d e g r a d e
t h i s a s p e c t o f human p e r fo r m a n c e , and
5. how d i f f e r e n t sy ste m c o n f i g u r a t i o n s r e f l e c t
c h a n g e s in t h e o p e r a t o r ’ s in fo r m a tio n
h a n d lin g c a p a c i t y .
I t s h o u ld be n o te d t h a t t h i s d i s s e r t a t i o n t r e a t s
a l l e le m e n ts n o te d a b o v e , to some d e g r e e . S p e c i f i c a l l y ,
G arvey ( 5 2 ) i n t r o d u c e s th e word " s t r e s s " in t h e s e s t a t e
m e n ts. S in c e a c c e l e r a t i o n and d i f f i c u l t y o f t h e t a s k a r e
so m etim es o p e r a t i o n a l l y d e f in e d a s " s t r e s s o r s , ” t h e work
o f C h il e s (34) i s r e l e v a n t a t t h i s p o i n t .
C h ile s d e f i n e s s t r e s s by a t l e a s t t h r e e in d e p e n d e n t
o p e r a t i o n s : (1 ) p h y s i o l o g i c a l s t r e s s , w h ich a r i s e s o u t o f
c o n d i t i o n s a s e x tr e m e s o f te m p e r a tu r e , o x y g en d e p r i v a t i o n ,
and r a p id a c c e l e r a t i o n in s p a c e ; (2 ) p s y c h o l o g i c a l s t r e s s ,
w h ich o c c u r s u n d er c o n d i t i o n s o f c o m p le te s e n s o r y
d e p r i v a t i o n , p h y s i c a l i s o l a t i o n , i n t e n s e s e n s o r y s t i m u l a
t i o n , and t h r e a t s o f b o d i l y harm; (3 ) t a s k in d u c e d s t r e s s .
18
w h ich o c c u r s when r a d i c a l c h a n g e s t a k e p l a c e in t h e t a s k
r e q u ir e m e n ts o r c o n d i t i o n s o f c o n t r o l c o n f r o n t i n g t h e
o p e r a to r in a t a s k - o r i e n t e d s i t u a t i o n . The p r e s e n t s t u d y
was d i r e c t l y c o n c er n e d w ith ite m s ( l ) and (3 ) w it h some
sm a ll e le m e n t o f ite m (2 ).
B ased on t h e ab ove d i s c u s s i o n s , t h e r e s u l t s o f th e
p r e s e n t s tu d y makes a v a i l a b l e s p e c i f i c e x p e r im e n ta l d a ta
p e r t i n e n t t o e a ch o f th e f o l l o w i n g a r e a s o f needed
r e s e a r c h .
1 . How d i f f e r e n t sy s te m c o n f i g u r a t i o n s r e f l e c t
ch a n g es in t h e o p e r a t o r ’ s in f o r m a tio n h a n d lin g c a p a c i t y .
The t h r e e d i f f e r e n t t i m e - l a g s a r e , i n e f f e c t , d i f f e r e n c e s
in t h e r a t e o f in f o r m a tio n t r a n s m i s s io n and r e s u l t a n t e r r o r
s c o r e s , t h e r e f o r e , a re a m easurem ent o f t h e o p e r a t o r ’ s
h a n d lin g a b i l i t i e s o f v a r io u s r a t e s o f in f o r m a tio n f e e d
b a ck .
2 . How d i f f e r e n t t y p e s o f s t r e s s a c t on human
p e r fo r m a n c e . S in c e t r a n s v e r s e a c c e l e r a t i o n i s one o f t h e
in d e p e n d e n t v a r i a b l e s , m a n ip u la tio n o f m a g n itu d e s p r o v id e s
a means f o r e v a lu a t in g one e le m e n t o f t h i s s t r e s s a s p e c t .
M oreover, t h e t h r e e d i f f e r e n t t i m e - l a g s may be c o n s id e r e d
a s a t a s k - in d u c e d s t r e s s and m easu rem en ts t h e r e o f c o n t r i b
u t e t o a n o th e r e le m en t o f t h i s p rob lem .
3 . How t r a i n i n g e n h a n c e s human p e r fo r m a n c e . The
tw o -d a y l e a r n i n g p e r io d showed l e a r n i n g phenomena w h ich
a r e d i r e c t l y p e r t i n e n t to t h i s a s p e c t .
19
4 . The param etric e v a lu a tio n o f c o n tr o l system
v a r ia b le s and a c c e le r a t io n m agnitudes p r o v id e s in fo r m a tio n
which i s not y e t a v a ila b le from o th e r so u rc es and b ea rs
d i r e c t l y on cu rren t manned sp ace f l i g h t r e se a r c h
a c t i v i t i e s .
On th e q u e stio n o f how s t u d ie s in e n g in e e r in g
p sy ch o lo g y may le a d to fu r th e r b a s ic r e s e a r c h , Skinner
(1 0 5 ), in an e x c e ll e n t a r t i c l e on how p ig e o n s were tr a in e d
to serv e as a guidance system in a m i s s i l e , s t a t e s :
Som ething happened during th e b r i e f l i f e o f
P r o je c t P igeon which i t has taken a lo n g tim e to
a p p r e c ia te . The p r a c t i c a l ta s k b e fo re us c r e a te d
a new a t t i t u d e toward th e b eh avior or organ ism s.
W e had to maximize th e p r o b a b ilit y th a t a g iv en
form o f b eh avior would occur at a g iv en tim e . W e
cou ld n o t e n jo y th e lu x u ry o f o b s e r v in g one v a r ia b le
w h ile a llo w in g o th e r s t o change in what we hoped was
a random fa s h io n . W e had to d is c o v e r a l l r e le v a n t
v a r ia b le s and submit them to exp erim en tal c o n tr o l
whenever p o s s i b l e .
and:
M oreover, in th e seven y e a rs which have fo llo w e d
th e l a s t o f th e s e r e p o r t s , a g r e a t d e a l o f r e le v a n t
in fo rm a tio n has been a cq u ired . The c o lo r v i s i o n o f
th e p igeon i s now th o ro u g h ly u n d erstood ; i t s g e n e r a l
i z a t i o n alo n g s i n g le p r o p e r tie s o f a stim u lu s has
been record ed and a n a ly zed ; and th e m aintenance o f
beh avior through sc h e d u lin g o f rein fo r ce m en t has been
d r a s t i c a l l y im proved, p a r t ic u la r ly in th e developm ent
o f te c h n iq u e s fo r p a cin g r e sp o n se s fo r l e s s e r r a t i c
and s t e a d ie r s i g n a l s .
On th e q u e stio n o f whether doin g r e se a r c h on
problems o f manned space f l i g h t i s removed from th e more
u su a l b e h a v io r a l s t u d i e s , M elton (88) p o in t s out t h a t:
Space f l i g h t i s b ein g approached w ith w e l l -
e s t a b lis h e d r e se a r c h m eth o d o lo g ies and no one has
20
su g g e ste d t h a t we need d iv o r c e th e s e m eth o d o lo g ies
from th o s e o f th e p a s t , nor i s i t f e l t th a t we are
in need o f a unique "space p sy c h o lo g y ." R ath er, i t
i s apparent t h a t th e human f a c t o r s problem s o f sp ace
t r a v e l r e p r e se n t extrem e ran ges o f b eh avior lo n g
stu d ie d a t t h e i r l e s s e r extrem e p o in t s by th e
p s y c h o l o g is t .
In c o n c lu s io n , th e r e appears to be both a p p lie d
and b a s ic c o n tr ib u tio n s o f t h i s d i s s e r t a t i o n . There are
a ls o broader im p lic a t io n s th a t th e f i e l d o f e n g in e e r in g
p sy ch o lo g y i s in f a c t , when th e s c i e n t i f i c method i s u se d ,
another approach in th e i n v e s t i g a t io n o f th e s tr u c tu r e o f
human b eh a v io r.
SECTION TW O
BACKGROUND OF THE STUDY
CHAPTER I I I
A HISTORY OF THE H U M A N AS A CONTROLLER
A. THE COMPLEXITY OF THE PROBLEM
A very la r g e number o f exp erim en tal s tu d ie s
reg a rd in g human tr a c k in g perform ance have been r e p o r te d in
th e p s y c h o lo g ic a l l i t e r a t u r e in th e p a st d eca d e. T his
c h a p te r, t h e r e f o r e , w i l l p r e se n t background in fo rm a tio n
r e le v a n t to such t o p ic s a s: c o m p e n sa to r and p u r s u it
tr a c k in g t a s k s , v a r io u s ty p e s o f t im e - la g s and o th er
machine v a r ia b le s , elem en ts o f in fo r m a tio n th e o r y , and
c e r ta in a s p e c ts o f th e le a r n in g o f s k i l l e d motor t a s k s .
For more d e t a ile d coverage o f o th e r a s p e c ts o f th e human-
c o n t r o lle r problem , th e read er i s r e fe r r e d t o th e fo llo w in g
p e r tin e n t b ib lio g r a p h ic and exp erim en tal l i t e r a t u r e : (7 ,
29, 30, 42, 45, 47, 6 7 , 34, 37, gg, 1 0 2 , 103, 109, 1 1 0 ,
1 1 4 ).
F i t t s (47) p o in ts out th a t th e r e are a g r e a t
number o f v a r ia b le s th a t in flu e n c e p ercep tu a l-m o to r
a c t i v i t i e s . A few o f th e s e are: (1) stim u lu s p r o p e r t i e s ,
such a s , freq u en cy , co h e re n c e, a m p litu d e, and d i r e c t io n o f
m otion; (2) resp o n se p r o p e r t i e s , such a s , d i r e c t io n ,
a m p litu d e, req u ired f o r c e , seq u en cin g and tim in g o f
22
23
m ovem ents; and ( 3 ) m achine p r o p e r t i e s , su ch a s l a g s , n o i s e ,
i n t e r m i t t a n c e , and number o f in f o r m a t io n s o u r c e s .
The p rob lem o f d i s c o v e r i n g optimum c o n t r o l
c h a r a c t e r i s t i c s and o f s p e c i f y i n g human p e r fo r m a n c e a s a
f u n c t i o n o f t h e many v a r i a b l e s , a c c o r d in g t o F i t t s (U7),
i s t h a t many o f t h e s e v a r i a b l e s have been e x p e r i m e n t a ll y
fou n d t o i n t e r a c t w ith one a n o t h e r . T h is , o f c o u r s e ,
makes t h e d ev elo p m en t o f a t h e o r y a v e r y d i f f i c u l t p ro b lem .
When a r e s e a r c h e r p l a c e s t h e t r a c k i n g t a s k in a
h o s t i l e e n v ir o n m e n t, t h e t a s k o f th e o r y -d e v e lo p m e n t i s
f u r t h e r i n c r e a s e d . McRuer and K rendel (36) s t a t e t h a t :
The b e h a v io r o f human b e in g s as e le m e n t s in
company w it h o t h e r com ponents o f c o n t r o l sy s te m s
w i l l depend b oth uoon t h e c a p a b i l i t i e s o f t h e human
and on th e e x t e r n a l e n v ir o n m e n t. By h i s a b i l i t y t o
m o d ify h i s c h a r a c t e r i s t i c s t o m atch a p p r o p r i a t e ly
t h e many p o s s i b l e c o n t r o l s i t u a t i o n s , t h e human m ust
be c o n s id e r e d a u n iq u e sy s te m com p onent. The v e r y
f a c t o f t h i s a d a p t a tio n m akes d e s c r i p t i o n o f t h e o p e r
a t o r en o rm o u sly com p lex when v iew ed in t h e l a r g e , and
makes i t d e s i r e a b l e t o t r y t o s e t up some s i m p l i f i e d ,
c o n s t a n t s i t u a t i o n s w it h in w h ich on e may have some
hope o f o b t a i n in g a r e a s o n a b ly s im p le b e h a v io r a l m o d e l.
T h is , o f c o u r s e , i s t h e b a s i s f o r t h e i r a ttem p t t o
d e s c r ib e th e human in ter m s o f m a th e m a tic a l p r o p e r t i e s
c a l l e d " t r a n s f e r f u n c t i o n s . ” More w i l l be s a i d about t h i s
s u b j e c t l a t e r i n t h i s c h a p t e r .
B. CONTROL SYSTEM DYNAMICS
S tim u lu s v a r i a b l e s
There a r e many d i f f e r e n t t y p e s o f s t i m u l i o r in p u t s
24
u s e d i n th e c u r r e n t l i t e r a t u r e . The m ost f r e q u e n t l y u s e d
a r e (a ) s t e p , (b ) ramp, (c ) s i n e , and (d) co m p lex wave
form s (4 2 ). F ig u r e 2 i s a g e n e r a l g r a p h ic p r e s e n t a t i o n
sh o w in g each t y p e o f s t i m u l u s .
In g e n e r a l , i t may be s a i d t h a t human r e s p o n s e s t o
t h e s e s t i m u l i a r e s i m i l a r (42). T here i s , h o w ev e r, one
s i g n i f i c a n t e x c e p t i o n . In s t e p , ramp, and s i n e fo r m s, t h e
o p e r a t o r can r e a d i l y l e a r n t h e s t im u lu s p r o p e r t i e s b e c a u se
t h e s t im u lu s t e n d s t o become c y c l i c . The o p e r a t o r , t h e r e
f o r e , can a n t i c i p a t e th e n e x t s t i m u l u s . In com p lex wave
fo r m s, h o w ev er, t h e r e i s a c h a r a c t e r i s t i c human p h a se l a g
due t o a r ed u c ed a n t i c i p a t o r y s i t u a t i o n . S in c e th e s t i m
u l u s i n t h e p r e s e n t stu d y was a com p lex wave form , t h e
r e a d e r sh o u ld be aware o f th e in f o r m a t io n a l d i f f e r e n c e from
t h e o u t s e t .
T im e -la g s
There a r e t h r e e b a s ic t y p e s o f c o n t r o l t i m e - l a g s :
(a ) e x p o n e n t i a l , (b) s ig m o id , and ( c ) t r a n s m i s s i o n . F ig u r e
3 shows t h e r e s p o n s e t o a s t e p in p u t w ith ea ch o f t h e t h r e e
d i f f e r e n t l a g s .
C o n k lin ( 3 6 ) w h il e d i s c u s s i n g t r a n s m i s s io n l a g s ,
p o i n t s o u t t h a t f o l l o w i n g a c o n t r o l m ovem ent, a f i x e d tim e
i n t e r v a l e x p i r e s b e f o r e in f o r m a tio n r e l a t i v e t o th e
movement i s v i s u a l l y d i s p l a y e d . E x p o n e n tia l l a g , h o w ev e r,
p r o d u ce s an e x p o n e n t ia l o u tp u t o f t h e c o n t r o l d is p la c e m e n t
25
RAMP
STEP
COMPLEX
L U
SINE
TIME
FIG. 2 - VARIOUS TYPES OF INPUT STIMULI, AFTER ELY,
BOWEN AND ORLANSKY ( 4 2 ) .
26
INPUT
C . V T
\s
TRANSMISSION
■ ■ ■ — ' '■ »
T I ME
FIG. 3 - RESPONSE TO STEP INPUT WITH THREE DIFFERENT
KINDS OF LAG, AFTER ELY, BOWEN AND ORLANSKY(42).
and i s d e f in e d a s th e tim e i n t e r v a l b etw een th e c o n t r o l
in p u t and 63% o f th e maximum o u tp u t. The c o n t r o l movement,
t h e r e f o r e , i s im m ed ia te ly p e r c e iv e d but a t t a i n e d c o m p le tio n
as an e x p o n e n tia l f u n c t io n o f tim e . I t i s c l e a r , t h e n ,
t h a t a t r a n s m is s io n l a g i s a co m p lete i n t e r r u p t i o n , or
l o s s , o f v i s u a l in fo r m a tio n , w h e r e a s, e x p o n e n tia l l a g i s
o n ly a p a r t i a l l o s s . B ased on c l a s s i c a l le a r n i n g t h e o r y
($5), one would p r e d ic t t h a t perform an ce would be b e t t e r
w ith e x p o n e n tia l l a g th a n w ith t r a n s m is s io n la g , w ith
sigm oid l a g s f a l l i n g somewhere betw een t h e tw o. T h is h a s
n ot o n ly been d em on strated e x p e r im e n t a lly , b u t, from a
m easurem ent p o in t o f v ie w , e r r o r i s g e n e r a l ly m easured a s
a f u n c t io n o f t i m e . H ence, w h ile t h e o p e r a to r i s w a it in g
fo r th e r e sp o n s e from th e t r a n s m is s io n l a g , e r r o r w i l l ,
o f c o u r s e , be a c cr u e d .
E ly , Bowen, and O rla n sk y (42) p o in t ou t t h a t
t r a n s m is s io n l a g s n o r m a lly degrade p erform an ce even though
th e l a g s may be so sm a ll t h a t th e o p e r a to r i s unaware o f
them . E x p o n e n tia l and sig m o id l a g s may e i t h e r im prove o r
degrade p erfo rm a n ce, d ep en d in g on t h e i r i n t e r a c t i o n s w ith
o th e r p a r a m e te r s. T hese f a c t s sh o u ld be n o te d , s i n c e th e
p r e s e n t stu d y in c o r p o r a te d v a r io u s e x p o n e n t ia l t i m e - l a g s
as one in d ep en d en t v a r i a b l e .
O pen-loop and c lo s e d - lo o p
c o n t r o l sy ste m s
There a re two b a s ic t y p e s o f c o n t r o l sy ste m s:
2a
(a ) o p e n - lo o p , and (b) c l o s e d - l o o p . E ly , Bowen, and
O rlan sk y (42) d e f in e an o p e n -lo o p as a sy stem in w hich no
in fo r m a tio n i s fe d b a ck . F i t t s (45) s t a t e s t h a t in a
human a n a lo g y , t h e o p e n -lo o p sy stem r e s e m b le s a p a t i e n t
w ith t a b e s d o r s a l i s who can send s i g n a l s t o h i s own
m u s c le s , bu t u n l e s s he w a tc h e s t h e r e s u l t i n g movement,
r e c e i v e s no r e tu r n s i g n a l s t o t e l l him what h i s arm i s
d o in g .
E ly , Bowen, and O rla n sk y (42) d e f i n e a c lo s e d - lo o p
a s a system in w hich in fo r m a tio n about an o u tp u t i s fe d
back to an e a r l i e r s ta g e in th e sy s te m . F i t t s (45) p o i n t s
o u t t h a t in t h e c l o s e d - l o o p , o r serv o sy s te m , th e b e h a v io r
o f th e se r v o i s g o v ern ed , n o t by th e s i g n a l a lo n e , bu t by
th e d i f f e r e n c e betw een t h e in p u t and some f u n c t io n o f th e
o u tp u t. The normal human s u b j e c t i s , o f c o u r s e , a c l o s e d -
lo o p sy stem .
C o n tro l o rd er
The c o n tr o l o rd er i s th e m a th em a tica l o rd er o f t h e
d i f f e r e n t i a l e q u a tio n d e s c r ib in g th e tr a n s m is s io n
p r o p e r t ie s o f th e m ach ine. The v a r io u s c o n t r o l o r d e r s a r e
a s f o llo w s ( 4 2 ):
Z e r o -o r d e r . — The o p e r a t o r ’ s c o n t r o l o u tp u t d i r e c t l y
d e ter m in e s t h e m achine o u tp u t. T his i s commonly c a l l e d
p o s i t i o n c o n t r o l .
F i r s t - o r d e r . --T h e o p e r a t o r ’ s c o n t r o l o u tp u t
29
d i r e c t l y d e ter m in e s th e r a t e o f change o f th e m achine
o u tp u t. T h is i s commonly c a l l e d r a t e c o n t r o l or v e l o c i t y
c o n t r o l . The f i r s t - o r d e r c o n t r o l can a l s o in c lu d e th e
p o s i t i o n term and would be c a l l e d r a t e - a id e d o r v e l o c i t y -
a id e d c o n t r o l .
S e c o n d -o r d e r . — The o p e r a t o r ’ s o u tp u t d i r e c t l y
d e ter m in e s th e a c c e l e r a t i o n o f th e m achine o u tp u t. T h is i s
commonly c a l l e d a c c e l e r a t i o n c o n t r o l . S eco n d -o rd er c o n tr o l
can a ls o in c lu d e a l l lo w e r -o r d e r term s and i s commonly
c a ll e d a c c e le r a t i o n - a i d e d c o n t r o l.
N th -o r d e r . — The o p e r a t o r ’ s c o n t r o l ou tp u t d i r e c t l y
a f f e c t s th e nth d e r iv a t i v e o f th e m achine o u tp u t and can
a ls o a f f e c t a l l lo w e r -o r d e r te r m s.
I t sh ou ld be n o te d t h a t t h e p r e s e n t stu d y i s
con cern ed w ith a p o s i t i o n o r z e r o -o r d e r t a s k . However,
when th e e x p o n e n tia l t i m e - l a g s are in tr o d u c e d in t o th e
c o n tr o l system and th e o p e r a to r nc l o s e s - t h e l o o p , ” by
d e f i n i t i o n o f e x p o n e n t ia l, a se c o n d -o r d e r c o n t r o l i s
o b ta in e d .
G. H U M A N DYNAMICS
A human c o n t r o l sy stem model
H ollan d (66) p r e s e n t s an i n t e r e s t i n g s t im u lu s -
r e sp o n s e model f o r a sim p le human c o n t r o l sy ste m . F ig u r e
4 shows t h e f u n c t io n a l r e l a t i o n s h i p betw een t h e t h r e e
b a s ic com ponents o f a human c o n tr o l system ; (a ) c e n t r a l
I
i
I
DECISION STIMULUS
CENTRAL
NERVOUS
SYSTEM
MOTOR
► ELEMENT AND
CONTROL LOAD
SENSORY
ELEMENTS
RESPONSE
FEEDBACK
SENSORY
ELEMENTS
FIG. 4 - A SIMPLE STIMULUS-RESPONSE MODEL
FOR A HUMAN CONTROL SYSTEM.
v _ o
O
31
n e r v o u s s y s te m , (b ) m otor e le m e n t s , and ( c ) fe e d b a c k
e le m e n t s .
H o lla n d (66) s t a t e s t h a t th e c e n t r a l n e r v o u s
s y s te m , c o m p r is in g t h e b r a in and a s s o c i a t e d n e r v e s ,
sa m p le s t h e in p u t w it h fe e d b a c k d a ta t h a t i s s t o r e d by a
s h o r t term memory. The a n a l y s i s tim e i s a p p r o x im a te ly
0 .3 s e c o n d . A d e c i s i o n i s th e n r e a c h e d and an e l e c t r i c a l
s i g n a l i s s e n t t o t h e m otor e le m e n t w h ich y i e l d s t h e
r e s p o n s e . D uring t h e a c t i v a t i n g p e r io d o f t h e m otor
e le m e n t, t h e c e n t r a l n e r v o u s sy ste m m o n ito r s t h i s r e s p o n s e
and no a t t e n t i o n i s u t i l i z e d f o r t h e r e c e i v i n g o f new
in c o m in g s t i m u l i . T h is tim e i n t e r v a l i s a p p r o x im a te ly
0 .2 s e c o n d . A t t e n t io n i s th e n s w it c h e d back t o new
s t i m u l i c o m p le tin g one sa m p lin g c y c l e o f t h e human c o n t r o l
sy ste m .
D i s c r e t e and c o n t in u o u s m ovem ents
S e v e r a l a u th o r s (45, 6 4 , 66, 1 1 1 ) h a v e s t a t e d t h a t
t h e human o p e r a to r d o e s n o t make c o n tin u o u s c o n t r o l
m ovem ents, bu t r a t h e r , h e m akes d i s c o n t i n u o u s m ovem ents.
F i t t s (45) s t a t e s t h a t t h e r e i s u s u a l l y a s u c c e s s i o n o f
" m o r e - o r - le s s d i s c o n t in u o u s m ovem ents w here e a c h movement
i s a s e p a r a t e e f f o r t t o r e d u c e t h e e r r o r ."
Woodworth (1 1 8 ) c a l l e d t h e f i r s t o f su ch a s e r i e s
o f m ovem ents an " i n i t i a l im p u lse" and fo u n d t h a t i t l a s t e d
ab ou t 0 . 2 s e c o n d . The se c o n d a r y m ovem ents w ere c a l l e d
32
" c u r r e n t c o n t r o l . ” W oodworth r e p o r t e d a v a l u e o f a b o u t
0 . 5 s e c o n d f o r t h e i n t e r v a l b e tw e en t h e i n i t i a t i o n o f
s u c c e s s i v e a d j u s t m e n t s d u r in g c u r r e n t c o n t r o l i n a o n e
d im e n s io n a l t a s k .
P e t e r s and W enbourne ( 9 3 ) , s t u d y i n g t h e t im e
p a t t e r n s o f r a p id arm m ovem ents e x e c u t e d i n m ovin g a
s t y l u s a lo n g a s p i r a l p a t h , c o n c lu d e d t h a t c o n t r o l w as
a c c o m p lis h e d b y m eans o f a s e r i e s o f m o r e - o r - l e s s s e p a r a t e
and s u c c e s s i v e v a r i a t i o n s i n r a t e . M o r e o v e r , t h e s e
s e p a r a t e "m otor im p u ls e e f f e c t s " w ere c o m p l e t e l y d e te r m in e d
by p r o c e s s e s t h a t p r e c e d e d e a c h p h a se o f t h e m o v em en ts.
S t e t s o n and M c D ill (1 0 $ ) show ed e v id e n c e t h a t s lo w
o r c o n t r o l l e d m ovem ents can be m o d if ie d a t an y p o i n t i n
t h e i r c o u r s e , b u t t h i s i s n o t t r u e f o r f a s t m ovem en ts.
E l l s o n , H i l l , and Gray ( 4 1 ) , a s s u p p o r t f o r
H o lla n d ’ s (66) m o d e l, i d e n t i f i e d two t y p e s o f t r a c k i n g i n
a p u r s u i t t a s k u s i n g a p o s i t i o n c o n t r o l s y s t e m . R a t e -
t r a c k i n g r e s p o n s e s a p p ea r e d a f t e r t h e o p e r a t o r had
a c h ie v e d a r e l a t i v e l y s m a ll p o s i t i o n e r r o r and p o s i t i o n -
t r a c k i n g r e s p o n s e s w ere e v id e n c e d b y s i n g l e o r s u c c e s s i v e
h a l f - c y c l e w a v efo rm s w h ic h w e re i n t e r p r e t e d t o be d i s c r e t e
c o n t r o l m o v em en ts. The a u t h o r s c o n c lu d e d t h a t s k i l l e d
m ovem ents i n c o n t in u o u s t a s k s a r e n o t u n d e r c o n t in u o u s
v i s u a l c o n t r o l b u t , l i k e e le m e n t s i n d i s c r e t e c o r r e c t i v e
m ovem en ts, a r e made i n u n i t s .
O th e r r e s e a r c h e r s h a v e r e p o r t e d v a l u e s w h ic h
33
e s s e n t i a l l y s u b s t a n t i a t e Woodworth (1 1 £ ) and H o lla n d (66)
i n t h e i r tim e e s t i m a t e s and s k i l l e d m otor p r o c e d u r e s .
B a te s ( 5 ) , E l ls o n and H i l l (40), H ick ( 6 4 ) , and T u s tin
(1 1 3 ) a l l r e p o r t t h a t v i s u a l l y c o n t r o l l e d a im in g and
t r a c k i n g b e h a v io r u s u a l l y shows a c y c l i c p a t t e r n w it h a
mean fr e q u e n c y o f ab ou t two r e s p o n s e s p e r s e c o n d .
R e a c t io n tim e and t h e p s y c h o l o g i c a l
r e f r a c t o r y p e r io d "
E ly , Bowen, and O rla n sk y (42) s t a t e t h a t th e
(a ) s e n s e u s e d , (b ) s i g n a l c h a r a c t e r i s t i c s , ( c ) s i g n a l
c o m p le x it y , (d ) s i g n a l r a t e , and ( e ) a n t i c i p a t o r y in fo r m a
t i o n a r e f a c t o r s a f f e c t i n g r e a c t i o n t i m e , o r "human tim e
l a g s . " T hese two ter m s a r e u se d sy n o n y m o u sly i n a " c o n t r o l
sy s te m se n se " so t h a t t h e y a r e d e f in e d a s th e tim e i n t e r v a l
e l a p s i n g b etw een t h e b e g in n in g o f t h e s i g n a l ( s t i m u l u s )
and t h e c o m p le tio n o f t h e o p e r a t o r 1s r e s p o n s e . Hence, i t
i n c l u d e s t h e tim e r e q u ir e d by t h e o p e r a t o r t o s e n s e t h e
s i g n a l ( s e n s in g t i m e ) , p lu s t h a t r e q u ir e d t o d e c id e what
r e s p o n s e t o make ( d e c i s i o n tim e o r t h i n k i n g t i m e ) , p lu s
t h a t r e q u ir e d t o r e s p o n d (movement t im e ). I t s h o u ld be
n o te d by t h e r e a d e r t h a t t h e more c l a s s i c a l s t a t e m e n t s
d e f i n e r e a c t i o n tim e a s e n d in g when t h e o p e r a t o r s t a r t s
t o make h i s r e s p o n s e r a th e r th a n when he f i n i s h e s m aking
i t . For a d e t a i l e d c o v e r a g e o f r e a c t i o n tim e and
a s s o c i a t e d i n f l u e n c i n g f a c t o r s , t h e r e a d e r i s r e f e r r e d t o
Bryan (16).
34
D a v is (37) d e f i n e s t h e " p s y c h o l o g i c a l r e f r a c t o r y
p e r io d " a s t h e p e r i o d f o l l o w i n g t h e p r e s e n t a t i o n o f t h e
f i r s t s t i m u l u s d u r in g w h ic h a s e c o n d s t i m u l u s w o u ld g i v e
r i s e t o a d e la y e d s e c o n d r e a c t i o n . I n o p e r a t i o n a l t e r m s ,
F i t t s (45) s t a t e s t h a t
f o r t a s k s r e q u i r i n g r a p id c o r r e c t i v e m ovem en ts i f tw o
s t i m u l i S]_ and So o c c u r i n r a p i d s e q u e n c e , t h e n t h e
r e s p o n s e c a l l e d f o r by S 2 c a n n o t b e i n i t i a t e d u n t i l
t h e p r im a r y m ovem ent i n r e s p o n s e t o h a s b e e n
c o m p le te d o r u n t i l an a p p r o p r i a t e t im e i n t e r v a l h a s
e l a p s e d .
T h is i s , o f c o u r s e , s i m i l a r t o t h e " p h y s i o l o g i c a l a b s o l u t e
r e f r a c t o r y p e r i o d ” o f n e u r o n s . F or a d i s c u s s i o n o f t h e
l a t t e r , t h e r e a d e r i s r e f e r r e d t o Morgan and S t e l l a r ( 6 9 ) .
T h ere h a s b e e n some d is a g r e e m e n t i n t h e l i t e r a t u r e
(37, 6 4 , &3, 112) o n t h e e x a c t n a t u r e o f t h e p s y c h o l o g i c a l
r e f r a c t o r y p e r i o d . H ic k ( 6 4 ) , f o r e x a m p le , s t a t e s :
I t i s c l e a r l y im p o r ta n t f o r t h e l e a r n i n g p r o c e s s
t h a t t h e s t i m u l u s and i t s r e s p o n s e s h o u ld n o t be
c o n f u s e d and o b s c u r e d by o t h e r s t i m u l u s - r e s p o n s e
p a i r s r u n n in g m ore o r l e s s c o n c u r r e n t l y . Hence,
t h e r e i s a p r o b a b i l i t y , w i t h some i n t r o s p e c t i v e
s u p p o r t , t h a t t h e o p e r a t o r w a i t s u n t i l t h e r e i s
r e c o g n i z a b l e and r e l e v a n t r e s u l t from h i s p r e v io u s
r e s p o n s e b e f o r e c o n s i d e r i n g a f u r t h e r o n e . Where
t h e r e s p o n s e i s a m ovement o f d e f i n i t e e x t e n t - i . e . ,
p o s i t i o n a l t r a c k i n g , i t w i l l n o r m a lly t a k e a b o u t
0 .1 5 s e c o n d b e f o r e i t becom es p e r c e p t i b l y r i g h t o r
w r o n g , so t h a t , a d d in g 0 .3 5 s e c o n d f o r r e a c t i o n
t im e ( w it h r e f r a c t o r y d e l a y ) , t h e i n t e r v a l o f
i n t e r m i t t e n t f u n c t i o n i n g w i l l be a b o u t 0 . 5 s e c o n d .
D a v is ( 3 7 ) , h o w e v e r , p o i n t s o u t t h a t t h e 0 . 5
se c o n d l i m i t i s n o t n e c e s s a r i l y t h e c a s e . He r e p o r t s ,
from r e s u l t s o f a b a r - p r e s s i n g e x p e r im e n t , t h a t when t h e
i n t e r v a l b e tw e e n s i g n a l s i s l e s s t h a n t h e r e a c t i o n t im e t o
35
th e f i r s t s i g n a l , d e la y s i n th e r e a c t io n tim e t o th e second
s i g n a l s o ccu rred in th e u s u a l l y p r e d ic t e d manner. When
th e i n t e r v a l i s g r e a t e r than th e f i r s t r e a c t i o n tim e no
such d e la y s a re fou n d .
Of im port h ere i s t h a t in t r a c k in g t a s k s th e
maximum r a te o f r e sp o n s e by t h e o p e r a to r i s two o r th r e e
tim e s p er seco n d , r e g a r d le s s o f how h ig h th e demand r a te
may b e . T h is maximum r a te i s due i n p a r t , a c c o r d in g t o
Eljr, Bowen, and O rlan sk y (42), "to m an's i n a b i l i t y to
resp on d to a new s i g n a l w h ile th e p r e v io u s s i g n a l and i t s
a s s o c ia t e d d e c is io n are b e in g p r o c e s s e d , i . e . , man i s in
a ’p s y c h o lo g ic a l r e f r a c t o r y p e r i o d . ’ ”
In t h i s r e g a r d , and in o p e r a t io n a l terras, H ollan d
(66) s t a t e s t h a t th e upper l i m i t o f s t a b i l i t y i s rea ch ed
when th e freq u en cy o f t h e in p u t s t i m u l i becomes such t h a t
th e m o n ito r in g tim e i s to o sm all t o a f f o r d r e l i a b l e
feed b ack t o th e b r a in w hich com p en sates fo r th e in c r e a s in g
r e a c t io n t im e . M oreover, " f a ilu r e o f th e human o p e r a to r
to m a in ta in a o n e - to - o n e c o rresp o n d en ce a t h ig h e r f r e
q u e n c ie s co u ld stem from i n s u f f i c i e n t feed b a ck tim e or
d a ta n e c e s s a r y to a f fo r d th e c o r r e c t amount o f com p en sation
r e q u i r e d .”
H ollan d (66) g o e s on to sa y t h a t under c e r t a i n
c o n d it io n s , th e o p e r a to r w i l l f a l l sh o r t o f t h i s o n e - t o -
one c o rr esp o n d en ce , th e two prim ary c a u s e s o f w hich a r e :
(a) t i m e - l a g a t t r ib u t e d t o m ental a n a l y s i s , term ed c h o ic e
r e a c t io n tim e , and (2 ) t i m e - l a g c o n tr ib u te d by th e n eu ro
m uscular sy stem .
In th e way o f summary, t h e r e a re two f a c t o r s
r e le v a n t to th e p r e s e n t stu d y :
a . The human o p e r a to r sh o u ld n ot be e x p e c te d
t o respond a c c u r a t e ly t o s t i m u l i sp aced a t i n t e r v a l s o f
l e s s th an one se c o n d . H ollan d (66) s t a t e s t h a t i t i s
b e t t e r in term s o f r e l i a b i l i t y and a c cu ra c y o f c o n t r o l
t o m a in ta in an i n t e r v a l o f a p p ro x im a te ly 2 .0 se c o n d s .
b. The neurom uscular l a g - t im e sh ou ld be kep t t o
a r e a so n a b ly lo w v a lu e . Gibbs (55 p o in t s o u t t h a t th e
r o u n d -tr ip tim e r e q u ir e d f o r a n erv e im p u lse t o ca u se
th e m uscle to a c t and to r e tu r n a s ig n a l i s o n ly 1 9 -3 6
m i ll i s e c o n d s . T h is tim e d oes not, how ever, in c lu d e th e
t i m e - l a g stem ming from th e co m p lia n ce o f th e m u scle and
t h e i n e r t i a o f th e lim b and i t s a s s o c i a t e d l o a d . As n oted
by W ilk ie (117) a com b in ation o f a 1 0 -2 0 pound c o n tr o l
lo a d and a n e c e s s a r y c o n s id e r a b le movement or v e l o c i t y
d i c t a t e s a 1 5 0 -2 0 0 m illis e c o n d t i m e - l a g . T h e r e fo r e , i f
lo w v a lu e s o f neurom uscu lar t i m e - l a g s a re to be m a in ta in e d ,
i t i s n e c e s s a r y t h a t th e o p e r a to r be r e q u ir e d to e f f e c t
o n ly sm all movements w ith sm a ll l o a d s . Faber (44) r e p o r te d
s im ila r r e s u l t s .
37
D. MAN-MACHINE DYNAMICS
I n f o r m a t io n t h e o r y
I n f o r m a t io n t h e o r y h a s b e e n u s e d r e c e n t l y a s t h e
b a s i s f o r some e x p e r im e n t a l s t u d i e s r e g a r d i n g t h e a b i l i t i e s
o f humans a s p r o c e s s o r s o f i n f o r m a t i o n .
K r u le e (79) s t a t e s t h a t
t h e f u n c t i o n p e r fo r m e d b y human o p e r a t o r s i n m an-
m a c h in e s y s t e m s a r e p r i m a r i l y t h o s e o f c o n t r o l o f
t h e e n e r g y s o u r c e s o f t h e s y s t e m . C o n tr o l f u n c t i o n s
i n v o l v e , by t h e i r v e r y n a t u r e , t h e a v a i l a b i l i t y o f
r e l e v a n t i n f o r m a t i o n and t h e o p p o r t u n i t y t o t r a n s m i t
c o n t r o l d e c i s i o n s r e a c h e d on t h e b a s i s o f t h i s
i n f o r m a t i o n .
He c o n t i n u e s by p o i n t i n g o u t t h a t o n e p o s s i b l e h y p o t h e s i s
c o n c e r n in g humans a s p r o c e s s o r s o f i n f o r m a t io n i s __
e q u i v a l e n t t o t i m e : t h a t t h e c o m p l e x i t y o f an y d e c i s i o n
i s d i r e c t l y r e l a t e d t o t h e am ount o f i n f o r m a t i o n i n v o l v e d
i n t h a t d e c i s i o n . T h is i s a r e s u l t c o n s i s t e n t w i t h th e
f i n d i n g s o f Hake and G arner ( 5 9 ) , H ick (63) and Hyman (70)
a l l i n d i c a t i n g t h a t human r e a c t i o n tim e i n c r e a s e s a s t h e
amount o f i n f o r m a t io n t o be p r o c e s s e d i s i n c r e a s e d .
P o u lto n (9 5 ) , r e p o r t i n g on an i n v e s t i g a t i o n on t h e
b a s i s o f p e r c e p t u a l a n t i c i p a t i o n i n t r a c k i n g , s t a t e s t h a t
t h e s u b j e c t can u s e tw o s o u r c e s o f i n f o r m a t io n i n o r d e r t o
p r e d i c t t h e in p u t o f t h e im m e d ia te f u t u r e . F i r s t , i t i s
p o s s i b l e t o p r e d i c t t h e c h a n g e s i n t h e p o s i t i o n and r a t e
o f m ovem ent o f t h e in p u t from i t s p r e s e n t r a t e and
a c c e l e r a t i o n . S e c o n d ly , c e r t a i n s t a t i s t i c a l p r o p e r t i e s
3 3
o f t h e in p u t ca n be l e a r n e d , su c h a s i t s mean and maximum
a m p lit u d e .
In a s u b s e q u e n t s t u d y on t h e s t a t i s t i c a l p r o p e r t i e s
o f t h e i n p u t , P o u lt o n (94) r e p o r t s t h a t t h e e x p e r im e n t w as
d e s ig n e d : ( a ) t o d e te r m in e t h e s u b j e c t ’ s a b i l i t y t o l e a r n
and u s e h i s k n o w led g e o f t h e s t a t i s t i c a l p r o p e r t i e s o f t h e
i n p u t , and (b ) t o com pare t h e e f f e c t i v e n e s s o f v i s u a l
in f o r m a t io n a b o u t a c o u r s e a c q u ir e d b e f o r e t r a c k i n g , w i t h
v i s u a l - k i n a e s t h e t i c i n f o r m a t io n a c q u ir e d d u r in g t h e t a s k .
P o u lt o n r e p o r t s t h a t v i s u a l in f o r m a t io n a c q u ir e d b e f o r e
t r a c k i n g w as fo u n d t o be l e s s e f f e c t i v e th a n v i s u a l -
k i n a e s t h e t i c in f o r m a t io n a c q u ir e d w h il e t r a c k i n g .
In r e f l e c t i n g on P o u l t o n ’ s w ork , S e n d e r s (102)
p o i n t s o u t t h a t a lt h o u g h a c q u ir e d k n o w led g e o f t h e in p u t
s i g n a l c h a r a c t e r i s t i c s i s im p o r ta n t and n e c e s s a r y i n b o t h
k in d s o f t r a c k i n g , i t i s m ore im p o r ta n t i n c o m p e n sa to r y
t r a c k i n g , s i n c e t h e in p u t s i g n a l i s o b s c u r e d b y t h e p r o c e s s
o f t r a c k i n g .
The d i f f e r e n c e s b e tw e e n p u r s u i t and c o m p e n sa to r y
t a s k s a r e o f t e n shown a s e x a m p le s o f t h e i n f o r m a t i o n a l
a s p e c t o f t h e p r o b le m . McRues and K re n d el (£6, $7) d e f i n e
e a c h a s f o l l o w s :
P u r s u i t . — In p u r s u i t b e h a v io r p a s t e x p e r i e n c e
p r o v i d e s t h e t r a c k e r w it h in f o r m a t io n a b o u t w hat t o e x p e c t
i n a f u t u r e i n p u t , b u t he m ust o p e r a t e i n a c l o s e d l o o p
f a s h i o n w it h v i s u a l fe e d b a c k a b o u t h i s r e s p o n s e s . I n t h i s
39
form o f t r a c k i n g t h e o p e r a t o r ’ s c o r r e c t i v e r e s p o n s e s can
be d i s t i n g u i s h e d from h i s i n p u t .
C o m p en sa to r y . — C om p en satory t r a c k i n g i s t h e same
a s p u r s u i t e x c e p t t h a t t h e v i s u a l l y d i s p l a y e d e f f e c t s o f
t h e c o n t r o l l e r ’ s r e s p o n s e s a r e n o t d i s t i n g u i s h a b l e from
t h e s y s t e m ’ s i n p u t . S in c e t h e v i s u a l d i s p l a y i s t h e
s y s te m f o r c i n g f u n c t i o n m inu s t h e m o d if ie d c o n t r o l
r e s p o n s e , t h e o p e r a t o r can d e te r m in e t h e e f f e c t s o f
c o n t r o l m o tio n a lo n e o n l y u n d er z er o in p u t c o n d i t i o n s .
One g e n e r a l f i n d i n g i s t h a t , f o r b o th c o m p e n sa to r y
and p u r s u i t t r a c k i n g , e r r o r i n c r e a s e s p r o g r e s s i v e l y a s
t a r g e t f r e q u e n c y i n c r e a s e s ( 4 7 ). C h e r n ik o f f and T a y lo r
( 3 2 ) r e p o r t t h a t a lth o u g h a p u r s u i t d i s p l a y i s g e n e r a l l y
s u p e r io r a t h ig h e r f r e q u e n c i e s , t h e d i f f e r e n c e becom es
l e s s and i t b ecom es i n f e r i o r t o c o m p e n sa to r y a t lo w
t a r g e t f r e q u e n c i e s when a r a t e - a i d e d sy s te m i s u s e d .
S im ila r r e s u l t s w ere r e p o r t e d by C h e r n ik o f f and T a y lo r
(33) when t h e m achine i n c l u d e s l a g s su c h a s i s t h e c a s e o f
c o n t r o l l i n g an a i r c r a f t .
Hartman and F i t t s (6 l) p o i n t o u t t h a t a s t h e
s u b j e c t im p r o v es h i s p e r fo r m a n c e w it h a p u r s u i t d i s p l a y
he c o n t i n u e s t o h av e a v a i l a b l e c o m p le te in f o r m a tio n
r e g a r d in g t a r g e t r a t e s and movement r a t e s . H ow ever,'"th§
b e t t e r h i s p e r fo r m a n c e w it h a c o m p en sa to r y d i s p l a y , t h e
l e s s in f o r m a t io n he r e c e i v e s , s i n c e w it h p e r f e c t t r a c k i n g
t h e t a r g e t r e m a in s m o t i o n l e s s i n t h e c e n t e r o f t h e d i s p l a y .
40
They c o n c lu d e t h a t t h e o n l y a p p a r e n t a d v a n ta g e o f t h e
c o m p en sa to ry d i s p l a y i s t h e p o s s i b i l i t y o f d e p i c t i n g
g r e a t e r m a g n i f i c a t i o n o f t h e e r r o r .
L e a r n in g and m o t iv a t io n
I t may be n o te d t h a t " in f o r m a t io n fe e d b a c k " i s
m e r e ly a n o th e r term f o r th e more c l a s s i c a l term "know ledge
o f r e s u l t s " u s e d w i d e l y in p s y c h o l o g i c a l l i t e r a t u r e on
su ch t o p i c s a s l e a r n i n g , m o t i v a t i o n , e t c . McGeoch and
I r i o n ($5) in d i s c u s s i n g t h e "Law o f E f f e c t " s t a t e t h a t in
many s t u d i e s o f human l e a r n i n g , in f o r m a t io n (k n o w led g e o f
r e s u l t s ) h a s b een a so u r c e o f r e in f o r c e m e n t and
W ithou t in f o r m a t io n , l i t t l e o r no l e a r n i n g
r e s u l t s . On t h e o t h e r hand, when in f o r m a tio n i s
g i v e n , l e a r n i n g o c c u r s and b ecom es more e f f i c i e n t
o v e r w id e l i m i t s a s t h e p r e c i s i o n o f t h e u s e f u l
in fo r m a tio n i n c r e a s e s . The more e x a c t t h e in f o r m a t io n ,
t h e more e x a c t can th e sta n d a r d become and t h e more
p r e c i s e may be t h e s e l e c t i o n among r e s p o n s e s .
They c o n c lu d e t h a t (a ) f o r m ost e f f i c i e n t l e a r n i n g
k n ow led ge o f r e s u l t s sh o u ld be a d m in is t e r e d a s q u ic k ly and
a s s p e c i f i c a l l y a s p o s s i b l e , (b ) l e a r n i n g w i l l be m ost
r a p id un der c o n d i t i o n s w here in f o r m a t io n i s g iv e n
f r e q u e n t l y and s p e c i f i c a l l y , and ( c ) in f o r m a tio n w h ich i s
g iv e n be r e l e v a n t t o some m o tiv e o f t h e o b s e r v e r .
There have b een a number o f e x p e r im e n ts r e p o r t e d
w hich b e a r d i r e c t l y on t h i s i n f o r m a t i o n - l e a r n i n g s i t u a t i o n .
Hunt (69) r e p o r t e d an im p o r ta n t s t u d y o f co m p en sa to r y
t r a c k i n g a t two l e v e l s o f d i f f i c u l t y a s a f u n c t i o n o f fo u r
u
degrees o f s p e c i f i c i t y o f error in fo r m a tio n . Performance
improved in a n e g a t iv e ly a c c e le r a te d fa sh io n as th e number
o f c a te g o r ie s o f in fo rm a tio n in c r e a se d but t h i s improvement
was r e l a t i v e l y u n a ffe c te d by the d i f f i c u l t y o f th e ta s k .
Control motion sc o r e s g e n e r a lly d ecreased w ith p r a c tic e
and as p r a c tic e proceeded, th e c o n tr o l motion sc o r e s de
creased r e l a t i v e l y more on th e "easy’1 ta s k than th e y did
on th e " d i f f i c u l t ” ta s k .
Smode (106) conducted an experim ent d esign ed to
provide an independent assessm ent o f performance e f f e c t s
in a compensatory d is p la y . High and low inform ation
feedback c o n d itio n s d if f e r e d in term s o f th e a ggregate
e f f e c t o f th e fo llo w in g th r e e param eters: (a) th e amount
o f in fo rm a tio n , (b) th e sen so ry mode o f p r e s e n ta tio n , and
(c) th e tem poral c h a r a c t e r is t ic s o f p r e s e n ta tio n . For
both tim e -o n -ta r g e t and a b so lu te in te g r a te d erro r s c o r e s ,
a l l groups showed c o n s is t e n t improvement over t r a in in g
t r i a l s , however, th e high in form atio n feedback groups were
su p erio r a t th e end o f th e f i r s t 90 seconds t r i a l and
m aintained t h i s s u p e r io r it y throughout th e t r a in in g
p e r io d . Thus, th e h ig h - le v e l in form ation feedback c le a r ly
f a c i l i t a t e d perform ance.
On th e su b je c t o f m o tiv a tio n , Smode (106) r e p o r ts
th a t achievem ent inform ation feedback (a) in c r e a s e s th e
l e v e l o f performance in ta s k s th a t are h ig h ly o v e r -le a r n e d ,
(b) in c r e a s e s th e r a te o f improvement e a r ly in p r a c tic e on
a new t a s k , and (c ) in c r e a s e s t h e freq u en cy o f r e p o r ts
t h a t t a s k s are more i n t e r e s t i n g and l e s s f a t i g u i n g . These
th r e e f e a t u r e s , combined t o g e t h e r , l e d th e au th or t o th e
in f e r e n c e t h a t knowledge o f achievem en t has a m o tiv a tin g
e f f e c t on b e h a v io r . T h is i s in agreement w ith t r a d i t i o n a l
in f e r e n c e s .
E ly , Bowen, and O rlansky (42) p o in t o u t th a t
m o tiv a tio n v a lu e i s dependent p r im a r ily on two f a c t o r s .
F i r s t , i t i s dependent on th e d egree t o w hich man e x e r c i s e s
c o n tr o l o v er th e system o u tp u t. I f he has no o p p o r tu n ity
to b e n e f it from p r a c t ic e or t o e x e r c i s e any judgment
co n cern in g th e m achine, m o tiv a tin g f a c t o r s w i l l have l i t t l e
i n f l u e n c e . M o tiv a tio n i s a s i g n i f i c a n t f a c t o r o n ly when
system ou tp u t i s c o n s id e r a b ly a f f e c t e d by o p e r a to r
perform ance. S e c o n d ly , t h e o p e r a to r g a in s from knowledge
about th e good n ess o f h i s perform ance and n ot o n ly a id s in
le a r n in g th e job but a ls o a c t s as an i n c e n t iv e toward
improved p erform ance.
With regard to t r a n s f e r e f f e c t s , B r ig g s , e t . a l ..
(1 0 , 1 1 , 12) and Gagne and F o s te r (49) r e p o r t t h a t t h e r e
i s l i t t l e e f f e c t o f v a r y in g such c o n tr o l param eters as
f o r c e and am p litu d e on le a r n in g a s measured by t r a n s f e r
t a s k s , a lth o u g h th e perform ance l e v e l i s a l t e r e d .
A ndreas, e t . a l . (2) r e p o r ts t h a t t h e r e i s l i t t l e i n t e r
t a s k t r a n s f e r betw een p u r s u it and com pensatory t r a c k in g .
With reg a rd to t h e e f f e c t s o f p h y s ic a l c o n s ta n ts
43
and p r o p r io c e p t iv e fe e d b a c k on l e a r n i n g and p erfo rm a n ce,
Howland and N ob le ( 6 8 ) and B a h rick , e t . a l . . ( 3 , 4 ) r e p o r t
t h a t d i f f e r e n t sy stem c o n s t a n t s i n th e c o n t r o l r e s u l t e d in
s i g n i f i c a n t d i f f e r e n c e s in mean t i m e - o n - t a r g e t p erfo rm a n ce.
In g e n e r a l, perform ance was b e s t f o r c o n d it io n s c o n t a in in g
th e s p r in g , n e x t b e s t f o r a damping v i s c o s i t y elem en t and
p o o r e s t f o r t h o s e c o n t a in in g t h e moment o f i n e r t i a . In
c o n j u n c t io n , W eiss (115) r e p o r te d t h a t f o r p o s i t i o n i n g
r e s p o n s e s made in th e a b se n c e o f v i s u a l fe e d b a c k , d i s p l a c e
ment was t h e more c r i t i c a l d im en sion o f th e f o r c e -
d isp la c e m e n t r e l a t i o n s h i p .
For e x p e r im e n ta l c o v e r a g e o f o th e r f a c t o r s in th e
le a r n in g - m o t iv a t io n a r e a , t h e r e a d e r i s r e f e r r e d t o :
F i t t s ( 4 6 ) and Hick (6 3 ) on th e in fo r m a tio n c a p a c it y o f
th e human m otor sy stem ; A l l u s i , e t . a l ., (1) on a
com parison o r v e r b a l and m otor r e s p o n s e s ; Jon es (72) on
th e i n f l u e n c e o f s t r e s s ; and Griew (57) on age and t a s k s
in in t e r r u p t e d p r e v ie w .
P r i n c i p l e s o f s k i l l e d perform ance
M elton (SB) i n d i c a t e s t h a t th e o r y d evelop m en t on
s k i l l e d p erform ance c o n tin u e s t o be one o f th e m ost a c t i v e
r e s e a r c h a r e a s in e n g in e e r in g p s y c h o lo g y . He s t a t e s :
The modes o f a t t a c k in v o lv e d a r e v a r ie d and in
many c a s e s q u it e in g e n io u s . The ap p roach es ta k e n
ra n g e from t h e m o le c u la r r e s e a r c h on t h e p s y c h o lo g ic a l
r e f r a c t o r y ph ase t o m olar r e s e a r c h , su ch as t h e
a tte m p ts t o d eterm in e t r a n s f e r f u n c t io n f o r t h e human
o p e r a to r in a v a r i e t y o f com plex c o n t r o l t a s k s .
44
The major problem in th e o r y c o n s t r u c t io n i s
a p p a r e n tly t h e in h e r e n t a d a p t a b i l it y o f th e human o p e r a to r
in a sy stem , p a r a d o x ic a lly th e major a s s e t o f th e human,
making i t v i r t u a l l y im p o s s ib le to fo rm u la te a g e n e r a l
t h e o r y . There a r e , how ever, a number o f p r i n c i p l e s which
may s u b s t it u t e in th e in te r im .
H elson (62), based on h i s own r e s e a r c h w ith v a r io u s
t y p e s and param eters o f c o n t r o l sy s te m s , and some o th e r
r e le v a n t ex p erim en ta l d a ta , has fo rm u lated f i v e p r i n c i p l e s
o f "optim al human o p e r a tio n ." These a r e : (a) th e U-
h y p o th e s is , (b) p r i n c ip l e o f g e n e r a l it y or t r a n s f e r o f th e
o p tim a l, (c ) p r i n c ip l e o f o f f s e t and com prom ise, (d)
h y p o th e s is o f par or t o l e r a n c e , (e ) p r i n c i p l e s o f
a n t i c ip a t io n and a v e r a g in g . S in c e o n ly th e f i r s t two are
u sed in th e p r e se n t stu d y , o n ly th e y w i l l be d e t a i l e d .
The U - h y p o th e s is . — Human perform ance w i l l te n d to
be o p tim al a s judged by a c cu ra c y , e f f i c i e n c y , and c o m fo r t,
over a more or l e s s broad band o f v a lu e s fo r a g iv e n
s t im u lu s - v a r ia b le o u t s id e o f which i t becomes n o t ic e a b ly
p o o r e r. When perform ance i s p lo t t e d in term s o f e r r o r or
th e r e c ip r o c a l o f a c c u r a c y , th e r e s u l t a n t curve i s r o u g h ly
U -shaped. W ithin th e m inim al band perform ance i s l e s s
a f f e c t e d by changes in th e v a r ia b le th an on e it h e r s i d e .
The U -h y p o th e s is e x p r e s s e s th e f a c t t h a t organism s can
adapt to a f a i r l y w ide range o f s tim u lu s v a lu e s and fu n c
t i o n o p t im a lly in t h i s r a n g e .
45
G e n e r a lity or t r a n s f e r o f th e o p t im a l. — S tim u lu s -
v a lu e s in th e o p tim a l band ten d to s t a y op tim al when
a c c e s s o r y c o n d it io n s a re changed. The v a l i d i t y o f t h i s
p r i n c ip l e i s a t t e s t e d by such f i n d in g s as th e fo llo \\rin g :
low gear r a t i o r e q u ir in g f a s t tu r n in g g i v e s b e t t e r
perform ance w ith heavy a s w e ll as l i g h t , la r g e a s w e ll as
s m a ll, f r i c t i o n - l o a d e d a s w e ll a s f r e e l y tu r n in g hand
w h e e ls; w ith d i f f i c u l t as w e ll as e a sy c o u r s e s , lo n g as
w e ll as sh o r t p e r io d s o f work, dou ble as w e ll as s i n g l e
c o n t r o l s , s id e as w e ll as f r o n t c r a n k s, and green as w e ll
as s k i l l e d o p e r a to r s . That th e upper l i m i t may be reach ed
soon er under some c o n d it io n s than o t h e r s , does n o t
i n v a l i d a t e th e p r i n c i p l e .
The former i s u sed in th e p r e s e n t stu d y t o p r e d ic t
th e e f f e c t s o f e x p o n e n tia l t im e - la g c o n s ta n ts ; t h e l a t t e r ,
to p r e d ic t th e e f f e c t s o f a c c e le r a t i o n on th e r e l a t i v e
order o f erro r s c o r e s w ith th e v a r io u s t im e - la g c o n s t a n t s .
T im e-la g s and th e U -h y p o th e s is
F i t t s (45) i n d ic a t e s t h a t l a g i s an im portant
problem in d e s ig n in g c o n tr o l system s and t h a t :
Lag a t any p o in t in a man-machine system
in c r e a s e s th e e r r o r in c o n tin u o u s c o n tr o l
f u n c t io n s . . . . C on sidered in term s o f c o n tin u o u s
c o n tr o l p r o c e s s e s , tim e l a g s and in a c c u r a c ie s a re
synonymous.
On f i r s t g la n c e , th e r e would be a major d i f f i c u l t y
in p r e d ic t in g a U -fu n c tio n w ith v a r y in g t i m e - l a g s i f th e
46
above sta te m e n t were a b s o l u t e l y c o r r e c t . In r e a l i t y , t h i s
i s n o t th e c a s e . F i t t s d o e s n o t q u it e make i t c le a r t h a t
he i s d i s c u s s i n g o n ly t r a n s m is s io n l a g s and, t h e r e f o r e ,
in t h i s c o n t e x t , h i s sta te m en t i s v a l i d . The a v era g e
r e a d e r , u n f a m ilia r w ith t h i s problem , m ight be m is le d .
In f a c t , a c c o r d in g to S en d ers (102) and E ly , Bowen,
and O rlan sk y ( 4 2 ) , e x p o n e n tia l and sig m o id l a g s may e i t h e r
im prove o r degrade p erform an ce, d epend ing on i n t e r a c t i o n s
w ith o th e r p a r ts o f t h e machine dyn am ics.
L e v in e (BO) and C on klin ( 3 6 ) , on th e one hand,
r e p o r t t h a t when t h e g a in i s o p t im a lly s e t , th e a d d it io n o f
an e x p o n e n tia l l a g betw een th e o p e r a t o r 's c o n t r o l o u tp u t
and th e machine o u tp u t w i l l degrade p erform a n ce. L e v in e
(BO) u sed d e la y s up to 2 .7 se c o n d s , w h erea s, C on k lin (3 6 )
u sed d e la y s up to 16 se c o n d s .
Rockway ( 9 6 ) , on th e o th e r hand, r e p o r te d t h a t i f
th e g a in were to o h ig h c a u sin g c o n t in u a l o v e r s h o o tin g ,
th e a d d it io n o f a l a g would s e r v e to red u ce th e o u tp u t
a m p litu d e and, th e r e b y , improve p erform an ce.
T h ere.h av e been a number o f r e c e n t ex p e rim en ts
r e p o r te d w hich su p p ort th e U -h y p o t h e s is . A few o f them
are r e p o r te d h e r e . Hartman ( 6 0 ) , w h ile s tu d y in g th e
e f f e c t o f j o y s t i c k l e n g t h on p u r s u it t r a c k in g p erfo rm a n ce,
found a U -shaped f u n c t io n w ith an IB in c h movement b e in g
o p tim a l. C h e r n ik o ff and T aylor (3 1 ) s tu d ie d th e e f f e c t s
o f c o u r se fre q u en cy and a id e d tim e c o n s t a n t s o f 0 , 0 . 5 ,
47
and ©o on p u r s u it and com pensatory t r a c k in g . A U -shaped
fu n c tio n was found f o r b oth c a s e s w ith th e op tim al a id ed
tim e c o n sta n t b e in g 0 .5 secon d. I t sh ou ld be n o ted th a t
th e a u th o rs did not r e c o g n iz e th e U -fu n c tio n as su ch .
P e a r l, e t . a l . , (91) rep o rted a stu d y in which th e
s u b je c t was req u ired to keep a cu rso r a lig n e d w ith a
moving t a r g e t by a d j u s tin g a handwheel crank. V a r ia tio n s
in th e o v e r a ll ta r g e t speed were in tro d u ced by a d ju s tin g
a v a r ia b le -s p e e d motor to sp eed s o f 23, 30, and 37 RPM.
A id e d -tr a ck in g tim e c o n s ta n ts o f 0 .2 5 , 0 .5 and 1 .0 second
were u sed . The tim e c o n sta n t o f 0 .5 second rem ained o p t i
mum over th e range o f t a r g e t sp eed s u sed in t h i s stu d y
althou gh th e r e was n ot 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 iff e r e n c e between th e 0 .2 5 and 0 .5 second tim e c o n s ta n ts
at any o f th e th r e e t a r g e t sp ee d s. A gain, th e au th o rs did
not r e c o g n iz e th e support fo r th e U -h y p o th e sis or th e
P r in c ip le o f G e n e r a lity .
Garvey and Henson (50) in v e s t i g a t e d th e i n t e r a c t io n
between d is p la y g a in and ta s k induced s t r e s s . F iv e manual
c o n tr o l sy stem s, a l l o f which had th e same dynam ics but
d if f e r e d in d is p la y m a g n ific a tio n were u sed . The r e s u l t s
in d ic a te d th a t s t r e s s in c r e a se d erro r in a l l sy ste m s, but
th e order o f m erit o f th e v a r io u s sy stem s was unchanged by
s t r e s s . T his i s , th e read er may n o t e , a statem en t o f th e
P r in c ip le o f G e n e r a lity . The r e s u l t s fo r th e system erro r
show th e f i r s t h a l f o f a U -fu n c tio n fo r d is p la y g a in s up
t o 1 . 0 se co n d and, o f c o u r s e , t h e p a r a m e tr ic c u r v e f o r th e
s t r e s s e d t a s k .
In summary, i t m ight be s a i d t h a t t h e r e a re many
exam p les in t h e e x p e r im e n ta l l i t e r a t u r e o f t h e two
p r i n c i p l e s o f co n cern and t h a t in many c a s e s , th e y a r e n o t
r e c o g n iz e d , o r a t l e a s t d e f in e d , by t h e r e s e a r c h e r .
CH APTER IV
A HISTORY OF THE H UM AN AS A CONTROLLER
IN THE ACCELERATION ENVIRONMENT
In exam in in g th e h i s t o r y o f r e se a r c h on th e t o p ic
o f human c a p a b i l i t i e s in an a c c e l e r a t i o n en v iro n m en t, one
f i n d s t h r e e d e f i n i t e s t a g e s o f d ev elo p m en t. From th e
1 9 3 0 ’ s to t h e end o f World War I I , th e prime con cern was
t h e e x p e rim en ta l d e te r m in a tio n o f human t o le r a n c e ca p a
b i l i t i e s and o th e r p h y s i o l o g i c a l phenomena w h ile exp osed
t o p o s i t i v e a c c e l e r a t i o n . The works o f Gauer (5 4 ) and
B uhrlen (17) from th e German c e n t r i f u g e f a c i l i t y may be
c o n sid e r e d a s r e p r e s e n t a t iv e o f r e s e a r c h a t t h i s s t a g e o f
d ev elo p m en t.
At th e end o f World War I I and up u n t i l th e e a r l y
1950 ’ s we f in d th e secon d s t a g e , nam ely, th e em phasis o f
r e s e a r c h b e in g p la c e d on t h e stu d y o f human perform ance
c a p a b i l i t i e s , but a g a in , under c o n d it io n s where th e human
s u b j e c t i s exp osed t o p o s i t i v e a c c e l e r a t i o n . Much o f t h i s
l a t e r work was con d u cted a t t h e U n iv e r s it y o f Southern
C a l i f o r n i a . An e x c e l l e n t a r t i c l e by Brown and L ech n er (15)
sum m arizes th e p u b lis h e d r e s e a r c h f o r th e f i r s t and secon d
s t a g e s o f d evelo p m en t.
49
50
We are p r e s e n t l y in th e t h i r d s t a g e w here t h e r e
are two major ch an ges o v e r p a s t r e s e a r c h a c t i v i t i e s .
F i r s t , p h y s i o l o g i s t s and p s y c h o l o g is t s are w orking
c o n c u r r e n tly on th e problem s o f t o l e r a n c e and p erform a n ce,
r e s p e c t i v e l y . Second, th e major i n t e r e s t now i s on th e
e f f e c t s o f t r a n s v e r s e r a th e r than p o s i t i v e a c c e l e r a t i o n .
These ch an ges are due t o th e in c r e a s e d r eq u irem en ts fo r
e x p e rim en ta l d ata r e g a r d in g man’ s t o l e r a n c e and perform ance
c a p a b i l i t i e s in c u r r e n t and proposed sp a ce v e h i c l e sy s te m s .
A. REACTION TIME
Many s t u d i e s o f t h e v a r io u s t y p e s o f r e a c t io n tim e
have been condu cted w h ile th e human o p e r a to r has been
exposed to d i f f e r e n t t y p e s and l e v e l s o f a c c e le r a t i o n (1 6 ).
S in ce r e a c t io n tim e i s a c r i t i c a l e lem en t in c o n tin u o u s
t r a c k in g s i t u a t i o n s , s e v e r a l o f t h e s e s t u d i e s w i l l be
b r i e f l y d e s c r ib e d .
C a n f ie ld , Comrey, and W ilson (24) s t u d ie d th e
e f f e c t s o f p o s i t i v e a c c e le r a t i o n s o f 3*0 g and 5.0 g
m agnitudes on r e a c t io n tim e to both v i s u a l and a u d ito r y
s t i m u l i . I t was found t h a t r e a c t io n tim e f o r th e a u d ito r y
stim u lu s was l e s s at a l l g l e v e l s and i t was n ot as
a f f e c t e d by in c r e a s e d a c c e l e r a t i o n . I t i s i n t e r e s t i n g to
n o te t h a t t h i s i s a sta te m e n t o f t h e P r in c ip le o f
G e n e r a lity a t th e sim p le r e a c t io n tim e l e v e l . M oreover,
C a n fie ld ( 2 2 , 23) in a n o th er stu d y on th e e f f e c t s o f
51
p o s i t i v e a c c e l e r a t i o n , a t l e v e l s o f 3 .0 g and 5.0 g , on
sp eed and a ccu ra cy o f m ovem ents, m easured r e a c t i o n tim e
and found i t t o in c r e a s e w ith in c r e a s e d a c c e l e r a t i o n .
Bryan ( 1 6 ) , B u rm eister ( l S ) , and Brown and Burke
(1 3 ) p r e se n t s im ila r r e s u l t s i n d i c a t i n g t h a t sim p le
r e a c t io n tim e i s in c r e a se d a s a f u n c tio n o f p o s i t i v e
a c c e le r a t io n and, f u r t h e r , g e n e r a lly a g ree t h a t t h i s
in c r e a s e i s due to m uscular lo a d in tu rn due to th e
m agnitude o f th e a c c e l e r a t i v e f o r c e .
K aehler and Meehan (74) have r e p o r te d sim p le
r e a c t io n tim e m easures o b ta in e d from s u b j e c t s exposed to
f r o n t - t o - b a c k and b a c k - t o - f r o n t a c c e l e r a t i o n s . Mean
r e a c t io n tim e was found to in c r e a s e from 0.23 secon d a t
r e s t to 0.33 second at 8.0 g w h ile exposed t o f r o n t - t o - b a c k
a c c e l e r a t i o n s . T h is r e p r e s e n t s a n e t in c r e a s e o f 0 .1
se co n d . For b a c k - t o - f r o n t a c c e l e r a t i o n s , mean r e a c t io n
tim e was found to be 0.22 second a t r e s t to 0.2 8 a t 4 .0 g.
These in c r e a s e s were s i m i l a r l y a t t r i b u t e d to in c r e a s e d
m uscular lo a d .
S e c k e l , H a ll, KcGruer, and W eir (1 0 1 ) r e p o r te d an
i n t e r e s t i n g stu d y in which an attem p t was made t o d eterm in e
th e d i f f e r e n c e in p i l o t t r a c k in g b eh a v io r r e s u l t i n g from
d i f f e r e n c e s betw een f l i g h t and ground s im u la to r c o n tr o l
e n v iro n m en ts. Among o th e r t h i n g s , th e a u th o r s r e p o r te d
t h a t th e p i l o t ’ s e f f e c t i v e r e a c t io n tim e d e la y fo r both
th e l a t e r a l and lo n g i t u d in a l c o n t r o l mode was found t o be
52
l o n g e r i n f l i g h t t h a n i n t h e g ro u n d s i m u l a t o r by a p p r o x i
m a t e ly 0 .1 2 s e c o n d f o r l o n g i t u d i n a l c o n t r o l and 0 . 2 0 f o r
l a t e r a l c o n t r o l .
The a u t h o r s s t a t e t h a t t h e m ajor com p onent f a c t o r s
c a u s i n g t h e o b s e r v e d f l i g h t - s i m u l a t o r d i f f e r e n c e s a r e :
1 . D i f f e r e n c e s i n ,fs e t t o r e s p o n d ” f a c t o r s
2 . A d d i t i o n a l c o n f l i c t i n g dem ands i n t h e f l i g h t
s i t u a t i o n , l a r g e l y v i s u a l , and
3 . A d d i t i o n a l e f f e c t i v e p i l o t a c t u a t i n g s i t u a t i o n s ,
l a r g e l y a c c e l e r a t i o n s .
The a b o v e m ig h t a l s o b e s a i d t o b e i n c l u d e d i n
a p p a r e n t d i f f e r e n c e s in m ea su r em e n ts o b t a in e d s t a t i s t i c a l l y
and d u r in g c e n t r i f u g a t i o n .
A l l o f t h e a c c e l e r a t i o n s t u d i e s c i t e d a b o v e , w h ic h
a r e r e p r e s e n t a t i v e o f a l a r g e r body o f d a ta r e p o r t e d i n
t h i s a r e a , a g r e e t h a t t h e human o p e r a t o r Ts r e a c t i o n t im e
i s le n g t h e n e d and i s due t o i n c r e a s e d m u s c u la r l o a d due
t o t h e m a g n itu d e o f t h e a c c e l e r a t i v e f o r c e .
B . PERG EP TU AL - 140 TOE P ERFORfoANC E
We h a v e s e e n t h a t r e a c t i o n t im e i s a f f e c t e d by
i n c r e a s e d a c c e l e r a t i o n . We m ig h t , t h e n , e x p e c t t h a t
r e s p o n s e s r e q u i r i n g g r o s s m otor a c t i v i t i e s w i l l a l s o be
s i m i l a r l y a f f e c t e d . A lth o u g h t h e r e a r e num erous r e p o r t s
on t h e a b i l i t y o f human s u b j e c t s t o p e r fo r m p e r c e p t u a l -
m o to r a c t i v i t i e s , in t h e i n t e r e s t s o f b r e v i t y , o n l y
r e p r e s e n t a t i v e s t u d i e s w i l l be p r e s e n t e d h e r e . The
i n t e r e s t e d r e a d e r w i l l f i n d an e x c e l l e n t c o v e r a g e in
Brown ( 1 5 ) .
C a n f ie ld (2 0 ) m easured r e a c t i o n t im e , movement
tim e and t h e a c c u r a c y o f c e r t a i n r e a c h in g m ovem ents in
r e l a t i o n t o in c r e a s e d p o s i t i v e a c c e l e r a t i o n . The s u b j e c t
resp o n d ed t o a b u zz e r s i g n a l by s t r i k i n g a t a r g e t w h ich
was l o c a t e d in one o f fo u r p o s i t i o n s . R e a c tio n tim e was
d e f in e d a s t h a t tim e e l a p s i n g b etw een th e so u n d in g o f t h e
b u zz e r and th e r e l e a s e o f a s t a r t i n g p o in t s w it c h . As
was n o te d e a r l i e r , r e a c t i o n tim e in c r e a s e d w ith an
i n c r e a s e i n t h e m agn itu d e o f t h e p o s i t i v e a c c e l e r a t i v e
f o r c e . Movement tim e was d e f in e d a s th e tim e e l a p s i n g
from t h e r e l e a s e o f t h e s t a r t i n g p o i n t s w itc h u n t i l
c o n t a c t w ith t h e t a r g e t . Movement tim e and r e a c h in g
a c c u r a c y w ere foun d t o be d ecrem en ted a s a f u n c t i o n o f
in c r e a s e d a c c e l e r a t i o n .
Bryan (1 6 ) c o n d u c tin g a f o l lo w - o n s tu d y t o
C a n f i e l d Ts r e p o r te d t h e same g e n e r a l r e s u l t s . He d id
s u g g e s t , how ever, t h a t t h e r e m igh t be a d i f f e r e n t i a l
e f f e c t o f t h e a c c e l e r a t i v e f o r c e on r e a c h in g m ovem ents.
T h is d i f f e r e n t i a l e f f e c t i n d i c a t e s t h a t r e a c h in g movements
in o p p o s i t i o n t o t h e d i r e c t i o n o f t h e a c c e l e r a t i v e f o r c e
a re more a f f e c t e d th a n t h o s e w h ich a r e i n a d i r e c t i o n
p e r p e n d ic u la r t o th e a c c e l e r a t i v e f o r c e .
K a eh ler and Meehan (7 4 ) r e p o r t e d a s tu d y c o n cern ed
w ith t h e m easurem ent o f r e a c t i o n , r e a c h in g and a d ju stm e n t
r e s p o n s e s f o r v a r io u s t y p e s o f c o n t r o l s l o c a t e d in
54
s e v e r a l w ork p lace p o s i t i o n s w h ile s u b j e c t s w ere exp osed
t o d i f f e r e n t t y p e s and l e v e l s o f t r a n s v e r s e a c c e l e r a t i o n .
The s u b j e c t s w ere r e q u ir e d to m a n ip u la te f i v e
t y p i c a l a i r c r a f t c o n t r o l s in c lu d in g a h o r i z o n t a l l e v e r ,
r o t a r y knob, tr im w h e e l, p u s h - t o - t e s t b u tto n , and t o g g l e
s w it c h . R e a c tio n tim e was d e f in e d as th e tim e e la p s i n g
betw een th e ap p earan ce o f a r e d l i g h t s tim u lu s and th e
rem oval o f th e s u b j e c t ’ s hand from a s e n s i t i v e la p s w it c h .
Reach tim e was d e f in e d as t h e tim e e la p s i n g from th e
rem oval o f th e s u b j e c t ’ s hand from t h e la p s w itc h u n t i l
he tou ch ed th e c o n t r o l . A djustm ent tim e was d e fin e d as
t h e tim e e la p s i n g betw een th e f i r s t to u c h o f t h e d e s ig n a te d
c o n t r o l and t h e f i n a l proper p o s i t i o n i n g o f t h e c o n t r o l .
I t was found t h a t a l l t h r e e p a ra m eters o f t o t a l
r e sp o n s e tim e was a f f e c t e d by in c r e a s e d f r o n t - t o - b a c k
a c c e l e r a t i o n . The tim e t o c o m p le te each t a s k was found
t o b e , in m a th em a tica l te r m s, a p o s i t i v e l y a c c e le r a t e d
f u n c t i o n , w ith th e g r e a t e s t r a t e o f change o c c u r in g from
6 . 0 g t o 6 .0 g .
A d i f f e r e n t i a l e f f e c t was found f o r b oth rea ch and
ad ju stm en t tim e m easu rem en ts. R ea ch in g movem ents to
c o n s o l e s r e q u ir in g m o tio n s in d i r e c t o p p o s i t i o n t o th e
a c c e l e r a t i v e v e c t o r r e q u ir e d lo n g e r tim e i n t e r v a l s than t o
c o n s o le s r e q u ir in g p e r p e n d ic u la r m o tio n s. A d ju stm en ts in
t h e d i r e c t i o n o f t h e a c c e l e r a t i v e f o r c e , w hich w ere l o c a t e d
on c o n s o le s p e r p e n d ic u la r t o th e d i r e c t i o n o f t h e f o r c e ,
55
a ls o r e q u ir e d lo n g e r tim e i n t e r v a l s th a n t h o s e r e q u ir in g
a d ju stm e n ts p e r p e n d ic u la r to t h e f o r c e d i r e c t i o n .
The d i f f e r e n t i a l e f f e c t i s r e l e v a n t in t h i s
in s t a n c e in t h a t p i t c h movements a r e in o p p o s it io n t o a
f r o n t - t o - b a c k a c c e l e r a t i o n v e c t o r , w h e r e a s, r o l l m o tio n s
are p e r p e n d ic u la r t o t h i s f o r c e d i r e c t i o n . One would
p r e d i c t , t h e r e f o r e , t h a t r o l l m o tio n s , would be l e s s
a f f e c t e d by th e f r o n t - t o - b a c k a c c e l e r a t i o n th an p i t c h
m o tio n s .
In a stu d y on t h e amount o f f o r c e w hich a p i l o t
can e x e r t w h ile exp osed t o p o s i t i v e a c c e l e r a t i o n , C a n fie ld
(2 5 ) found t h a t in c r e a s e d a c c e l e r a t i o n up to 5.0 g had
o n ly sm a ll e f f e c t s on t h e c o n t r o l f o r c e e x e r t e d . I t
sh ou ld be n o t e d , h ow ever, t h a t in t h i s o a r t i c u l a r e x p e r i
m ent, th e d i r e c t i o n o f th e e x e r te d c o n t r o l f o r c e was
p e r p e n d ic u la r to t h e d i r e c t i o n o f th e a c c e l e r a t i o n f o r c e .
W e m ight e x p e c t , t h e r e f o r e , to o b t a in l a r g e r d ecrem en ts
i f t h e c o n tr o l f o r c e were in t h e d i r e c t i o n o f th e a c c e l e r
a t io n v e c t o r as p er t h e d i f f e r e n t i a l e f f e c t n o te d ab ove.
C. COGNITIVE PROCESSES
In t h e p h y s i o l o g i c a l r e s p o n s e t o p o s i t i v e a c c e l e r
a t i o n , t h e oxygen su p p ly t o th e b r a in i s r e d u c e d , i f n o t
c o m p le te ly e lim in a t e d , dependent on th e m agnitude and
d u r a tio n o f t h e a c c e l e r a t i v e f o r c e . There have been
s p e c u l a t i o n s (15) r e g a r d in g t h e a b i l i t y o f th e human
o p e r a to r t o c a r r y on c o g n i t i v e p r o c e s s e s d u rin g an
a c c e l e r a t i v e e x p o su re s i n c e one m ight s u s p e c t a d is tu r b a n c e
t o t h e c e n t r a l n ervou s sy s te m . There have been o n ly a
v e r y few e x p e r im e n ts c o n d u cted to d a te con cern ed w ith th e
e v a lu a t io n o f human c a p a b i l i t y t o perform com plex m en tal
t a s k s under v a r io u s en v iro n m en ta l c o n d i t i o n s . T h is problem
i s r e le v a n t to th e p r e s e n t d i s s e r t a t i o n s i n c e , a s may be
n o te d by F ig . 4 t h e human o p e r a to r i s r e q u ir e d t o make
a lm o st c o n tin u o u s d e c i s i o n s t o a d e q u a te ly c o n t r o l h i s
v e h i c l e .
C a n f ie ld , Comrey, W ilso n , and Zimmerman (2 7 ) in a
d is c r im in a t io n r e a c t i o n tim e stu d y r e q u ir e d s u b j e c t s t o
d eterm in e th e d i r e c t i o n t h a t a r e d l i g h t l a y in r e l a t i o n
to a g r ee n one on a t e s t p a n el and th e n to make a r e s p o n s e
w hich i n d ic a t e d t h e p rop er d i r e c t i o n w henever a r e d l i g h t
was p r e s e n t . I t was r e p o r te d t h a t p o s i t i v e a c c e l e r a t i o n
o f 5.0 g had no a f f e c t on tim e r e q u ir e d to r e a c t t o th e
e x p e r im e n ta l s t im u lu s .
In a n oth er e x p e r im e n t, C a n f ie ld , Comrey, and
W ilson (2 6 ) r e q u ir e d s u b j e c t s to s e l e c t t h e one o f fo u r
s im ila r f i g u r e s in a p a t t e r n w hich e x a c t l y m atched a
c e n t r a l f i g u r e . S tim u lu s f i g u r e s in c lu d e d s h i p s , c l o c k s ,
and j u g s . The r e s u l t s do n o t show a s i g n i f i c a n t e f f e c t
o f p o s i t i v e a c c e l e r a t i o n on th e number o f e r r o r s f o r f i x e d
e x p o su r e s o f th e p a t t e r n s .
In a r e c e n t s tu d y , K aeh ler and Meehan (7 6 )
57
e v a lu a te d th e a b i l i t y o f human s u b j e c t s to s o l v e sim p le
a r it h m e t ic problem s w h ile exp osed t o : ( l ) f r o n t - t o - b a c k
a c c e l e r a t i o n s o f 3 .0 g and 6 .0 g , ( 2 ) p o s i t i v e a c c e l e r a
t i o n s o f 2 .0 g and 4 .0 g , (3 ) sim u la te d t h r e e - s t a g e r o c k e t
a c c e l e r a t i o n p r o f i l e s o f S.O g , 6 .0 g , and 6 . 0 g , and
(4 ) sim u la te d a n o x ic c o n d it io n s r e p r e s e n t a t iv e o f a l t i t u d e s
o f 24,000 f e e t .
The t e s t p a n el c o n s is t e d o f two v i s u a l i n d i c a t o r s ,
one c ir c u la r and one v e r t i c a l , w h ic h , when a c tu a t e d ,
p r o v id e d th e s u b j e c t w ith two num bers. O ther l i g h t s on
th e p a n el a d v ise d th e s u b je c t w hich a r ith m e tic o p e r a tio n
to perform on th e numbers d is p la y e d on th e p a n e l. The
t a s k d i f f i c u l t y was v a r ie d so t h a t sp eed and a c cu ra c y
m easurem ents were o b ta in e d f o r ( l ) sim p le r e a c t i o n tim e ,
(2 ) sim p le a r it h m e t ic problem s o l u t i o n , (3 ) r e v e r s a l o f
i n s t r u c t i o n s , and (4 ) a judgment problem .
I t was found th a t t h e r e were d i f f e r e n c e s among t h e
v a r io u s t a s k s , a s m ight be e x p e c te d , but none o f th e
e x p e rim en ta l c o n d it io n s e f f e c t e d t h e sp eed or a c cu ra cy o f
r e s p o n s e s .
A ll o f th e above ex p erim en ts ten d t o show th a t
motor r e sp o n s e s are a f f e c t e d by in c r e a s e d a c c e l e r a t i o n ,
but c o g n i t iv e p r o c e s s e s a r e n o t , a t l e a s t n o t a s lo n g a s
th e s u b je c t i s c o n s c io u s and a b le t o p e r c e iv e th e t e s t
s t i m u l i .
53
D. CONTINUOUS CONTROL PERFORMANCE
In r e v ie w in g t h e e x p e r im e n t a l l i t e r a t u r e , t h e
r e a d e r w i l l f i n d a s u r p r i s i n g and s e r i o u s l a c k o f r e p o r t e d
s t u d i e s r e g a r d in g t h e human o p e r a to r a s a c o n tin u o u s
c o n t r o l l e r in a p h y s i c a l s t r e s s e n v ir o n m e n t. The m a j o r it y
o f p erfo rm a n ce s t u d i e s r e p o r t e d , ex a m p les o f w h ich h ave
b een d i s c u s s e d e a r l i e r , have been c o n f in e d s t r i c t l y t o t h e
d i s c r e t e p e r c e p t u a l- m o t o r v a r i e t y and , h e n c e , o f f e r l i t t l e
in t h e way o f p r e c i s e p e r fo r m a n c e c a p a b i l i t i e s o f a human
o p e r a to r in a c o n tin u o u s c o n t r o l s i t u a t i o n .
P r e sto n -T h o m a s, e t . a l . . (9 7 ) p u b lis h e d one o f t h e
e a r l i e s t w orks a s l a t e a s 1 9 5 5 . H is s u b j e c t s w ere
r e q u ir e d t o t r a c k a two d im e n s io n a l c o m p en sa to r y problem
w h ile e x p o se d t o s im u la te d t h r e e - s t a g e r o c k e t a c c e l e r a
t i o n s . U n f o r t u n a t e ly , he r e p o r t s no s p e c i f i c d a ta but
c o n c lu d e s t h a t t h e r e a r e o n ly sm a ll d e c r e m e n ts i n
p erfo rm a n ce a lth o u g h some s u b j e c t s showed no d e c re m e n ts
w h il e o t h e r s showed a g r e a t d e a l .
The n e x t p u b lis h e d e x p e rim en t w as t h a t o f K a e h le r
( 7 3 ) . T h is s tu d y was p r i m a r i ly d e s ig n e d t o e v a lu a t e
human c o n t r o l p erfo rm a n ce on a c o m p en sa to r y c o n t r o l t a s k
w ith a sta n d a r d c e n t e r c o n t r o l s t i c k and an e x p e r im e n ta l
r i g h t hand c o n t r o l s t i c k d u r in g v a r i a b l e a c c e l e r a t i o n s
p r e d i c t e d from a n a l o g i c a l s t u d i e s o f b o o s t and r e - e n t r y
p h a s e s o f t h e X -1 5 e x p e r im e n ta l r o c k e t s h i p .
I t was c o n c lu d e d t h a t (1 ) t r a c k i n g p erfo rm a n ce
d a ta w it h t h e r i g h t hand s t i c k was c o n s i s t e n t l y b e t t e r
th a n t h a t w it h t h e c e n t e r s t i c k a lth o u g h 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 was n o t fo u n d , ( 2 ) s u b j e c t s 1
comments i n d i c a t e d a p r e f e r e n c e f o r t h e r i g h t hand s t i c k
p r i n c i p a l l y due t o t h e amount o f p h y s i c a l e f f o r t r e q u ir e d
t o p r o p e r ly o p e r a t e t h e c e n t e r s t i c k u n d er c e n t r i f u g a t i o n ,
( 3 ) t h e r e was e v id e n c e o f a g r e a t d e a l o f l e a r n i n g b etw een
t h e v a r io u s c o n t r o l s y s te m s and d i f f e r e n t a c c e l e r a t i o n
c o n d i t i o n s , and ( 4 ) t h e r e was a s i g n i f i c a n t d i f f e r e n c e in
r o l l m easu rem en ts b etw een s u b j e c t s w h ich w as a t t r i b u t e d t o
t h e n o n - p i l o t s in t h e s u b j e c t g r o u p .
F l e t c h e r , C o l l i n s , and Brown (4 # ) f o l l o w i n g t h e
ab ove e x p e r im e n t, r e q u ir e d t h e i r s u b j e c t s t o f l y an a i r - t o -
a i r p u r s u i t p ro b lem . I t was foun d t h a t t h e l e v e l o f
a c c e l e r a t i o n a f f e c t e d t h e t i m e - o n - t a r g e t t r a c k i n g s c o r e s
and t h a t t h e r i g h t hand s t i c k g a v e s m a lle r e r r o r s th a n t h e
c o n v e n t io n a l c e n t e r s t i c k .
Brown and C o l l i n s (1 4 ) r e p o r t e d a s t u d y in w h ich
t h e s u b j e c t c l o s e d t h e lo o p around t h e c e n t r i f u g e and
c o n t r o l l e d t h e m o tio n o f t h e c e n t r i f u g e . The p roblem was
a l s o an a i r - t o - a i r t r a c k i n g p ro b lem i n w h ich t h e a i r c r a f t
d yn am ics w ere s im u la t e d and t h e s u b j e c t s a tte m p te d t o k eep
t h e t a r g e t a i r c r a f t in t h e c e n t e r o f t h e s c o p e . The
m o tio n s o f t h e c e n t r i f u g e e x p o se d t h e s u b j e c t t o a p a t t e r n
o f a c c e l e r a t i o n t h a t w as p r o p o r t io n a l t o t h e c o n t r o l
i n p u t . The d a ta i n d i c a t e d t h a t p e r fo r m a n c e o f t h e
60
t r a c k in g t a s k showed a decrem ent d u rin g a c c e l e r a t i o n .
Chambers and D o e r fe l (2 8 ) and E g g le s to n and
Cheatham (39) have r e p o r te d e x p e r im e n ta l work on human
c o n tin u o u s c o n tr o l perform ance and p h y s i o l o g i c a l t o le r a n c e
d u rin g r e - e n t r y c o n d it io n s fo r t h r e e t y p e s o f sp a ce
v e h i c l e s : (1 ) h ig h -d r a g l o w - l i f t w inged v e h i c l e , ( 2 ) h ig h
drag c a p s u le , and (3) g l i d e c a p s u le . The r e s u l t s o f t h e s e
s t u d i e s s u g g e s t t h a t t h e human o p e r a to r can make p i l o t e d
e n t r i e s a t a n g le s up t o -6 d e g r e e s w ith o u t e x c e e d in g 8 .0 g
and t h a t th e p i l o t can m a in ta in c o n tr o l o f h i s v e h i c l e f o r
s e v e r a l m in u te s, even under c o n d it io n s o f p r o lo n g e d
a c c e le r a t i o n in v e h i c l e s h a v in g v e r y lo w dynamic s t a b i l i t y .
In p a r t i c u l a r , Chambers and D o e r fe l (2 8 ) p o in t o u t
t h a t d u rin g s t a t i c and dynamic s im u la tio n i t was in d ic a t e d
t h a t t h e p i l o t s g e n e r a lly d id b e t t e r under m o d e ra te ly h ig h
g (4 .0 g - 6 .0 g) th an t h e y d id under s t a t i c c o n d i t i o n s .
At th e h ig h e r ra n g e s ( 6 .0 g - 8 .0 g ) , how ever,, th e dynamic
r u n s were " c le a r l y more d i f f i c u l t and were som etim es
accom panied by a b o r tio n s o r e x c e s s i v e o s c i l l a t i o n s due to
poor p erform an ce." T h is l a t t e r s ta te m e n t, in g e n e r a l,
a g r e e s w ith th e f in d in g s o f K aeh ler and Meehan ( 7 4 ) , t h a t
p e r c e p tu a l-m o to r e r r o r i s a p o s i t i v e l y a c c e le r a t e d f u n c t io n
o f in c r e a s e d fo r c e m agn itu d e,
K aehler and Romano (7 7 ) r e c e n tl} ' r e p o r te d a stu d y
in w hich t h e q u e s tio n o f p i l o t c a p a b i l i t y to s u c c e s s f u l l y
c o n t r o l a w inged v e h i c l e from la u n c h t o o r b i t was
e x p e r im e n ta lly e v a lu a t e d .
The s u b j e c t was s e a te d in, a normal p o s i t i o n on th e
USC Human C e n tr ifu g e and was p ro v id ed w ith a s i d e
c o n t r o l l e r t o c o n t r o l an a i r c r a f t r e p r e s e n t a t io n p r e s e n te d
on an o s c i l l o s c o p e . The l o n g i t u d in a l a c c e l e r a t i o n s were
sc h e d u le d a g a in s t th e a n t i c ip a t e d l o n g i t u d in a l s t a b i l i t y
l e v e l s and t h e f l i g h t p ath a n g le r e q u ir e d t o p la c e th e
v e h i c l e in t o o r b i t . The req u irem en t fo r s u c c e s s f u l o r b i t
e s ta b lis h m e n t was f o r th e p i l o t to h o ld t h e p i t c h a n g le
w it h in — 1 d e g r e e . S ix e x p e r im e n ta l t e s t p i l o t s se rv e d
a s s u b j e c t s f o r t h i s e v a lu a t io n . The r e s u l t s showed t h a t
a l l s i x p i l o t s w ere a b le t o c o n t r o l th e v e h i c l e w ith in
± 0 .5 d e g r e e s , w e ll w it h in th e t o le r a n c e r a n g e .
I t may be n o ted t h a t t h e r e a re two s e r io u s
l i m i t a t i o n s o f th e c o n tin u o u s c o n t r o l s t u d i e s r e p o r te d in
t h e a c c e le r a t i o n l i t e r a t u r e to d a te : (1 ) t h e r e i s l i t t l e
q u a n t it a t iv e d a ta , th e bu lk b e in g q u a l i t a t i v e , and (2 ) th e
work w hich has been r e p o r te d , h as been done w ith s p e c i f i c
v e h i c l e s w hich have in h e r e n t ly v a r y in g a c c e le r a t i o n
p r o f i l e s . R egard ing th e l a t t e r sta te m e n t, t h e r e i s a
s e r i o u s la c k o f s t u d ie s in w hich t h e a c c e le r a t i o n
m agn itu d es and d i r e c t i o n s are u sed p r o p e r ly as c l a s s i c a l l y
c o n t r o l l e d in d ep en d en t v a r i a b l e s . T h is d i s s e r t a t i o n i s ,
t h e r e f o r e , one o f th e f i r s t t o h o ld th e a c c e le r a t i o n
m agn itu d es and d i r e c t i o n s in t h e i r proper p e r s p e c t iv e a s
m a n ip u la tiv e in d ep en d en t v a r i a b l e s .
SECTION THREE
PROCEDURE
CH APTER V
APPARATUS AND SUBJECT GROUP
A. APPARATUS
The human c e n t r if u g e
The r e s e a r c h r e p o r te d in t h i s d i s s e r t a t i o n was
con d u cted on th e human c e n t r i f u g e l o c a t e d a t th e U n iv e r s i t y
o f Southern C a l i f o r n ia . T h is c e n t r i f u g e c o n s i s t s o f
t h r e e main p a r t s : (a) t h e power s o u r c e , (b) th e f l y w h e e l ,
and (c ) t h e s u p e r s t r u c t u r e . Each a re d e s c r ib e d b r i e f l y
b elow ( 2 1 ):
a . The power so u r c e i s a w a t e r - c o o le d , s i x
c y lin d e r a u to m o b ile e n g in e which h as been c o n v e r te d to
o p e r a te on n a tu r a l g a s . The c r a n k sh a ft o f th e e n g in e i s
d i r e c t l y co n n ected t o a d r iv e s h a f t in o r d e r t h a t power i s
tr a n s m itte d from th e d r iv e s h a f t t o t h e u n d e r s u r fa c e o f
t h e fly w h e e l by means o f an au tom ob ile t i r e . Changes in
th e sp eed o f th e system a re governed by ch an ges i n th e
sp eed o f th e en g in e w hich i s , in t u r n , c o n t r o l l e d by th e
o p e r a tio n o f a t h r o t t l e lo c a t e d in t h e c o n t r o l b o o th .
b . The e ig h t e e n - t o n fly w h e e l r o t a t e s in th e
h o r iz o n t a l p la n e d i r e c t l y below th e f l o o r in th e chamber
and may be c lu tc h e d t o t h e s u p e r s tr u c t u r e by means o f a
63
64
h y d r a u lic c l u t c h . When t h e c lu t c h i s i n i t i a t e d , th e
s u p e r s tr u c t u r e i s a c c e le r a t e d and t h e fly w h e e l i s d e c e l
e r a te d u n t i l th e t o t a l sy stem becom es s t a b i l i z e d and th e
combined u n i t r o t a t e s a t th e same r a t e .
c . The s u p e r s tr u c tu r e i s f i f t y f e e t in l e n g t h ,
r o t a t e s about i t ’ s c e n t e r , w e ig h s a p p r o x im a te ly f i v e t o n s
and i s l o c a t e d i n a c i r c u l a r chamber p r o t e c t e d by th r e e
f e e t o f s t e e l r e in f o r c e d c o n c r e t e . There a r e p o s i t i o n s
a v a ila b le fo r anim al o r human e x p e r im e n ta tio n a t e i t h e r
end. On one end, t h e r e i s a g o n d o la w h ich i s f r e e t o
r o t a t e and, th e r e b y , f o l lo w s th e r e s u l t a n t v e c t o r o f th e
c e n t r i f u g a l f o r c e produced by t h e m otion o f th e c e n t r i f u g e
and th e norm al a c c e l e r a t i o n due to g r a v i t y . When s e a t e d
in t h i s g o n d o la , th e s u b j e c t e x p e r ie n c e s p o s i t i v e
a c c e l e r a t i o n .
On t h e o th e r end o f th e s u p e r s t r u c tu r e i s a w ork
sp ace l a r g e enough t o f a c i l i t a t e th e p lacem en t o f an
e n t i r e c o c k p it mockup. The r e s e a r c h r e p o r te d in t h i s
d i s s e r t a t i o n was con d u cted u t i l i z i n g t h i s end o f th e
s u p e r s t r u c t u r e . By f a c i n g th e s e a t e d s u b je c t tow ard th e
w a ll (o u tb o a r d ) , he e x p e r ie n c e s b a c k - t o - f r o n t ( n e g a t iv e
t r a n s v e r s e ) a c c e l e r a t i o n . By f a c i n g t h e s e a te d s u b j e c t
tow ard th e c e n te r o f r o t a t i o n ( in b o a r d ), he e x p e r ie n c e s
f r o n t - t o - b a c k ( p o s i t i v e t r a n s v e r s e ) a c c e l e r a t i o n . The
s u b j e c t s p a r t i c i p a t i n g in t h i s i n v e s t i g a t i o n were p la c e d
in t h i s l a t t e r p o s i t i o n a t an e f f e c t i v e r a d iu s o f 1 5 .5 f t .
65
The m achine i s o p e r a te d by a t r a in e d c e n t r if u g e
o p e r a to r p o s it io n e d in th e c o n t r o l booth w hich o v e r lo o k s
t h e e n t i r e chamber. F ig u r e 5 shows th e c e n t r i f u g e o p e r a to r
in th e c o n t r o l b o o th m o n ito r in g th e s u b je c t s e a te d on th e
c e n t r i f u g e in p o s i t i o n to e x p e r ie n c e f r o n t - t o - b a c k
a c c e l e r a t i o n . V o ice com m unication i s m a in ta in ed th rou gh ou t
a l l c e n t r if u g e runs w ith th e s u b j e c t , c e n t r i f u g e o p e r a to r ,
r e c o r d in g room and f l i g h t su rgeon on th e same com m unication
lo o p . A c lo s e d - lo o p t e l e v i s i o n camera was a ls o a v a i la b l e
f o r d i r e c t m o n ito r in g o f th e s u b j e c t by th e f l i g h t su rgeon
d u rin g c e n t r if u g e r u n s .
The e q u a tio n s fo r c a l c u l a t i n g th e RPM req u ire m en ts
t o produce th e d e s ir e d a c c e le r a t i o n l e v e l s a t t h e 1 5 .5 f t .
r a d iu s are shown in Appendix C. I t was determ in ed t h a t a
f i n a l v e l o c i t y o f 24 RPM and 34 RPM was r e q u ir e d to
produce t h e t e s t v a lu e s o f 3 .0 g and 6 .0 g , r e s p e c t i v e l y .
The t a s k ap p aratu s
The t a s k ap p a ra tu s c o n s is t e d o f s i x e le m e n ts:
(a) a n a lo g com puter, (b) t i m e - l a g c o n s t a n t s , (c ) c u r v e -
f o l lo w e r s , (d) o s c i l l o s c o p e d i s p l a y , (e ) c o n t r o l sy ste m ,
( f ) r e c o r d e r . F ig u r e 6 i s a b lo c k diagram show ing th e
r e l a t i o n s h i p o f th e s i x elem en ts o f th e t a s k a p p a ra tu s and
th e human s u b j e c t . Each o f t h e s e e le m e n ts a re d is c u s s e d
b elow :
A nalog com p u ter. — B r i e f l y , an a n a lo g com puter i s a
66
FIG. 5 . THE SUBJECT AS VIEWED 3Y THE CENTRIFUGE
OPERATOR POSITIONED IN THE CONTROL BOOTH
CURVE
FOLLOWERS
OSCILLOSCOPE
DISPLAY— k
RECORDER
TIME-LAG
CONSTANT
CONTROL
FIG. 6 - BLOCK DIAGRAM SHOWING THE INTERACTION
OF THE SUBJECT AND APPARATUS.
d e v ic e f o r th e s o l u t i o n o f p h y s i c a l problem s by c o n s t r u c
t i o n o f a m a th e m a th ica l m odel o f th e sy s te m un der
c o n s i d e r a t io n (7& ). Bekey ( 6 ) s t a t e s t h a t t h e com ponents
o f t h e a n a lo g com puter a r e d e v ic e s f o r p e r fo r m in g t h e b a s ic
m a th e m a tic a l o p e r a t i o n s , su ch a s a d d i t i o n , i n t e g r a t i o n o r
m u l t i p l i c a t i o n . By i n t e r c o n n e c t io n o f t h e s e b a s ic b u ild in g
b lo c k s a m a th e m a tic a l m odel o f a p h y s i c a l sy stem can be
c o n s t r u c t e d and i t s b e h a v io r o b s e r v e d . Each com p uting
elem en t p erfo rm s i t s o p e r a t io n on a p h y s i c a l q u a n t i t y , in
t h i s c a s e e l e c t r i c a l v o l t a g e s , w hich i s a n a lo g o u s t o th e
m a th e m a tic a l problem v a r i a b l e b e in g r e p r e s e n t e d . A nalog
com p uters v a r i a b l e s a r e c o n tin u o u s v a r i a b l e s as d i s t i n
g u is h e d from d i g i t a l com puter v a r i a b l e s w h ich a r e d i s c r e t e .
For t h e i n t e r e s t e d r e a d e r , Korn and Korn (7 $ ) and E tk in
(4 3 ) p r e s e n t exam p les o f th e way a n a l o g i c a l m ethods a r e
u sed in t h e s o l u t i o n o f a i r c r a f t and m i s s i l e p r o b le m s.
The a n a lo g com puter u se d i n th e p r e s e n t stu d y was t h e
o r i g i n a l d e s ig n and p r o p e r ty o f Worth Am erican A v ia t io n ,
I n c .
T im e -la g c o n s t a n t s . — E x p o n e n tia l t i m e - l a g c o n s t a n t s
o f 0 . 1 , 1 . 0 , and 2 .0 w ere s e l e c t e d a s t e s t v a lu e s f o r t h i s
s tu d y . Apart from g e n e r a l agreem ent w it h o t h e r s t u d i e s in
t h i s a r e a , t h e s e c o n s t a n t s w ere s e l e c t e d s i n c e t h e y
" b r a c k e t” e x tr e m e s o f h ig h p erform an ce a i r c r a f t aerodynam ic
r e s p o n s e c h a r a c t e r i s t i c s . More d e t a i l e d in fo r m a tio n on
t h e o v e r a l l a n a lo g s im u la t io n and t h e p r o d u c tio n o f
69
e x p o n e n tia l tim e - la g c o n s ta n ts are p r e se n te d in Appendix B.
C u r v e -fo llo w e r s . — Two c u r v e - fo llo w e r s were u sed
fo r p r e s e n tin g th e ta s k to th e s u b j e c t , one f o r th e p it c h
mode, th e o t h e r , fo r th e r o l l mode. Each ta s k mode was a
complex wave form su g g ested by r e p r e s e n t a t iv e s o f North
American A v ia tio n , I n c . , as ap p roxim ating a h ig h perform
ance a i r c r a f t in tu r b u le n t c o n d it io n s . The tim e d u ra tio n
o f th e ta s k was made to be s i x t y secon ds so t h a t i t would
be in agreement w ith o th e r s t u d ie s o f t h i s n atu re and a ls o
to r e q u ir e th e su b je c t to be exposed to th e a c c e le r a t i v e
environment f o r a s u it a b le amount o f tim e . F igu re 7 shows
th e c u r v e - f o llo w e r s , in a s s o c ia t io n w ith th e an alog
com puter, in th e r eco rd er room.
O s c illo s c o p e d i s p l a y . — The complex wave forms
noted above were u sed to d is tu r b a h o r iz o n ta l l i n e on th e
c e n te r o f th e o s c i l l o s c o p e f a c e . The l i n e r e p r e se n te d
th e s u b je c t* s own a i r c r a f t and was programmed to move
v e r t i c a l l y to in d ic a t e p itc h and r o t a t e about i t s c e n te r
to in d ic a t e r o l l . The s u b je c t was req u ired to h o ld th e
a i r c r a f t r e p r e s e n ta tio n at zero d e g r ee s in p it c h and r o l l
a n g le s , any d e v ia tio n from th e h o r iz o n t a l- c e n t e r p o s i t i o n
r e p r e s e n tin g a tr a c k in g e r r o r . Two markers were p la c e d
on th e o s c i ll o s c o p e fa c e in ord er to denote th e c e n te r
as an a d d itio n a l cue fo r th e s u b j e c t . F ig u re & shows th e
a i r c r a f t r e p r e s e n ta tio n in a p o s i t i o n d e p ic t in g a la r g e
erro r in th e r o l l mode. In t h i s c a se th e su b je c t would
70
FIG. 7 . THE CURVE-FOLLOWERS AND THE ANALOG COM PUTER
IN THE CONTROL ROOM .
71
FIG. g . THE AIRCRAFT REPRESENTATION ON THE OSCILLO
SCOPE SHOWING A ROLL ERROR BUT NO PITCH
ERROR.
72
h a v e t o make a r o l l m o tio n t o t h e r i g h t t o c o r r e c t f o r
t h i s e r r o r .
C o n t r o l s y s t e m . — The c o n t r o l s t i c k u s e d i n t h i s
program w as t h e p r o t o t y p e X -1 5 r i g h t hand c o n t r o l l e r . I t
w as d e s ig n e d so t h a t t h e p i l o t s ’ w r i s t ( u l n a r s t y l o i d )
w as t h e p i v o t p o i n t f o r b o th p i t c h and r o l l m o d es. B e fo r e
d a t a r u n s w e r e b e g u n , t h e s t i c k w as "m ass b a la n c e d " so
t h a t i t w o u ld n o t be d i s p l a c e d by t h e a c c e l e r a t i v e f o r c e ,
t h e r e b y i n d u c i n g e r r o r s w h ic h w o u ld n o t be a t t r i b u t a b l e
t o t h e v o l u n t a r y c o n t r o l m o t io n s o f t h e s u b j e c t . An
a d j u s t a b l e a r m r e s t w as p r o v id e d so t h a t e a c h s u b j e c t c o u l d
p o s i t i o n h i m s e l f c o m f o r t a b ly i n r e l a t i o n t o t h e c o n t r o l
c o lu m n . The a r m r e s t w as a d j u s t a b l e v e r t i c a l l y and
l o n g i t u d i n a l l y . F ig u r e 9 sh ow s t h e r e l a t i v e p o s i t i o n s o f
t h e s u b j e c t , t h e c o n t r o l s t i c k and t h e o s c i3 .1 o s c o p e ;
F ig u r e 10 sh ow s a c l o s e - u p v ie w o f t h e a r m r e s t and c o n t r o l
s t i c k ; F ig u r e 11 show s an o v e r a l l v i e w o f t h e s u b j e c t
s e a t e d on t h e human c e n t r i f u g e p e r fo r m in g t h e t r a c k i n g
t a s k d u r in g a s t a t i c r u n .
R e c o r d e r . — The r e c o r d e r u s e d in t h i s s t u d y w as an
e i g h t c h a n n e l O f f n e r D yn ograp h . Fotir c h a n n e l s o f in f o r m a
t i o n w ere u s e d f o r e a c h o f p i t c h and r o l l m e a s u r e m e n ts ,
a s f o l l o w s : (1 ) t a s k i n p u t ( s t i m u l u s ) , ( 2 ) s t i c k in p u t
( r e s p o n s e ) , ( 3 ) a b s o l u t e e r r o r ( t h e d i f f e r e n c e b e tw e e n 1
and 2 ) , and (4 ) t h e i n t e g r a t i o n o f t h e a b s o l u t e e r r o r .
The i n t e g r a t e d e r r o r i n v o l t s , f o r e a c h m ode, i s u s e d a s
73
F IG . 9 . THE RELATIVE POSITION OF THE SUBJECT, THE
CONTROL STICK, AND THE OSCILLOSCOPE ON THE
HUM AN CENTRIFUGE.
74
FIG. 1 0 . A CLOSE-UP OF THE RIGHT HARD SIDE CONTROL
STICK.
75
FIG . 1 1 . THE SUBJECT SEATED IlM POSITION TO EXPERIENCE
FRONT-TO-BACK ACCELERATION ON THE HUM AN
CENTRIFUGE.
7 6
t h e d e p e n d en t v a r i a b l e f o r t h i s s t u d y . F ig u r e 12 show s
t h e r e c o r d e r i n o p e r a t i o n d u r in g a c e n t r i f u g e r u n . F ig u r e
13 p r e s e n t s a t y p i c a l r e c o r d sh o w in g ea ch o f t h e e i g h t
c h a n n e l s .
3 . SUBJECT GROUP
T h i r t y - f i v e m ale s t u d e n t s a t The 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 s e r v e d a s s u b j e c t s f o r t h i s i n v e s t i
g a t i o n . They ra n g ed i n a g e from t w e n t y - o n e t o t w e n t y - s i x .
The v a s t m a j o r i t y o f t h e s u b j e c t s w ere members o f t h e
N aval R e s e r v e O f f i c e r s T r a in in g C orps on t h e cam pus. As
su c h , t h e y w e re a group o f s u b j e c t s who m ig h t be e x p e c t e d
t o become N a v a l A v ia t o r s w i t h i n t h e n e x t two y e a r s .
M o reo v er, t h e m e n ta l and p h y s i c a l r e q u ir e m e n ts f o r
a c c e p t a n c e t o t h e N .R .O .T .C . program i s e v id e n c e f o r t h e
h ig h c a l i b e r o f t h e s u b j e c t g r o u p . The rem a in d er o f t h e
s u b j e c t grou p w ere i n d i v i d u a l s who had b een s u b j e c t s f o r
o t h e r e x p e r im e n ts and p o s s e s s e d t h e same h ig h q u a l i t i e s
o f t h e N .R .O .T .C . g r o u p .
Each p r o s p e c t i v e s u b j e c t was a sk e d t o v i s i t t h e
c e n t r i f u g e f a c i l i t y w here a s t a f f member d i s c u s s e d t h e
p u r p o s e s o f t h e program and g a v e a g e n e r a l o r i e n t a t i o n on
t h e o p e r a t i o n o f t h e c e n t r i f u g e . I f t h e i n d i v i d u a l
d e s i r e d t o p a r t i c i p a t e , and was m e d i c a l l y a p p r o v e d , h i s
name w as added t o a s e l e c t i o n l i s t . From t h i s l i s t ,
t h i r t y - s i x s u b j e c t s w ere ran d om ly s e l e c t e d and a s s ig n e d
F IG . 1 2 . THE ANALOG COMPUTER OPERATOR NOTING
INFORMATION ON THE RECORDER DURING A
CENTRIFUGE RUN.
7S
r * ~ T ' ■ ‘ T'Tf-rri- t-ri -M -;-r-\-r-‘ r • “
r t r lT■Txm TTyTh^tlTT1~ ,t: . .
- ..-4 - - . . > — .
INTEGRATED-
FIG . 1 3 . A TYPICAL RECORD SHOWING THE USE OF EIGHT
CHANNELS FOR DATA RECORDING AND REDUCTION.
t o on e o f t h r e e g r o u p s , o n e f o r e a c h t i m e - l a g c o n s t a n t .
T h is s e l e c t i o n w as made b y u s e o f a T a b le o f Random
Numbers ( 3 # ) . One s u b j e c t s u b s e q u e n t l y d ro p p ed from t h e
program , l e a v i n g e l e v e n s u b j e c t s i n t h e 2 . 0 t i m e - l a g
g r o u p . S i n c e t h e e x p e r im e n t a l d e s i g n d id n o t r e q u i r e
e q u a l num bers in t h e e x p e r im e n t a l g r o u p s , he w as n o t
r e p l a c e d . A l l s u b j e c t s w ere p a id f o r t h e i r s e r v i c e s a s
a m o t i v a t i n g a g e n t .
CHAPTER VI
PROCEDURE AM D DESIGN OF THE EXPERIMENT
A. PROCEDURE
An o p e r a t i n g c re w o f f i v e p e r s o n s c o m p r is in g
(1 ) e x p e r im e n t e r , ( 2 ) c e n t r i f u g e o p e r a t o r , ( 3 ) a n a lo g
co m p u ter o p e r a t o r , (4 ) e l e c t r o n i c t e c h n i c i a n , and ( 5 )
f l i g h t s u r g e o n w e re i n v o l v e d i n t h e c o n d u c t o f t h e
e x p e r im e n t .
The e x p e r im e n t e r w as r e s p o n s i b l e f o r t h e g e n e r a l
h a n d lin g o f t h e s u b j e c t s , d i s c u s s i n g t h e program and
a n s w e r in g an y q u e s t i o n s w h ic h m ig h t a r i s e d u r in g t h e
c o u r s e o f t h e e x p e r im e n t . He a l s o e s c o r t e d t h e s u b j e c t
i n t o t h e c e n t r i f u g e cham ber b e f o r e t h e r u n s b e g a n and
c h e c k e d w it h him a f t e r e a c h e x p o s u r e t o t h e a c c e l e r a t i v e
c o n d i t i o n s .
The c e n t r i f u g e o p e r a t o r w as r e s p o n s i b l e f o r t h e
s a f e o p e r a t i o n o f t h e m ach in e and f o r p r o d u c in g t h e
r e q u ir e d a c c e l e r a t i o n l e v e l s . The a n a lo g co m p u ter
o p e r a t o r was r e s p o n s i b l e f o r t h e s e t - u p o f t h e t a s k ,
c o n t r o l d yn am ics r e c o r d e r , and t h e s e q u e n c e o f t h e t a s k
d u r in g t h e s t a t i c and dynam ic r u n s . The e l e c t r o n i c
t e c h n i c i a n a d j u s t e d t h e eq u ip m en t on t h e c e n t r i f u g e ,
SO
& L
i n c l u d i n g t h e s u b j e c t s * a r m r e s t , and p e r fo r m e d s a f e t y
c h e c k s w it h t h e e x p e r im e n t o r p r i o r t o t h e s t a r t i n g o f
dynam ic r u n s . The f l i g h t s u r g e o n w as r e s p o n s i b l e f o r t h e
m e d ic a l m o n it o r in g o f t h e s u b j e c t d u r in g c e n t r i f u g a t i o n .
D u rin g t h e dynam ic r u n s , t h e e x p e r im e n t e r , f l i g h t
s u r g e o n , c e n t r i f u g e o p e r a t o r , a n a lo g co m p u ter o p e r a t o r ,
and t h e s u b j e c t w e r e on t h e same c o m m u n ic a tio n l o o p so
t h a t a l l p a r t i e s w e re i n c o n t in u o u s c o m m u n ic a tio n .
A f t e r t h e e x p e r im e n t e r and t h e e l e c t r o n i c
t e c h n i c i a n made c e r t a i n t h a t t h e s u b j e c t w as p r o p e r ly
s e c u r e d and made v i s u a l i n s p e c t i o n s o f a t t a c h e d a p p a r a t u s ,
t h e y l e f t t h e c e n t r i f u g e ch am b er. At t h i s t i m e , t h e
c e n t r i f u g e o p e r a t o r a s k e d , " S u b je c t R eady?" I f a f f i r m a
t i v e , he a s k e d , "A nalog R eady?" I f a f f i r m a t i v e , h e a s k e d ,
" M on itor R eady?" I f a f f i r m a t i v e , h e g a v e a f i v e s e c o n d
c o u n t-d o w n and s t a r t e d t h e m a ch in e a t " z e r o ." Upon
r e a c h i n g t h e p r o p e r a c c e l e r a t i o n l e v e l , t h e c e n t r i f u g e
o p e r a t o r s a i d , "g" w h ic h w as t h e s i g n a l f o r t h e a n a lo g
com p u ter o p e r a t o r t o s t a r t t h e t a s k . Upon c o m p le t io n o f
t h e t a s k , t h e a n a lo g co m p u ter o p e r a t o r s a i d , "End T e st"
and t h e c e n t r i f u g e o p e r a t o r b r o u g h t t h e m a ch in e t o a f u l l
s t o p . The r e a d e r s h o u ld n o t e t h a t t h e s u b j e c t t r a c k e d
o n l y u n d e r c o n d i t i o n s o f s t e a d y - s t a t e a c c e l e r a t i o n , n o t
d u r in g t h e b u i ld - u p o r l e t - d o w n .
S2
B. DESIGN OF THE EXPERIMENT
The ex p erim en t was d e s ig n e d so t h a t t h e d a ta c o u ld
be s u b j e c t t o s t a t i s t i c a l tr e a tm e n t by th e a n a l y s i s o f
v a r ia n c e m ethod. The s p e c i f i c d e s ig n was a L in q u is t ( S i )
"Type I Mixed" d e s ig n .
In many f a c t o r i a l e x p e r im e n ts th e number o f
tr e a tm e n t-c o m b in a tio n s i s so l a r g e t h a t i t i s n o t
p r a c t i c a b l e t o a d m in is t e r a l l o f them t o each s u b j e c t .
L in d q u is t ( S i ) p o i n t s o u t t h a t i t i s p o s s i b l e t o s e t - u p
a d e s ig n in w hich each s u b j e c t t a k e s more th a n one b u t n o t
a l l o f th e c o m b in a tio n s so t h a t some o f t h e tr e a tm e n t
com p arison s a r e i n t e r - s u b j e c t and some a re i n t r a - s u b j e c t .
T h is , by d e f i n i t i o n , i s a "mixed" d e s ig n . T h is "mixed"
d e s ig n was c h o se n , r a th e r th a n a c o m p lete f a c t o r i a l d e s ig n ,
in v ie w o f t h e h ig h c o s t s i n tim e and money t o p r o c e s s each
s u b j e c t on t h e c e n t r i f u g e and th e a n a lo g com p u ter.
The "Type I" d e s ig n i s a two f a c t o r (A X B) d e s ig n
in w hich each o f t h e "A" tr e a tm e n ts i n c o m b in a tio n w ith any
one "B” tr e a tm e n t i s a d m in is te r e d t o th e same s u b j e c t , bu t
w ith each "B" tr e a tm e n t a d m in is te r e d t o a d i f f e r e n t group
o f s u b j e c t s .
In th e p r e s e n t c a s e , th e "A" tr e a tm e n t was t h e
f r o n t - t o - b a c k a c c e l e r a t i o n l e v e l s o f ( l ) s t a t i c (0 g in
t h e t r a n s v e r s e d i r e c t i o n ) , (2 ) 3 .0 g and (3 ) 6 .0 g . The
"B" tr e a t m e n ts w ere e x p o n e n t ia l t i m e - l a g c o n s t a n t s o f
( l ) 0 .1 , (2 ) 1 . 0 and (3 ) 2 .0 s e c o n d s . As was n o te d
33
e a r l i e r , th e s u b j e c t s w ere random ly a s s ig n e d t o one o f th e
t i m e - l a g groups ("B" t r e a t m e n t s ) . A ll s u b j e c t s , t h e r e f o r e ,
r e c e iv e d a l l o f t h e a c c e l e r a t i o n ("A") tr e a tm e n ts but
perform ed t h e t r a c k in g t a s k w ith o n ly th e one a s s ig n e d
t i m e - l a g c o n s t a n t . The i n t r a - s u b j e c t com parison w as,
t h e r e f o r e , betw een a c c e l e r a t i o n t r e a t m e n t s , and t h e i n t e r
s u b j e c t com p arison , betw een t i m e - l a g c o n s t a n t s .
Each s u b j e c t was g iv e n tw e n ty s t a t i c , fo u r 3 . 0 g
and fo u r 6 .0 g t r i a l s o v e r a two day p e r io d . On th e f i r s t
day, t h e s u b j e c t s r e c e iv e d te n s t a t i c t r i a l s in two b lo c k s
o f f i v e e a c h . Each t r i a l was s e p a r a te d by a o n e -m in u te
r e s t p e r io d , and t h e b lo c k s , by a t h r e e m in u te r e s t p e r io d .
The r e s t p e r io d s w ere p r o v id e d t o red u ce f a t i g u e e f f e c t s .
A fte r th e l a s t s t a t i c t r i a l , t h e s u b j e c t s w ere ex p o sed t o
a c c e l e r a t i o n l e v e l s in th e f o l lo w in g m a gn itu d es and o r d e r :
3.0 g , 6 .0 g , 3.0 g , 6 .0 g . There was a minimum r e s t
p e r io d o f th r e e m in u te s betw een t h e c e n t r i f u g e e x p o s u r e s .
On t h e seco n d day, t h e s u b j e c t s r e c e i v e d t h e same
o r d e r up to and in c lu d in g t h e f i r s t ex p o su re t o 3 .0 g and
6 .0 g . Each t i m e - l a g group was random ly d ic h o to m iz e d ;
one h a l f r e c e i v i n g th e f i n a l 3.0 g run p r io r t o th e 6 .0 g ,
and t h e o th e r h a l f r e c e i v e d t h e f i n a l 6 .0 g run p r io r t o
th e 3 .0 g ru n . T h is was a c co m p lish ed t o c o u n te r b a la n c e
p o s s i b l e f a t i g u e and p r a c t i c e e f f e c t s .
The m easurem ents u se d f o r d a ta e v a lu a t io n in th e
a n a l y s i s o f v a r ia n c e w ere th e l a s t s t a t i c , 3.0 g , and
S4
6 .0 g runs on th e second day. A s t a t i c run was n ot u sed
to c o u n te rb a la n c e th e dynamic runs a s n oted ab ove, s in c e
th e l i n e on th e o s c i l l o s c o p e " d r ifte d " a s a fu n c tio n o f
a c c e le r a t io n and r eq u ired a s i g n i f i c a n t tim e d e la y w a it in g
fo r th e scope l i n e to r e tu r n to th e normal p o s i t i o n . The
e rro r due to "scope d r i f t " was determ ined e x p e r im e n ta lly
and was su b se q u e n tly " in te g r a te d out" o f th e f i n a l e r r o r
m easurem ents.
The g e n e r a l ex p erim en ta l h y p o th e se s were s t a t e d
in Chapter I I and are now s t a t e d , fo r th e p u rp oses o f th e
s t a t i s t i c a l a n a l y s i s , on th e o p e r a tio n a l l e v e l :
1 . Mean p it c h and r o l l in t e g r a t e d e rr o r s c o r e s
w i l l d e c re a se s i g n i f i c a n t l y w ith a t im e - la g v a lu e o f 0.1
second to a v a lu e o f 1 .0 second and in c r e a s e again a t 2.0
se co n d s, th e r e b y produ cin g a U-shaped cu r v e.
2 . Mean p it c h and r o l l in t e g r a t e d e rr o r s c o r e s
w i l l be s i g n i f i c a n t l y la r g e r f o r m easures o b ta in e d at
3.0 g th an fo r m easures o b ta in e d in a normal se a te d p o s i
t i o n ( s t a t i c ) ; error s c o r e s o b ta in ed a t 6.0 g w i l l be
s i g n i f i c a n t l y la r g e r th an t h o s e o b ta in e d a t 3.0 g.
3. Mean p itc h and r o l l in t e g r a t e d e rr o r s c o r e s
o b ta in e d a t 3*0 g and 6 .0 g w i l l form a fa m ily o f U -shaped
cu rves when p lo t t e d as a fu n c tio n o f t im e - la g c o n s ta n ts
so t h a t t im e - la g c o n s ta n ts prod u cin g t h e l a r g e s t s c o r e s
s t a t i s t i c a l l y w i l l produce th e l a r g e s t s c o r e s a t in c r e a s e d
a c c e le r a t io n l e v e l s .
SECTION FOUR
RESULTS AND DISCUSSION
CHAPTER V II
RESULTS AND DISCUSSION
The d a ta f o r p it c h and r o l l m easurem ents were
e v a lu a te d s e p a r a t e ly by th e a n a l3 ' s i s o f v a r ia n c e method
o u t lin e d in Chapter VI. Appendix C p r e s e n t s t h e means
and standard d e v ia t io n s fo r a l l d a ta runs and c o n tr o l
m odes. In a d d it io n , t - r a t i o s and product-m om ent c o e f f i
c i e n t s o f c o r r e la t io n were in c lu d e d to f u r t h e r a n a ly ze
th e r e s u l t s . Appendix D p r e s e n t s some comments on th e
assu m p tion s o f th e s t a t i s t i c a l a n a l y s i s .
A. PITCH MODE
F ig u re 14 p r e s e n t s th e mean p it c h in t e g r a t e d e rr o r
v a lu e s a s a f u n c tio n o f th e number and ty p e o f p r a c t ic e
t r i a l s . A v i s u a l in s p e c t io n o f th e f i g u r e i n d ic a t e s th e
f o llo w in g r e s u l t s :
1 . The erro r s c o r e s and t h e i r r e l a t i v e p o s i t i o n
are s t a b l e by t h e end o f th e s t a t i c t r i a l s on th e second
day. T h is amount o f p r a c t ic e b e fo r e s t a b i l i z a t i o n i s in
agreem ent w ith r e s u l t s on s im ila r t r a c k in g t a s k s r e p o r te d
by Gordon ( 56 ) , Gagne7 and F o ste r (4 9 ) and o t h e r s .
2 . There are r e l a t i v e l y l a r g e d i f f e r e n c e s from
th e f i r s t t o th e second o f each a c c e le r a t io n l e v e l on th e
86
M EA N PITCH INTEGRATED ERROR— I N VOLTS.
5.0
TIME-LAG CONSTANTS
* 0.1 SEC.
4.5
—-A 1 .0 SEC.
4.0 2.0 SEC.
o—
3.5
3.0
2.5
2.0
1.5
Ok.
>0"' £—j V .
- * ■ - * CL,. ' Y r - ;
1. 0
— o
I 2 3 4 5 6 7 8 9 10 3.0 6.0 3.0 6.0 I 2 3 4 5 6 7 8 9 10 3.0 6.0 3 0 6.0
S T A T IC TRIA LS g TRIALS STATIC TRIALS g TRIALS
F I R S T DAY S E C O N D DAY
03-
FIG. 1 4 - MEAN PITCH ERROR VALUES AS A FUNCTION OF PRACTICE TRIALS CONDUCTED ^
OVER A TWO DAY PERIOD.
gg
f i r s t day. T h is i s n o t t r u e , how ever, f o r m easures on th e
secon d day, i n d i c a t i n g t h a t t h e d ata are becom ing asymp
t o t i c and t h a t le a r n i n g , a t l e a s t in t h e r e l a t i v e s e n s e ,
i s m in im ized .
3 . The 0 .1 secon d l a g c o n s i s t e n t l y p ro d u ces h ig h e r
e r r o r s c o r e s f o r s t a t i c and a c c e l e r a t i v e c o n d i t i o n s .
4 . There i s a s i z e a b le d i f f e r e n c e in th e r a t e o f
le a r n in g betw een th e 1 .0 and 2.0 secon d s l a g s in th e e a r ly
p r a c t ic e t r i a l s .
5. There i s a d e f i n i t e r e v e r s a l in th e r e l a t i v e
o rd er a f t e r th e s i x t h t r i a l on th e secon d d ay. P r io r t o
t h i s tim e , a U -fu n c tio n was i n d ic a t e d , in t h a t th e 1 . 0
second t im e - l a g c o n sta n t produced th e l e a s t amount o f
e r r o r , as p r e d ic t e d . L a te r in th e p r a c t i c e s e r i e s ,
how ever, th e 2.0 seco n d s l a g r e v e r s e s p o s i t i o n w ith th e
1 .0 second l a g .
A f e a s i b l e e x p la n a tio n f o r th e r e v e r s a l n oted
above i s in term s o f th e in fo r m a tio n -le a r n in g a s p e c t s
n o te d in Chapter I I I . In p a r t i c u l a r , McGeoch and I r io n
( # 5 ) con clu d ed t h a t fo r most e f f i c i e n t l e a r n i n g , know ledge
o f r e s u l t s sh ou ld be a d m in iste r e d a s q u ic k ly and as
s p e c i f i c a l l y a s p o s s i b l e . When ite m s 4 and 5, a b o v e , a r e
c o n s id e r e d t o g e t h e r , i t i s app arent t h a t s in c e t h e 2.0
second l a g p r o v id e s l e s s feed b a ck o f in fo r m a tio n , or
r e in fo r c e m e n t, t h e le a r n in g w i l l ta k e p la c e a t a slo w e r
r a t e and, h e n c e , r e q u ir e a lo n g e r p e r io d o f tim e f o r th e
S9
perform ance s c o r e to reach i t s a sy m p to te.
A lthough t h i s le a r n in g phenomenon has e s s e n t i a l l y
’’d e str o y ed " t h e p r e d ic t e d p i t c h U - f u n c t io n , i t s e r v e s as
an e x c e l l e n t exam ple o f th e problem s o f d o in g r e s e a r c h
w ith human s u b j e c t s . F i r s t , th e p r o b le m a tic , e v e r p r e s e n t
a d a p t a b i l it y o f th e human, as was n o ted e a r l i e r a t g r e a t
l e n g t h , makes p r e d ic t io n a v ery d i f f i c u l t t a s k . S e c o n d ly ,
r e s e a r c h e r s in t h e a rea o f human perform ance should be
c r i t i c a l o f le a r n in g phenomena so t h a t t h e y a v o id th e
p i t f a l l o f making c o n c lu s io n s b e fo r e th e y a r e c e r t a i n t h a t
com p lete a d a p ta tio n or a l i m i t has been r e a c h e d .
Table 1 p r e s e n t s th e mean p it c h in t e g r a t e d e r r o r
fo r th e l a s t s t a t i c , 3 .0 g and 6 .0 g t r i a l s . F ig u re 15
p r e s e n t s t h e s e r e s u l t s g r a p h ic a lly and, as p r e d ic t e d , t h e
a c c e le r a t i o n d a ta p rod u ces a c o n s i s t e n t fa m ily o f c u r v e s .
The U - fu n c tio n , o f c o u r s e , was n ot o b ta in e d a lth o u g h th e
r e s u l t a n t curve m ight be d e s c r ib e d as a " h a lf" U - f u n c t io n .
P r e s e n tin g th e r e s u l t s in a n o th er way, F ig u r e 16 i n d i c a t e s
t h a t in c r e a s e d a c c e le r a t i o n in c r e a s e s mean p it c h e r r o r .
F ig u re 1 7 i s a t h r e e d im e n sio n a l p r e s e n t a t io n o f
th e r e s u l t s shown in F ig u r e s 15 and 16 in o rd er to make
d i r e c t com parison w ith th e g e n e r a l model shown a s F ig u r e
1 . There i s a resem b lan ce e x c e p t f o r t h e e x p e r im e n ta lly
o b ta in e d " h a lf" U - fu n c tio n .
Table 2 p r e s e n t s th e r e s u l t s o f th e a n a l y s is o f
v a r ia n c e o f p i t c h e r r o r s c o r e s . S t a t i s t i c a l l y s i g n i f i c a n t
90
TABLE 1
MEAN PITCH INTEGRATED ERROR, IN VOLTS, OBTAINED
FOR THE VARIOUS ACCELERATION LEVELS
AND TIME-LAG CONSTANTS
TIME-LAG CONSTANTS
A c c e l e r a t i o n
L e v e l s 0 .1 S e c . • 1 . 0 S e c . 2 . 0 S e c .
S t a t i c
1 . S3
1 .0 6
0 .9 5
3 . 0 g
2 . 4 7 1 . 4 0 1 . 3 2
6 . 0 g
3 .5 5
2 .36
2 .1 5
91
ACCELERATION LEVELS
m
* STATIC
> 5.0 3.0 g
6.0 g
4 .0
Ui
St 3 .0
2.0
1 . 0
Ui
2.0 1 . 0 0 .1
TIME LAG CONSTANTS IN SECONDS.
FIG. 15 - MEAN PITCH ERRO R AS A FUNCTION OF
VARIOUS TIM E-LA G CONSTANTS AND
ACCELERATION LEVELS.
M E A N PIT C H INTEGRATED ERROR
92
5 .0
TIM E-LA G CONSTANTS
4 .0 1.0 SEC.
2 .0 SEC.
3.0
2.0
1 . 0
0
0 3.0 6.0
FRONT-TO-BACK ACCELERATION IN g UNITS.
FIG . 1 6 - MEAN PITCH ERROR AS A FUNCTION OF
INCREASED ACCELERATION AND VARIOUS
TIM E-LA G CONSTANTS.
93
4.0
3.0
A " '
- 2.0
- 1.0
0 .1 2.0 1 .0
TIME-LAG CONSTANTS IN SECONDS
FIG. 17 — THREE DIMENSIONAL PRESENTATION
OF EXPERIMENTAL RESU LTS IN THE
PITCH MODE.
MEAN
INTEGRATED
ERROR IN
V O LT S.
94
TABLE 2
ANALYSIS OF VARIANCE RESULTS FOR PITCH ERROR SCORES
Source o f V a r ia tio n d f M S F
Between S u b je c ts 34
Tim e-Lags (L ) 2
1 2 .2 7
6 .9 3 * ^
Error (b)
32 1 .7 7
W ithin S u b je c ts 70
--
A c c e le r a tio n (A) 2
I S . 29 1 5 .3 7 * * *
A X L 4 4 .0 3 3 .3 9 *
Error (w)
64 1 .1 9
T o ta l
104
*p = . 025 ; **p = . 005 ; ***p = .0 0 1 ; L i n d q u i s t ( S i ) .
95
F - r a t i o s w e r e fo u n d f o r t i m e - l a g c o n s t a n t s , a c c e l e r a t i o n ,
and i n t e r a c t i o n a t t h e . 0 2 5 , .005 and .001 s i g n i f i c a n c e
l e v e l s , r e s p e c t i v e l y .
Two g r o u p s o f t - r a t i o s w e re c a l c u l a t e d f o r t h e
v a r i o u s c o m b in a t io n s o f a c c e l e r a t i o n l e v e l s and t i m e - l a g
c o n s t a n t s i n t h e p i t c h m ode. I n t h e f i r s t g r o u p , t h e
t - r a t i o s b e tw e e n m eans f o r a c c e l e r a t i o n l e v e l s , f o r ea ch
o f t h e t i m e - l a g c o n s t a n t s , show ed 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 c r e a s e s f o r 3 . 0 g and 6 . 0 g . T h ese w ere s i g n i f i c a n t a t
t h e .0 1 l e v e l . T h ese f i n d i n g s s u p p o r t t h e e x p e r im e n t a l
h y p o t h e s i s t h a t t h e m e a s u r e s o b t a i n e d a t 3 . 0 g w o u ld b e
s i g n i f i c a n t l y l a r g e r th a n t h o s e o b t a i n e d s t a t i s t i c a l l y and
t h a t m e a s u r e s o b t a i n e d a t 6 . 0 g w o u ld be s i g n i f i c a n t l y
l a r g e r th a n t h o s e o b t a i n e d a t 3 .0 g .
I n t h e s e c o n d g r o u p , t h e t - r a t i o s b e tw e e n m eans o f
t h e t i m e - l a g c o n s t a n t s a t e a c h o f t h e a c c e l e r a t i o n l e v e l s
show ed t h a t a l l b u t t h e 1 . 0 and 2 . 0 s e c o n d l a g s a t 3 . 0 g
and a g a in a t 6 . 0 g w e r e fo u n d t o be s i g n i f i c a n t l y
d i f f e r e n t . S in c e t h e mean e r r o r f o r t h e 0 .1 s e c o n d l a g
w as s i g n i f i c a n t l y l a r g e r th a n t h e 1 . 0 and 2 .0 s e c o n d s
l a g s , and t h e y i n t u r n , w ere n o t s i g n i f i c a n t l y d i f f e r e n t
from o n e a n o t h e r , t h i s w o u ld a p p e a r t o be t h e e x p l a n a t i o n
o f t h e 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 t e r a c t i o n F - r a t i o . I n
s im p le r t e r m s , t h e m o st d i f f i c u l t t a s k ( 0 .1 s e c o n d )
w it h o u t a c c e l e r a t i o n i s a f f e c t e d m ost b y i n c r e a s e d a c c e l e r
a t i o n . T h is r e s u l t m e e ts w i t h p r e d i c t i o n by t h e P r i n c i p l e
o f G e n e r a lit y .
T ab le 3 p r e s e n t s t h e r e s u l t s o f com p uting p r o d u c t-
moment c o r r e l a t i o n c o e f f i c i e n t s f o r p i t c h m easu rem en ts.
I t vras found t h a t t h e 3 .0 g - 6 . 0 g com p arison f o r a l l t im e -
l a g s produced s t a t i s t i c a l l y s i g n i f i c a n t c o e f f i c i e n t s ,
w h e r e a s, no o th e r co m b in a tio n was s t a t i s t i c a l l y s i g n i f i
c a n t .
One im p l ic a t i o n from t h e s e r e s u l t s f o r e n g in e e r in g
p s y c h o l o g i s t s i s t h a t one can n ot r e l i a b l y p r e d i c t human
p erform ance m easures un der dynamic c o n d it io n s from s t a t i c
m ea su r es. However, i t i s a ls o i n d ic a t e d t h a t a sm a ll
amount o f s t r e s s i s s u f f i c i e n t t o r e l i a b l y p r e d ic t b e h a v io r
a t h ig h e r l e v e l s . T h is r e s u l t q u e s t io n s t h e v a l i d i t y o f
grou n d -b ased f l i g h t s im u la t o r s a s a method f o r o p t im iz in g
c o n t r o l sy ste m s f o r v e h i c l e s w hich may e n c o u n te r a h o s t i l e
environ m en t d u rin g i t s m is s io n .
B. ROLL M ODE
F ig u re l £ p r e s e n t s th e mean r o l l i n t e g r a t e d e r r o r
v a lu e s a s a f u n c t io n o f t h e number and ty p e o f p r a c t i c e
t r i a l s . I t may be n o te d , by v i s u a l i n s p e c t i o n , t h a t :
1 . The e r r o r s c o r e s a r e r e l a t i v e l y s t a b l e by th e
end o f th e s t a t i c t r i a l s on t h e secon d d ay.
2 . The 2 . 0 secon d l a g , i n t h e f i r s t f i v e t r i a l s ,
p ro d u ces t h e g r e a t e s t amount o f e r r o r . By th e s t a t i c
t r i a l s on t h e seco n d d ay, i t d e f i n i t e l y moves b etw een t h e
97
TABLE 3
PRO D U C T-MQMEN T CORRELATION COEFFICIENTS FOR PITCH
MEASUREMENTS OBTAINED FOR THE VARIOUS
COMBINATIONS OF EXPERIMENTAL
CONDITIONS AND TIME-LAG
CONSTANTS
T im e-L ag
C o n s ta n ts
A c c e l e r a t i o n L e v e ls
S t a t i c - 3 . 0 g 3 .0 g - 6 . 0 g S t a t i c - 6 . 0 g
0 .1
.2 3 7
. 9 0 9 **
.1 1 5
o
•
i — 1
.1 3 7 . q sa** .3 3 6
2 .0 .AOS
.6 1 9 * - .0 3 9
* < . 0 5 , ** < . 0 1 , fro m E dw ards (3$).
M E A N ROLL INTEGRATED ERROR— I N VOLTS.
36.0 —
32.0 —
28.0
24.0 —
20.0 —
V
" V
2 3 4 5 6 7 8 9
STATIC TRIALS
R S T
10 3.0 6.0 3.0 6.0
g TRIALS
D A Y
i i r
TIME-LAG CONSTANTS
■— -M— M—— J1 _
X X 0.1 SEC.
1.0 SEC.
2 0 SEC.
i I I I I I 1 1
I 2 3 4 5 6 7 8 9 10 3.0 6.0 3.0 6.0
STATIC TRIALS g TRIALS
S E C O N D DAY
FIG. 1 8 - MEAN ROLL ERROR VALUES AS A FUNCTION OF PRACTICE TRIALS CONDUCTED
OVER A TWO DAY PERIOD.
M D
oa
0 .1 and t h e 1 . 0 secon d l a g s .
3 . The 1 . 0 secon d l a g g e n e r a l l y p ro d u ce s t h e
l e a s t amount o f e r r o r , a lth o u g h t h e r e a r e a sm all number
o f r e v e r s a l s .
The r o l l d a t a , from t h e f i r s t t r i a l o n , d e f i n i t e l y
show a U - f u n c t io n . As p r a c t i c e c o n t i n u e s , t h e 2 .0 se co n d s
l a g r e v e r s e s p o s i t i o n w ith (p ro d u ces l e s s e r r o r th a n ) t h e
0 .1 second l a g . T h is r e v e r s a l does n o t , how ever, change
t h e U -shape s i n c e th e 1 . 0 secon d l a g i s a lw a ys optimum.
The i n f o r m a t i o n - le a r n in g e x p la n a t io n f o r t h e 2 . 0 secon d
l a g r e v e r s a l in p i t c h would appear t o s a t i s f y th e p r e s e n t
r e v e r s a l .
Table 4 p r e s e n t s th e mean r o l l i n t e g r a t e d e r r o r
f o r t h e l a s t s t a t i c , 3 .0 g and 6 . 0 g t r i a l s . F ig u r e 19
p r e s e n t s t h e s e r e s u l t s in g rap h ic form and, as was found
w ith p i t c h , a c c e l e r a t i o n data form a c o n s i s t e n t f a m ily o f
c u r v e s . M oreover, a rough U - f u n c t io n was fou n d , as was
p r e d i c t e d . F ig u re 20 shows t h e i n c r e a s e o f mean r o l l
e r r o r a s a f u n c t io n o f each l e v e l o f in c r e a s e d a c c e l e r a
t i o n .
F ig u re 21 i s a t h r e e d im e n sio n a l p r e s e n t a t i o n o f
th e e x p e r im e n ta l r e s u l t s shown in F ig u r e s 19 and 20. I t
may be n o te d t h a t F ig u r e 21 i s a v e r y c l o s e a p p ro xim atio n
o f t h e g e n e r a l model shown as F ig u r e 1 . At l e a s t in term s
o f t r e n d s , a l l h y p o th e s e s were p r e d i c t e d a c c u r a t e l y .
Table 5 p r e s e n t s t h e r e s u l t s o f t h e a n a l y s i s o f
TABLE 4
M EAN ROLL INTEGRATED ERROR, IN VOLTS, OBTAINED
FOR THE VARIOUS ACCELERATION LEVELS
AND TIME-LAG CONSTANTS
TIME-LAG CONSTANTS
A c c e le r a tio n
L e v e ls 0 .1 Sec. 1 . 0 Sec. 2 .0 Sec.
S t a t ic 5.2 9
3 .7 6 5.21
3 .0 g
9 .7 5
4 .4 6
5.49
6 .0 g
1 1 .9 5
7.60 6.26
101
ACCELERATION LEVELS 14.0
* STATIC
12.0 3.0 g
6.0 g
o io.o
8.0
4.0
2.0
0 .1 1 .0 2.0
TIME LAG CONSTANTS IN SECONDS.
FIG. 19 - MEAN ROLL INTEGRATED ERROR AS A
FUNCTION OF VARIOUS TIME LAG CONSTANTS
AND ACCELERATION LEVELS.
M E A N R O L L INTEGRATED E R R O R I N VOLTS.
102
14.0
TIME-LAG CONSTANTS
* 0.1 SEC.
1.0 SEC.
2.0 SEC.
10 . 0
8.0
6.0
o-
4.0
2.0
0 3.0 6.0
FRONT-TO-BACK ACCELERATION IN g UNITS.
FIG. 2 0 - MEAN ROLL ERROR AS A FUNCTION OF
INCREASED ACCELERATION AND VARIOUS
TIME-LAG CONSTANTS.
103
A —
0 . 1 1 .0 2.0
TIME-LAG CONSTANTS IN SECONDS
FIG. 21 - THREE DIMENSIONAL PRESENTATION
OF EXPERIMENTAL RESULTS IN THE
ROLL MODE.
MEAN
INTEGRATED
ERROR IN
VOLTS
1 0 4
TABLE 5
ANALYSIS OF VARIANCE RESULTS FOR ROLL ERROR SCORES
S o u rc e o f V a r i a t i o n d f MS F
Between S u b j e c t s
34
Tim e-Lags (L ) 2
1 2 S .0 9 9 .2 6 *
Error (b) 32 1 4 . 0 9
W ith in S u b j e c t s 70
A c c e l e r a t i o n (A) 2 1 9 0 .1 0
1 9 . 1 4 *
A X L
4
5$. S7 5 .9 3 *
E rror (w)
64 9 .9 3
T o ta l
10 4
*p = .0 0 1 ; L i n d q u i s t ( S i ) .
105
v a r i a n c e o f r o l l e r r o r m ea su rem en ts. S t a t i s t i c a l l y
s i g n i f i c a n t F - r a t i o s w ere found f o r t i m e - l a g s , a c c e l e r a t i o n
and t h e i r i n t e r a c t i o n a t t h e . 0 0 1 , .02 5 and .0 5 s i g n i f i
ca n c e l e v e l s , r e s p e c t i v e l y .
Two grou p s o f t - r a t i o s w ere c a l c u l a t e d f o r t h e
c o m b in a tio n o f a c c e l e r a t i o n l e v e l s and t i m e - l a g c o n s t a n t s
in t h e r o l l mode. In t h e f i r s t g r o u p , t h e t - r a t i o s betw een
means f o r a c c e l e r a t i o n l e v e l s , f o r e a ch o f t h e t i m e - l a g
c o n s t a n t s , showed 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 c r e a s e s f o r
3 . 0 g and 6 . 0 g a t t h e .01 s i g n i f i c a n c e l e v e l . T h is i s
t h e same r e s u l t a s was shown f o r t h e p i t c h m easurem ents
and, a g a i n , s u p p o r ts t h e h y p o t h e s i s t h a t i n c r e a s e d a c c e l e r
a t i o n s i g n i f i c a n t l y i n c r e a s e s e r r o r s c o r e s .
In th e secon d g rou p , t h e t - r a t i o s b etw een t h e t i m e -
l a g c o n s t a n t s a t e a ch a c c e l e r a t i o n l e v e l i n d i c a t e d t h a t
t h e e r r o r produced by u s e o f th e 0 .1 se co n d l a g a t 3 . 0 g
and 6 . 0 g i s s i g n i f i c a n t l y l a r g e r th a n t h a t prod u ced b y t h e
o t h e r two l a g s . There was 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 b etw een t h e 1 . 0 and 2 . 0 se c o n d l a g in t h i s c a s e .
I t i s i n t e r e s t i n g t o n o t e , h o w ev er, t h a t a " t r u e ”
U - f u n c t io n i s found under s t a t i c c o n d i t i o n s . T h is was
d e m o n stra te d by t h e r e s u l t t h a t t h e 0 .1 seco n d l a g i s
s i g n i f i c a n t l y l a r g e r th a n t h e 1 . 0 l a g , and t h e 2 . 0 seco n d
l a g i s s i g n i f i c a n t l y l a r g e r th a n t h e 0 .1 l a g , b u t t h e 0 .1
and 2 . 0 l a g s a r e n o t s i g n i f i c a n t l y d i f f e r e n t . I n c r e a s i n g
t h e a c c e l e r a t i o n l e v e l , how ever, d i s t o r t s t h i s
r e l a t i o n s h i p .
T a b le 6 p r e s e n t s t h e r e s u l t s o f co m p u tin g t h e
produ ct-m om ent c o r r e l a t i o n c o e f f i c i e n t s f o r r o l l m e a s u r e
m e n ts . I t w as fou n d t h a t a l l b u t one a r e s t a t i s t i c a l l y
s i g n i f i c a n t . T h is i s c o n t r a r y t o what w as fo u n d f o r p i t c h ,
i n t h a t f o r r o l l m easu rem en t, a c c u r a t e p r e d i c t i o n s o f
p e r fo r m a n c e u n d e r a c c e l e r a t i o n can be made from m e a s u r e
m en ts o b t a i n e d from s t a t i c c o n d i t i o n s .
G. SOME INTERPRETATIONS OF THE RESULTS
From t h e a n a l y s i s o f t h e r e s u l t s , i t a p p e a r s t h a t
a l l t h r e e e x p e r im e n t a l h y p o t h e s e s w ere d e m o n s tr a te d i n
t h i s s t u d y . H ow ever, s e v e r a l i n t e r e s t i n g r e l a t i o n s h i p s
o c c u r e d w h ich b e a r f u r t h e r d i s c u s s i o n .
The r e v e r s a l s i n t h e l e a r n i n g c u r v e s f o r t h e 2 . 0
se c o n d s t i m e - l a g c o n s t a n t , i n b o th p i t c h and r o l l m odes,
w ere a t t r i b u t e d t o an i n f o r m a t i o n - l e a r n i n g s i t u a t i o n in
l i g h t o f w e l l d e f i n e d c l a s s i c a l n o t i o n s . In so f a r a s t h e
d a t a a r e c o n s i s t e n t , o n e m ig h t c o n c lu d e t h a t t h e in f o r m a
t i o n t h e o r y app roach i s one s o l u t i o n f o r s k i l l e d m otor
t h e o r y c o n s t r u c t i o n . I f t h i s w ere t h e c a s e , how d o e s on e
o b t a i n a U - f u n c t i o n ? I n f o r m a t io n t h e o r y d o e s e x p l a i n t h e
" r ig h t hand" s i d e o f t h e U, b u t what a b o u t t h e " l e f t hand"
s i d e ?
In l o o k i n g a t t h i s s t u d y from an i n f o r m a t i o n a l
p o i n t o f v i e w , t h e s u b j e c t i s r e c e i v i n g c o n s i d e r a b l y more
1 0 7
TABLE 6
PRO DUG T-MOMENT CORRELATION COEFFICIENTS FOR ROLL
MEASUREMENTS OBTAINED FOR THE VARIOUS
COMBINATIONS OF EXPERIMENTAL
CONDITIONS AND TIME-LAG
CONSTANTS
Time-Lag
C o n sta n ts
A c c e l e r a t i o n C om parisons
S t a t i c - 3 . 0 g 3 . 0 g - 6 . 0 g S t a t i c - 6 . 0 g
0 .1 . 642*
.9 7 1 * *
. 484
1 . 0 .66 3 ** . 981 **
.9 1 1 * *
2 . 0
. 907**
. 899 **
. 736**
* < . 0 2 , * * < . 0 1 , from Edwards ( 3 8 ) .
1 0 3
fe e d b a c k i n f o r m a t i o n p e r u n i t tim e w i t h t h e 0 .1 se c o n d
t i m e - l a g c o n s t a n t th a n t h a t w i t h t h e 1 . 0 se co n d t i m e - l a g .
Why, t h e n , s h o u ld more e r r o r be a c c r u e d w it h t h e g r e a t e r
in f o r m a t io n fe e d b a c k ?
I t may be r e c a l l e d t h a t Hunt (6 9 ) found t h a t
p erfo rm an ce im proved i n a n e g a t i v e l y a c c e l e r a t e d f a s h i o n
a s t h e amount o f in f o r m a tio n i n c r e a s e d . I t may be i n f e r r e d
from a n e g a t i v e l y a c c e l e r a t e d c u rv e t h a t p e r fo r m a n c e w i l l
r e a c h a l i m i t o r maximum v a l u e , ev en th o u g h i t may l a t e r
d e c l i n e r a t h e r th a n become a s y m p t o t ic .
McCormick ( 3 4 ) , in a m achine a n a lo g y , p o i n t s o u t
t h a t any g iv e n com m u nication ch a n n el h a s a l i m i t o r
c a p a c i t y . In i n v e s t i g a t i o n s o f t h e human a s a communica
t i o n s y s te m , Mackworth and Mackworth (3 3 ) c d n c lu d e t h a t
each s e n s e m o d a lit y h a s a c a p a c i t y i n terras o f t h e
in f o r m a t io n lo a d and sp ee d w hich i t can h a n d le . L oad ,
a c c o r d in g t o t h e s e a u t h o r s , a s a p p l i e d t o t h e in p u t
th r o u g h t h e s e n s e s , r e f e r s t o t h e v a r i e t y o f s t i m u l i t o
w hich d i f f e r e n t i a l r e s p o n s e s must be made. Thus, i f t h e
o p e r a t o r must d i s c r i m i n a t e among s e v e r a l d i f f e r e n t c l a s s e s
o f v i s u a l s t i m u l i , th e l o a d on t h e v i s u a l sy ste m i s g r e a t e r
th a n i f t h e d i s c r i m i n a t i o n i s o f o n l y o n e t y p e . S p ee d , on
t h e o t h e r hand, r e l a t e s t o t h e number o f s t i m u l i p e r u n i t
t i m e . I t may be n o te d t h a t t h e p i t c h and r o l l modes may
be c o n s i d e r e d t h e l o a d , and t h e l a g s t h e s p e e d , i n t h e
p r e s e n t s t u d y .
109
McCormick (3 4 ) i n d i c a t e s , b a s e d on t h e r e s u l t s o f
a number o f e x p e r im e n t a l e v a l u a t i o n s , t h a t sp e e d and l o a d
a r e somewhat in d e p e n d e n t t a s k v a r i a b l e s . W h ile p erfo rm a n ce
f o r any lo a d i s a f f e c t e d by s p e e d , t h e r e a r e d i s t i n c t
d i f f e r e n c e s i n p erform an ce f o r v a r y in g l o a d s . A g e n e r a l
s ta te m e n t i s t h a t t h e g r e a t e r t h e number o f s o u r c e s o f
in f o r m a tio n t o w hich r e s p o n s e s a re made, t h e p o o r e r t h e
t o t a l p erfo rm a n ce ( 3 4 ) .
F i t t s (4 6 ) and H ick ( 6 3 ) have r e p o r t e d c l a s s i c a l
work i n t h i s a r e a . Based on many e x p e r im e n ts , t h e y a g r e e
t h a t t h e p erfo rm a n ce c a p a c i t y o f t h e human m otor s y s te m ,
t o g e t h e r w it h i t s a s s o c i a t e d v i s u a l and p r o p r i o c e p t i v e
fe e d b a c k m echan ism s, when m easured in in f o r m a t io n u n i t s ,
i s c o n s t a n t . F i t t s ( 4 6 ) r e p o r t s t h e optimum l e v e l t o be
b etw een 1 0 and 12 b i t s per s e c o n d , w h e r e a s, H ick ( 6 3 )
r e p o r t s i t t o be in t h e o r d e r o f $ b i t s p e r s e c o n d . T hese
n u m e r ic a l d i f f e r e n c e s a r e n o t l i m i t i n g t o t h e g e n e r a l
v a l i d i t y o f in f o r m a t io n t h e o r y , b u t r a t h e r , A l l u s i , e t .
a l . . ( l ) r e p o r t s t h a t i t i s t h e c o m b in a tio n s o f s t i m u l i
and r e s p o n s e s (S-R i n t e r a c t i o n s ) t h a t d e te r m in e s t h e
p erfo rm a n ce l e v e l a t t a i n e d . The d i f f e r e n c e s n o t e d above
a r e no doubt due t o t h e c o n d i t i o n s o f t h e v a r io u s
e x p e r im e n t s .
I t i s now e v i d e n t t h a t t h e r e i s a l i m i t i n g
c o n d i t i o n w h ich can be a c c o u n te d f o r by in f o r m a t io n t h e o r y .
E a r l i e r i n t h i s d i s s e r t a t i o n a n o th e r l i m i t a t i o n was n o t e d ,
110
namely, th e p s y c h o lo g ic a l r e f r a c t o r y p e r io d . I t was
s t a te d t h a t th e g e n e r a lly accep ted maximum r a te o f resp on se
o f th e o p e r a to r i n a tr a c k in g t a s k i s two or th r e e tim e s
per second r e g a r d le s s o f how high th e demand r a te may be.
In agreement w ith th e sta te m en ts o f E ly, Bowen, and
Orlansky (42) on t h i s m a tter, namely, t h a t man i s in a
’’p s y c h o lo g ic a l r e fr a c to r y p e r io d ” w h ile d e c is io n s are
being p r o c e ss e d , F i t t s ( 4 6 ) p o in ts out t h a t ’’th e fix e d
in fo rm a tio n -h a n d lin g c a p a c ity o f th e motor system probably
r e f l e c t s a f i x e d c a p a c ity o f c e n tr a l mechanisms fo r
m onitorin g th e r e s u l t s o f th e ongoing motor a c t i v i t y
w h ile at th e same tim e m a in ta in in g th e n e c e ss a r y degree o f
o r g a n iz a tio n w ith r e s p e c t to th e magnitude and tim in g o f
s u c c e s s iv e m ovements.” These f i n d in g s , o f c o u r se ,
s u b s t a n t ia t e H o lla n d ’ s (66) model d is c u s s e d in Chapter I I I .
I t i s apparent t h a t th e above s i t u a t i o n e x is t e d in
th e p resen t stu dy and accounted fo r the h a l f and f u l l
U -fu n c tio n s o b ta in ed fo r p i t c h and r o l l , r e s p e c t i v e l y .
I t may be r e c a l l e d t h a t Rockway (9 6 ) r ep o rted th a t th e
a d d itio n o f a l a g would se rv e to reduce th e output
am plitude i f the g a in were too high and caused co n tin u a l
o v e r sh o o tin g . A high g a in , t h e r e f o r e , would probably
i n t e r f e r e w ith th e " p sy c h o lo g ic a l r e f r a c t o r y p e r io d ."
Comments by th e o p e r a tin g crew, s e v e r a l exp erim en tal t e s t
p i l o t s and o th e r v i s i t o r s , who had the o p p o rtu n ity to
tr a c k w ith a l l th r e e t im e - la g c o n s t a n t s , unanim ously
I l l
rep o rted th a t th e a d d itio n o f a l a g made th e t a s k " e a s i e r ”
and a ls o req u ired l e s s c o n tr o l m o tio n s. V isu a l in s p e c t io n
o f th e data su p p orts t h i s l a t t e r sta te m en t. One o f th e
t e s t p i l o t s s a id t h a t " tra ck in g w ith th e 0 .1 second l a g
was l i k e f l y i n g an F-100 in a r a in sto r m .” T h is , he
r e p o r te d , was n ot tr u e w ith th e in c r e a se d t i m e - l a g s .
There are s e v e r a l im p lic a t io n s t h a t should be put
to t e s t from th e above d is c u s s io n : (a) p it c h and r o l l
t a s k s should be conducted s e p a r a t e ly , f o llo w in g th e " loa d ”
p r i n c i p l e , to determ ine optimum p o in t s s i n g l y , (b) p it c h
and r o l l measures should be o b ta in ed to g e th e r w ith a l l o f
th e com binations o f t i m e - l a g s , fo r example, th e 0.1 second
l a g in p itc h should be combined w ith the 1 . 0 and 2 .0
seconds la g in r o l l , e t c . , to determ ine t h e i r i n t e r r e l a
t i o n s h i p s , (c) e le ctro m y o g ra p h ic, and tim e and motion
s t u d ie s should be conducted to determ ine energy and m uscle
p o t e n t i a l changes w ith in c re a se d e x p o n e n tia l l a g s , (d) a
sy stem a tic e v a lu a tio n o f th e stim u lu s gain p r o p e r tie s
should be made t o determ ine th e i n f l e c t i o n p o in t from a
l i n e a r ( c o n s is t e n t d egrad ation o f perform ance) error
fu n c tio n to a U -fu n c tio n .
Another i n t e r e s t i n g occu rence i s th e c o n s i s t e n t
i n t e r a c t io n o f th e a c c e le r a t io n l e v e l s w ith th e 0 .1 second
l a g . This would appear t o be due to th e in c r e a se d
muscular req u irem en ts, as was n oted by v i s u a l in s p e c t io n
o f th e data and s u b j e c t iv e r e p o r t , fo r th e 0 .1 second l a g
112
as compared w ith th e o th e r l a g s .
I t may be r e c a ll e d from Chapter I I I t h a t H olland
(66) su g g ested th e neuromuscular la g - tim e be kept to a
minimum s in c e i t i s one o f th e prime c a u se s o f f a l l i n g
sh ort o f th e ’’o n e -to -o n e c o rr esp o n d en ce .” T his was
supported by tr a c k in g r e s u l t s o f Faber (44) and W ilk ie
(1 1 7 ). A n a ly sis o f movement tim e s under v a r io u s t y p e s and
l e v e l s o f a c c e le r a t i o n , Bryan ( 1 6 ) , Brown and Burke ( 1 3 ),
C a n fie ld ( 2 ) , and Kaehler and Meehan (74) a t t r i b u t e
in c re a se d motion tim es to in c re a se d muscular lo a d as a
fu n c tio n o f th e magnitude and d i r e c t io n o f th e a c c e l e r a t i v e
f o r c e .
I t becomes e v id e n t th a t th e rep orted i n t e r a c t i o n
i s due to in c re a se d neuromuscular resp on se tim es caused
by th e requirem ent fo r more m uscle a c t i v i t y and, hence, i s
more prone to be a f f e c t e d by in c r e a se d a c c e le r a t i o n .
A f i n a l o b s e r v a tio n i s th a t o f th e d i f f e r e n t i a l
r e s u l t s o f th e c o r r e l a t io n c o e f f i c i e n t s fo r th e p it c h and
r o l l mode. I t may be r e c a ll e d th a t s t a t i s t i c a l l y s i g n i f i
cant c o e f f i c i e n t s in p it c h were found o n ly fo r th e 3 .0 g -
6 .0 g comparison. In th e r o l l mode, however, a l l but one
were 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 may a lso be r e c a l l e d
th a t Bryan (16) and Kaehler and Meehan (74) rep o rted a
d i f f e r e n t i a l e f f e c t o f the d ir e c t io n o f th e a c c e l e r a t i v e
fo r c e on th e tim e to make c e r ta in movements. In e s s e n c e ,
i t was found t h a t m otions p erp en d icu la r to th e d i r e c t io n
113
o f th e fo r c e was l e s s a f f e c t e d than th o s e in th e same
d i r e c t io n . T his f a c t i s im portant in th a t th e p it c h
m otions are in th e d i r e c t io n o f th e a c c e l e r a t i v e fo r c e
under f r o n t- t o - b a c k a c c e le r a t i o n , w hereas, th e r o l l m otions
are p erp en d icu la r to i t .
The p it c h c o r r e la t io n c o e f f i c i e n t s in d ic a t e t h a t
some amount o f th e a c c e le r a t i v e c o n d itio n i s n e c e ssa r y to
make r e l i a b l e p r e d i c t i o n s . This might be a r e l a t i v e l y
important c o n s id e r a t io n f o r th e u s e r s o f s t a t i c sim u la to r s
s in c e t h e i r p r e se n t goal i s to p r e d ic t human c o n tr o l
performance from s t a t i c c o n d it io n s to space m issio n s where
h o s t i l e environm ents are to be encou n tered . S in ce th e
r o l l c o e f f i c i e n t s were not so a f f e c t e d , th e d i f f e r e n t i a l
p r in c ip le i s in d ic a t e d as th e probable rea so n .
SECTION FIVE
SUM M ARY AND CONCLUSIONS
CHAPTER. V I I I
SUM M ARY AM D CONCLUSIONS
A. SUM M ARY
A study was conducted to determ ine th e e f f e c t s and
in t e r a c t io n s o f in c r e a s e d fr o n t - t o - b a c k tr a n s v e r s e
a c c e le r a t i o n s and v a r io u s e x p o n e n tia l t im e - la g c o n s ta n ts
on human c o n tr o l perform ance.
T h ir t y - f iv e male undergraduate stu d e n ts serv ed as
s u b j e c t s fo r t h i s i n v e s t i g a t i o n . A "mixed" s t a t i s t i c a l
d esig n was used so th a t each s u b je c t would tra c k w ith o n ly
one v a lu e o f ex p o n e n tia l t im e - la g in th e c o n tr o l system ,
but would be exposed to a l l o f th e a c c e le r a t i o n c o n d it io n s .
For th e purposes o f t h i s stu d y , e x p o n e n tia l t im e - la g
c o n sta n ts o f 0 .1 , 1 . 0 and 2 .0 seconds were chosen s i n c e
th e y bracket th e aerodynamic resp on se c h a r a c t e r i s t i c s o f
high performance a i r c r a f t . Measurements were ob ta in ed
under a c c e le r a t io n c o n d itio n s o f s t a t i c or zero tr a n s v e r s e
g, 3 .0 g and 6 .0 g. The maximum g valu e i s th a t p r e d ic te d
f o r manned sp ace v e h i c l e b o o st c o n d it io n s .
The tr a c k in g t a s k c o n s is t e d o f a h o r iz o n t a l l i n e
" ' s»-
on th e fa c e o f a cathode ra y o s c i l l o s c o p e which moved
v e r t i c a l l y to i n d ic a t e p i t c h and r o ta te d about i t s c e n te r
115
t o i n d i c a t e r o l l . T h is was a two d im e n sio n a l compensatory-
problem r e q u i r i n g t h e s u b j e c t t o h o ld t h e d i s p l a y a t zero
d e g r e e s i n p i t c h and r o l l a n g le . Any d e v i a t i o n from t h e
h o r i z o n t a l - c e n t e r p o s i t i o n would i n d i c a t e a t r a c k i n g e r r o r .
The s t i m u l u s , in each mode, was a com plex wave form
r e p r e s e n t a t i v e o f an a i r c r a f t f l y i n g i n t u r b u le n t c o n d i
t i o n s , w ith a d u r a tio n o f 60 s e c o n d s . The c o n t r o l s t i c k
was a r ig h t- h a n d s i d e c o n t r o l l e r d e s ig n e d so t h a t th e
p i l o t ’ s w r i s t i s th e p i v o t p o i n t f o r b o th p i t c h and r o l l .
E x p o n en tia l t i m e - l a g c o n s t a n t s were produced by u s e o f an
a n a log com puter. The measurement o f t r a c k in g p erform ance
was t h e i n t e g r a t i o n o f t h e a b s o lu t e e r r o r in both c o n t r o l
modes. The s u b j e c t s w ere g iv e n tw e n ty s t a t i c p r a c t i c e
t r i a l s and e ig h t c e n t r i f u g e t r i a l s . The d a ta u sed f o r th e
s t a t i s t i c a l e v a lu a t io n were th e l a s t s t a t i c , 3 . 0 g and
6 . 0 g measurement f o r each s u b j e c t . A c c e l e r a t io n s were
produced on th e U n i v e r s i t y o f Southern C a l i f o r n i a Human
C e n t r if u g e . A n a ly s is o f th e d a ta was a c co m p lish ed by
a n a l y s i s o f v a r ia n c e , t - r a t i o and c o r r e l a t i o n s t a t i s t i c a l
m eth o d s.
A summary o f th e r e s u l t s i s a s f o l l o w s :
1 . Some l e a r n i n g phenomena were en c o u n te re d in
th e c o u r se o f th e e x p erim en t:
a . For both p i t c h and r o l l m easurem ents,
t h e e r r o r s c o r e s were s t a b i l i z e d by t h e
end o f t h e s t a t i c t r i a l s on th e secon d
For p itc h measurements, th ere were
r e l a t i v e l y la r g e d if f e r e n c e s from th e
f i r s t to th e second o f each a c c e le r a
t io n l e v e l on th e f i r s t day. This was
not tru e on the second day.
There were se v er a l r e v e r s a ls fo r r o l l
a c c e le r a tio n data between th e f i r s t and
second days.
For both p itc h and r o l l measurements,
th e 2 .0 seconds tim e -la g constant
produced the lo w e st le a r n in g r a te ,
but subsequently reversed p o s it io n s
in r e l a t i v e order, w ith th e 1 .0 second
t im e - la g .
For p itc h measurements, th e 0.1 second
tim e -la g c o n s i s t e n t l y produced th e
h ig h e s t error sc o res fo r s t a t i c and
a c c e le r a t iv e c o n d itio n s throughout th e
le a r n in g period .
For r o l l measurements, from the end o f
the f i r s t s t a t i c block o f f i v e t r i a l s ,
th e 0 .1 second tim e -la g produced th e .
h ig h e s t error s c o r e s .
There was a s i z a b l e d iff e r e n c e in th e
r a te o f le a r n in g between 1 . 0 and 2 .0
seconds t im e - la g s fo r p itc h measure
ments, in th e e a r ly t r i a l s .
With regard to th e experim ental h yp oth eses,
i t was found t h a t :
a. The a n aly ses fo r p itc h and r o l l revea led
s t a t i s t i c a l l y s i g n i f i c a n t F - r a t io s
for t im e - la g s , a c c e le r a t io n , and t h e i r
in t e r a c t io n .
b. A "half" U -fu n ctio n was found fo r p itc h
measurements by the end o f the complete
p r a c tic e s e r i e s . P rior to t h i s tim e,
a U -fu nction was in d ic a te d , in t h a t ,
th e 1 .0 second tim e -la g produced th e
l e a s t amount o f erro r, as was
p r e d ic te d . L ater in th e p r a c tic e
t r i a l s , however, the 2 .0 seconds l a g
reversed p o s itio n w ith th e 1 . 0 second
l a g . This was a ttr ib u te d to d i f f e r
ences in le a r n in g due to inform ation al
content o f th e stim u lu s-resp o n se
complex.
c . A U -fu nction was found fo r r o l l error
measurements w ith th e optimum la g bein g
1 .0 seconds, as was p r e d ic te d .
Subsequent t - r a t i o s showed th a t th e
optimum 1 . 0 second la g produced
s i g n i f i c a n t l y l e s s error than the
oth er two l a g s .
d. A fam ily o f curves was produced by th e
a c c e le r a tio n data in both modes which
support th e p red icted h y p o th esis and
the P r in c ip le o f G en er a lity .
e . T -r a tio s determined that th e in t e r a c t io n
in both modes was due to the a c c e le r a
t io n e f f e c t s on the 0.1 second la g ,
which again supports the P r in c ip le o f
G en erality in th a t the most d i f f i c u l t
ta sk under s t a t i c c o n d itio n s was
a f fe c t e d most by the increased
a c c e le r a t io n , e t c .
f . Subsequent t - r a t i o s between a c c e le r a t io n
l e v e l s , showed th a t in a l l c a se s fo r
p itc h and r o l l measurements, th e means
obtain ed at 3 .0 g were s i g n i f i c a n t l y
la r g e r than th o se obtained under
s t a t i c c o n d itio n s and means obtain ed
at 6 .0 g were s i g n i f i c a n t l y la r g e r
than th o se obtain ed at 3 .0 g. These
r e s u l t s are in complete agreement
w ith th e p r e d ic tio n s made.
With regard to product-moment c o r r e la t io n
c o e f f i c i e n t s between th e a c c e le r a t io n
l e v e l s :
a. In th e p itc h mode, o n ly the 3»0 g - 6 .0 g
c o r r e la t io n c o e f f i c i e n t s were found
to be s t a t i s t i c a l l y s i g n i f i c a n t .
These r e s u l t s , however, were c o n s is t e n t
fo r a l l th ree t im e - la g s .
b. In the r o l l mode, a l l but one combina
t i o n was found to be s t a t i s t i c a l l y
s i g n i f i c a n t . These s i g n if ic a n c e o f
th e se r e s u l t s were d is c u s s e d .
B. CONCLUSIONS
W ithin th e l i m i t s o f t h i s experim ent, a number o f
con clu sio n s are p resen ted .
1 . In g e n e ra l, th e experim ental hypotheses were
supported by th e r e s u l t s o b ta in ed . The r e s u lt a n t data,
when so p lo t t e d , show a s t r ik in g resem blance to th e th ree
dimensional model o f the hypotheses a t th e general l e v e l .
2. Only th e f i r s t h a l f o f a U -fu n ctio n was found
fo r the p itc h mode. During the e a r ly p r a c tic e t r i a l s ,
however, th ere was a d e f i n i t e U -fu n ction w ith th e 1 . 0
second tim e -la g being op tim al. Subsequently th e r e was a
r e v e r sa l making the 2 .0 seconds t im e - la g op tim al. This
fin d in g does n o t, however, r e j e c t th e U -fu n c tio n . I t may
be noted th a t the error i s decreased as tim e -la g i s
in c re a se d , which i s th e major is s u e o f th e U -fu n c tio n .
121
3. A d e f i n i t e U - fu n c t io n was found in t h e r o l l
mode. Measurements o b ta in e d a t th e s t a t i c l e v e l showed
t h e 1 .0 second t i m e - l a g t o a c c r u e s i g n i f i c a n t l y l e s s
e r r o r than t h e o th e r tw o.
4 . In c r e a se d m agnitud es o f a c c e l e r a t i o n s i g n i f i
c a n t ly in c r e a s e d e r r o r s c o r e s in both c o n t r o l modes.
5. C o n s is t e n t f a m i l i e s o f c u r v es were produced
which support p r e d i c t i o n s from t h e P r i n c i p l e o f G e n e r a li t y .
6 . H e lso n ’ s U -H y p o th esis and P r i n c i p l e o f
G e n e r a lit y were s u b s t a n t i a t e d and proved to be e x tr e m e ly
u s e f u l fo r p r e d i c t i o n .
7 . C o e f f i c i e n t s o f c o r r e l a t i o n betw een a c c e l e r a
t i o n l e v e l m easurem ents in d ic a t e d t h a t , fo r t h e p i t c h mode,
a sm all amount o f a c c e l e r a t i o n was r e q u ir e d to p r e d i c t
perform ance a t h ig h e r l e v e l s . For th e r o l l mode, th e data
were s u f f i c i e n t l y r e l i a b l e t o make p r e d i c t i o n s from s t a t i c
m easurem ents. These r e s u l t s su p p ort t h e " d i f f e r e n t i a l
e f f e c t " f i n d i n g s o f some r e s e a r c h e r s and are o f p r a c t i c a l
im port in view o f th e g reat amount o f " c o n tr o l sy ste m
o p tim iz a tio n " a c t i v i t i e s u s in g s t a t i c s im u la t o r s .
$ . The use o f c o n c e p ts from in fo r m a tio n th e o r y
appear t o e x p la in c e r t a i n o f th e l e a r n i n g phenomena
o c c u r r in g in th e experim en t and, c r i t i c a l l y , o f f e r e d an
e x p la n a tio n on why a U - fu n c t io n may be a c h ie v e d under
c e r t a i n s t im u lu s - r e s p o n s e c o n d i t i o n s .
122
G. RECOMMENDATIONS FOR FUTURE RESEARCH
\
The a p p l i c a t i o n o f in fo r m a tio n t h e o r y t o problem s
o f human b e h a v io r i s s t i l l in th e f i r s t s t a g e s o f d e v e lo p
m ent. As was found in t h i s stu d y , in fo r m a tio n c o n c e p ts
do p ro v id e a means f o r e x p la in in g unusual phenomena, such
a s a U - f u n c t io n . In order to f u r t h e r d ev elo p t h e s e i d e a s ,
t h e f o llo w in g are s t u d i e s which would p ro v id e e x tr e m e ly
u s e f u l c o r r o b o r a tiv e d a ta .
1 . P it c h and r o l l t a s k s should be conducted
s e p a r a t e l y in ord er to in d e p e n d e n tly d eterm ine optimum
p o i n t s .
2. P it c h and r o l l m easures sh ould be o b ta in e d
w ith a l l com b in ation s o f t i m e - l a g s in each mode.
3. E lectrom yograph ic and tim e and m otion s t u d i e s
sh ould be conducted to determ ine en ergy and m uscle
p o t e n t i a l changes w ith in c r e a s e d e x p o n e n tia l l a g s .
4. A s y s te m a t ic e v a lu a t io n o f th e stim u lu s
p r o p e r t ie s should be made to determ ine th e i n f l e c t i o n
p o in t from a l i n e a r ( c o n s i s t e n t d e g r a d a tio n o f perform ance)
er r o r f u n c t io n t o a U - f u n c t io n .
APPENDIX A
MEANS A lM D STANDARD DEVIATIONS OF PITCH AND
ROLL MEASUREMENTS OBTAINED ON THE
FIRST AND SECOND DAYS
M EANS A I M 'D STANDARD DEVIATIONS FOR RO LL M EASUREM ENTS
OBTAINED O N THE FIRST D A Y
Time-Lag C o n sta n ts
T r ia l
0 .1 S ec. 1 . 0 S ec. 2 .0 S e c .
Mean S. D. Mean S. D. Mean S. D.
1 29.2 3 1 4 .6 5
25 .6 6 1 1 .2 0 3 1 .3 3 1 9 .0 0
2 1 3 .7 6 3 .3 5 1 7 .4 3 1 0 .0 3 2 2 .6 3
1 2 .3 1
3
1 5 .2 6 6 .3 6
1 4 .6 3 7 .2 5
2 2 .0 0
1 3 .3 5
4
1 3 .5 2 5.71 1 1 .0 7 6 .3 7 1 4 .3 4
1 0 .3 0
5 1 1 .3 9 6 .3 3
9 .3 0
4 .1 5 1 4 .6 5
1 0 .3 0
6 1 0 .0 6
4 • 04 5.73 3 .0 9 3 .7 4
6 .4 2
7 9 .4 3 5 .0 9 6 .0 3 3 .9 6
3 .5 4
6 .5 0
3
3 .7 3
5 .0 3
7 .0 4
3 .7 0
9 .2 7
5 .1 0
9 1 0 .4 1
4 .5 6 6 .7 5
3.61 9 .3 0
6 .5 3
10 3 .7 2
4 .3 9
7 .3 0 3 .3 3
3 .9 3 7 .4 5
3 .0 g
1 9 .0 4 1 0 .4 3
9 .4 0 3 .3 2 1 1 .9 7 1 4 .4 5
6 . 0 g
1 3 .4 1
3 .2 0 1 1 .3 6 1 4 .1 0 1 4 .5 0
1 3 .1 1
3 .0 g 1 2 .7 0 5 .3 0
3 .3 9
1 2 .9 0 7 .2 3 4 .3 3
6 .0 g 1 4 .6 3
6 .3 7
9 .7 6 1 1 .6 0 1 1 .2 3
5.62
124
125
M EANS A N D STANDARD DEVIATIONS FO R R O L L M EASUREM ENTS
OBTAINED O N TH E SECOND D A Y
Time-Lag C o n sta n ts
T r ia l 0 ,1 S ec. 1 . 0 S e c . 2 . 0 S e c .
Mean S. D. Mean S. D. Mean S. D.
1 £ .0 6
6 .3 1 4 .5 1
2.62
5 .7 7 2 .9 S
2 £ .3 2
£ .3 3 4 .3 2 2 .6 6
6 .0 7 6 .9 5
3
6 .2 0 3 .9 6
4 .6 7 2 .4 8 5.S3 4.S 3
4
7 .2 6 4 .0 £
4 .3 7 2 .5 1
6 .1 6 5 .0 6
5
7 . SO 6 .6 0
4 .3 4
2 .4 6 6 .9 0
7 .7 8
6
7 .4 7 5.9 S 3 .4 5 2 .4 4 3 .6 7 2 .1 2
7 5 .£ 9 3 .4 7 3 .4 5 2 .1 4
3 .S 6 7 .1 6
£ 6 . 56
4 .4 6 3 .1 7 1 .6 3 5 .3 0
4 .1 5
9
5 .0 2
2 .3 4 3. £2 2 . l £ 6 .2 1 6 .1 0
10
5 .2 9 2 .5 3
3 .7 6 2 .2 4 5 .2 1 5 .5 8
3 .0 g
£ .9 7
3 .9 6
6 .7 7 6 .3 5
£ .6 8
7 .5 9
6 . 0 g 1 1 .4 6 6 .5 0 9 .1 2 9 .9 0 1 1 .5 7 £ .2 £
3 .0 g
9 .7 5
6 .4 6
4 .4 £ *3 .6 4 5 .4 9 4 . SO
6 .0 g
1 1 .9 5
9 .1 2
7 .8 0 7 .6 0 £ .2 £
6 .1 5
1 2 6
MEANS AND STANDARD DEVIATIONS FOR PITCH MEASUREMENTS
OBTAINED ON THE FIRST DAY
Time-Lag C on stan ts
T r ia l 0 .1 Sec. 1 .0 S e c . 2 .0 S ec.
Mean S. D. Mean S. D. Mean S. D.
1 4 .8 9 3.66
3 .5 4 1 .9 5 4 .3 3
4 .1 0
2 3.68 2.28
1 .7 3 0 .7 1
3.80
2 .7 9
3 4 .2 3 3 .0 4
1 .8 6
0 .7 7 2 .7 9 3 .1 9
4 3 .7 2 2 .5 6 1 .5 2 0 .8 8
2 .5 7 2 .7 5
5 3 .5 3
2 .3 6 1 .9 0 0 .9 8 3 .3 2 4 .3 2
6
3 .2 5
2.61
1 .5 5
0 .8 0
1 .6 9 1 .0 0
7 2 .6 3 2.56 1 .4 7 0 .7 5 1 .4 2
0 .9 3
8
2 .9 5 2 .5 5
1 .6 0
0 .9 9 1 .3 7 1 .0 7
9 2 .7 5 1 .5 2 1 .2 3 0 .5 1 1 .5 4 1 .0 5
10
2 .4 3
1 .1 8 1 .2 6
0 .4 7 1 .4 8 0 .9 2
3 .0 g 2.61 1 .5 2 1 .6 0 1 .5 2 2 .3 4 1 .1 8
6 .0 g
4 .4 5
6 .6 2
2 .1 5
1 .8 8 4.08
3 .1 7
3 .0 g 3.81 5.22 1 .0 2
0 .6 4 1 .9 4
1 .2 1
6 .0 g
4 .4 9 3.43
1 .6 2 1 .1 9 3 .3 6 2 .0 0
127
MEANS AND STANDARD DEVIATIONS FOR PITCH MEASUREMENTS
OBTAINED ON THE SECOND DAY
Time-Lag C o n sta n ts
T r ia l 0 .1 S ec. 1 . 0 S e c . 2 .0 S e c .
Mean S. D. Mean S. D. Mean S. D.
1 1 .9 7 0 .9 7 1 . 1 4
0 .2 0 1 .2 1
0 .7 9
2
1 .9 4 0 .9 4 0 .9 5 0 .3 0 1 .1 4 0 .5 3
3 1 .9 4 0 .9 8
0 .9 5 0 .4 7 1 .0 3
0 . 56
4 2.12 1 .1 8 1 .0 6 0 .5 0 1 .0 7 0 . 51
5 1 .9 7 1.11 1 .1 4
0 .5 3 1 .2 1
0 .7 1
6 1 .8 2
0 .7 4 1 .1 4 0 .5 9 0 .9 9 0 .3 9
7 1 .9 1
0 .7 0
1 .1 4
0 .6 0 0 .9 2 0 .3 0
8
1 .8 7 0.8 0 0 .96 0 .6 7 0 .9 6 0 .2 5
9 1 .9 1 0 .8 7 1 .0 4 0 .5 5 1 .0 4 0 .4 5
10
1 .8 3
1 .1 2 1 .0 6
0 .5 1 0 .9 5 0 .3 3
3 .0 g 2.22 0.82 1 .4 2 0 .8 9 1 .7 7
1 .7 8
6 .0 g
3.&3
4.22
2 .5 3
2.08 1 .8 2
0 .6 9
3 .0 g
2 .4 7 1 .1 4
1 .4 0 1 .0 3 1 .3 2 0 .4 2
6 .0 g
3 .5 5
2.12 2.36
1 .7 5 2 .1 5
0 .8 8
APPENDIX B
ANALOG MECHANIZATION AND PRODUCTION
EXPONENTIAL TIME-LAG CONSTANTS
A. ANALOG MECHANIZATION
F ig u re 1 p r e s e n t s th e e l e c t r o n i c system d e v is e d to
p r e sen t in p u ts and e x p o n e n tia l t i m e - l a g c o n s ta n ts in two
c o n tr o l m odes, p i t c h and r o l l , f o r t h e compensatory
tr a c k in g t a s k . S in ce th e p i t c h and r o l l modes are
i d e n t i c a l in so fa r as an a log m ech a n iza tio n i s con cern ed ,
th e f o llo w in g d i s c u s s i o n i s l i m i t e d to th e p i t c h mode.
The outp ut from c u r v e - f o llo w e r 1 , a complex wave
form t o be p r e sen ted t o t h e s u b j e c t , i s fed in t o a m p lif ie r
2. This a m p lif ie r i s u sed t o unload th e outp u t o f th e
curve fo llo w e r p o te n tio m e te r and i s a ls o used to b ia s th e
o s c i l l o s c o p e p r e s e n t a t io n t o th e zero p o s i t i o n , s i n c e th e
problem inp ut has both p o s i t i v e and n e g a t iv e v a l u e s . The
output o f a m p lif ie r 2 i s fe d to th e f u n c t io n a l gain
p o te n tio m e te r d e sig n a te d a s f t which i s n e c e s s a r y to
m aintain th e tr a c k in g imag;e in th e bounds o f t h e o s c i l l o
scope f a c e . The outp ut from th e c o n tr o l s t i c k i s a
d isp lacem en t o f a l i n e a r p o te n tio m e te r which i s fe d to
a m p lif ie r 1 in order to b ia s th e c o n t r o l s t i c k to z e r o .
The s ig n a l th e n goes to A, which i s th e a n a lo g m echaniza
t i o n o f a sim p le f i r s t - o r d e r e x p o n e n tia l t i m e - la g
f u n c t io n . The output from A and p o te n tio m e te r are mixed
a t a m p lif ie r 7. The r e s u l t i n g s ig n a l i s th e n th e a lg e b r a ic
129
BIAS
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STICK
PITCH
BIAS
I _ _
TO R E C O R D E R S
PITCH
ROLL
ELECT
RONICS
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► TO OSCILLOSCOPE
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F IG . I — SCHEMATIC OF ANALOG MECHANIZATION.
1 3 0
sum o f th e o u t p u t s from c u r v e - f o l lo w e r 1 and t h e
e x p o n e n t i a l l y t im e - la g g e d c o n t r o l s t i c k . I f t h e o u tp u t
o f a m p l i f i e r 7 i s z e r o , t h i s would i n d i c a t e t h a t t h e r e was
no t r a c k in g e r r o r .
The o u tp u t o f a m p l i f i e r 7 i s fe d t o C and E. In
t h e f i r s t c a se C , which i s t h e e r r o r i n t e g r a t o r , t a k e s t h e
a b s o lu t e v a lu e o f t h i s s i g n a l and i n t e g r a t e s t h i s v a lu e as
a f u n c t i o n o f tim e f o r t h e d u r a tio n o f th e t r a c k i n g
problem . This th en p r o v id e s t h e t o t a l summation o f t h e
a b s o lu t e v a lu e o f th e t r a c k in g e r r o r . The o u tp u t from
G i s r ec o rd ed on t h e Dynagraph m u lt i- c h a n n e l r e c o r d e r .
In th e second c a s e , E, t h e p i t c h - r o l l e l e c t r o n i c s ,
t a k e s t h e s i g n a l from a m p l i f ie r 7 and makes i t c o m p a tib le
t o th e o s c i l l o s c o p e . A m p lif ie r s 9 and 10 are u sed t o
e x c i t e t h e ou tp u t p o t e n t io m e te r o f t h e c u r v e - f o l l o w e r s and
th e c o n t r o l s t i c k , r e s p e c t i v e l y . I n t e g r a t o r 11 i s u t i l i z e d
in d r i v i n g th e c u r v e - f o l lo w e r s o v e r t h e com plex wave form .
B. PRODUCTION OF THE EXPONENTIAL
TIME-LAG CONSTANTS
F ig u re 2 i s t h e a n a lo g m e c h a n iz a tio n o f a f i r s t -
o rd e r e x p o n e n tia l t i m e - l a g .
O V0UT
F i g u r e 2
1 3 2
U sin g servom echanism th e o r y and sim p le L a p la c e
t r a n s f o r m a t io n s , F ig u r e 2 may be shown a s F ig u r e 3 :
V|NO -O V0UT
F ig u r e 3
The c l o s e d lo o p t r a n s f e r f u n c t io n o f VOUT t o V IN
may be e x p r e ss e d in t h e form:
V qut [- H ] [
—------- = — ------------ ; -| r = — (E q u a tion 1)
IN 00+ (— ) L- HsJ S + o <
The s o l u t i o n o f e q u a tio n (1 ) i s o b ta in e d by
a p p ly in g L a p la c e t h e o r y which y i e l d s :
d C [ S h- c< ] = — ^ (E q u a tion 2)
where < A th e system t i m e - l a g c o n s ta n t i s eq u al t o % . To
a s s e r t a i n th e tim e r e s p o n s e o f th e system d e s c r ib e d by
e q u a tio n ( l ) , w ith a s t e p in p u t f o r V)N , t h e f o l l o w i n g
a p p l i e s :
- A
s( s
= (l — ^ * ) (E q u ation 3 )
133
E q uation (3) can be p l o t t e d i n g e n e r a l term s as a
f u n c t io n o f tim e as shown in F ig u r e 3 in th e body o f t h e
d i s s e r t a t i o n . I t sh ould be n o te d t h a t th e num erator g a in
o f alw ays m a in ta in s a s t e a d y s t a t e v a lu e o f u n i t y
r e g a r d l e s s o f t h e m agnitude o f t h e t i m e - l a g d e s i r e d . The
n e g a t i v e s i g n o f < X in t h e num erators o f t h e e q u a tio n s
stem s from t h e f a c t t h a t a n a lo g a m p l i f i e r s or i n t e g r a t o r s
a r e s ig n c h a n g e r s. These e q u a t io n s a r e v a l i d f o r e i t h e r
p o s i t i v e or n e g a t i v e v a lu e s o f V|N .
APPENDIX. C
DERIVATION OF EQUATION FOR CALCULATING
RPM REQUIREMENTS FOR PRODUCING VARIOUS
ACCELERaTION LEVELS ON THE U. S. C.
HUMAN CENTRIFUGE
135
The f o l l o w i n g i s a d e s c r i p t i o n o f t h e e q u a tio n s
in v o lv e d in th e c a l c u l a t i o n o f v e l o c i t y r eq u ire m en ts to
produce d e sig n a c c e l e r a t i o n l e v e l s on th e human c e n t r i f u g e
( 100).
The b a s i c e q u a tio n s a r e:
ck = to z T (E qu ation 1)
where < k i s th e r a d i a l a c c e l e r a t i o n , ^ i s th e an gu lar
v e l o c i t y and 1* i s t h e r a d iu s , and:
to = Z irf (E qu ation 2)
where -f i s e x p r e ss e d in r e v o l u t i o n s per second (RPS).
To c o n v e rt f to r e v o l u t i o n s per m inute (RPM):
-P = R.PS =
RPM
GO
(E quation 3)
To c o n v e rt ck in to a g r a v i t a t i o n a l u n i t system :
— < k
° 3 2 .2
By s u b s t i t u t i o n :
< X = 4 - tr‘ l-p zr
To s o l v e f o r (RPS)^:
r*2 = ^
4*Tr2 r
To c o n v e rt t o g r a v i a t i o n a l u n i t s :
f z = 'b z -1(^
4irl r
To s o l v e f o r RPS and s im p l i f y :
To s o lv e f o r RPM:
RPM = 6 0 (V^r J ( V "
L et -A eq u al a c o n s ta n t:
VIS
(E qu ation 1+)
(E quation 5)
(E quation 6 )
(E qu ation 7)
(E quation 8)
(E qu ation 9)
(E qu ation 10)
136
By s u b s t i t u t i o n , th e r e s u l t i s a s i m p l i f i e d
g e n e r a l e q u a tio n by which RPM may be determ ined d i r e c t l y
from t h e g l e v e l d e s ir e d w ith a known :
RPM = *\p$ (E quation 11)
To s o lv e f o r w ith th e r a d iu s o f 1 5 .5 f e e t used
in t h i s stu d y (from Equation 1 0 ) :
= 1 3 . 6 0 (E quation 12)
The RPM r eq u irem en ts were determ ined to be: fo r
3 .0 g , 23.91 or 2 4 .0 c o r r e c t e d ; and f o r 6 . 0 g , 33.$1 or
3 4 .0 c o r r e c t e d .
APPENDIX D
SOME COMMENTS ON THE STATISTICAL ANALYSIS
136
There are th r ee problems in th e u se o f th e
p a r t ic u la r s t a t i s t i c a l t e s t s w ith the exp erim en ta l data
o b tain ed in t h i s stu d y. The f i r s t and t h ir d have to do
w ith h e t e r o g e n ie t y o f v a r ia n c e and, th e second, w ith th e
use o f a sim ple t - t e s t as a "post mortem" e v a lu a tio n a f t e r
an F - t e s t .
H e te r o g e n e ity o f v a r ia n c e in
a s t a t i s t i c a l e v a lu a tio n by
th e a n a ly s is o f v a r ia n ce
tech n iq u e
I n s p e c t io n o f th e exp erim en tal r e s u l t s in Appendix
C r e v e a ls th a t not o n ly are th e means in c r e a s e d by
experim ental tr e a tm e n ts, but th e standard d e v ia t io n s as
w e l l . Two a r t i c l e s by Box (&, 9) t r e a t t h i s problem
d i r e c t l y . In e v a lu a tio n s o f one-way and two-way
c l a s s i f i c a t i o n s he r e p o r t s , in e s s e n c e , th a t th e r e i s
l i t t l e e f f e c t on th e a n a l y s is w ith moderate d i f f e r e n c e s in
v a r ia n ce . L in d q u ist ( B l ) r e f l e c t i n g on the "Horton Study"
s t a t e s :
In g e n e r a l , when th e h e t e r o g e n e it y in form or
v a r ia n ce i s "marked" but not "extrem e," allow ance
may be made f o r t h i s f a c t by s e t t i n g a high er
"apparent" l e v e l o f s i g n i f i c a n c e f o r th e t e s t s o f
tre a tm en ts e f f e c t s than would o th e r w ise be employed.
In c a s e s o f very marked h e t e r o g e n e it y , fo r example,
i f one w ish es th e r is k o f a type I e r r o r not to
exceed 5%, he might r e q u ir e th e e f f e c t to be
" s ig n if ic a n t " at th e 2 . 5% l e v e l .
Sin ce th e F - r a t i o s o b tain ed in th e p r e se n t
experim ent were g e n e r a lly above th e .025 l e v e l , d i r e c t
in t e r p r e t a t i o n o f th e r e s u l t s i s c o n sid er ed l e g i t i m a t e .
139
F o llo w in g th e F - t e s t w ith t - t e s t s
There appears t o be a g r ea t deal o f i n t e r e s t on
t h i s q u e stio n at th e p r e se n t tim e and a cco r d in g to some
w r i t e r s , i t w i l l reach t h e p r o p o r tio n s o f th e " o n e - t a il
versu s t w o - t a i l " c o n tr o v e r s y . G uilford (5$) p o in ts out
th a t th e f i r s t requirem ent i s t h a t th e F t e s t be s i g n i f i
c an t, which o f course i s met in th e p r e sen t c a se . He
co n tin u es by p o in tin g out t h a t , "we are not j u s t i f i e d in
in t e r p r e t in g t Ts found a f t e r making an F t e s t as i f no
t e s t s had preceded them ." Ryan (99) in a r e c e n t paper
p o in ts out th a t t - t e s t s are not ap p rop ria te as m u ltip le
comparisons fo llo w in g an F t e s t . The i s s u e i s not c le a r ,
however, s in c e he a l s o made some assum ptions which r eq u ire
v a l i d a t i o n .
This is s u e a r i s e s because o f th e in c re a se d number
o f t - r a t i o com binations p o s s i b l e in a complex a n a l y s is o f
v a ria n ce d e sig n . As th e number o f com binations in c r e a s e ,
th e number o f 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 a t any
given s i g n i f i c a n c e l e v e l , due to chance a lo n e , a l s o
i n c r e a s e s .
A search was made o f the Journal o f Experim ental
Psychology in order t o determ ine i f (1) t - t e s t s are used
f o llo w in g an F t e s t and (2) i f so , are th e r e any th a t
f o llo w a L indquist model. Three such a r t i c l e s were found
in th e 195^-1959 i s s u e s : Hodge (6 5 ), N orcross (9 2 ), and
S p ie lb e r g e r (1 0 7 ). I n t e r e s t i n g l y , S p ie lb e r g e r (107)
1 4 0
r e p o r t e d , in a f o o t n o t e , t h a t h i s d a ta " e v id e n c e d v a r y in g
d e g r e e s o f h e t e r o g e n e i t y o f v a r ia n c e " b u t, r e f e r r i n g to
L in d q u is t ( £ l ) , i n t e r p r e t e d t h e F - r a t i o s and t - r a t i o s
d i r e c t l y . A lthough t h e s e methods a r e no doubt somewhat
l i m i t i n g , t h e y appear t o be a c c e p t a b l e , a t l e a s t a t th e
p r e s e n t tim e , t o t h e g e n e r a l a u d ie n c e o f e x p e r im e n ta l
p s y c h o l o g i s t s .
H e t e r o g e n e it y o f v a r ia n c e and
t - t e s t s
F o llo w in g from th e above p rob lem s, t h e q u e s t io n
i s now how to u se t - t e s t s when t h e r e i s some d eg ree o f
h om ogeneity o f v a r ia n c e . Edwards (3$) s t a t e s t h a t th e
t w o - t a i l e d t - t e s t w i l l be r e l a t i v e l y l i t t l e i n f l u e n c e d
by d e p a r tu r e s from n o r m a lity . H is s u g g e s t io n s f o l l o w
t h a t o f L in d q u is t a b ove. S in c e a lm ost a l l o f t h e s t a t i s
t i c a l l y s i g n i f i c a n t t - r a t i o s in t h i s stu d y were found to
be a t th e .01 s i g n i f i c a n c e l e v e l , i t i s f e l t t h a t th e
r e s u l t s may be i n t e r p r e t e d d i r e c t l y .
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Creator Kaehler, Richard Charles (author)

Core Title The Effects Of Transverse Accelerations And Exponential Time-Lag Constants On Compensatory Tracking Performance

Degree Doctor of Philosophy

Degree Program Psychology

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

Tag OAI-PMH Harvest,psychology, experimental

Language English

Contributor Digitized by ProQuest (provenance)

Advisor Warren, Neil D. (committee chair), Grings, William W. (committee member), Meehan, John P. (committee member), Ruch, Floyd L. (committee member)

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