Scholarship at UWindsor
Scholarship at UWindsor
Electronic Theses and Dissertations Theses, Dissertations, and Major Papers
1-1-1983
Effect of information load, angles of discrete hand motion with
Effect of information load, angles of discrete hand motion with
multiple levels of index of difficulty in a combined manual and
multiple levels of index of difficulty in a combined manual and
decision task.
decision task.
Thomas Kanjirath Joseph University of Windsor
Follow this and additional works at: https://scholar.uwindsor.ca/etd
Recommended Citation Recommended Citation
Joseph, Thomas Kanjirath, "Effect of information load, angles of discrete hand motion with multiple levels of index of difficulty in a combined manual and decision task." (1983). Electronic Theses and
Dissertations. 6778.
https://scholar.uwindsor.ca/etd/6778
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T w o e x p e r i m e n t a l s t u d i e s w e r e c o n d u c t e d f o r a c o m b i n e d
m a n u a l a n d d e c i s i o n t a s k ( C M D T ) . F o r S t u d y I, 8 d i r e c t i o n s of
m o v e e q u a l l y s p a c e d b e t w e e n 2 0 ° - 1 6 0 ° , w i t h a l l c o m b i n a t i o n s of
3 f i x e d l e v e l s of i n d e x o f d i f f i c u l t y (3, 4 a n d 5 I b i t s ) a n d
t h r e e l e v e l s o f i n f o r m a t i o n l o a d (3, 4 a n d 4 . 5 8 B i t s ) w e r e
u s e d . 7 c o n f i g u r a t i o n s ( C O N F ) w e r e u s e d to i n c o r p o r a t e t h e s e
l e v e l s w i t h 5 r i g h t - h a n d e d m a l e s u b j e c t s . E a c h C O N F w a s a l s o
i d e n t i f i e d b y i t s l e v e l of i n f o r m a t i o n l o a d i n v o l v e d . D a t a w a s
a n a l y s e d b y e a c h l e v e l of i n d e x of d i f f i c u l t y ( I D ) a n d
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I D = 3 I b i t s a n d I D = 4 I b i t s b u t i n s i g n i f i c a n t f o r I D = 5 I b i t s
( p < 0 . 0 5 ) . F o r e a c h l e v e l o f ID, a l l C O N F w i t h t h e s a m e l e v e l
o f H w e 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 . T h e d i r e c t i o n o f m o v e
( A N G ) w a s f o u n d to b e s i g n i f i c a n t f o r a l l l e v e l s o f H a n d ID.
T h e m i n i m u m p e r f o r m a n c e t i m e w a s n o t e d f o r t h e i n n e r a n g l e s of
m o v e a n d i n c r e a s i n g i n t h e o u t w a r d l y d i r e c t i o n .
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1 2 0 ° ) w e r e t e s t e d f o r t w o l e v e l s of I D (3 a n d 4 I b i t s ) a n d f i v e
l e v e l s of i n f o r m a t i o n l o a d ( 3 , 3 . 5 8 . 4 , 4 . 1 7 a n d 4 . 5 8 B i t s ) i n
S t u d y II. A 5 x 2 x 4 r a n d o m i s e d f a c t o r i a l d e s i g n w a s u s e d
w i t h 8 r i g h t h a n d e d m a l e s u b j e c t s . A l l t h e m a i n e f f e c t s (II, I D
a n d A N G ) w e r e f o u n d to be s i g n i f i c a n t ( p < 0 . 0 5 ) . T h e r e s u l t s
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i s i n c r e a s e d f r o m 3 to 4 I b i t s . T h e m i n i m u m P e r f o r m a n c e t i m e
w a s n o t e d to b e i n t h e d i r e c t i o n 1 0 0 ° - 1 2 0 ° . F r o m t h e t h e d a t a
c o l l e c t e d , a l i n e a r r e g r e s s i o n m o d e l w a s d e v e l o p e d . A l s o , t h e
p r i o r i t y r e g i o n s b a s e d o n t h e m i n i m u m p e r f o r m a n c e t i m e w a s
m a p p e d f o r t h e l e v e l s o f t h e H a n d A N G t e s t e d , f o r e a c h l e v e l
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s t u d i e s . T h e r e s u l t s i n d i c a t e s t h e H R V t o b e s e n s i t i v e to b o t h
t h e m a n u a l as w e l l a s t h e d e c i s i o n l o a d w i t h t h e d e c i s i o n l o a d
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t h e t h i s v a r i a b l e is s u g g e s t e d f o r d e t e r m i n i n g t h e t h e w o r k l o a d
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f o r h i s e n c o u r a g e m e n t , g u i d a n c e a n d f o r s t i m u l a t i n g i n t e r e s t
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a n a l y s i s . T o P r o f . N. S h k l o v , D r . R . S . L a s h k a r i a n d D r . E.
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t h r o u g h o u t t h e p r o j e c t .
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f o r t h e i r a i d i n t h e d e s i g n , c o n s t r u c t i o n a n d m a i n t a i n e n c e of
t h e e x p e r i m e n t a l a p p a r a t u s .
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t h e i r u n f a i l i n g e n c o u r a g e m e n t a n d h e l p i n t h e p r o b l e m a n d to
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A B S T R A C T ... i i i
D E D I C A T I O N ... v
A C K N O W L E D G E M E N T S ... v i L I S T O F T A B L E S ... i x L I S T O F F I G U R E S ... x
L I S T O F A P P E N D I C E S ... x i C H A P T E R I. I N T R O D U C T I O N ... 1
I I . L I T E R A T U R E S U R V E Y ... 6
2 . 1 M e a s u r e m e n t o f t h e i n f o r m a t i o n a l l o a d i n a d e c i s i o n t a s k ... 6
2 . 2 I n f o r m a t i o n a l c o n t e n t i n c o n t r o l l i n g t h e a m p l i t u d e o f m o v e m e n t ... 7
2 . 3 E x p e r i m e n t a l f i n d i n g s r e l a t e d to T y p e II t a s k s ... 10
2 . 4 H e a r t R a t e V a r i a b i l t y a s a P h y s i o l o g i c a l V a r i a b l e ... 14
2 . 4 . 1 A p p l i c a t i o n s o f H R V ... 14
2 . 4 . 2 S c o r i n g M e t h o d s o f H e a r t R a t e V a r i a b i l t y ... 19
I I I . E X P E R I M E N T A L S E T U P ... 22
3 . 1 I n t r o d u c t i o n ... 22
3 . 2 S i g n a l - R e s p o n s e U n i t ... 22
3 . 3 T a p e - R e a d e r a n d R a n d o m N u m b e r T a p e ... 23
3 . 3 . 1 T a p e — r e a d e r ... 26
3 . 3 . 2 R a n d o m N u m b e r T a p e ... 26
3 . 4 T i m e M e a s u r i n g a n d R e c o r d i n g U n i t ... 27
3 . 4 . 1 T i m e M e a s u r i n g U n i t ... 2 7 3 . 4 . 2 R e c o r d i n g U n i t ... 27
3 . 4 . 3 P e r f o r m a n c e T i m e D a t a C o n v e r s i o n a n d I n t e r p r e t a t i o n ... 28
3 . 5 H e a r t R a t e M o n i t o r i n g a n d R e c o r d i n g P r o c e d u r e s . 28 3 . 5 . 1 B e c k m a n E l e c t r o d e s ... 29
3 . 5 . 2 G r a s s P o l y g r a p h ... 29
3 . 5 . 3 P D P 1 1 / 0 3 M i n i c o m p u t e r ... 29
3 . 5 . 4 H R a n d H R V s c o r i n g ... 30
4 . 1 I n t r o d u c t i o n a n d O b j e c t i v e s ... 32
4 . 2 E x p e r i m e n t a l C o n d i t i o n s ... 33
4 . 2 . 1 A n g l e s of M o v e ... 33
4 . 2 . 2 R e a c h D i s t a n c e s / I n d e x o f D i f f i c u l t y ... 35
4 . 2 . 3 S u b j e c t s ... 36
4 . 2 . 4 I n f o r m a t i o n a l L o a d ... 36
4 . 3 D a t a C o l l e c t i o n ... 37
4 . 4 A n a l y s i s o f D a t a ... 39
4 . 4 . 1 A n a l y s i s o f P T b y e a c h l e v e l o f H ... 39
4 . 4 . 2 A n a l y s i s b y e a c h l e v e l o f I D ... 41
4 . 4 . 3 H R V O b s e r v a t i o n ... 42
4 . 5 Re s u i t s ... 42
4 . 5 . 1 A n a l y s i s f o r e a c h l e v e l o f H ... 4 2 4 . 5 . 2 R e s u l t s f o r e a c h l e v e l o f I D ... 49
4 . 5 . 3 R e s u l t s o f H R V ... 53
4 . 6 C o n c l u s i o n ... 55
V. S T U D Y II ... 56
5 . 1 I n t r o d u c t i o n ... 56
5 . 2 E x p e r i m e n t a l C o n d i t i o n s a n d C h o i c e o f L e v e l s . . . 57
5 . 2 . 1 I n f o r m a t i o n a l L o a d ... 57
5 . 2 . 2 I n d e x o f D i f f i c u l t y ... 58
5 . 2 . 3 D i r e c t i o n s o f M o v e ... 58
5 . 2 . 4 S u b j e c t s ... 58
5 . 3 E x p e r i m e n t a l D e s i g n ... 59
5 . 4 M e t h o d o l o g y ... 5 9 5 . 5 A n a l y s i s ... 60
5 . 5 . 1 A n a l y s i s o f P e r f r o m a n c e T i m e d a t a ... 61
5 . 5 . 2 H R V O b s e r v a t i o n s ... 62
5 . 6 R e s u l t s ... 63
5 . 6 . 1 A N O V A f o r P e r f o r m a n c e T i m e ... 63
5 . 6 . 2 A N O V A f o r E a c h L e v e l o f I D ... 65
5 . 6 . 3 A N O V A f o r E a c h L e v e l of H ... 67
5 . 6 . 4 A N O V A f o r E a c h L e v e l o f A N G ... 69
5 . 6 . 5 G r a p h P l o t t i n g ... 71
5 . 7 P r e d i c t i o n E q u a t i o n ... 72
5 . 8 C o n t o u r P l o t t i n g ... 72
5 . 9 H R V O b s e r v a t i o n ... 75
5 . 1 0 A p p l i c a t i o n s o f R e s u l t s ... 77
V I . D I S C U S S I O N A N D C O N C L U S I O N S ... 78
R E F E R E N C E S ... 83
A P P E N D I C E S ... 87
V I T A A U C T O R I S ... 1 9 3
P a g e
T A B L E 2 . 1 S u m m a r y o f F i n d i n g s R e l a t e d to C M D T
( T y p e II T a s k s ) ... 13
T A B L E 2 . 2 S u m m a r y of T a s k / C o n d i t i o n U s e d W i t h H R V i n L i t e r a t u r e ... 16
T A B L E 4 . 1 E x p e r i m e n t a l C o n d i t i o n s i n S t u d y I ... 34
T A B L E 4 . 2 L e v e l s of D i r e c t i o n of M o v e s i n S t u d y I ... 34
T A B L E 4 . 3 ID L e v e l s i n S t u d y I ... 3 4 T A B L E 4 . 4 O b s e r v a t i o n s i n S t u d y I ... 38
T A B L E 4 . 5 A D a t a C l a s s i f i c a t i o n b y E a c h L e v e l of H ... 39
T A B L E 4 . 5 B D a t a C l a s s i f i c a t i o n b y E a c h L e v e l of ID... 41
T A B L E 4 . 6 A - 4 . 6 C A N O V A f o r E a c h L e v e l of H ... 44
T A B L E 4 . 7 A D u n c a n ' s M u l t i p l e R a n g e T e s t o f M e a n s of ID f o r e a c h L e v e l o f H ... 47
T A B L E 4 . 7 B D u n c a n ' s M u l t i p l e R a n g e T e s t o f M e a n s of A N G f o r E a c h L e v e l o f H ... 4 8 T A B L E 4 . 8 A N O V A f o r E a c h L e v e l o f I D ... 5 0 T A B L E 4 . 9 A D u n c a n ' s M u l t i p l e R a n g e T e s t o f M e a n s of C O N F f o r E a c h L e v e l o f ID ... 51
T A B L E 4 . 9 B D u n c a n ' s M u l t i p l e R a n g e T e s t o f M e a n s of A N G f o r E a c h L e v e l of I D ... 52
T A B L E 4 . 1 0 H R V S c o r e s ( I n c r e a s i n g O r d e r ) f o r E a c h C o n f i g u r a t i o n ... 54
T A B L E 5 . 1 L e v e l s of I n f o r m a t i o n L o a d i n S t u d y I I ... 57
T A B L E 5 . 2 A N O V A f o r F i x e d E f f e c t s ... 63
T A B L E 5 . 3 D U N C A N ' s T e s t f o r M a i n E f f e c t s f o r S t u d y I I ... 64
T A B L E - 5 . 4 D U N C A N 's M u l t i p l e R a n g e T e s t f o r E a c h L e v e l o f ID ... 66
T A B L E 5 . 5 D U N C A N ' s M u l t i p l e R a n g e T e s t f o r E a c h L e v e l o f I n f o r m a t i o n L o a d ... 6 8 T A B L E 5 . 6 D U N C A N ' s M u l t i p l e R a n g e T e s t f o r E a c h L e v e l o f A N G ... 7 0 T A B L E 5 . 7 R a n k i n g of C o n d i t i o n s i n A s c e n d i n g o r d e r o f H R V ... 76 T A B L E B . l R e s p o n s e L i g h t s i n C o n f i u r a t i o n I n S t u d y I ... 1 0 4 T A B L E B . 2 S e q u e n c e o f E x p e r i m e n t a l C o n d i t i o n s f o r S u b j e c t
i n S t u d y I ... 1 0 5 T A B L E B . 3 - B . 4 E M S C a l c u l a t i o n s f o r E a c h L e v e l o f H ... 1 0 6 T A B L E B . 5 E M S C a l c u l a t i o n f o r E a c h L e v e l of I D ... 1 0 8 T A B L E C . l D e t a i l s o f S u b j e c t s ( S t u d y II) ... 1 1 5 T A B L E C . 2 R a n d o m i s e d S e q u e n c e o f E x p e r i m e n t a l C o n d i t i o n
f o r E a c h S u b j e c t f o r S t u d y II ... 1 1 5 T A B L E C . 3 R e s p o n s e L i g h t s i n E a c h C o n d i t i o n f o r S t u d y II . . . . 1 1 6 T A B L E C . 4 - C . 7 E M S C a l c u l a t i o n s f o r S t u d y II ... 1 1 8 T A B L E E . 1 - E . 4 A N O V A T a b l e s f o r S t u d y II ... 1 3 4
ix
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F I G U R E 3 . 1 L a y o u t o f S i g n a l - R e s p o n s e U n i t ... 23
F I G U R E 3 . 2 S c h e m a t i c L a y o u t o f S - R U n i t i n t h e V e r t i c a l P l a n e ... 24
F I G U R E 5 . 1 P e r f o r m a n c e T i m e ( M s e c ) R e g i o n s f o r I D = 3 I b i t s . . 72
F I G U R E 5 . 2 P e r f o r m a n c e T i m e ( M s e c ) R e g i o n s f o r I D = 4 I b i t s . 73 F I G U R E A . l A n g u l a r D i r e c t i o n s o f S - R U n i t P a n e l ... 8 8 F I G U R E A. 2 R e s p o n s e L i g h t C o d e s of S - R U n i t ... 89
F I G U R E A. 3a R e s p o n s e - S w i t c h C a p ... 9 0 F I G U R E A . 3 b S t y l u s u s e d i n S t u d y ... 90
F I G U R E A . 4 E x p e r i m e n t a l S e t - u p ... 91
F I G U R E A. 5 S - R U n i t P a n e l ... 92
F I G U R E A . 6 B e c k m a n s E l e c t r o d e s A t t a c h e d to S u b j e c t ... 93
F I G U R E A . 7 P D P 1 1 / 0 3 M i n i - C o m p u t e r U s e d f o r H R V P r o g r a m ... 94
F I G U R E A . 8 C o n t r o l B o x U s e d F o r C o n t r o l l i n g t h e H R V P r o g r a m 95 F I G U R E B . 1 - B . 5 S - R U n i t P a n e l L a y o u t s i n S t u d y I ... 96 F I G U R E C . 1 - C . 5 S - R U n i t P a n e l L a y o u t s i n S t u d y II ... 1 1 0 F I G U R E D . 1 - D . 3 G r a p h s o f M e a n P T V s . A n g l e o f M o v e f o r
1 0 = 3 , 4 a n d 5 I b i t s ( S t u d y I) ... 1 2 7 F I G U R E D . 4 — D . 6 G r a p h s o f M e a n P T V s . A n g l e o f M o v e f o r
H = 3 , 4 a n d 4 . 5 8 B i t s ( S t u d y I ) ... 1 3 0 F I G U R E E . l — E . 5 G r a p h s o f M e a n P T V s . A n g l e o f M o v e f o r
H = 3 , 3 . 5 8 , 4 , 4 . 1 7 a n d 4 . 5 8 B i t s ( S t u d y I I ) ... 1 A 0
F I G U R E E . 6 — E .7 G r a p h s o f M e a n P T V s . A n g l e of M o v e f o r
I D = 3 a n d 3 I b i t s ( S t u d y I I ) ... 1 4 4 F I G U R E E . 8 — E . l l C o m p a r i s o n o f P r e d i c t e d a n d O b s e r v e d V a l u e s .. 1 4 6
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A P P E N D I X A E x p e r i m e n t a l S e t U p ...
A P P E N D I X B E x p e r i m e n t a l C o n d i t i o n s - S t u d y I ...
A P P E N D I X C E x p e r i m e n t a l C o n d i t i o n s - S t u d y II ...
A P P E N D I X D R e s u l t s of S t u d y I ...
A P P E N D I X E R e s u l t s of S t u d y I I ...
A P P E N D I X F . I M e a n P e r f o r m a n c e T i m e s i n S t u d y I ... 1 4 7
A P P E N D I X F. 2 H R V of S u b j e c t s i n S t u d y I ...
A P P E N D I X F . 3 M e a n P e r f o r m a n c e T i m e s i n S t u d y I I ...
A P P E N D I X F. 4 H R V of S u b j e c t s i n S t u d y II ...
A P P E N D I X G C o m p u t e r O u t p u t o f A N O V A S ...
A P P E N D I X H C o m p u t e r P r o g r a m s ...
I N T R O D U C T I O N
I n m a n y i n d u s t r i a l t a s k s , t y p i c a l l y t h o s e e n c o u n t e r e d i n
a n a s s e m b l y l i n e , t h e w o r k e r is r e q u i r e d to m o v e h i s a r m s a n d
f o r e a r m s o v e r a s t a t i o n a r y w o r k a r e a , i n t h e p r o c e s s of
c o l l e c t i n g v a r i o u s c o m p o n e n t s o r p a r t s n e e d e d f o r t h e w o r k .
S u c h t a s k s a r e r e p e t i t i v e , t h u s c o n s i d e r a b l e t i m e c a n b e s a v e d
if t h e l a y o u t of t h e w o r k a r e a f a c i l i t a t e s e a s y r e a c h a n d
h a n d l i n g a n d t h e r e b y r e d u c e s t h e m o v e m e n t t i m e f o r e a c h c y c l e .
I n t h i s r e g a r d w o r k s t u d y r e s e a r c h e r s h a v e e x t e n s i v e l y s t u d i e d
t h e e f f e c t of f a c t o r s s u c h a s r e a c h d i s t a n c e , a n g l e o f
m o v e m e n t , i n w a r d o u t w a r d m o v e m e n t , o u t w a r d i n w a r d m o v e m e n t a n d
m o v e m e n t to t h e l e f t a n d r i g h t o n t h e s p e e d a n d a c c u r a c y of
t h e w o r k b e i n g p e r f o r m e d ( B r o w n a n d A r t h u r 1 9 4 9 , B r i g g s 1 9 5 5 ,
S c h m i d t k e a n d S t e i r 1 9 6 1 , F i t t s a n d P e t t e r s o n 1 9 6 4 , K o n z 1 9 6 7
a n d S c h o l e s 1970, R o a u f a n d A r o r a 1 9 8 0 ) . T h e r e s u l t s o f t h e s e
e x p e r i m e n t s h a v e p r o v i d e d v a l u a b l e d a t a f o r t h e d e s i g n a n d
l a y o u t o f t h e w o r k a r e a w i t h r e s p e c t to f a c t o r s s u c h as t h e
a n g l e o f m o v e a n d r e a c h d i s t a n c e s f o r a c c u r a c y a n d s p e e d .
I n s o m e o t h e r t a s k s f r e q u e n t l y e n c o u n t e r e d i n t h e
i n d u s t r y , t h e o p e r a t o r is r e q u i r e d to m a k e a d e c i s i o n , i n
c o n t r o l l i n g h i s m o v e m e n t s , w h i c h d o n e t n e c e s s a r i l y r e m a i n
t h e s a m e i n e a c h c y c l e . T y p i c a l e x a m p l e s i n c l u d e t h o s e of
i n s p e c t i o n , m o n i t o r i n g a n d c o n t r o l l i n g w h i c h a r e e n c o u n t e r e d
m o r e o f t e n w i t h i n c r e a s e d a u t o m a t i o n i n i n d u s t r y . S u c h t a s k s
r e q u i r e t h e o p e r a t o r to r e s o l v e s o m e u n c e r t a i n t y i n s e l e c t i n g
a r e s p o n s e , w h i c h a f f e c t s t h e o v e r a l l m o v e m e n t t i m e , m a k i n g
it d i f f e r e n t f r o m t h e t y p e of t a s k d i s c u s s e d e a r l i e r . A g a i n
i n s u c h s i t u a t i o n s t h e o p e r a t o r m a y b e r e q u i r e d to r e s o l v e
t w o t y p e s of u n c e r t a i n t y , n a m e l y : —
(i) T i m e u n c e r t a i n t y - t h e u n c e r t a i n t y e n c o u n t e r e d i n t h e
e x a c t t i m i n g o f t h e o c c u r r e n c e o f a s t i m u l u s .
( i i ) C h o i c e u n c e r t a i n t y - t h e u n c e r t a i n t y i n t h e o c c u r r e n c e o f a
s t i m u l u s f r o m a g i v e n s e t o f s t i m u l i .
I n r e s o l v i n g s u c h u n c e r t a i n t y t h e o p e r a t o r is f o r c e d i n t o
m a k i n g a " d e c i s i o n " .
F o r e x p e r i m e n t a l p u r p o s e s t h e t w o t y p e s o f t a s k
d i s c u s s e d a b o v e h a v e b e e n c l a s s i f i e d b y w o r k s t u d y
r e s e a r c h e r s i n t o t w o c l a s s . T h e f o r m e r t y p e o f t a s k s w h i c h
a r e r e p e t i t i v e f r o m c y c l e to c y c l e a r e c a l l e d t y p e I t a s k s
( R a o u f a n d H e h r a 1 9 7 4 ) . T h e l a t t e r w h i c h i n v o l v e s c o m b i n e d
m o t i o n a n d d e c i s i o n , a r e s t u d i e d as t y p e I I t a s k s ( S a d o s k y
1 9 6 8 , T h o m a s 1 9 7 1 , R a o u f a n d H e h r a 1 9 7 4 , R a o u f a n d J o s e p h ,
1 9 8 2 ) . H e n c e f o r t h , t h e a p p r o p r i a t e t e r m w i l l b e u s e d w h i l e
r e f e r r i n g to t y p e o f t a s k d i s c u s s e d .
W i t h i n c r e a s i n g a u t o m a t i o n i n i n d u s t r y m o r e of t y p e II
t a s k s a r e f o u n d i n i n c r e a s i n g n u m b e r s . T h e h u m a n f u n c t i o n i n
s u c h t a s k s is m o r e of c o n t r o l l i n g a n d m o n i t o r i n g i n n a t u r e ,
r e s u l t i n g i n i n c r e a s i n g n u m b e r s of c o n t r o l p a n e l s i n t h e s e
s i t u a t i o n s . T y p i c a l e x a m p l e s a r e i n t h e p e t r o l e u m a n d
c h e m i c a l i n d u s t r i e s , w h e r e t h e h u m a n o p e r a t o r is r e q u i r e d to
i n t e r v e n e o n l y w h e n s o m e t h i n g is r a d i c a l l y w r o n g . N u c l e a r
p l a n t s t o o , p r o v i d e a r e a s w h e r e s u c h t a s k s a r e f r e q u e n t l y
e n c o u n t e r e d . S l i g h t e s t e r r o r o r a d e l a y e d a c t i o n b y t h e
h u m a n o p e r a t o r i n s u c h c a s e s c a n p r o v e to b e v e r y c r u c i a l a n d
c o s t l y . T h e p i l o t o f a n a i r c r a f t is a l s o f a c e d w i t h s i m i l i a r
s i t u a t i o n , h i s f u n c t i o n b e i n g m a i n l y o f m o n i t o r i n g a n d
c o n t r o l l i n g .
I n s u c h a s e t u p n o r m a l l y w h a t is e n c o u n t e r e d is t h a t
f o r e a c h d i r e c t i o n o f m o v e m e n t , t h e r e m a y b e m o r e t h a n o n e
r e a c h d i s t a n c e p o s s i b l e . T h a t is, g i v e n a d i r e c t i o n o f
m o v e m e n t t h e o p e r a t o r m a y h a v e to c h o o s e a r e s p o n s e f r o m a
s e t w i t h m o r e t h a n o n e p o s s i b l e r e a c h d i s t a n c e . F o r e x a m p l e ,
i n a m o n i t o r i n g t a s k t h e l a y o u t o f p a n e l s w o u l d b e s u c h t h a t ,
t h e r e m a y b e m o r e t h a n o n e c o n t r o l s w i t c h i n a n y g i v e n
d i r e c t i o n , d u e to r e s t r i c t i o n o n t h e s p a c e . A n o t h e r e x a m p l e
w o u l d b e i n t h e c a s e o f a n i n s p e c t i o n a n d s o r t i n g t a s k , w h e r e
a g a i n t h e o p e r a t o r e n c o u n t e r s m o r e t h a n o n e r e a c h d i s t a n c e
f o r a n y p a r t i c u l a r a n g l e o f m o v e . T h e o p e r a t o r i n t h i s c a s e
h a s t o s e l e c t t h e i n s p e c t e d i t e m as q u i c k i l y a s p o s s i b l e , as
i n m o s t c a s e s e n c o u n t e r e d , t h e i t e m s a r e m o v e d a t a f i x e d
r a t e o r s p e e d o n a c o n v e y o r .
R e a l i s i n g t h e i m p o r t a n c e o f s u c h t a s k s , d u e
c o n s i d e r a t i o n n e e d s to b e g i v e n to t h e i d e a l w o r k p l a c e
d i m e n s i o n s . V a r i o u s c o n t r o l s a n d d i s p l a y s n e e d to b e l o c a t e d
r e s p o n s e t i m e w i t h m i n i m u m n u m b e r o f e r r o r s . D u e to t h e f a c t
t h a t t h e r e is t h e d e c i s i o n e l e m e n t i n v o l v e d i n t y p e II t a s k s
a n d d u e to i t s i n t e r a c t i o n w i t h t h e o t h e r f a c t o r s a f f e c t i n g
m o v e m e n t , s u c h t a s k s h a v e to b e i n v e s t i g a t e d s e p a r a t e l y a n d
i n d e p e n d e n t l y to s t u d y f a c t o r s t h a t h a v e b e e n f o u n d
s i g n i f i c a n t to t y p e I t a s k . W i t h t h i s i n t e n t i o n s o m e
i m p o r t a n t i n v e s t i g a t i o n s h a v e b e e n c o n d u c t e d i n l a b o r a t o r i e s
b y w o r k s t u d y r e s e a c h e r s .
I n t h e l i t e r a t u r e t h e r e a r e n o d o c u m e n t e d w o r k a v a i l a b l e
w h i c h p e r t a i n s to t h e e f f e c t of t h e c h a n g e i n t h e p o s s i b l e
r e a c h d i s t a n c e s w i t h a n g u l a r d i r e c t i o n o f m o v e w i t h e a c h c y c l e
f o r a t y p e II t a s k . S u c h s i t u a t i o n s a r e m o r e r e a l i s t i c to
p r a c t i c a l s i t u a t i o n s a s m e n t i o n e d . W i t h t h i s i n t e n t i o n to
p r o v i d e s o m e s e t g u i d e l i n e s t h a t c o u l d b e d i r e c t l y u s e d b y
w o r k s t a t i o n d e s i g n e r s , t w o e x p e r i m e n t a l s t u d i e s w e r e
c o n d u c t e d ( S t u d y I a n d S t u d y I I ) . A s i g n a l — r e s p o n s e u n i t to
s i m u l a t e s u c h a s i t u a t i o n w a s s p e c i a l l y d e s i g n e d a n d b u i l t f o r
t h e p u r p o s e . D a t a c o l l e c t e d f r o m s t u d y I w a s d e s i g n e d to
i n c o r p o r a t e t h e e n t i r e w o r k a r e a s u b j e c t to t h e l i m i t a t i o n s o f
t h e e q u i p m e n t . O n t h e b a s i s o f t h e r e s u l t s o f t h i s s t u d y t h e
s e c o n d e x p e r i m e n t a l s t u d y w a s c o n d u c t e d f o r t h e w o r k a r e a
w h e r e a s e t p a t t e r n i n t h e r e s u l t s w a s n o t e d . A g e n e r a l
l i n e a r r e g r e s s i o n q i o u c1 w a s c n e n d e v e l o p e d f r o m t h e o b s e r v e d
d a t a . T h e e x p e r i m e n t a l s e t u p a l s o h e l p e d to i n v e s t i g a t e t h e
e f f e c t o f i n c r e a s e d l e v e l s o f i n f o r m a t i o n a l l o a d p r e v i o u s l y n o t
s t u d i e d b e f o r e f o r t y p e II t a s k s .
F o r d e t e r m i n i n g t h e w o r k l o a d i n a t a s k , r e s e a r c h e r s h a v e
f r e q u e n t l y u s e d v a r i o u s p h y s i o l o g i c a l v a r i a b l e s as i n d i c a t o r s .
A m o n g s u c h p h y s i o l o g i c a l v a r i a b l e s is t h e h e a r t r a t e
v a r i a b i l t i t y ( H R V ) o f t h e s u b j e c t s ( K a l s b e e k 1 9 6 4 , S h a r i t a n d
S a l v e n d y 1 9 8 2 , T s u c h i y a 1 9 8 2 e t c . ) , s p e c i a l l y i n t a s k s
i n v o l v i n g s o m e f o r m o f m e n t a l l o a d . I n t h e l i t e r a t u r e t h e r e
a r e n o d o c u m e n t e d w o r k w h i c h h a s s t u d i e d t h e e f f e c t o n t h e
H e a r t R a t e V a r i a b i l t y ( H R V ) of t h e s u b j e c t s w h i l e p e r f o r m i n g
T y p e I I t a s k s . I n t h e c a s e o f a c o m b i n e d m a n u a l a n d d e c i s i o n
t a s k , t h e w o r k l o a d c o u l d b e i n d e p e n d e n t l y a s s o c i a t e d w i t h b o t h
t h e m a n u a l as w e l l a s t h e d e c i s i o n c o m p o n e n t l o a d s . T h e H R V of
t h e s u b j e c t s w a s m o n i t o r e d i n b o t h t h e e x p e r i m e n t a l s t u d i e s t o
o b s e r v e f o r a n y t r e n d s w i t h c h a n g e s i n t h e e x p e r i m e n t a l
c o n d i t i o n s d u e to t h e i n h e r e n t w o r k l o a d i n t e r m s of t h e m e n t a l
a n d m a n u a l l o a d s .
L I T E R A T U R E S U R V E Y
2 . 1 M e a s u r e m e n t of t h e i n f o r m a t i o n a l l o a d i n a d e c i s i o n t a s k .
A c c o r d i n g t o i n f o r m a t i o n t h e o r y a s p u t f o w a r d b y S h a n n o n
a n d W e a v e r , i n f o r m a t i o n is m e a s u r e d q u a n t i t a t i v e l y i n t e r m s
o f " b i t s " ( c o n d e n s a t i o n o f b i n a r y d i g i t ) . It is g e n e r a l l y
g i v e n b y t h e r e l a t i o n
H = l o g2 n b i t s , w h e r e n = l / p
a n d w h e r e H is t h e i n f o r m a t i o n c o n t e n t o r e n t r o p y , n i s t h e
n u m b e r of e q u a l l y p r o b a b l e a l t e r n a t i v e a n d t h u s p is t h e
p r o b a b i l i t y of o c c u r r e n c e o f a n a l t e r n a t i v e .
T h e e n t r o p y o r a v e r a g e i n f o r m a t i o n p r o c e s s e d f o r a
s e r i e s of p r o b a b i l i t i e s pj_, P 2 > * * « * P n * s g i v e n b y t h e r e l a t i o n
H = - ^ P i l o g 2 P i b i t s
A m o r e g e n e r a l f o r m u l a d e r i v e d b y S h a n n o n i s g i v e n b y
t h e r e l a t i o n
H = “ i>Pi £lj p ij i o g a ^ i j )
blts
w h e r e p i is t h e p r o b a b i l t y t h a t i o c c u r r s f r o m a f i n i t e s e t
of a l t e r n a t i v e s (1 = 1 , 2 , 3 , ... n) a n d P ^ j i s t h e c o n d i t i o n a l
p r o b a b i l t y of s t i m u l u s j o c c u r r i n g g i v e n t h a t s t i m u l u s i
o c c u r r e d i n t h e p r e v i o u s c y c l e .
It h a s b e e n s h o w n t h a t a s t h e i n f o r m a t i o n c o n t e n t i n
b i t s i n c r e a s e s t h e t i m e f o r t h e d e c i s i o n t a s k a l s o
6
c o r r e s p o n d i n g l y i n c r e a s e s . T h e r e a c t i o n t i m e ( R T ) w a s f o u n d
t o b e w e l l p r e d i c t e d b y t h e f o l l o w i n g r e l a t i o n , w i t h i n a
c e r t a i n r a n g e of t h e i n f o r m a t i o n l o a d :
-RT=* a + b l o g2 n
w h e r e : a is t h e c o n s t a n t f o r t h e r a n g e
b is t h e s l o p e o r b i t s / r e s p o n s e f o r t h e r e l a t i o n
2 . 2 I n f o r m a t i o n a l c o n t e n t i n c o n t r o l l i n g t h e a m p l i t u d e of m o v e m e n t .
F i t t s ( 1 9 5 4 ) u s e d t h r e e s e t s of e x p e r i m e n t s i n a n a t t e m p t
to q u a n t i f y t h e r e l a t i o n b e t w e e n t h e e x t e n t a n d a c c u r a c y o f
m o v e m e n t f o r d e t e r m i n i n g t h e p e r f o r m a n c e t i m e i n t e r m s of
t h e s e p a r a m e t e r s . T h e s e t a s k s w e r e :
-(1) A t a p p i n g t a s k w h e r e t h e s u b j e c t a l t e r n a t e l y t a p p e d
b e t w e e n t w o p l a t e s s e p a r a t e d a t f i x e d d i s t a n c e s a n d w i t h
f i x e d w i d t h s , u s i n g a s t y l u s . T h e d i s t a n c e s a n d t h e w i d t h s
w e r e v a r i e d w i t h e a c h e x p e r i m e n t a l c o n d i t i o n .
(2) T r a n s f e r of w a s h e r s f r o m o n e p i n to a n o t h e r . T h e
d i s t a n c e s b e t w e e n t h e p i n s a n d t h e t o l e r e n c e s w e r e v a r i e d
w i t h e a c h c o n d i t i o n .
(3) T r a n s f e r of p i n s f r o m o n e h o l e to a n o t h e r . T h e d i s t a n c e s
b e t w e e n t h e h o l e s a n d t h e t o l e r e n c e s w e r e a g a i n v a r i e d w i t h
e v e r y c o n d i t i o n .
O n t h e b a s i s of t h e r e s u l t s o b t a i n e d f r o m t h e s e
e x p e r i m e n t s , F i t t s d e r i v e d t h e i n f o r m a t i o n c o n t e n t o f t h e
m o v e m e n t a n d d e f i n e d i t as t h e I n d e x o f D i f f i c u l t y ( I D ) ,
g i v e n b y
I D = l o g 2 2 A / W b i t s / r e s p o n s e
w h e r e A is t h e a m p l i t u d e of m o v e m e n t , i . e . , t h e d i s t a n c e
b e t w e e n t h e c e n t e r o f t w o t a r g e t s u s e d i n t h e e x p e r i m e n t , W
is t h e t o t a l t o l e r a n c e f o r e r r o r i n t e r m i n a t i n g t h e m o v e m e n t
o r t h e w i d t h of t h e r e s p o n s e s w i t c h ( d i a m e t e r o f t h e s w i t c h
if c i r c u l a r ) . F i t t s u s e d t h e u n i t ' b i t ' to m e a s u r e t h i s
i n d e x o f d i f f i c u l t y , t h o u g h n o t r e l a t e d w i t h t h e u n i t of
i n f o r m a t i o n a l l o a d , h o w e v e r u s e d w i t h t h e s a m e i m p l i c a t i o n s
s u g g e s t e d b y i n f o r m a t i o n a l l o a d .
I t w a s a l s o f o u n d b y F i t t s a n d s u b s e q u e n t l y v e r i f i e d b y
o t h e r s t h a t t h e m o v e m e n t t i m e ( M T ) c o u l d w e l l b e p r e d i c t e d
u s i n g t h e f o l l o w i n g r e l a t i o n
M T = a + b 1 o g 2 2 A / W ,
w h i c h is q u i t e s i m i l i a r to t h e r e l a t i o n g i v i n g t h e r e a c t i o n
t i m e ( R T ) o f a d e c i s i o n t a s k w i t h ' n ' p o s s i b l e a l t e r n a t i v e s
a s g i v e n b e l o w
R T = a + b l o g2 n
T h i s r e l a t i o n o f I n d e x o f D i f f i c u l t y is f r e q u e n t l y r e f e r r e d
to a s ' F i t t s L a w ' . B y t h e s i m i l a r r e a s o n i n g u s i n g t h e i n f o r m a t i o n
t h e o r y o f S h a n n o n a n d W e a v e r ( 1 9 4 9 ) , F i t t s d e f i n e d t h i s i n d e x
o f d i f f i c u l t y a s t h e i n f o r m a t i o n c o n t e n t i n e a c h m o v e m e n t i n
t e r m s of b i t s / r e s p o n s e . T h e r e a s o n f o r m u l t i p l y i n g t h e r a t i o
o f A a n d W b y 2 b e f o r e t h e L o g a r i t h m o f b a s e 2 is t a k e n o f
t h e r a t i o , is to f o r c e a p o s i t i v e v a l u e of t h e ID, w i t h a n
e f f e c t o f a d d i n g 1 b i t p e r r e s p o n s e to t h e t o t a l .
V a r i o u s r e s e a r c h e r s h a v e t e s t e d t h e v a l i d i t y of t h i s
r e l a t i o n o f m o v e m e n t t i m e ( M T ) , a s g i v e n a b o v e , a n d h a v e f o u n d
s a t i s f a c t o r y c o m p l i a n c e , s h o w i n g M T to b e p r o p o r t i o n a l to t h e
i n d e x o f d i f f i c u l t y . F i t t s a n d P e t e r s o n ( 1 9 6 4 ) e x t e n d e d t h i s
c o n c e p t to a s i m p l e c o m b i n e d m a n u a l a n d d e c i s i o n t a s k
i n v o l v i n g t w o b i n a r y c h o i c e s . T h e y f o u n d a h i g h p o s i t i v e
c o r r e l a t i o n ( . 9 9 ) b e t w e e n m o v e m e n t t i m e a n d i n d e x of
d i f f i c u l t y f o r t h e r a n g e 2 . 6 to 7 . 6 b i t s p e r r e s p o n s e .
S c h o l e s ( 1 9 7 0 ) s t u d i e d t h e e f f e c t of 7 d i r e c t i o n s of
m o v e a n d 3 l e v e l s of I D f o r d i s c r e t e m o t o r r e s p o n s e s
i n v o l v i n g n o u n c e r t a i n t y . H e f o u n d t h e d i r e c t i o n of m o v e m e n t
d i r e c t l y a f f e c t i n g t h e m o v e m e n t t i m e b u t i t d i d n o t a f f e c t
t h e r e a c t i o n t i m e s i g n i f i c a n t l y . H e a l s o f o u n d a h i g h
P o s i t i v e c o r r e l a t i o n b e t w e e n t h e m o v e m e n t t i m e a n d t h e i n d e x
o f d i f f i c u l t y .
F i t t s a n d R a d f o r d ( 1 9 6 6 ) e x t e n d e d t h e f i n d i n g s u p p o r t i n g
t h e c o n c l u s i o n t h a t t h e h u m a n m o t o r s y s t e m h a s r e l a t i v e l y
c o n s t a n t i n f o r m a t i o n c a p a c i t y o v e r w i d e l i m i t s . F r o m t h e i r
s t u d y t h e y c o n c l u d e d t h e i n f o r m a t i o n c a p a c i t y o f t h e h u m a n
m o t o r s y s t e m to b e r e l a t i v e l y i n v a r i a n t f o r c o g n i t i v e s e t s
f o r s p e e d a n d a c c u r a c y .
R a o u f a n d T s u i ( 1 9 7 9 ) . i n t h e i r e x p e r i m e n t a l s t u d y w i t h a
c o m b i n e d m a n u a l d e c i s i o n t a s k i n v o l v i n g p o s i t i o n i n g , d e f i n e d t h e
t a s k d i f f i c u l t y i n t e r m s of i n d e x of d i f f i c u l t y . He u s e d 12
l e v e l s o f i n d e x of d i f f i c u l t y r a n g i n g f r o m 5 . 8 to 1 2 . 0 b i t s
a n d f o u n d it w a s h i g h l y s i g n i f i c a n t o n t h e p e r f o r m a n c e t i m e .
R a o u f a n d A r o r a ( 1 9 8 0 ) u s e d t h e i n d e x o f d i f f i c u l t y f o r
q u a n t i f y i n g t h e t a s k d i f f i c u l t y f o r a c o m b i n e d m a n u a l a n d
d e c i s i o n t a s k , i n v o l v i n g i n f o r m a t i o n a l l o a d . T s u c h i y a ( 1 9 8 2 )
d e f i n e d h i s t a s k d i f f i c u l t y , f o r a s i m u l t a n e o u s p o s i t i o n i n g
t a s k , i n t e r m s o f i n d e x o f d i f f i c u l t y . B o t h t h e s e s t u d i e s
s h o w e d a s i g n i f i c a n t e f f e c t o f I D w i t h r e s p e c t to t h e
p e r f o r m a n c e t i m e .
2 . 3 E x p e r i m e n t a l f i n d i n g s r e l a t e d t o T y p e I I t a s k s
F o r t h e p r e d i c t i o n o f m e a n c y c l e t i m e o f t y p e I I t a s k s ,
S a d o s k y ( 1 9 6 9 ) d e v e l o p e d a m e t h o d u s i n g t h e c r i t i c a l p a t h
m e t h o d . I n t h e m e t h o d h e a d o p t e d , a l l t h e m a n u a l e l e m e n t s
a n d t h e d e c i s i o n e l e m e n t w e r e r e p r e s e n t e d i n t h e f o r m o f a
n e t w o r k , u s i n g t h e a r r o w s to i n d i c a t e t h e s e q u e n t i a l
r e l a t i o n s h i p . T h e t a s k s i n v o l v e d i n h i s i n v e s t i g a t i o n
i n c l u d e d t h e m a n u a l e l e m e n t s r e a c h , g r a s p , m o v e a n d p o s i t i o n
p e r f o r m e d s i m u l t a n e o u s l y w i t h a d e c i s i o n e l e m e n t o f c h o o s i n g
to p r e s s o n e b u t t o n f r o m a s e t o f f o u r b u t t o n s , w i t h t h e s a m e
p r o b a b i l i t y o f o c c u r r e n c e . T h e d e c i s i o n t i m e s w e r e e s t i m a t e d
" s i n g t h e c o n c e p t o f I n f o r m a t i o n p r o c e s s i n g r a t e .
T h o m a s ( 1 9 7 1 ) d e a l t w i t h s o m e o f t h e p r o b a b l i s t i c
a s p e c t s of t h e p e r f o r m a n c e t i m e s f o r c o m b i n e d m a n u a l a n d
d e c i s i o n t a s k s . H e u s e d t h e s a m e t a s k as t h e o n e e m p l o y e d b y
S a d o s k y ( 1 9 6 9 ) b u t u s e d v a r i o u s t y p e s of p r o b a b i l i t y
d i s t r i b u t i o n s f o r t h e o c c u r r e n c e of e a c h a l t e r n a t i v e f r o m a
s e t of 4. H e f o u n d t h e p e r f o r m a n c e t i m e to b e g a m m a
d i s t r i b u t e d b u t t e n d i n g to be n o r m a l as s u b j e c t s p r o g r e s s e d
to l e a r n e d s t a t e . In c a s e of s u b j e c t s w h o w e r e f u l l y l e a r n e d
t h e p e r f o r m a n c e t i m e of t h e m a n u a l e l e m e n t s w a s n o r m a l l y
d i s t r i b u t e d . T h e p e r f o r m a n c e t i m e a s s o c i a t e d w i t h t h e
d e c i s i o n c o m p o n e n t of t h e t a s k w a s f o u n d to be a d i r e c t
f u n c t i o n of t h e i n p u t u n c e r t a i n t y o r t h e n u m b e r o f c h o i c e s .
R a o u f ( 1 9 7 3 ) u s e d t h e i n f o r m a t i o n p r o c e s s i n g r a t e ( I P R )
f o r t h e p r e d i c t i o n of t y p e II t a s k s . H e h a s s h o w n t h a t t h e
a v e r a g e i n f o r m a t i o n p r o c e s s i n g r a t e is n o t a d e s i r a b l e
e s t i m a t o r f o r p r e d i c t i n g d e c i s i o n t i m e s f o r t y p e II t a s k s ,
e v e n w h e n t h e c o n d i t i o n s , w h i c h a r e k n o w n to e f f e c t t h e
o u t c o m e of a c h o i c e r e a c t i o n t a s k e x p e r i m e n t s , a r e k e p t
i n v a r i a n t .
R a o u f a n d H e h r a ( 1 9 7 4 ) i n c o r p o r a t e d t h e m a n u a l e l e m e n t
' r e a c h ' a t d i f f e r e n t l e v e l s w i t h v a r y i n g i n f o r m a t i o n a l l o a d .
T h e y f o u n d p e r f o r m a n c e t i m e w a s m i n i m u m f o r m i n i m u m r e a c h
d i s t a n c e s a n d i n c r e a s e d w i t h i n c r e a s i n g i n f o r m a t i o n a l l o a d .
R a o u f a n d E l s a y e d ( 1 9 7 5 ) e x t e n d e d t h e p r e v i o u s
i n v e s t i g a t i o n a n d i n c o r p o r a t e d t w o a n g l e s o f m o v e w i t h t h r e e
t e a c h d i s t a n c e s a n d t h r e e l e v e l s of i n f o r m a t i o n a l l o a d . T h e
e f f e c t of t h e t w o a n g l e s of m o v e t e s t e d o n t h e p e r f o r m a n c e
t i m e w a s f o u n d i n s i g n i f i c a n t , w i t h t h e r e a c h d i s t a n c e a n d
i n f o r m a t i o n a l l o a d b e i n g f o u n d to b e s i g n i f i c a n t .
I n t h e i r s t u d y u s i n g t y p e II t a s k , R a o u f a n d A r o r a ( 1 9 8 0 )
i n v e s t i g a t e d t h e e f f e c t of i n f o r m a t i o n a l l o a d , i n d e x of
d i f f i c u l t y ( t r a n s f o r m e d f r o m r e a c h d i s t a n c e s ) a n d p l a n e a n g l e s
o f m o v e o n t h e p e r f o r m a n c e t i m e . T h i s s t u d y i n v e s t i g a t e d t h e
e f f e c t of u n c e r t a i n i t y i n o c c u r r e n c e o f t h e a n g u l a r d i r e c t i o n
of m o v e w i t h e a c h c y l c e f o r t y p e II t a s k . 3 l e v e l s o f i n d e x
of d i f f i c u l t y ( t r a n s f o r m e d f r o m 3 l e v e l s of r e a c h d i s t a n c e s ) ,
3 l e v e l s o f i n f o r m a t i o n a l l o a d , 4 a n g l e s o f m o v e ( f r o m a
p o s s i b l e o f 10) a n d 6 p l a n e a n g l e s w e r e t e s t e d o n t h e
p e r f o r m a n c e t i m e . I n f o r m a t i o n a l l o a d , i n d e x o f d i f f i c u l t y a n d
a n g l e o f m o v e w e r e f o u n d to b e s i g n i f i c a n t f a c t o r s a f f e c t i n g
p e r f o r m a n c e t i m e . T h e p l a n e a n g l e d i d n o t s h o w a n y
s i g n i f i c a n t e f f e c t o n t h e p e r f o r m a n c e t i m e .
A t p r e s e n t t h e r e a r e n o s t u d i e s d o c u m e n t e d w i t h t y p e II
t a s k s , w h i c h h a s s t u d i e d t h e e f f e c t of u n c e r t a i n i t y i n t h e
o c c u r r e n c e of r e a c h d i s t a n c e s a n d a n g u l a r d i r e c t i o n of m o v e
w i t h e a c h c y c l e . T h o u g h P M T S p r o v i d e s s o m e i n f o r m a t i o n f o r
t y p e I t a s k s , n o i n f o r m a t i o n is c u r r e n t l y a v a i l a b l e f o r t y p e
I I t a s k s f o r t h e s i t u a t i o n m e n t i o n e d .
T a b l e 2 . 1 b r i e f l y s u m m a r i z e s s o m e o f t h e r e s u l t s o f
r e l a v e n t s t u d i e s w h e r e a c o m b i n e d m a n u a l a n d d e c i s i o n t a s k w a s
t e s t e d .
TABLE 2.1 Summary of Findings Related to CMDT (Type II Tasks)
Authors Year Conditions Commments
Sadosky 1969 Pre d i c t i o n of Cycle
time u s i n g Critical Path Method.
M T M m o t i o n time used for ma n u a l elemental times and Information processing rate for de cision times.
Thomas 1971 Study of Probablistic aspects associated w i t h p r e d i c t i o n of times.
Dealt w i t h the various types of prob. distr i b u t ion governing the o c c u r ences of each alternative in the decision element.
R aouf & M e h r a
1974 CMDT w i t h element reach w i t h d i f f e r e n t levels
of Information Load.
PT affected by 'reach' w i t h significant i n ter
actions w i t h information l o a d .
Raouf & Elsayed
R a o u f &
1975 CMDT w i t h 2 levels of Angles of M o v e and element Reach.
Angle of mo v e found to be not s i g n i f l e a n t (5%). Reach and Information found significant.
Tsui
1 9 7 9 CMDT w i t h 'positioning' u sing Index of D i f f i c ulty w i t h male and female subjects.
Index of D i f ficulty and Information Load w e r e significa n t ( p < 0 . 05) but sex found to be insign-f l e a n t .
R aouf & Arora
1 9 8 0V
•I
CMDT w i t h 4 angles of move, Inf. Load, Index of d i f f i c u l t y and Plane Angle. Inf. Load < 3.32 Bits.
All factors except the the plane angle found
to be s i g n i f l e a n t ( p < 0 . 05).
2 . 4 H e a r t R a t e V a r i a b i l t y a s a P h y s i o l o g i c a l V a r i a b l e
2 . 4 . 1 A p p l i c a t i o n s of H R V
It is n o w a r e c o g n i s e d f a c t t h a t t h e h e a r t r a t e o f a
p e r s o n i n c r e a s e s w i t h p h y s i c a l w o r k a n d is o f t e n u s e d as
a m e a s u r e of t h e p h y s i c a l w o r k l o a d f o r d i f f e r e n t t y p e s of
t a s k a n d a c t i v i t y ( B r o u h a 1 9 6 0 ) . T h e h i g h c o r r e l a t i o n of
h e a r t r a t e a n d p a c e of p h y s i c a l t a s k l e a d to t h e
s u g g e s t i o n of i t s u s e to r a t e o p e r a t o r p e r f o r m a n c e ( Y o u n g
1 9 5 6 ) .
M o r e t h a n h e a r t r a t e , t h e i r r e g u l a r i t y o f h e a r t r a t e f r o m
b e a t to b e a t , k n o w n as h e a r t r a t e v a r i a b i l t y ( H R V ) , h a s b e e n
s h o w n to b e a r e l i a b l e i n d i c a t o r , e s p e c i a l l y i n t h e a s s e s m e n t
° f t h e m e n t a l l o a d of t h e t a s k . T h i s p h e n o m e n o n , a l s o k n o w n a s
s i n u s a r r h y t h m i a w a s r e p o r t e d b y K a l s b e e k a n d E t t e m m a ( 1 9 6 3 ) ,
w h o n o t i c e d a n i r r e g u l a r i t y of t h e h e a r t r a t e p e r u n i t t i m e
f r o m b e a t to b e a t a n d a n o t i c e a b l e c h a n g e i n p a t t e r n u n d e r
d i f f e r e n t k i n d s o f a c t i v i t y . H e n o t i c e d a f l u c t a t i o n of u p t o
2 0 b e a t s p e r m i n u t e f o r a s u b j e c t a t r e s t . T h i s d i m i n i s h e d w h e n
t h e s u b j e c t w a s p e r f o r m i n g a b i n a r y c h o i c e r e a c t i o n t a s k t h u s
i m p l y i n g a n e g a t i v e c o r r e l a t i o n of H R V a n d m e n t a l l o a d i n a
t a s k . R e s e a r c h e r s h a v e s i n c e b r o a d e n e d t h e a p p l i c a t i o n s of H R V
to s t u d y i t s e f f e c t w h e n p e r s o n s a r e p e r f o r m i n g v a r i o u s t a s k s
a n d s i t u a t i o n s .
T h e s u p p r e s s i o n of H R V h a s b e e n r e p o r t e d i n a w i d e r a n g e
of tasks i n v o l v i n g some f o r m of m e n t a l load ( K a l s b e e k and
E t t e m m a 1965, 1965a, B o n s p e r 1970, K a l s b e e k and Z i e l u i s 1971,
R o h m e r t et al 1973, B o y c e 1974, S h a r i t and S a l v e n d y 1982).
This p h e n o m e n o n has al s o b e e n r e p o r t e d in m e n t a l task, to a
v e r y m a r g i n a l e x t e n t in con j u n c t i o n w i t h h i g h le v e l s of
p h y s i c a l ef f o r t ( O p m e e r 1969) and also in s i t u a t i o n s
i n v o l v i n g e m o t i o n a l e f f o r t (Krol and O p m e e r 1970, R o h m e r t et
al 1973). T h e r e are also a few v a l u a b l e c o n t r i b u t i o n s by
r e s e a r c h e r s w i t h r e s p e c t to the t h e o r e t i c a l d e s c r i p t i o n ,
s c o r i n g and i n t e r p r e t a t i o n of this p h e n o m e n o n in the
l i t e r a t u r e ( L u c z a k and L a u r i g 1973, H y n d m a n and G r e g o r y 1974,
L u c z a k 1977, M u l d e r 1977).
W i t h r e s p e c t to its u s e f u l n e s s and a p p l i c a b i l t y of HRV,
K a l s b e e k (1971) has a p t l y m e n t i o n e d it as a p h y s i o l o g i c a l
v a r i a b l e as a " f u n c t i o n of the n u m b e r of m o m e n t s of
c o n s c i o u s c o n t r o l per m i n u t e " than just an i n d i c a t o r of the
a p p a r e n t i n f o r m a t i o n a l load in 'bits' or n u m b e r of c h o i c e s
per m i n u t e of the task. L u c z a k (1979) c o n d u c t e d a s t u d y in
w h i c h he f r a c t i o n e d the H R V as a f u n c t i o n of the f o l l o w i n g
c o m p o n e n t s viz: the l e vel of H e art rate, the m o t o r part of
s t r a i n of task, the m e n t a l part of s t r a i n of the task, the
e m o t i o n a l part of s t r a i n of the task and the i n d i v i d u a l
d i f f e r e n c e s i n h e r e n t of the s u b j e c t s . He also b r o u g h t out
the c o r r e l a t i o n of some of these f a c t o r s w i t h the HRV.
S h a r i t and S a l v e n d y (1982) used H R V in d i s t i n g u i s h i n g
b e t w e e n t h e p a c i n g c o n d i t i o n s v i z , s e l f p a c e d a n d m a c h i n e
p a c e d , o f t a s k s w h i c h i n v o l v e d i n f o r m a t i o n p r o c e s s i n g u n d e r
t w o c o n d i t i o n s v i z , i n t e r n a l a n d e x t e r n a l . H o w e v e r , t h e y
r e p o r t t h e M e a n H e a r t R a t e ( M H R ) to b e m o r e s e n s i t i v e t h a n H R V
i n d i s t i n g u i s h i n g b e t w e e n t h e t y p e o f i n f o r m a t i o n p r o c e s s i n g
i n h e r e n t i n t h e t a s k .
R e c e n t l y T s u c h i y a ( 1 9 8 2 ) u s e d a n i n d e x o f H R V w i t h t h e
r e s p o n s e t i m e ( H R V I ) of t h e c o n d i t i o n to s t u d y i t s s e n s i t i v i t y
w i t h d i f f e r e n t c o n d i t i o n s f o r a s s y m e t r i c a l s i m u l t a n e o u s t a s k s .
In t h i s t a s k t h e r e w a s n ' t a n y a p p a r e n t m e n t a l l o a d i n t e r m s o f
b i t s o r n u m b e r o f c h o i c e s i n v o l v e d , a n d H R V I s e e m e d to b e a f a i r
i n d i c a t o r of t h e l e v e l o f c o n c e n t r a t i o n r e q u i r e d f o r e a c h
c o n d i t i o n .
T h e a p p l i c a b i l t y o f H R V as a p h y s i o l o g i c a l v a r i a b l e i n
d e t e r m i n i n g t h e w o r k l o a d i n h e r e n t i n t h e t a s k as w e l l a s i n t h e
e x t e r n a l e n v i r o n m e n t h a s b e e n f a i r l y w e l l d e m o n s t r a t e d a n d
d o c u m e n t e d . T h e T a b l e - 2 . 2 b r i e f l y s u m m a r i z e s s o m e of t h e t a s k s
u s e d i n v a r i o u s s t u d i e s u s i n g H R V a s a p h y s i o l o g i c a l v a r i a b l e .
TABLE 2.2 Summary of T a s k / C o n d i t i o n Used Wi t h HRV in the Literature
Authors Year T a s k / C ondition (s) Comments
Kalsbeek & Ettemma
Kalsbeek & Ettemma
1963
1965
Kalsbeek & Ettemma
Opmeei
1965a
1969
Bonsper
Kalsbeek & Zieluis
Rohmert et al
1970
1971
1973
A u d i t o r y binary choice
reaction task. Ta s k d i f ficulty increased by increasing the n umber of choices per minute.
Hearing a Spanish text read aloud. Liste n i n g to Spanish text by counting the number of times the article 'los' o c c u r r e d .
A u d i t o r y bi n a r y choice task w i t h increasing num b e r of c h o i c e s .
Noise at 80 db.
A u d i t o r y bin a r y choice task at 50% and 80% of subjects m a x i m u m capacity in addition
to dynamic physical load on the biscycle ergonometer.
Information processing task w i t h 1,2,3 & 4 equiprobable a l t e r n a t i v e s .
Aud i t o r y binary choice task w i t h 20, 30, 40 & 50 signals per minute.
(a) Sports-Fencing & Shooting (b) Travelling mail clerk
handling mail bags & sorting letters.
(c) A i r traffic controllers-approaching and center control.
(d) Uni v e r s i t y examin a t i o n s -diploma and doctorol thesis (e) Binary choice task with
varying mental load.________
HRV found to decrease wi t h task difficulty.
HRV was less for the condition which involved
' l i s t e n i n g ' .
H R V decreased by increasing no. of choices. L ower HRV.
HRV decreased m a r g i n a l y w i t h increased dynamic load, for higher mental load though not sensitive enough in conjunction w i t h hi g h levels of
physical load.
HRV decreased wi t h increased mental load.
HRV decreased wi t h increased mental l o a d .
H R V generally decreased with these activities
cont'd
TABLE 2.2 cont'd
Authors Year
Boyce 1974
Luczak 1979
Kitchen et al.
1980
|Weber
et al 1980
(Sharit & jSaivendy
1982
Task/Condition (s)
Mental Arithmetic- 2 single digits presented every second over the headphone. Subject required to add the digits and respond with a stylus. Physical load varied by adding weight from 0.2 to 1. kg to stylus.
(a) Auditory binary choice task with signals presented at different rates wi t h and without defined physical movements
involving hand, hand & arm and hand, arm & upper part of body.
(b) Multiple choice reaction task with task difficulty increased wi t h increased no. of alternatives
Auditory mental task. Subject listened to pre recorded digits through heaphones and required to respond to specific odd-even -odd sequence.
Four repetitive tasks.
(a) Simple m o t o r task-filling a box with ball bearings. (b) Discrimination
task-discriminate between two ball bearings sizes.
(c) Counting task- count ball bearings in specific lots.
(d) Counting and discrimination-} of ball bearings.
Two m a i n types of task namely self paced and machine paced involving two types of inform ation processing namely Internal] and external environments.
Comments
HRV significant with physical as well as mental
load (alpha=0.05) Interactions were found to be
insignificant.
H RV was found to be be lower for both conditions of physical load. The correlation between informa tion load & HRV higher w i t h mental l o a d .
HRV decreased with increased task difficulty. Motor load did not affect the HRV.
HRV decreased
with task difficulty.
HRV higher with in task without discrimination i.e.,(a) & (c) than with discrimination i.e. (b) & (d).
HRV found to sensitive to to pacing con d i t i o n s . MHR more sensi -tive to type of processing.
