UBC Theses and Dissertations

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UBC Theses and Dissertations

Location of clicks in short temporal intervals Cameron, Norman David 1971

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THE LOCATION OF CLICKS IN SHORT TEMPORAL INTERVALS by NORMAN DAVID CAMERON B . S c , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1965 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n t h e DEPARTMENT OF PSYCHOLOGY We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA J u l y , 1971 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my Department o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Depa rtment The U n i v e r s i t y o f B r i t i s h C o l umbia V a n c o u v e r 8, Canada A b s t r a c t Two e x p e r i m e n t s examined t h e a b i l i t y o f s u b j e c t s t o l o c a t e c l i c k s o c c u p y i n g v a r i o u s p o s i t i o n s i n u n s t r u c t u r e d 2, 4, and 6 s e c . i n t e r v a l s o f t i m e . In E x p e r i m e n t I, i t was found t h a t t h e e f f e c t s on t h e s u b j e c t i v e l o c a t i o n o f t h e c l i c k o f t h e e x p e r i m e n t a l f a c t o r s o f i n t e r v a l f i l l i n g , i n t e r v a l d u r a t i o n , c l i c k p o s i t i o n , and d a i l y t e s t i n g s e s s i o n s , were t o m o d i f y u n d e r l y i n g r e s p o n s e t e n d e n c i e s . The a p p a r e n t r e s p o n s e t e n d e n c i e s were a c e n t r a l tendency and a r i g h t b i a s . E x p e r i m e n t I I i n v e s t i g a t e d t h e h y p o t h e s i s t h a t t h e r i g h t b i a s r e s u l t e d from t h e s u b j e c t i v e a s s o c i a t i o n o f d i f f e r e n t i a l amounts o f mental c o n t e n t w i t h t h e d u r a t i o n s p r e c e d i n g and f o l l o w i n g t h e c l i c k . The r e s u l t s d i d not s u p p o r t t h e h y p o t h e s i s b u t d i d s u g g e s t t h a t t h e r i g h t b i a s r e s u l t e d from t h e m i s p e r c e p t i o n o f t h e l o c a t i o n o f t h e c l i c k by a c o n s t a n t amount o f t i m e r e g a r d l e s s o f t h e o b j e c t i v e p o s i t i o n o f t h e c l i c k w i t h i n t h e i n t e r v a l . An a l t e r n a t e h y p o t h e s i s based upon t h e p e r c e p t i o n o f t h e c l i c k as h a v i n g an a p p r e c i a b l e d u r a t i o n was proposed t o a c c o u n t f o r t h e r i g h t b i a s . I i T a b l e o f C o n t e n t s A b s t r a c t 1 L i s t o f T a b l e s * * 1 i v L i s t o f F i g u r e s Acknowledgement I n t r o d u c t i o n ' E x p e r i m e n t I Method • 16 18 ResuIts t . . . . . 26 D i s c u s s i o n ' • E x p e r i m e n t H » 3 ' Method 3 3 34 R e s u l t s 42 D i s c u s s ton . . . . 47 R e f e r e n c e s • 72 A p p n d ii i I L i s t o f Tab I es T a b l e I P o s s i b l e C l i c k P o s i t i o n s f o r Each o f Three D u r a t i o n s . . . . . 52 T a b l e 2 A n a l y s i s o f V a r i a n c e Summary T a b l e : Magnitude o f E r r o r . E x p e r i m e n t I 53 T a b l e 3 D i r e c t i o n and Magnitude i n l O t h s o f a Second o f t h e Mean E r r o r s t o t h e 30 B a s i c I n t e r v a l s . E x p e r i m e n t I 54 T a b l e 4 A n a l y s i s o f V a r i a n c e Summary T a b l e : P e , r . E x p e r i m e n t I 55 T a b l e 5 P e , r f o r t h e 30 B a s i c I n t e r v a l s . E x p e r i m e n t I . . 56 T a b l e 6 A n a l y s i s o f V a r i a n c e Summary T a b l e : Magnitude o f E r r o r . E x p e r i m e n t II 57 T a b l e 7 D i r e c t i o n and Magnitude i n l O t h s o f a Second of t h e Mean E r r o r s t o t h e 30 B a s i c I n t e r v a l s . E x p e r i m e n t II 53 T a b l e 8 A n a l y s i s o f V a r i a n c e Summary T a b l e : P e , r . E x p e r i m e n t II 59 T a b l e 9 P e , r f o r t h e 30 B a s i c I n t e r v a l s . E x p e r i m e n t II . . 60 T a b l e 10 A n a l y s i s o f V a r i a n c e Summary T a b l e : D u r a t i o n E s t i m a t e s . E x p e r i m e n t II . . . . 61 L i s t o f F i g u r e s F i g u r e I E f f e c t o f c l i c k p o s i t i o n on s u b j e c t i v e l o c a t i o n o f t h e c l i c k , (a) Average p e r c e i v e d c l i c k p o s i t i o n i n r e l a t i o n t o a c t u a l c l i c k p o s i t i o n ; (b) Magnitude o f e r r o r i n l O t h s of a second 62 F i g u r e 2 F i l l i n g x d u r a t i o n i n t e r a c t i o n 63 F i g u r e 3 E f f e c t o f c l i c k p o s i t i o n on p r o p o r t i o n of e r r o r s t o t h e r i g h t ( P e , r ) 64 F i g u r e 4 Decrease i n P e , r a c r o s s c l i c k p o s i t i o n s f o r t h r e e d u r a t i o n s 65 F i g u r e 5 Response tendency o f "sub I imina I s u b j e c t s . . . 66 F i g u r e 6 Development o f p o s i t i v e t i m e - e r r o r a c r o s s s e s s i o n s 67 F i g u r e 7 M a gnitude o f e r r o r , (a) F i l l i n g x c l i c k p o s i t i o n s ; (b) D u r a t i o n x c l i c k p o s i t i o n s . . . 68 F i g u r e 8 E f f e c t o f c l i c k p o s i t i o n on magnitude of d u r a t i o n e s t i m a t e s . . . . 69 F i g u r e 9 D u r a t i o n e s t i m a t e z - s c o r e s a v e r a g e d a c r o s s s u b j e c t s a t each c l i c k p o s i t i o n f o r each of t h r e e c a t e g o r i e s of c l i c k l o c a t i o n r e s p o n s e . . 70 F i g u r e 10 Average p e r c e i v e d c l i c k p o s i t i o n s f o r 30 b a s i c i n t e r v a l s . E x p e r i m e n t I , above t h e r e s p o n s e l i n e ; E x p e r i m e n t I I , below the r e s p o n s e l i n e . (Response l i n e 2x a c t u a l l e n g t h 71 AcknowIedgment The i u t h o r would l i k e t o exp.ess h i s g r a t i t u d e t o Dr. A r t h u r Reber f o r h i s i d e a s and encouragement. The h e l p f u l s u g g e s t i o n s and c r i t i c i s m s o f Dr. M i c h a e l Humphreys a r e a l s o g r a t e f u l l y acknowledged. In a d d i t i o n , t h e a u t h o r would l i k e t o t h a n k J o e Young f o r c r e a t i n g t h e o r i g i n a l s t i m u l u s m a t e r i a l s and C a r o l e K i n g f o r h e r c a r e f u l t y p i n g o f t h e m a n u s c r i p t . F i n a l l y , t h e a u t h o r would l i k e t o thank h i s w i f e , Annabel I e , f o r h e r i n v a l u a b l e h e l p i n s c o r i n g and r e s c o r i n g d a t a , and f o r h e r p a t i e n c e and encouragement. The r e s e a r c h r e p o r t e d i n t h e p r e s e n t paper was s u p p o r t e d i n p a r t by NRC g r a n t 337. T h i s paper p r e s e n t s two e x p e r i m e n t s which i n v e s t i g a t e d t h e a b i l i t y o f human s u b j e c t s t o l o c a t e a u d i t o r y s t i m u l i In s h o r t I n t e r v a l s o f t i m e . The problem and t h e methodology f o r t h e s e e x p e r i m e n t s were o r i g i n a l l y d e r i v e d from a s e r i e s o f s t u d i e s e x p l o r i n g t h e p s y c h o l o g i c a l 1 r e a l i t y o f grammar ( c l i c k s t u d i e s ) and n o t , as m i g h t be e x p e c t e d , from t h e l a r g e body o f l i t e r a t u r e on t i m e p e r c e p t i o n . The s t u d i e s o f grammar, however, were o n l y a p o i n t o f d e p a r t u r e , t h e e x p e r i m e n t s were c o n c e r n e d , n o t w i t h grammar b u t w i t h temporal l o c a t i o n and t h e p r o b l e m and r e s u l t s were I n t e r p r e t e d w i t h i n t h e c o n c e p t u a l framework o f t i m e p e r c e p t i o n . T h i s b e i n g t h e c a s e , t h e f o l l o w i n g r e v i e w w i l l c o n c e n t r a t e on r e l e v a n t a r e a s o f t h e t i m e p e r c e p t i o n l i t e r a t u r e . D i s c u s s i o n o f s t u d i e s on t h e p s y c h o l o g i c a l r e a l i t y of grammar w i l l be l i m i t e d t o t h e e x t e n t n e c e s s a r y t o d e m o n s t r a t e t h e c o n n e c t i o n between c l i c k s t u d i e s and t i m e p e r c e p t i o n . A c h a r a c t e r i s t i c o f t h e human an i m a l I s t o be c o n s c i o u s o f t h e passage o f t i m e . Each i n d i v i d u a l i s a b l e t o o r g a n i z e t h e e v e n t s t h a t mark h i s e x i s t e n c e i n t o a t e m p o r a l s e r i e s and from t h i s s e r i e s t o d e t e r m i n e , w i t h v a r y i n g degrees o f p r e c i s i o n , how long some e v e n t o r p e r i o d l a s t e d , o r whether one e v e n t preceded o r f o l l o w e d a n o t h e r e v e n t , o r how much t i m e s e p a r a t e d one e v e n t from a n o t h e r . We a r e a l l f a m i l i a r w i t h t h e e x p e r i e n c e o f t i m e but what e x a c t l y do we e x p e r i e n c e and w i t h what do we e x p e r i e n c e i t ? Time has no o b v i o u s p h y s i c a l b a s i s l i k e t h e l i g h t waves o f s i g h t o r t h e a i r b o r n e p a r t i c l e s o f s m e l l and t h e r e Is no o b v i o u s o r g a n o f t i m e a n a l o g o u s t o t h e eyes o r t h e nose. The a p p a r e n t absence o f an e x t e r n a l o r g a n prompted p h i l o s o p h e r s and p s y c h o l o g i s t s t o s e a r c h f o r an I n t e r n a l mechanism o r p r o c e s s t h a t would e x p l a i n t i m e e x p e r i e n c e . Most p h i l o s o p h i c a l i n q u i r i e s i n t o t i m e a r e o f i n t e r e s t s o l e l y f o r t h e i n s i g h t t h e y g i v e I n t o t h e systems o f t h e i r p r o p o n e n t s b u t a few p h i l o s o p h e r s have made s u g g e s t i o n s w i t h p s y c h o l o g i c a l r e l e v a n c e . A r i s t o t l e ( F r a s e r , 1966) s p e c u l a t e d t h a t ". . . I f any movement t a k e s p l a c e i n t h e mind we suppose t h a t some t i m e has e l a p s e d , and t h e t i m e t h a t has passed i s always t h o u g h t t o be i n p r o p o r t i o n t o t h e movement." John Locke (1959) c l e a r l y adumbrated modern t h e o r i e s o f t i m e when he c l a s s i f i e d t i m e p e r c e p t i o n as p a r t s e n s a t i o n and p a r t r e t e n t i o n . The e a r l y e x p e r i m e n t a l i n v e s t i g a t i o n o f t i m e ( N i c h o l s , 1890) c o n c e n t r a t e d on whether o r not i t was s u b j e c t t o Webers' Law. Data a c c u m u l a t e d on t h i s p roblem d u r i n g t h e f i r s t h a l f o f t h e p r e s e n t c e n t u r y ( B l a k e l y , 1933; Henry, 1948; S t o t t , 1933; Woodrow, 1930) u n t i l Woodrow (1951) was a b l e t o c o n c l u d e t h a t one o f t h e few t h i n g s known w i t h r e a s o n a b l e c e r t a i n t y about t i m e p e r c e p t i o n was t h a t , f o r s h o r t I n t e r v a l s a t l e a s t , Weber's Law d i d not h o l d . In t h e i r s e a r c h f o r t h e Weber f r a c t i o n f o r t i m e , most o f t h e e a r l y w o r k e r s proceeded on t h e a s s u m p t i o n t h a t t h e r e was a t i m e sense i n some way a n a l o g o u s t o t h e o t h e r s e n s e s . W i l l i am James (1890) had argued t h a t t h e i d e a o f a s p e c i a l t i m e s e n s e was as u n t e n a b l e as t h e i d e a o f a s p e c i a l space sense., but t h e main t h r u s t o f t h e o r y and e x p e r i m e n t a t i o n remained d i r e c t e d towards d e s c r i b i n g and/or d i s c o v e r i n g t h e t i m e s e n s e . V i e r o r d t ( 1 8 6 8 ) , a f t e r g a t h e r i n g e s t i m a t e s o f i n t e r v a l s r a n g i n g from 0.25 t o 8.0 seconds i n l e n g t h , s t a t e d t h e p r i n c i p l e t h a t " . . . o v e r -e s t i m a t i o n i s a s s o c i a t e d w i t h s h o r t i n t e r v a l s o f t i m e and u n d e r e s t i m a t i o n w i t h l o n g i n t e r v a l s . " The p r i n c i p l e i m p l i e d t h a t t h e r e was a p o i n t where o v e r e s t i m a t i o n changed t o u n d e r e s t i m a t i o n , t h a t i s , t h e r e was some i n t e r v a l where s u b j e c t i v e t i m e c o i n c i d e d w i t h t h e ' r e a l ' t i m e o f c l o c k s . V i e r o r d t c a l l e d i t t h e " i n d i f f e r e n c e i n t e r v a l " and t h e s e a r c h f o r i t has o c c u p i e d a g r e a t number o f r e s e a r c h e r s . The most commonly r e p o r t e d v a l u e s f o r t h e i n d i f f e r e n c e i n t e r v a l a r e from 0.6 t o 0.3 seconds ( F r a i s s e , 1963) but t h e range e x t e n d s from under 0.36 t o o v e r 5.0 seconds (Woodrow, 1951). A number o f r e v i e w e r s ( M c K e l l a r , 1968; Woodrow, 1951) s u g g e s t t h a t p e o p l e b u i l d up frames o f r e f e r e n c e depending upon t h e range of i n t e r v a l s t o which they a r e exposed. M c K e l l a r c o n c l u d e d t h a t t h e whole s e a r c h f o r an i n d i f f e r e n c e i n t e r v a l had been a waste o f t i m e . F r a i s s e (1963, p. 116-118), however, m a i n t a i n e d t h a t i t was a l e g i t i m a t e c o n c e p t . S t a r t i n g from a f i n d i n g by G a s t a u t (1949) t h a t a l i g h t s t i m u l u s caused a c o r t i c a l p o t e n t i a l t h a t l a s t e d 0.5 t o 0.6 s e c o n d s , F r a i s s e argued t h a t t h e o n s e t o f an i n t e r v a l caused a comparable p o t e n t i a l and i f t h e o f f s e t o c c u r s b e f o r e t h e p o t e n t i a l f o r t h e o n s e t has s u b s i d e d , an e f f o r t i s r e q u i r e d t o p e r c e i v e an i n t e r v a l a t a l l . I t i s t h e e f f o r t i n v o l v e d which c a u s e s t h e o v e r e s t i m a t i o n . In l o n g e r i n t e r v a l s , i f t h e o f f s e t o c c u r s more th a n a few t e n t h s o f a second a f t e r t h e o n s e t p o t e n t i a l has s u b s i d e d , an e f f o r t i s r e q u i r e d t o a s s o c i a t e t h e p a s t and t h e p r e s e n t b u t i n t h i s c a s e t h e e f f o r t c a u s e s u n d e r e s t i m a t i o n . The f i r s t p a r t o f t h e argument i s i n t e r e s t i n g b u t on t h e whole i t i s unconvi n c i ng. The supposed e x i s t e n c e o f an i n d i f f e r e n c e i n t e r v a l s u g g e s t e d t o many t h e o r i s t s t h a t t h e p o i n t o f c o r r e s p o n d e n c e between s u b j e c t i v e and o b j e c t i v e t i m e r e p r e s e n t e d t h e p e r i o d o f some p h y s i o l o g i c a l rhythm and t h a t t h e t i m e sense e x i s t e d i n t h e form o f a b i o l o g i c a l c l o c k . In t h e s e a r c h f o r t h e b i o l o g i c a l c l o c k a l m o s t e v e r y r h y t h m i c a l b o d i l y p r o c e s s has had i t s p r o p o n e n t s . A f t e r o b s e r v i n g t h e e f f e c t o f a f e v e r on h i s w i f e ' s a b i l i t y t o j u d g e d u r a t i o n s , Hoagland (1933) r e p o r t e d t h a t t h e t i m e sense was dependent upon body t e m p e r a t u r e . He proposed b r a i n m e t a b o l i s m as t h e c l o c k and argued t h a t as t h e f e v e r i n c r e a s e d t h e r a t e o f m e t a b o l i s m i n h i s w i f e ' s b r a i n , h e r s u b j e c t i v e t i m e u n i t s s h o r t e n e d . O t h e r s u g g e s t i o n s have been: h e a r t b e a t ( r e p o r t e d i n Woodrow, 1951), EEG ( H o l u b a r , 1969), r e v e r b e r a t i n g n e u r a l c i r c u i t s ( C r e elman, 1962), and an u n d e f i n e d n e u r a l p u l s e g e n e r a t o r ( T r i e s m a n , 1963). The whole i d e a was c a r r i e d t o i t s l o g i c a l extreme by Gooddy (1966) who proposed t h a t a l l o f t h e p e r i o d i c and q u a s i - p e r i o d i c rhythms o f t h e human o r g a n i s m combined t o form t h e c l o c k . E v i d e n c e a g a i n s t m e t a b o l i c c l o c k s was r e p o r t e d by B e l l ( 1 9 6 5 ) . He found no d i f f e r e n c e i n t i m e e s t i m a t e s when he r a i s e d body t e m p e r a t u r e a r t i f i c i a l l y . Ochberg, P o l l a c k , and Meyer (1964) found no c o r r e l a t i o n between p u l s e r a t e and t i m e judgements, and a c o m p r e h e n s i v e i n v e s t i g a t i o n o f b i o l o g i c a l c l o c k s by Cahoon (1969) found no s i g n i f i c a n t r e l a t i o n s h i p between t i m e e s t i m a t e s and h e a r t r a t e , r e s p i r a t i o n r a t e , a l p h a r a t e , o r i n t e g r a t e d EEG a c t i v i t y . I f t h e i n d i f f e r e n c e i n t e r v a l a c t u a l l y does c o r r e s p o n d t o some b i o l o g i c a l rhythm, i t i s r e a s o n a b l e t o e x p e c t p e r i o d i c i n d i f f e r e n c e i n t e r v a l s . T h a t i s , o b j e c t i v e and s u b j e c t i v e t i m e s h o u l d c o r r e s p o n d on e v e r y b e a t o r e v e r y m u l t i p l e o f b e a t s o f t h e b i o l o g i c a l pendulum. E a r l y i n v e s t i g a t o r s d i d r e p o r t p e r i o d i c i n d i f f e r e n c e i n t e r v a l s ( N i c h o l s , 1890) b u t t h e p e r i o d s were a l l d i f f e r e n t and modern i n v e s t i g a t o r s a r e a b l e t o f i n d o n l y a s i n g l e i n d i f f e r e n c e i n t e r v a l . I t seems p o s s i b l e t o c o n c l u d e t h a t a l t h o u g h t h e c o n c e p t of a b i o l o g i c a l c l o c k has g e n e r a t e d a g r e a t deal of r e s e a r c h , i t has not p r o v i d e d a s a t i s f a c t o r y e x p l a n a t i o n o f t i m e e x p e r i e n c e . An e n t i r e l y d i f f e r e n t a p p roach i s e x e m p l i f i e d by t h e work o f F r a n k e n h a e u s e r ( 1 9 5 9 ) . She h y p o t h e s i z e d t h a t an i n d i v i d u a l l e a r n s t o j u d g e t h e a p p r o x i m a t e amount o f mental c o n t e n t t h a t c o r r e s p o n d s t o f a m i l i a r o b j e c t i v e t i m e u n i t s and t h e r e f o r e s u b j e c t i v e t i m e u n i t s a r e s t a n d a r d amounts of mental c o n t e n t . On t h e b a s i s of t h i s a s s u m p t i o n , i t f o l l o w s t h a t t h e e x p e r i e n c e of t i m e i s a f u n c t i o n of a t t e n t i o n , p e r c e p t i o n , and r e t e n t i o n . T hat i s , i f an i n d i v i d u a l pays c l o s e r t h a n normal a t t e n t i o n t o an e v e n t , both t h e amount p e r c e i v e d and t h e amount r e t a i n e d i n memory a r e h i g h , s u b j e c t i v e t i m e u n i t s a r e s h o r t , and t h e d u r a t i o n of t h e e v e n t i s o v e r e s t i m a t e d . A l t h o u g h t h e e x t r a p o l a t i o n t o p e r c e p t i o n and r e t e n t i o n i s seldom made, a number o f s t u d i e s have i n v e s t i g a t e d t h e e f f e c t of a t t e n t i o n on d u r a t i o n e s t i m a t e s . H u l s e r ( 1 9 2 4 ) , Q u a s e b a r t h ( 1 9 2 4 ) , Woodrow ( 1 9 5 1 ) , Von Sturmer 0 9 6 6 ) , and Von S t u r m e r , Wong, and C o l t h e a r t (1.968) a l l c o n c l u d e d t h a t t h e more a t t e n t i o n g i v e n t o t h e t a s k of j u d g i n g d u r a t i o n s , t h e l o n g e r a g i v e n i n t e r v a l i s judged t o be. C o n v e r s e l y , Wundt (1903) and Bokander (1.965) have both r e p o r t e d t h a t t h e f o c u s i n g of a t t e n t i o n l e a d s t o an u n d e r -e s t i m a t i o n o f d u r a t i o n . S i m i l a r l y , a l t h o u g h a t t e n t i o n i s not s p e c i f i e d , u n i n t e r e s t i n g t a s k s a r e j u d g e d as l o n g e r t h a n i n t e r e s t i n g ones ( L o e h l i n , 1959) and s i m p l e t a s k s a r e judged l o n g e r t h a n complex ones ( S m i t h , 1969). I n t e r e s t i n g l y enough, F r a n k e n h a e u s e r (1959) h e r s e l f r e p o r t s t h a t t h e s u b j e c t i v e l e n g t h e n i n g of i n t e r v a l s f i l l e d w i t h s i m p l e o r b o r i n g t a s k s i s a w ell-known phenomenon. She s u g g e s t s t h a t a n t i c i p a t i o n , o r t h e a c t i v e a t t e n d i n g t o t h e passage o f t i m e , i s a c o n c o m i t a n t o f boredom and g r e a t l y i n c r e a s e s t h e c o g n i t i v e c o n t e n t of an i n t e r v a l . O r n s t e i n (1969) e l a b o r a t e d on t h i s e x p l a n t i o n when he s t a t e d t h a t e x p e c t a n c y l e a d s t o an i n c r e a s e d s e n s i t i v i t y t o s t i m u l i . Whether t h e c o n t r o v e r s y o v e r t h e e f f e c t o f a t t e n t i o n can be c o n s i d e r e d r e s o l v e d o r n o t , F r a n k e n h a e u s e r ' s s e r i e s of e x p e r i m e n t s a p p a r e n t l y d e m o n s t r a t e d d i r e c t r e l a t i o n s h i p s between amount o f a t t e n t i o n , amount p e r c e i v e d , amount r e t a i n e d , and judgements of d u r a t i o n . She c o n c l u d e d t h a t memory i s an i n h e r e n t c h a r a c t e r i s t i c o f t i m e e x p e r i e n c e and t h e magnitude o f remembered d u r a t i o n depends upon t h e amount o f mental c o n t e n t a s s o c i a t e d w i t h an o b j e c t i v e t i m e u n i t . O r n s t e i n (1969) a g r e e s w i t h F r a n k e n h a e u s e r ' s p o s i t i o n b u t doas not t h i n k h e r t h e o r y goes f a r enough. He s u g g e s t s t h a t t h e economy w i t h which t h e i n p u t i s coded d e t e r m i n e s d u r a t i o n judgements. T h a t i s , i f a g r e a t d e a l o f i n p u t can be coded i n t o a few " b i t s " t h e d u r a t i o n a s s o c i a t e d w i t h t h a t i n p u t i s p e r c e i v e d as s h o r t . In a t y p i c a l e x p e r i -ment, O r n s t e i n ' s s u b j e c t s a t t e n d e d t o a complex s t i m u l i f o r a p e r i o d o f t i m e and t h e n some o f t h e s u b j e c t s were g i v e n a c l u e o r s t r a t e g y t h a t e c o n o m i c a l l y o r g a n i z e d t h e s t i m u l u s . The group w i t h t h e recoded i n p u t j udged t h e i n t e r v a l t o bo much s h o r t e r t h a n d i d t h e group t h a t was not g i v e n a r e c o d i n g s t r a t e g y . R e g a r d l e s s o f what f a c e t o f t i m e e x p e r i e n c e a p a r t i c u l a r s t u d y i s i n v e s t i g a t i n g , t h e d a t a c o l l e c t e d a r e u s u a l l y some form o f judgements o f t h e d u r a t i o n o f s h o r t i n t e r v a l s . The l e n g t h o f t h e i n t e r v a l s used i s u s u a l l y i n t h e o r d e r o f seconds o r m i n u t e s . Some p h y s i o l o g i c a l l y o r i e n t e d i n v e s t i g a t o r s p r e f e r t h e t i m e consuming method o f temporal c o n d i t i o n i n g ( H o l u b a r , 1969) but o t h e r w i s e t h e r e a r e f o u r s t a n d a r d methods by which e s t i m a t e s o f s h o r t d u r a t i o n s a r e o b t a i n e d ( W a l l a c e and R a b i n , I 9 6 0 ) . 1) V e r b a l e s t i m a t i o n — a n i n t e r v a l i s d e l i m i t e d o p e r a t i v e Iy by t h e e x p e r i m e n t o r and t h e s u b j e c t v e r b a l l y i n d i c a t e s t h e d u r a t i o n o f t h e i n t e r v a l . If t h e s u b j e c t o v e r e s t i m a t e s , i t i s i n t e r p r e t e d t o mean h i s s u b j e c t i v e temporal u n i t s a r e s m a l l e r t h a n o b j e c t i v e t e mporal u n i t s . 2) P r o d u c t i o n — t h e e x p e r i m e n t o r s t a t e s a d u r a t i o n v e r b a l l y i n o b j e c t i v e u n i t s and t h e s u b j e c t p r o d u ces an i n t e r v a l . I f t h e s u b j e c t o v e r e s t i m a t e s , t h a t i s , produces an i n t e r v a l l o n g e r i n o b j e c t i v e u n i t s t h a n t h e one asked f o r , i t i n d i c a t e s t h a t h i s s u b j e c t i v e temporal u n i t s a r e l o n g e r t h a n o b j e c t i v e ones. 3) R e p r o d u c t i o n — t h e e x p e r i m e n t o r o p e r a t i v e Iy produces an i n t e r v a l and t h e s u b j e c t a t t e m p t s t o r e p r o d u c e i t . In t h i s i n s t a n c e t h e terms o v e r -and u n d e r e s t i m a t i o n a r e m e a n i n g l e s s . The t a s k r e q u i r e d o f t h e s u b j e c t i s comparable t o v e r b a l e s t i m a t i o n and p r o d u c t i o n i n sequence. The s u b j e c t must f i r s t make an e s t i m a t e o f t h e i n t e r v a l p r e s e n t e d by t h e e x p e r f m e n t o r and t h e n produce an i n t e r v a l c o r r e s p o n d i n g t o t h a t e s t i m a t e . I f t h e r e a r e e r r o r s , i t i s i m p o s s i b l e t o d e t e r m i n e i f th e y were made i n t h e i n i t i a l e s t i m a t i o n , i n t h e p r o d u c t i o n , o r as i s most p r o b a b l e , a t both s t a g e s . 4) C o m p a r i s o n — t h e e x p e r i m e n t e r produces two i n t e r v a l s and t h e s u b j e c t must j u d g e t h e i r r e l a t i v e d u r a t i o n s . As w i t h t h e method of r e p r o d u c t i o n , t h e terms o v e r e s t i m a t i o n and u n d e r e s t i m a t i o n a r e ambiguous. If one i n t e r v a l i s ju d g e d t o be l o n g e r t h a n t h e o t h e r i n t e r v a l when th e y a r e i n f a c t o b j e c t i v e l y e q u a l , i t i s d i f f i c u l t t o d e c i d e whether t h e one was o v e r e s t i m a t e d o r t h e o t h e r u n d e r e s t i m a t e d . I t i s common i n t h e l i t e r a t u r e f o r r e s u l t s o b t a i n e d by one method t o be compared t o r e s u l t s o b t a i n e d w i t h o t h e r methods. T h i s p r a c t i c e i s c r i t i c i z e d because o f t h e l a c k o f knowledge about t h e e q u i v a l e n c e o f t h e methods ( G r a n t , 1967; M c K e l l a r , 1968). B i n d r a and Waksberg (1956) a t t e m p t e d t o engender t e r m i n o l o g i c a l e q u i v a l e n c e between methods but a number o f s t u d i e s ( C a r l s o n and F i n e b e r g , 1968; C l a u s e n , 1950; H o r n s t e i n and R o t t e r , 1969) have found t h a t f o r t h e methods o f v e r b a l e s t i m a t i o n , p r o d u c t i o n , and r e p r o d u c t i o n , t h e r e i s v e r y l i t t l e e q u i v a l e n c e between t h e d u r a t i o n e s t i m a t e s . For t h e t h r e e methods where an i n t e r v a l i s produced by t h e e x p e r i -mentor, v e r b a l e s t i m a t i o n , r e p r o d u c t i o n , and c o m p a r i s o n , t h e i n t e r v a l can be d e s c r i b e d as b e i n g e i t h e r empty o r f i l l e d . I f an i n t e r v a l i s empty, i t i s a p e r i o d of s i l e n c e 'with i t s l i m i t s marked by two c l i c k s , s h o r t t o n e s , o r f l a s h e s o f l i g h t . A t y p i c a l f i l l e d i n t e r v a l i s d e l i m i t e d by t h e o n s e t and o f f s e t o f a c o n t i n u o u s sound b u t i n t e r v a l s may be f i l l e d w i t h words, m u s i c , f l a s h i n g l i g h t s , e t c . ( L o e h l i n , 1959). Meumann (1896) r e p o r t e d t h a t f i l l e d i n t e r v a l s were p e r c e i v e d as l o n g e r t h a n empty ones. C l a u s e n ( 1 9 5 0 ) . however, r e p o r t e d t h a t t h e r e was no d i f f e r e n c e between t h e two t y p e s o f i n t e r v a l . S t u d i e s e m p l o y i n g t h e method of c o m p a r i s o n i n v a r i a b l y r e p o r t a phenomenon termed t h e t i m e - o r d e r - e r r o r o r s i m p l y t h e t i m e - e r r o r . . An e x p e r i m e n t by K o h l e r (1923) r e s u l t e d i n t h e f o l l o w i n g g e n e r a l i z a t i o n s a b o u t t i m e - e r r o r : I) i f t h e i n t e r s t i m u l u s i n t e r v a l C1-31 ) between two i n t e r v a l s t o be compared i s l e s s t h a n 3 seconds., t h e second i n t e r v a l i s j u dged s h o r t e r and t h e t i m e - e r r o r i s p o s i t i v e . 2) i f t h e 151 i s a p p r o x i m a t e l y 3 seconds t h e r e i s no t i m e - e r r o r . 3) as t h e ISI i s i n c r e a s e d from 3 t o 12 seconds t h e t i m e - e r r o r becomes i n c r e a s i n g l y n e g a t i v e and t h e second i n t e r v a l i s judged l o n g e r . K o h l e r found t h a t w i t h r e p e t i t i o n , t h e p o s i t i v e e r r o r d e c r e a s e d . He s u g g e s t e d t h a t t h e n e g a t i v e t i m e - e r r o r r e s u l t e d from t h e t r a c e o f t h e f i r s t i n t e r v a l f a d i n g w i t h t i m e b u t was u n a b l e t o p r o v i d e a s a t i s f a c t o r y e x p l a n a t i o n o f p o s i t i v e t i m e - e r r o r . Needham (1934) r e p o r t e d t h a t o v e r s u c c e s s i v e days o f e x p e r i m e n t a t i o n , t h e p o s i t i v e t i m e - e r r o r f i r s t d e c r e a s e d as i t had i n K o h l e r ' s s t u d y but t h e n began t o i n c r e a s e . In one s t u d y , Postman (1946) found r e s u l t s e x a c t l y comparable t o K o h l e r ' s b u t i n a l a t e r s t u d y (Postman, 1947) found a p o s i t i v e t i m e - e r r o r r e g a r d l e s s o f t h e I S I . S t o t t (1935) used a c o n s t a n t ISI o f 1.5 seconds and compared i n t e r v a l s o f l e n g t h s r a n g i n g from 0.2 t o 36.0 s e c o n d s . The second i n t e r v a l c o u l d be a maximum o f 201 s h o r t e r o r l o n g e r t h a n t h e f i r s t i n t e r v a l . He c o n c l u d e d t h a t t h e d i r e c t i o n o f t h e t i m e - e r r o r depended upon t h e l e n g t h s o f t h e i n t e r v a l s compared; i f l e s s t h a n 1.67 seconds t h e y were c h a r a c t e r i z e d by p o s i t i v e t i m e - e r r o r and i f t h e y were both g r e a t e r t h a n 1.67 s e c o n d s , by n e g a t i v e t i m e - e r r o r . A f t e r r e v i e w i n g t h e t i m e - e r r o r l i t e r a t u r e , P l u t c h i k and S c h w a r t z (1963) r e p o r t e d t h a t t h e t i m e - e r r o r can be a s c r i b e d t o such f a c t o r s as t h e t i m e between t h e two i n t e r v a l s , i n t e r p o l a t e d s t i m u l i , method of s t i m u l u s p r e s e n t a t i o n , and i n d i v i d u a l d i f f e r e n c e s . They c o n c l u d e d t h a t t h e d a t a on t i m e - e r r o r s i s i n c o n s i s t e n t and t h e t h e o r i e s t o e x p l a i n i t a r e vague. The g e n e r a l o p i n i o n o f t i m e - e r r o r a p p ears t o be t h a t t h e s u c c e s s i o n of s t i m u l i i n t r o d u c e s a d i s t o r t i o n i n t o t h e r e l e v a n t judgements; a d i s t o r t i o n t h a t c o u l d be removed w i t h t h e c o r r e c t methodology (Bjorkman and H o l m k v i s t , I 9 6 0 ) . F r a n k e n h a e u s e r ( 1 9 5 9 ) , however, has s u g g e s t e d t h a t s u c c e s s i o n i s i n h e r e n t i n t h e e x p e r i e n c e of t i m e and r a t h e r t h a n t h i n k i n g o f t i m e - e r r o r as an e r r o r , i t s h o u l d be i n v e s t i g a t e d as one of t h e i m p o r t a n t phenomena of t i m e p e r c e p t i o n . TemporaI L o c a t i o n and C I i c k S t u d i e s There i s a c o n s i d e r a b l e body o f e v i d e n c e ( r e v i e w e d by F r a i s s e , 1963) d e m o n s t r a t i n g t h e a b i l i t y o f i n d i v i d u a l s t o o r d e r memories i n t o t h e t e m poral sequence i n which t h e e v e n t s t h e y r e p r e s e n t a c t u a l l y o c c u r r e d , but t h e r e has been l i t t l e , i f any, d i r e c t i n v e s t i g a t i o n o f t h e a c c u r a c y w i t h which an i n d i v i d u a l i s a b l e t o l o c a t e an e v e n t i n terms of i t s r e l a t i v e t e m poral p r o x i m i t y t o a d j a c e n t e v e n t s i n a sequence. G i v e n t h r e e e v e n t s , A, B, and C such t h a t A and C a r e s e p a r a t e d by some i n t e r v a l o f t i m e and B f o l l o w s A and p r e c e d e s C, how a c c u r a t e l y can B be l o c a t e d w i t h r e s p e c t t o A and C? Guyau (1902) o b s e r v e d t h a t " H e a r i n g o n l y l o c a t e s s t i m u l i v e r y v a g u e l y i n s p a c e , b u t i t l o c a t e s them w i t h a d m i r a b l e p r e c i s i o n i n t i m e " b u t he d i d n o t e l a b o r a t e upon what he meant by p r e c i s i o n . P r e c i s e t e mporal l o c a t i o n o f a s t i m u l u s r e q u i r e s a q u a n t i t a t i v e judgement of t h e r e l a t i v e d u r a t i o n s of t h e i n t e r v a l s s e p a r a t i n g t h e s t i m u l u s from t h e e v e n t s on e i t h e r s i d e o f i t . R e p o r t e d l y , v e r y f i n e judgements o f r e l a t i v e d u r a t i o n a r e a p r e r e q u i s i t e o f l i n g u i s t i c meaning i n many languages ( P e t e r s o n and L e h i s t e , I960) so i t i s p r o b a b l e t h a t i n d i v i d u a l s a r e a b l e t o make them. I t i s a p p a r e n t t h a t a s i t u a t i o n r e q u i r i n g c o m p a r a t i v e judgements of t i m e i n t e r v a l s i s , i n many ways, s i m i l a r t o t h e method o f c o m p a r i s o n . In t h e method o f c o m p a r i s o n , however, t h e r e a r e two i n t e r v a l s , AB and CD, which u s u a l l y a r e equal o r d i f f e r by o n l y a s m a l l amount and t h e s u b j e c t i s r e q u i r e d o n l y t o make a q u a l i t a t i v e judgement t o t h e e f f e c t t h a t CD i s e i t h e r l o n g e r o r s h o r t e r t h a n AB. If BC i s t h o u g h t o f as an e v e n t t o be l o c a t e d w i t h r e s p e c t t o A and D, the n such a b i n a r y judgement g i v e s v e r y l i t t l e i n f o r m a t i o n a b out t h e a c c u r a c y o f l o c a t i o n . Any p o s s i b l e c o n c l u s i o n s a b out temporal l o c a t i o n d e r i v a b l e from t h e method o f co m p a r i s o n a r e confounded by t h e f a c t t h a t v a r i a t i o n o f t h e d u r a t i o n and f i l l i n g of i n t e r v a l BC i s a common e x p e r i m e n t a l m a n i p u l a t i o n . T h e r e i s however, an a r e a o f r e s e a r c h d i r e c t l y i n v o l v e d w i t h t h e s u b j e c t i v e l o c a t i o n o f s t i m u l i w i t h i n i n t e r v a l s . The e x p e r i m e n t s a r e c a l l e d c l i c k s t u d i e s and o s t e n s i b l y t h e y a r e i n v e s t i g a t i n g t h e p s y c h o l o g i c a l r e a l i t y o f grammar. The dependent v a r i a b l e i n c l i c k s t u d i e s i s t h e s u b j e c t i v e l o c a t i o n of a s h o r t c l i c k sound superimposed upon an a u d i t o r y message, u s u a l l y a s e n t e n c e . M i g r a t i o n o f t h e c l i c k from i t s o b j e c t i v e p o s i t i o n i s e x p l a i n e d on t h e b a s i s of c h u n k i n g of i n p u t ( L a d e f o g e d and B r o a d b e n t , i 9 6 0 ) , o r more o f t e n as r e s u I t i n g • f r o m t h e c o n s t i t u e n t s t r u c t u r e o f t h e s e n t e n c e ( B e v e r and L a c k n e r , 1969; Fodor and S e v e r , 1965; G a r r e t t , B e v e r , and Fodor, 1965). Fodor and B e v e r (1965) used s e n t e n c e s r a n g i n g i n l e n g t h from 8 t o 22 words and each s e n t e n c e had a s i n g l e c l i c k p l a c e d i n t h e major s y n t a c t i c b r e a k o r i n one of f o u r p o s i t i o n s on e i t h e r s i d e of i t . 80$ of t h e r e s p o n s e s were errors and 56% of t h e e r r o r s were toward t h e c e n t r a l c l i c k p o s i t i o n . In g e n e r a l , c l i c k s p l a c e d b e f o r e t h e major s y n t a c t i c b r e a k were p e r c e i v e d as o c c u r r i n g l a t e r i n t h e s e n t e n c e and c l i c k s p l a c e d a f t e r t h e s y n t a c t i c b reak were p e r c e i v e d as e a r l i e r . As a s u b s i d i a r y r e s u l t , t h e y r e p o r t e d t h a t d u r i n g e a r l y t r i a l s 55.5$ of t h e e r r o r s were t o t h e l e f t o f t h e a c t u a l c l i c k p o s i t i o n but d u r i n g l a t e r t r i a l s o n l y 41% o f t h e e r r o r s were t o t h e l e f t . Ladefoged and B r o a d b e n t (I960) r e p o r t e d a p e r s i s t e n t l e f t b i a s i n a l l c l i c k p o s i t i o n s b u t t h e i r s e r i e s was o n l y 8 t o 10 t r i a l s long and i t i s not c l e a r whether t h e y r e q u i r e d t h e i r s u b j e c t s t o w a i t u n t i l a s e n t e n c e was c o m p l e t e d b e f o r e l o c a t i ng t h e c l i c k . In a major i n v e s t i g a t i o n o f t h e c l i c k m i g r a t i o n phenomenon, Reber and Anderson (1970) used a g r a m m a t i c a l and anomolous word s t r i n g s i n a d d i t i o n t o s e n t e n c e s . A l l word s t r i n g s and s e n t e n c e s were a u n i f o r m 6 words i n l e n g t h and were read w i t h e i t h e r normal o r monotone i n t o n a t i o n . In a c c o r d w i t h Fodor and Bever (1965) t h e y found t h a t c l i c k s tended t o m i g r a t e toward t h e c e n t r a ! c l i c k p o s i t i o n . T h i s m i g r a t i o n , however, was not s y m m e t r i c a l as would be p r e d i c t e d by a c o n s t i t u e n t s t r u c t u r e h y p o t h e s i s , c l i c k s b e f o r e t h e c e n t r a l p o s i t i o n moved f u r t h e r t o t h e r i g h t t h a n c l i c k s a f t e r t h e c e n t r a l p o s i t i o n moved t o t h e l e f t . F u r t h e r m o r e , t h e y found s e m a n t i c s t o be i r r e l e v a n t and s y n t a x t o have o n l y a minor e f f e c t on t h e a c c u r a c y o f c l i c k l o c a t i o n . The f a c t o r s t h a t l a r g e l y d e t e r m i n e d magnitude and d i r e c t i o n of r e s p o n s e e r r o r were c l i c k p o s i t i o n and i n t o n a t i o n . C l i c k s p l a c e d e a r l y i n t h e word s t r i n g were l o c a t e d w i t h l e s s a c c u r a c y t h a n c l i c k s p l a c e d l a t e r and monotone i n t o n a t i o n r e s u l t e d i n g r e a t e r o v e r a l l a c c u r a c y of c l i c k l o c a t i o n and much l e s s s h i f t i n d i r e c t i o n a l b i a s w i t h l a t e r c l i c k p o s i t i o n s than d i d normal i n t o n a t i o n . The i n t o n a t i o n e f f e c t i s c o n f o u n d e d , however, by t h e f a c t t h a t t h e t i m e r e q u i r e d t o read s e n t e n c e s w i t h normal i n t o n a t i o n was o n l y h a l f t h a t r e q u i r e d t o read i n a monotone. They a l s o r e p o r t e d a s i g n i f i c a n t t r i a l s e f f e c t i n which r e s p o n s e s t o e a r l y t r i a l s showed an o v e r a l l l e f t b i a s and r e s p o n s e s t o l a t e r t r i a l s an o v e r a l l r i g h t b i a s . In a f o l l o w - u p e x p e r i m e n t , Reber and Anderson (1970) removed a l l l i n g u i s t i c f a c t o r s and used s i x 370 m i l l i s e c o n d b u r s t s o f w h i t e n o i s e as t h e p r i m a r y message. A g a i n t h e y found a d e c r e a s e i n e r r o r s w i t h l a t e r c l i c k p o s i t i o n s and an a s y m m e t r i c a l m i g r a t i o n o f t h e c l i c k s toward t h e c e n t r a l p o s i t i o n w i t h e a r l y c l i c k s moving more th a n l a t e r ones. In c o n t r a s t t o a I I t h e s t u d i e s u s i n g l i n g u i s t i c messages, t h e n o n I i n g u i s t i c message produced no i n i t i a l r e s p o n s e b i a s t o t h e l e f t but showed a r i g h t b i a s from t h e b e g i n n i n g t h a t d i d n o t change s i g n i f i c a n t l y w i t h l a t e r t r i a l s . The s i m i l a r p a t t e r n s o f r e s p o n s e error r e s u l t i n g from mossaqss d i v e r s e as g r a m m a t i c a l l y c o r r e c t s e n t e n c e s and w h i t e n o i s e prompted Reber and Anderson t o c o n c l u d e t h a t a c c u r a c y o f c l i c k l o c a t i o n depended p r i m a r i l y upon such non I i ngu i s t i c •''actors as memory, a t t e n t i o n , and r e s p o n s e b i a s e s . The Reber and Anderson n 970) n o n I i n g u i s t i c s t u d y was i m p o r t a n t , n o t o n l y because i t d e m o n s J r o ' f e d t h a t e r r o r s i n c l i c k l o c a t i o n d i d not depend upon s e m a n t i c o r s y n t a c t i c f a c t o r s , but a l s o because i t showed t h a t c l i c k . l o c a t i o n d i d not depend upon t h e message b e i n g composed o f words. I t seems o b v i o u s t h a t c l i c k s t u d i e s were based upon t h e t a c i t a s s u m p t i o n t h a t s u b j e c t s would l o c a t e t h e c l i c k by remembering t h e word w i t h which i t was a s s o c i a t e d . As l o n g as t h e message was composed of a s e r i e s o f u n i q u e e l e m e n t s , no p r o c e s s o t h e r t h a n an a s s o c i a t i o n between t h e c l i c k and an element was r e q u i r e d t o l o c a t e t h e c l i c k w i t h i n t h e message. In t h e Reber and Anderson s t u d y , however, t h e e l ements c o m p r i s i n g t h e message were i d e n t i c a l and an a s s o c i a t i o n between t h e c l i c k and an element d i d not s p e c i f y any u n i q u e l o c a t i o n w i t h i n t h e message. I t i s p o s s i b l e , o f c o u r s e , t o propose t h a t Ss gave a u n i q u e name t o each element as t h e message p r o g r e s s e d but t h e r e s u l t s a l s o s u g g e s t t h e a l t e r n a t e p o s s i b i l i t y t h a t t h e s t r u c t u r e of t h e message had l i t t l e o r no b e a r i n g on t h e s u b j e c t i v e l o c a t i o n o f t h e c l i c k . I t may be t h e c a s e t h a t S_s l o c a t e d t h e c l i c k by making q u a n t i t a t i v e judgements of t h e r e l a t i v e d u r a t i o n s s e p a r a t i n g t h e c l i c k from t h e o n s e t and t h e o f f s e t of t h e message and not by a s s o c i a t i n g i t w i t h an unique e l e m e nt. If t h e s u b j e c t s i n c l i c k s t u d i e s a r e l o c a t i n g t h e c l i c k by means of d u r a t i o n judgements, t h e n c l i c k s t u d i e s a r e i n v e s t i g a t i n g an a s p e c t of t i m e p e r c e p t i o n t h a t has a p p a r e n t l y been more o r l e s s i g n o r e d ; temporal l o c a t i o n . I t was mentioned e a r l i e r t h a t t h e c l a s s i c a l t e c h n i q u e which has t h e most r e l e v a n c e t o temporal l o c a t i o n i s t h e method o f c o m p a r i s o n . As a paradigm f o r t h e i n v e s t i g a t i o n o f t e mporal l o c a t i o n , t h e c l i c k s t u d y approach has a number of a d v a n t a g e s o v e r t h e method of c o m p a r i s o n . In t h e f i r s t p l a c e , t h e s t i m u l u s o r e v e n t t o be l o c a t e d i s s i m p l e and s t a n d a r d i z e d . S e c o n d l y , s t i m u l i a r e p l a c e d t h r o u g h o u t t h e i n t e r v a l i n s t e a d of b e i n g r e s t r i c t e d t o t h e immediate v i c i n i t y o f t h e c e n t r a l p o s i t i o n . The t h i r d a dvantage i s a c o n c o m i t a n t o f t h e c o m p arison of d u r a t i o n s t h a t may be o f v e r y d i f f e r e n t l e n g t h s ; t h e magnitude as w e l l as t h e d i r e c t i o n o f t h e e r r o r i s t a k e n i n t o c o n s i d e r a t i o n . The c o n c e p t u a l i z a t i o n o f c l i c k s t u d i e s as temporal l o c a t i o n s t u d i e s makes r e s p o n s e b i a s e s e q u i v a l e n t t o t i m e - e r r o r s . I t was reasoned t h a t an e x p l a n a t i o n of t i m e - e r r o r might be f a c i l i t a t e d by t h e q u a n t i f i c a t i o n p o s s i b l e w i t h t h e c l i c k s t u d y a p p r o a c h . The e x p e r i m e n t s r e p o r t e d below were an i n v e s t i g a t i o n o f t h e s u b j e c t i v e l o c a t i o n o f c l i c k s i n u n s t r u c t u r e d i n t e r v a l s o f t i m e . E x p e r i m e n t I was u n d e r t a k e n , f i r s t , t o d e t e r m i n e i f t h e p a t t e r n s o f e r r o r o b t a i n e d i n u n s t r u c t u r e d i n t e r v a l s were comparable t o t h o s e o c c u r r i n g i n c l i c k s t u d i e s i n g e n e r a l and t h e Reber and Anderson non-l i n g u i s t i c s t u d y i n p a r t i c u l a r . And second , t o e x p l o r e t i m e - e r r o r t hrough a n a l y s i s o f r e s p o n s e b i a s e s under a number of d i f f e r e n t c o n d i t i o n s . The second e x p e r i m e n t was based upon i n t e r p r e t a t i o n o f t h e f i r s t and was c o n c e r n e d w i t h an e x p l a n a t i o n o f r e s p o n s e b i a s e s . E x p e r i m e n t I The p r e s e n t e x p e r i m e n t was based upon t h e Reber and Anderson (1970) n o n l i n g u i s t i c s t u d y a l t h o u g h numerous m o d i f i c a t i o n s were i n s t i t u t e d i n l i n e w i t h t h e e x p e r i m e n t a l aims s t a t e d above. Reber and Anderson used a message composed of a l t e r n a t e p e r i o d s of w h i t e n o i s e and s i l e n c e . In t h i s e x p e r i m e n t t h e i n t e r v a l c o r r e s p o n d i n g t o t h e message was e i t h e r u n i n t e r r u p t e d w h i t e n o i s e o r u n i n t e r r u p t e d s i l e n c e . In t i m e p e r c e p t i o n t e r m s , both f i l l e d and empty i n t e r v a l s were used. In c o n t r a s t t o o t h e r c l i c k s t u d i e s , Reber and Anderson c o n t r o l l e d t h e d u r a t i o n o f t h e i r message but used o n l y a s i n g l e d u r a t i o n o f 2.77 s e c o n d s . They r e p o r t e d a s i g n i f i c a n t d i f f e r e n c e between t h e e r r o r s i n i n t e r v a l s o f a p p r o x i m a t e l y 3.0 seconds and t h o s e i n i n t e r v a l s o f 5.5 seconds i n t h e i r f i r s t l i n g u i s t i c e x p e r i m e n t b u t a t t r i b u t e d i t t o an i n t o n a t i o n f a c t o r . There i s , however, e v i d e n c e from t h e method o f c o m p a r i s o n i n d i c a t i n g t h a t d i r e c t i o n of t h e t i m e - e r r o r i s dependent upon t h e d u r a t i o n o f t h e i n t e r v a l s used ( S t o t t , 1935). The p r e s e n t e x p e r i m e n t , t h e n , used i n t e r v a l s o f t h r e e d i f f e r e n t d u r a t i o n s . Most c l i c k s t u d i e s have r e p o r t e d an o v e r a l l s h i f t i n t h e d u r a t i o n of t h e r e s p o n s e b i a s as t r i a l s p r o g r e s s e d ( F o d o r and B e v e r , 1955; Reber and Anderson l i n g u i s t i c e x p e r i m e n t s , 1970). In a d d i t i o n , s e v e r a l s t u d i e s u s i n g t h e method of c o m p a r i s o n have r e p o r t e d a s h i f t i n t h e d i r e c t i o n of t h e t i m e - e r r o r o v e r t r i a l s ( K o h l e r , 1923; Needharn, 1934; Postman, 1946). Reber and Anderson found no such s h i f t a f t e r 130 t r i a l s p e r s u b j e c t w i t h a nonI i n g u i s t i c message. On t h e e x p e c t a t i o n t h a t t h e e f f e c t may r e q u i r e a g r e a t e r number of t r i a l s , i n t h e p r e s e n t e x p e r i m e n t each s u b j e c t made' 900 r e s p o n s e s o v e r t h r e e days o f t e s t i n g . F o l l o w i n g Reber and A n d e r s o n , a " s u b l i m i n a l " c o n t r o l group was run where s u b j e c t s responded t o n o n e x i s t e n t c l i c k s . The c o n t r o l was t o i n v e s t i g a t e t h e r e s p o n s e d i s t r i b u t i o n which r e s u l t e d from g u e s s i n g . Beyond t h e p r e d i c t i o n t h a t t h e p a t t e r n s o f e r r o r o b t a i n e d would be s i m i l a r t o t h o s e r e p o r t e d by Reber and And e r s o n , t h e p r e s e n t e x p e r i m e n t was m a i n l y e x p l o r a t o r y i n n a t u r e . Method S u b j e c t s . 15 fema l e g r a d u a t e and u n d e r g r a d u a t e s t u d e n t s a t t h e U n i v e r s i t y o f B r i t i s h C o l umbia were r e c r u i t e d from t h o s e on campus d u r i n g t h e i n t e r s e s s i o n a I p e r i o d . They were p a i d $5.00 f o r t a k i n g p a r t i n t h r e e d a i l y l ^ - h o u r s e s s i o n s . Ages ranged from 18 t o 25. Ten s u b j e c t s were run i n t h e e x p e r i m e n t a l group and f i v e i n t h e s u b l i m i n a l c o n t r o l group. M a t e r i a I s . F i l l e d i n t e r v a l s were a p e r i o d o f c o n t i n u o u s w h i t e n o i s e (0-10,000 Hz, u n i f o r m d i s t r i b u t i o n ) . The l i m i t s o f t h e i n t e r v a l were t h e o n s e t and o f f s e t o f t h e w h i t e n o i s e . Empty i n t e r v a l s were an u n i n t e r r u p t e d p e r i o d o f s i l e n c e d e l i m i t e d by two s h o r t 1000 Hz t o n e s . I n t e r v a l s were e i t h e r 2, 4, o r 6 seconds i n l e n g t h . The c l i c k s were .05 m i l l i s e c o n d b u r s t s o f s q u a r e wave n o i s e , a p p r o x i m a t e l y equal i n i n t e n s i t y t o t h e t o n e s . A c l i c k was p l a c e d a t one of f i v e p o s s i b l e p o s i t i o n s i n each i n t e r v a l . The c l i c k p o s i t i o n s f o r each d u r a t i o n a r e i l l u s t r a t e d i n T a b l e I. I n s e r t T a b l e I about hero The w h i t e n o i s e and t h e t o n e s were r e c o r d e d on one channel o f a s t e r e o p h o n i c t a p e r e c o r d e r and t h e c l i c k on t h e second c h a n n e l . By i n d e p e n d e n t l y a l t e r i n g f i l l i n g , d u r a t i o n , and c l i c k p o s i t i o n , 30 b a s i c i n t e r v a l s were p r o d u c e d . Ton r e p l i c a t i o n s o f each i n t e r v a l were randomized i n t o f i v e b l o c k s o f 60 t r i a l s each w i t h t h e c o n s t r a i n t t h a t each i n t e r v a l o c c u r r e d t w i c e i n each b l o c k . The 300 i n t e r v a l s were p l a c e d on a t a p e a p p r o x i m a t e l y 6 seconds a p a r t . D u r i n g a 1.0 m i n u t e b r e a k between t r i a l b l o c k s , s u b j e c t s r e c e i v e d r e c o r d e d i n s t r u c t i o n s t o t u r n t o t h e n e x t page i n t h e i r r e s p o n s e b o o k l e t s . The t a p e was p l a y e d on an Uner Royal d e l u x e s t e r e o p h o n i c t a p e p l a y e r . S u b l i m i n a l s u b j e c t s heard t h e same t a p e as e x p e r i m e n t a l s u b j e c t s b u t w i t h t h e c l i c k channel d i s c o n n e c t e d . F o r t y - f i v e t e s t b o o k l e t s o f f i v e pages each were c o n s t r u c t e d . Each page had 60 numbered h o r i z o n t a l l i n e s 55 m i l l i m e t e r s i n l e n g t h . Each r e s p o n s e l i n e had i t s end p o i n t s marked w i t h v e r t i c a l l i n e s b u t between t h e end p o i n t s t h e r e were no marks o r i n t e r r u p t i o n s (Appendix A ) . P r o c e d u r e . S u b j e c t s were t e s t e d i n d i v i d u a l l y i n a q u i e t , w i n d o w l e s s room which was n o t s o u n d p r o o f e d . I n s t r u c t i o n s were read t o a l l s u b j e c t s i n f o r m i n g them t h a t t h e i r t a s k was t o l o c a t e a c l i c k w i t h i n an i n t e r v a l o f t i m e . The two t y p e s o f i n t e r v a l f i l l i n g were d e s c r i b e d t o them and t h e f o l l o w i n g p o i n t s were emphasized: I) t h a t a c l i c k d i d o c c u r i n e v e r y i n t e r v a l ; 2) t h e i n t e r v a l s were o f v a r i o u s l e n g t h s b u t i n e v e r y c a s e t h e whole l e n g t h o f t h e l i n e r e p r e s e n t e d t h e d u r a t i o n of t h e i n t e r v a l ; 3) they must w a i t u n t i l an i n t e r v a l was co m p l e t e d b e f o r e m a r k i n g t h e c l i c k ; 4) c l i c k s c o u l d o c c u r a t any p o i n t i n t h e i n t e r v a l . The method o f r e s p o n d i n g was d e s c r i b e d and d e m o n s t r a t e d . S u b l i m i n a l s u b j e c t s were t o l d a b o ut e x p e r i m e n t s where " e a t more po p c o r n " was f l a s h e d on t h e s c r e e n d u r i n g a movie a t such speed t h a t nobody was aware of s e e i n g i t but everybody a t e more po p c o r n . They were a s s u r e d t h a t a l t h o u g h t h e y d i d not c o n s c i o u s l y hear t h e c l i c k , t h e r e was a g r e a t e r t h a n chance p r o b a b i l i t y o f them r e s p o n d i n g c o r r e c t l y . None of them q u e s t i o n e d t h e b a s i c r e a l i t y o f s u b l i m i n a l p e r c e p t i o n . B e f o r e t h e a c t u a l e x p e r i m e n t began, a l l s u b j e c t s heard t e n randomly chosen i n t e r v a l s t o a c q u a i n t them w i t h t h e s t i m u l i and w i t h t h e amount of t i m e between t r i a l s . A t t h e c o n c l u s i o n of t h e t h i r d day's t e s t i n g , a l l s u b j e c t s were g i v e n a q u e s t i o n n a i r e (Appendix B) p r o b i n g t h e i r p e r c e p t i o n o f t h e s t i m u l i used and any r e s p o n s e s t r a t e g i e s t h e y might have been aware o f us i ng. R e s u I t s The s u b j e c t s i n t h e e x p e r i m e n t a l group made a t o t a l o f 9,000 r e s p o n s e s , 30 p e r s u b j e c t , t o each of t h e 30 b a s i c i n t e r v a l s . S e p a r a t e a n a l y s e s were performed on two r e s p o n s e measures. The f i r s t measure was c o n c e r n e d w i t h t h e a c c u r a c y of c l i c k l o c a t i o n and was t h e d i r e c t i o n and magnitude i n m i l l i m e t e r s o f t h e a v e r a g e d e v i a t i o n o f t h e 10 r e s p o n s e s made by each s u b j e c t t o each of t h e 30 b a s i c i n t e r v a l s i n each s e s s i o n . The f a c t t h a t t h e same 55 m i l l i m e t e r r e s p o n s e l i n e s were used f o r i n t e r v a l s of 2, 4, and 6 seconds d u r a t i o n meant t h a t t h e e r r o r s were not d i r e c t l y comparable i n terms o f t i m e . T hat i s , i f a s u b j e c t m i s p e r c e i v e d t h e l o c a t i o n o f a c l i c k by some c o n s t a n t amount of t i m e , . r e g a r d l e s s of t h e d u r a t i o n o f t h e i n t e r v a l , t h e r e s u l t i n g r e s p o n s e e r r o r would be t h r e e t i m e s as l a r g e f o r a 2 second i n t e r v a l as f o r a 6 second i n t e r v a l . E r r o r s , t h e r e f o r e , were t r a n s f o r m e d by d i v i d i n g t h e d e v i a t i o n s i n m i l l i m e t e r s by 2.750 f o r 2 second i n t e r v a l s ; 1.375 f o r 4 s e c o n d s ; and 0.917 f o r 6 s e c o n d s . T h i s t r a n s f o r m a t i o n , i n e f f e c t , made t h e 2 second r e s p o n s e l i n e 20 u n i t s l o n g , t h e 4 second r e s p o n s e l i n e 40 u n i t s l o n g , and ihe 6 second r e s p o n s e l i n e 60 u n i t s l o n g . E r r o r s were t h u s measured i n u n i t s t h a t were t h o u g h t of as l O t h s o f a s e c o n d . T h i s p r o c e d u r e had t h e drawback o f w e i g h t i n g random error t h e g r e a t e s t f o r 6 second i n t e r v a l s and t h e l e a s t f o r 2 second i n t e r v a l s b u t i t was f e l t t h a t c o m p a r a b i l i t y o f e r r o r s a c r o s s d u r a t i o n s made i t w o r t h w h i l e . A l t h o u g h t h e f i r s t measure c o n t a i n e d i n f o r m a t i o n about r e s p o n s e b i a s e s , i t was reasoned t h a t , s i n c e e r r o r s c o u l d be o f much g r e a t e r magnitude on one s i d e o f t h e c l i c k t h a n on t h e o t h e r i n a l l but t h e c e n t r a l c l i c k p o s i t i o n , a few l a r g e e r r o r s on t h e long s i d e o f t h e c l i c k c o u l d o b s c u r e an a c t u a l tendency t o respond on t h e s h o r t s i d e . The second r e s p o n s e measure, t h e n , was c o n c e r n e d s o l e l y w i t h d i r e c t i o n a l b i a s . I t was t h e p r o p o r t i o n of t o t a l e r r o r s t h a t were t o t h e r i g h t ( P e , r ) o v e r t h e 10 r e p l i c a t i o n s o f each i n t e r v a l p e r s u b j e c t p e r s e s s i o n . The e x p e r i m e n t was a p x q x r x s f a c t o r i a l d e s i g n w i t h r e p e a t e d measures on a l l f a c t o r s . A s e p a r a t e a n a l y s i s of v a r i a n c e was performed on each r e s p o n s e measure. Magnitude o f e r r o r . T a b l e 2 p r e s e n t s t h e a n a l y s i s o f v a r i a n c e summary t a b l e f o r t h e magnitude of e r r o r i n l O t h s of a s e c o n d . I n s e r t Tab Ie 2 about h e r e F o r t h e p u r p o s e s o f c o m p a r i s o n t o c l i c k s t u d y r e s u l t s , t h e o n l y r e l e v a n t v a r i a b l e was c l i c k p o s i t i o n . C l i c k p o s i t i o n had a h i g h l y s i g n i f i c a n t e f f e c t on magnitude and d i r e c t i o n of e r r o r ( F ( 4 , 3 6 ) = 12.73, p < .0(31). F i g u r e l a shows a v e r a g e p e r c e i v e d c l i c k p o s i t i o n i n r e l a t i o n t o a c t u a l c l i c k p o s i t i o n , and F i g u r e lb shows t h e magnitude o f t h e . e r r o r s i n l O t h s o f a second. I t i s a p p a r e n t t h a t magnitude o f e r r o r d e c r e a s e d toward t h e c e n t e r of t h e i n t e r v a l and t h a t t h e d i r e c t i o n o f t h e e r r o r s h i f t e d from r i g h t t o l e f t i n l a t e r c l i c k p o s i t i o n s . T h i s p a t t e r n of c l i c k m i g r a t i o n i s c l e a r l y s i m i l a r t o t h a t r e p o r t e d by Reber and Anderson (1970) . I n s e r t F i g u r e I about here There were no main e f f e c t s f o r t h e f a c t o r s o f i n t e r v a l f i l l i n g ( F ( l , 9 ) = 0.36, p > .20) o r i n t e r v a l d u r a t i o n ( F ( 2 , I 8 ) = 0.66, p > .20). There was, however, a s i g n i f i c a n t i n t e r a c t i o n between t h e two ( F ( 2 , I 8 ) = 6.31, p < .01). F i g u r e 2 shows t h a t c l i c k l o c a t i o n was m a r k e d l y more a c c u r a t e i n 6 second f i l l e d i n t e r v a l s t h a n i n any o t h e r c o m b i n a t i o n o f d u r a t i o n and f i l l i n g . I n s e r t F i g u r e 2 about here There was a s i g n i f i c a n t i n t e r a c t i o n between i n t e r v a l f i l l i n g and c l i c k p o s i t i o n (F(4,36) = 15.22, p < .001), and a three-way i n t e r a c t i o n between f i l l i n g , d u r a t i o n , and c l i c k p o s i t i o n (F(8,72) = 4.63, p < .001). T a b l e 3 l i s t s t h e d i r e c t i o n and magnitude i n t e n t h s o f a second o f t h e mean e r r o r s t o the 30 b a s i c i n t e r v a l s . I n s e r t T a b l e 3 about h e r e From T a b l e 3 i t i s c l e a r t h a t a l t h o u g h t h e r e was an a s y m m e t r i c a l c e n t r a l t endency i n f i l l e d i n t e r v a l s , i t was much more pronounced i n empty i n t e r v a l s . F u r t h e r m o r e , i n s p e c t i o n of T a b l e 3 d e m o n s t r a t e s t h a t d u r a t i o n had l i t t l e e f f e c t on e i t h e r t h e magnitude o r t h e asymmetry of t h e c e n t r a l tendency i n empty i n t e r v a l s b u t i t had a marked e f f e c t on on f i l l e d i n t e r v a l s . There i s a pronounced d i f f e r e n c e between 2 and 4 second f i l l e d i n t e r v a l s on t h e one hand and 6 second f i l l e d i n t e r v a l s on the o t h e r . Responses t o 6 second f i l l e d i n t e r v a l s had an a l m o s t s y m m e t r i c a l c e n t r a l t e n d e n c y , c l i c k s a t p o s i t i o n s 4 and 5 were p e r c e i v e d as f a r t o t h e l e f t as c l i c k s a t p o s i t i o n s 2 and I were p e r c e i v e d t o t h e r i g h t . The 2 and 4 second i n t e r v a l s showed a p e r s i s t e n t r i g h t b i a s t h a t changed v e r y l i t t l e from c l i c k I t o c l i c k 3 and d i d not become a l e f t b i a s u n t i I c I i c k 5„ A s i g n i f i c a n t s e s s i o n s main e f f e c t ( F ( 2 , I 8 ) = 4.96, p < .025), showed a marked i n c r e a s e i n t h e magnitude o f t h e o v e r a l l r i g h t b i a s from day I t o day 2 w i t h no f u r t h e r i n c r e a s e shown f o r day 3. A s i g n i f i c a n t two-way i n t e r a c t i o n between s e s s i o n s and c l i c k p o s i t i o n (F(8,72) = 3.73, p < .005), showed a marked i n c r e a s e i n t h e magnitude of r i g h t b i a s a t c l i c k p o s i t i o n s I , 2, and 3 from s e s s i o n I t o s e s s i o n 2 but no change i n t h e magnitude of t h e l e f t b i a s a t c l i c k p o s i t i o n s 4 and 5. From the s i g n i f i c a n t three-way i n t e r a c t i o n between s e s s i o n s , c l i c k p o s i t i o n s and d u r a t i o n s ( F ( I 6 , I 4 4 ) = 3.06, p < .001), i t appears t h a t a l t h o u g h an i n c r e a s e i n t h e magnitude of t h e r i g h t b i a s o c c u r r e d f o r a l l t h r e e d u r a t i o n s from s e s s i o n I t o s e s s i o n 2, t h e most d r a m a t i c change was by the 6 second i n t e r v a l s . D u r i n g t h e f i r s t s e s s i o n , t h e 6 second i n t e r v a l s showed a s m a l l r i g h t b i a s a t c l i c k p o s i t i o n I, no b i a s a t c l i c k 2, and a l e f t b i a s a t a l l o t h e r c l i c k p o s i t i o n s . By the second s e s s i o n t h e y had d e v e l o p e d a r i g h t b i a s a t c l i c k p o s i t i o n s I , 2, and 3 comparable i n magnitude t o t h a t shown by t h e o t h e r two d u r a t i o n s . The s e s s i o n s f a c t o r a l s o e n t e r e d i n t o an i n t e r a c t i o n w i t h i n t e r v a l f i l l i n g ( F ( 2 , I 8 ) = 4.63, p < .025), and a four-way i n t e r a c t i o n w i t h f i l l i n g , d u r a t i o n , and c l i c k p o s i t i o n ( F ( I 6 , I 4 4 ) = 2.07, p < .025). I n s p e c t i o n o f t h e d a t a s u g g e s t e d t h a t a major f a c t o r i n t h e s i g n i f i c a n c e of t h e two i n t e r a c t i o n s was a l a r g e and i n e x p l i c a b l e s h i f t i n t h e magnitude and d i r e c t i o n o f t h e e r r o r a t c l i c k p o s i t i o n I i n 4 second f i l l e d i n t e r v a l s d u r i n g s e s s i o n 3. A t a l l c l i c k p o s i t i o n s o t h e r t h a n t h e f i r s t , e r r o r magnitude and d i r e c t i o n were comparable t o t h e b i a s e s shown by t h e o t h e r f i v e c o m b i n a t i o n s o f d u r a t i o n and f i l l i n g . P r o p o r t i o n o_f_ t o t a I errors t o t h e r i g h t (Po, r) . Aga i n t h e ANOVA was a f o u r f a c t o r c o m p l e t e r e p e a t e d measures d e s i g n . The d a t a were s u b j e c t e d t o an A r c s i n / x t r a n s f o r m a t i o n t o a s s u r e homogeneity o f v a r i a n c e . T a b l e 4 p r e s e n t s t h e a n a l y s i s o f v a r i a n c e summary t a b l e f o r t h e P e , r d a t a . I n s e r t T a b l e 4 about h e r e C l i c k p o s i t i o n had a s i g n i f i c a n t e f f e c t on t h e P e , r (F(4,36) = 8.34, p < .001). F i g u r e 3 i l l u s t r a t e s t h e d e c r e a s e i n P e , r w i t h l a t e r c l i c k p o s i t i o n s and t h e s h i f t t o a l e f t b i a s f o r c l i c k p o s i t i o n 5. Thus o n l y f o r t h e v e r y l a s t c l i c k p o s i t i o n were a m a j o r i t y o f t h e c l i c k s p e r c e i v e d as o c c u r r i n g e a r l i e r t h a n t h e y o b j e c t i v e l y d i d . Comparison o f F i g u r e 3 t o F i g u r e lb shows t h a t t h e asymmetry o f t h e b i a s e s i s much more marked when t h e magnitude o f t h e e r r o r s i s i g n o r e d . I n s e r t F i g u r e 3 about here Reber and Anderson (1970) a l s o used P e , r as a re s p o n s e measure and, a l t h o u g h t h e a c t u a l v a l u e s a r e not d i r e c t l y comparable due t o s c o r i n g d i f f e r e n c e s , t h e p a t t e r n o f a r i g h t b i a s s h i f t i n g t o a l e f t b i a s t o t h e r i g h t of t h e c e n t r a l p o s i t i o n , i s i d e n t i c a l . As w i t h t h e f i r s t r e s p o n s e measure, t h e r e was no main e f f e c t f o r i n t e r v a l f i l l i n g ( F ( l , 9 ) = .785, p = n . s . ) . There was, however, a s i g n i f i c a n t d u r a t i o n main e f f e c t ( F ( 2 , I 8 ) = 5.94, p < .025). The and 4 second i n t e r v a l s w i t h P e , r ! s o f .527 and .616 r e s p e c t i v e l y , d i f f e r e d m arkedly from 6 second i n t e r v a l s w i t h a P e , r of .541. The s i g n i f i c a n t d u r a t i o n by f i l l i n g i n t e r a c t i o n ( F ( 2 , I 8 ) = 24.32, p < .001), showed t h a t t h e d e c r e a s e i n P e , r o f t h e 6 second i n t e r v a l s was s o l e l y a t t r i b u t a b l e t o t h e f i l l e d 6 second i n t e r v a l s . The empty 6 second i n t e r v a l s had a P e , r comparable i n magnitude t o t h o s e o f t h e 2 and 4 second empty i n t e r v a l s . In c o n t r a s t t o t h e f i r s t r e s p o n s e measure, P e , r showed a s i g n i f i c a n t d u r a t i o n by c l i c k p o s i t i o n i n t e r a c t i o n ( F ( 8 , 7 2 ) = 3.96, p < .001). F i g u r e 4 shows t h e d e c r e a s e i n P e , r a c r o s s c l i c k p o s i t i o n s f o r t h e d i f f e r e n t d u r a t i o n s . C l e a r l y t h e c e n t r a l tendency d e c r e a s e d as t h e d u r a t i o n i n c r e a s e d . I n s e r t F i g u r e 4 about here The f i l l i n g by c l i c k p o s i t i o n i n t e r a c t i o n (F(4,36) = 15.88, p < .001), i s s i m i l a r i n appearance t o t h e same i n t e r a c t i o n w i t h t h e magnitude and d i r e c t i o n r e s p o n s e ( T a b l e 3 ) . T a b l e 5 shows t h e P e , r f o r t h e 30 b a s i c i n t e r v a l s . I t i s a p p a r e n t from T a b l e 5 t h a t t h e r e was I n s e r t T a b l e 5 about here a much s t r o n g e r c e n t r a l tendency i n empty i n t e r v a l s . F i l l e d i n t e r v a l s , a l t h o u g h showing l e s s r i g h t b i a s i n t h e f i r s t two c l i c k p o s i t i o n s , m a i n t a i n e d t h e r i g h t b i a s a t a r e l a t i v e l y h i g h l e v e l f o r l a t e r c l i c k p o s i t i o n s . A t c l i c k p o s i t i o n 4, f u l l y .572 o f t h e e r r o r s t o f i l l e d i n t e r v a l s were t o t h e r i g h t o f t h e a c t u a l c l i c k p o s i t i o n . The t h r e e -way f i l l i n g by d u r a t i o n by c l i c k p o s i t i o n i n t e r a c t i o n (F(S,72) = 10.32, p < .001), shows t h a t i t i s t h e 2 and 4 second f i l l e d i n t e r v a l s which m a i n t a i n a s t r o n g r i g h t b i a s a t l a t e r c l i c k p o s i t i o n s , 6 second f i l l e d i n t e r v a l s showed a s t e a d y d e c r e a s e i n P e , r from c l i c k p o s i t i o n I t o c l i c k p o s i t i o n 5. From T a b l e 5 i t i s c l e a r t h a t t h e b i a s e s around t h e c e n t r a l c l i c k p o s i t i o n were h i g h l y a s y m m e t r i c a l f o r a l l c o m b i n a t i o n s of f i l l i n g and d u r a t i o n e x c e p t 6 second f i l l e d i n t e r v a l s . Not o n l y were t h e v a r i a t i o n s i n P e , r a c r o s s c l i c k p o s i t i o n s r e l a t i v e l y s m a l l f o r 6 second f i l l e d i n t e r v a l s , t h e y were a l s o s y m m e t r i c a l w i t h r e s p e c t t o t h e c e n t r e of the i n t e r v a I . The p r o p o r t i o n o f e r r o r s t o t h e r i g h t i n c r e a s e d a c r o s s s e s s i o n s ( F ( 2 , I 8 ) = 5.50, p < .025) from .538 i n s e s s i o n I t o .606 i n s e s s i o n 2 and .641 i n s e s s i o n 3. The i n c r e a s e i n P e , r c o n t i n u e d d u r i n g t h e t h i r d s e s s i o n b u t i t was not s i g n i f i c a n t l y d i f f e r e n t from t h e P e , r o f s e s s i o n 2 (p > .10, Duncan's M u l t i p l e Range T e s t ) . There were two s i g n i f i c a n t i n t e r a c t i o n s w i t h t h e s e s s i o n s e f f e c t ; s e s s i o n s by f i l l i n g ( F ( 2 , I 8 ) = 4.27, p < , 0 5 ) , and s e s s i o n s by c l i c k p o s i t i o n ( F(8,72) = 2.34, p < .05). The s e s s i o n s by f i l l i n g i n t e r a c t i o n i n d i c a t e s t h a t t h e i n c r e a s e i n P e , r a c r o s s s e s s i o n s was g r e a t e r f o r empty t h a n f o r f i l l e d i n t e r v a l s . P o s s i b l y i n t e r v a l f i l l i n g dampens whatever p r o c e s s i s r e s p o n s i b l e f o r t h e s e s s i o n s e f f e c t j u s t as i t a p p a r e n t l y dampened t h e c e n t r a l t e n d e n c y . The s e s s i o n s by c l i c k p o s i t i o n s i n t e r a c t i o n shows t h e s e s s i o n s e f f e c t t o be n o n e x i s t e n t a t c l i c k p o s i t i o n 5. The magnitude response measure a l s o i n d i c a t e d t h a t t h e s e s s i o n s e f f e c t was n e g l i g i b l e a t l a t e r c l i c k p o s i t i o n s b u t t h e r e seems no ready e x p l a n a t i o n as t o why t h i s s h o u l d be s o . S u b l i m i n a l c o n t r o l c o n d i t i o n . F o r t h e s u b l i m i n a l d a t a t h e 55 m i l l i -meter r e s p o n s e l i n e s were d i v i d e d i n t o e l e v e n 5 m i l l i m e t e r s e c t i o n s and r e s p o n s e s were s c o r e d on the b a s i s o f t h e s e c t i o n i n which t h e y o c c u r r e d . F i g u r e 5 shows t h e t o t a l number of r e s p o n s e s i n each s e c t i o n . I n s e r t F i g u r e 5 about here As e x p e c t e d , r e s p o n s e s showed a s t r o n g c e n t r a l t e n d e n c y . The mean of t h e d i s t r i b u t i o n i s 6.28 r e f l e c t i n g a s l i g h t tendency t o respond more o f t e n i n t h e second h a l f o f t h e i n t e r v a l . An a n a l y s i s o f v a r i a n c e showed no e f f e c t f o r t h e d u r a t i o n , f i l l i n g , o r s e s s i o n f a c t o r s . These r e s u l t s i n d i c a t e t h a t , f o r a l l of t h e c o n d i t i o n s o f t h e p r e s e n t e x p e r i m e n t , a s u b j e c t u n c e r t a i n o f t h e l o c a t i o n o f t h e c l i c k w i l l t e n d t o respond toward t h e c e n t r e o f t h e i n t e r v a l s . Responses t o p o s t q u e s t i o n n a i r e s The f i r s t two q u e s t i o n s ( A ppendix B) p e r t a i n e d t o t h e p e r c e i v e d d i s t r i b u t i o n o f t h e c l i c k s . The c l i c k s were p e r c e i v e d t o be e v e n l y d i s t r i b u t e d by f i v e o f t h e e x p e r i m e n t a l s u b j e c t s and t b be c o n c e n t r a t e d toward t h e m i d d l e o f t h e i n t e r v a l s by t h e o t h e r f i v e s u b j e c t s . Three o f t h e s u b l i m i n a l s u b j e c t s p e r c e i v e d t h e n o n e x i s t e n t c l i c k s t o be e v e n l y d i s t r i b u t e d and two p e r c e i v e d them as c o n c e n t r a t e d i n t h e second h a l f of th e i n t e r v a l s . Q u e s t i o n 3 e x p l o r e d t h e p e r c e i v e d d u r a t i o n o f t h e c l i c k . I t was c o n s i d e r e d by f o u r e x p e r i m e n t a l s u b j e c t s t o l a s t an a p p r e c i a b l e l e n g t h o f t i m e , one s u b j e c t s u g g e s t i n g a d u r a t i o n of .5 s e c o n d s . The s u b l i m i n a l s u b j e c t s a l l p e r c e i v e d t h e c l i c k as i n s t a n t a n e o u s . Q u e s t i o n 4 e x p l o r e d r e s p o n s e s t r a t e g i e s . The s u b l i m i n a l s u b j e c t s responded w i t h " i n t u i t i o n , " "guesswork," and "don't know." E i g h t of t h e e x p e r i m e n t a l s u b j e c t s c o n s c i o u s l y compared t h e t i m e b e f o r e t h e c l i c k t o t h e t i m e a f t e r t h e c l i c k , t h e o t h e r two compared c l i c k s a c r o s s i n t e r v a l s and one of t h e s e s t a t e d t h a t she had a tendency t o " b a l a n c e " t h e ' d i s t r i b u t i o n . F i v e o f t h e s u b j e c t s who compared d u r a t i o n s b e f o r e and a f t e r t h e c l i c k r e l i e d upon c o u n t i n g ; t h r e e made t h e i n t e r e s t i n g o b s e r v a t i o n t h a t t h e y c o unted u n t i l t h e c l i c k o c c u r r e d b u t o f t e n e i t h e r n e g l e c t e d o r f o r g o t t o c o n t i n u e c o u n t i n g a f t e r t h e c l i c k . P i s c u s s i o n The p a t t e r n of r e s p o n s e e r r o r s i s c l e a r l y s i m i l a r t o t h o s e r e p o r t e d by B e ver and Fodor (196.5) f o r l i n g u i s t i c messages and t o t h o s e r e p o r t e d by Reber and Anderson (1970) f o r both l i n g u i s t i c and n o n I i n g u i s t i c messages. The o v e r a l l P e , r of .595 i n t h e p r e s e n t s t u d y i s c o n s i d e r a b l y l a r g e r t h a n t h e .511 f o r l i n g u i s t i c messages and .527 f o r n o n I i n g u i s t i c messages r e p o r t e d by Reber and Anderson. I t seems r e a s o n a b l e t h a t s t r u c t u r e c o u l d have a r e s t r a i n i n g e f f e c t upon t h e magnitude o f t h e e r r o r b u t j u s t how i t c o u l d a f f e c t t h e d i r e c t i o n of t h e e r r o r i s u n c l e a r . I t i s t h o u g h t t o be much more p r o b a b l e t h a t t h e g r e a t e r P e , r i n t h e p r e s e n t e x p e r i m e n t r e s u l t e d from t h e g r e a t e r number o f t r i a l s . The P e , r o f .538 d u r i n g t h e f i r s t s e s s i o n i s c l o s e t o t h e v a l u e s r e p o r t e d i n t h e o t h e r s t u d i e s . In t h i s c o n n e c t i o n i t i s worth m e n t i o n i n g t h e s i g n i f i c a n t i n c r e a s e i n r i g h t b i a s a c r o s s s e s s i o n s . A s i m i l a r e f f e c t was r e p o r t e d by Fodor and Bever (1965) and by Reber and Anderson (1970) f o r l i n g u i s t i c messages but not f o r nonl i n g u i s t i c ones. Reber and A n d e r s o n , however, d i d r e p o r t a n o n s i g n i f i c a n t i n c r e a s e i n P e , r a c r o s s t h e 180 t r i a l s o f t h e i r e x p e r i m e n t . The d i s c r e p a n c y , t h e n , i s a g a i n a t t r i b u t e d t o t h e g r e a t e r number o f t r i a l s i n t h e p r e s e n t e x p e r i m e n t . The s u b j e c t s ' i n t r o s p e c t i v e r e p o r t s o f t h e i r s t r a t e g i e s s u p p o r t e d t h e i d e a o f c l i c k l o c a t i o n as a t a s k r e q u i r i n g judgements o f r e l a t i v e d u r a t i o n . As an i n v e s t i g a t i o n o f temporal l o c a t i o n , t h e n , t h e e x p e r i m e n t showed t h e e f f e c t s o f i n t e r v a l f i l l i n g , i n t e r v a l d u r a t i o n , c l i c k p o s i t i o n , and number of t e s t i n g s e s s i o n s , on t h e t i m e - e r r o r . O v e r a l l , t h e r e was a p o s i t i v e t i m e - e r r o r which became s t r o n g e r a c r o s s s e s s i o n s . F i g u r e 6 shows t h e development of p o s i t i v e t i m e - e r r o r i n t h e s i x c o m b i n a t i o n s of d u r a t i o n and f i l l i n g a c r o s s s e s s i o n s . O nly i n 6 second f i l l e d i n t e r v a l s d u r i n g s e s s i o n I was t h e r e a n e g a t i v e t i m e - e r r o r . I n s e r t F i g u r e 6 a b o u t here In g e n e r a l , empty i n t e r v a l s of a l l d u r a t i o n s produced p o s i t i v e t i m e - e r r o r s a t t h e f i r s t t h r e e c l i c k p o s i t i o n s and n e g a t i v e t i m e - e r r o r s a t t h e l a s t two. The 2 and 4 second f i l l e d i n t e r v a l s produced p o s i t i v e t i m e - e r r o r s f o r the f i r s t f o u r c l i c k p o s i t i o n s and a n e g a t i v e t i m e - e r r o r o n l y a t c l i c k p o s i t i o n 5. In c o n t r a s t , t h e 6 second f i l l e d i n t e r v a l produced an o v e r a l l p o s i t i v e t i m e - e r r o r o n l y a t t h e f i r s t two c l i c k p o s i t i o n s and a n e g a t i v e t i m e - e r r o r a t t h e l a s t t h r e e . The g e n e r a l i m p r e s s i o n r e c e i v e d from t h e d a t a i s of two r e s p o n s e b i a s e s , a c e n t r a l tendency and a r i g h t b i a s , t h e e f f e c t o f which confound each o t h e r . The o c c u r r e n c e of a c e n t r a l tendency i s common i n d u r a t i o n judgements ( F r a i s s e , 1963; G i l l i l a n d and Humphreys, 1943), and i n c o m p a r a t i v e d u r a t i o n judgements ( T u r c h i o e , 1948). F r a i s s e e x p l a i n e d i t as r e s u l t i n g from s u b j e c t s d e v e l o p i n g a s u b j e c t i v e a v e r a g e v a l u e and then m i n i m i z i n g d e v i a t i o n s from i t . I t f o l l o w s t h a t t h e l e s s s u r e a s u b j e c t i s of t h e a c t u a l l o c a t i o n o f a c l i c k , t h e c l o s e r t h e r e s p o n s e w i l l be t o t h e a v e r a g e v a l u e . In t h e p r e s e n t c o n t e x t , i t i s reasoned t h a t t h e a p p a r e n t l e s s e n i n g o f t h e c e n t r a l tendency i n f i l l e d i n t e r v a l s r e s u l t s from t h e w h i t e n o i s e k e e p i n g t h e s u b j e c t ' s a t t e n t i o n on t h e i n t e r v a l and t h u s l e s s e n i n g u n c e r t a i n t y a b out t h e l o c a t i o n o f the c l i c k . The r i g h t b i a s i s somewhat more d i f f i c u l t t o e x p l a i n . I t i s not c e r t a i n how much e x p l a n a t o r y power may be a t t r i b u t e d t o t h e s l i g h t r i g h t b i a s o b s e r v e d i n t h e s u b l i m i n a l r e s p o n s e d i s t r i b u t i o n , b u t i t i s t h o u g h t t o be v e r y l i t t l e . The two s u b j e c t s who, f o r an unknown r e a s o n , t h o u g h t t h e m a j o r i t y o f t h e n o n e x i s t e n t c l i c k s were i n t h e second h a l f o f t h e i n t e r v a l s , were p r o b a b l y r e s p o n s i b l e f o r t h i s b i a s . Reber and Anderson (.1970) a t t e m p t e d t o e x p l a i n t h e r i g h t b i a s t h a t appeared i n t h e i r s t u d i e s w i t h a N e o - T i t c h e n e r i a n (Neo-T) p r i o r e n t r y h y p o t h e s i s . The Neo-T h y p o t h e s i s i s based upon t h r e e a s s u m p t i o n s : I) t h e p e r c e p t u a l p r o c e s s i s a s i n g l e channel o p e r a t i o n w i t h o n l y one channel a t t e n d e d t o a t any one t i m e ( B r o a d b e n t , 1958); 2) Ss w i l l i n i t i a l l y a t t e n d t o t h e channel w i t h t h e most novel a u d i t o r y i n p u t ( C a n t o r , 1967); 3) i n p u t s i n t h e a t t e n d e d channel a r e p e r c e i v e d as o c c u r r i n g e a r l i e r i n t i m e t h a n c o n t i g u o u s i n p u t s i n t h e non-attended channel ( T i t c h e n e r , 1909: Law of P r i o r E n t r y ) . W i t h t h i s h y p o t h e s i s , t h e r i g h t b i a s i s t h e t i m e r e q u i r e d t o s w i t c h c h a n n e l s from t h e message t o t h e c l i c k . A problem a r i s e s , however, when t h e message i s a p e r i o d o f s i l e n c e . If t h e s i l e n c e i s presumed t o occupy a p e r c e p t u a l channel i n a f a s h i o n s i m i l a r t o an a u d i t o r y message, i t i s n e c e s s a r y t o p o s t u l a t e channel s w i t c h i n g a t t h e o n s e t and o f f s e t o f t h e message as w e l l as j u s t when t h e c l i c k o c c u r s . F o r example, c o n s i d e r an empty i n t e r v a l and a channel s w i t c h i n g t i m e o f .5 s e c o n d s . B e f o r e t h e s t a r t i n g t o n e , s i l e n c e i s o c c u p y i n g t h e s u b j e c t ' s p e r c e p t u a l c h a n n e l , when t h e tone o c c u r s a s w i t c h i n c h a n n e l s i s r e q u i r e d and t h e tone i s p e r c e i v e d as o c c u r r i n g .5 seconds l a t e r t h a n i t a c t u a l l y d i d . There i s a subsequent s w i t c h back t o s i l e n c e b u t i t does not a l t e r t h e t i m e r e l a t i o n s h i p s . When t h e c l i c k o c c u r s , t h e r e i s a n o t h e r s w i t c h r e q u i r e d and t h e c l i c k i s p e r c e i v e d .5 seconds l a t e . There i s a n o t h e r s w i t c h back t o s i l e n c e and the n a f i n a l s w i t c h when t h e o f f s e t t o n e o c c u r s so i t t o o i s p e r c e i v e d .5 seconds l a t e . The end r e s u l t i s t h a t t h e r e i s no change i n t h e r e l a t i v e p o s i t i o n o f t h e c l i c k w i t h r e s p e c t t o t h e e n d p o i n t s o f t h e i n t e r v a l . A r a t h e r d i f f e r e n t e x p l a n a t i o n o f d i r e c t i o n a l b i a s e s i s based upon F r a n k e n h a e u s e r ' s (1959) h y p o t h e s i s t h a t t h e s u b j e c t i v e d u r a t i o n o f an i n t e r v a l i s a f u n c t i o n o f t h e amount o f mental c o n t e n t a s s o c i a t e d w i t h t h a t i n t e r v a l . A d i r e c t i o n a l b i a s , t h e n , i s t h e r e s u l t o f a d i s -p r o p o r t i o n a t e amount of mental c o n t e n t a s s o c i a t e d w i t h t h e d u r a t i o n between t h e c l i c k and one of t h e l i m i t s o f the i n t e r v a l . Both the i n s t r u c t i o n s and t h e n a t u r e o f t h e t a s k emphasize t h e importance o f the c l i c k . T h e r e f o r e , b e f o r e t h e c l i c k t h e s u b j e c t i s a t t e n d i n g , a n t i c i p a t i n g , l i s t e n i n g i n t e n t l y , and o f t e n c o u n t i n g . When t h e c l i c k o c c u r s , t h e l e v e l o f t h i s c o g n i t i v e a c t i v i t y d e c r e a s e s ( n o t e t h e s u b j e c t s who o f t e n s t o p p e d c o u n t i n g when t h e c l i c k o c c u r r e d ) and as a r e s u l t t h e r e i s l e s s mental c o n t e n t a f t e r t h e c l i c k . The s i g n i f i c a n t s e s s i o n s e f f e c t s u g g e s t s t h a t t h i s i s a s t r a t e g y t h a t t h e s u b j e c t e i t h e r d e v e l o p s w i t h e x p e r i e n c e o r comes t o p r e f e r from a number o f a l t e r n a t i v e s . Responses t o 6 second f i l l e d i n t e r v a l s c o n s i s t e n t l y d i f f e r e d from r e s p o n s e s t o t h e o t h e r f i v e c o m b i n a t i o n s o f d u r a t i o n and f i l l i n g . In c o n t r a s t t o r e s p o n s e s t o t h e o t h e r f i v e t y p e s of i n t e r v a l , w hich showed a s t r o n g o v e r a l l r i g h t b i a s , r e s p o n s e s t o t h e 6 second f i l l e d i n t e r v a l s were s y m m e t r i c a l l y a t t r a c t e d toward t h e c e n t r e o f t h e i n t e r v a l . In e f f e c t , t h i s means t h a t t h e 6 second f i l l e d i n t e r v a l s were anomalous because t h e r i g h t b i a s was much weaker f o r them t h a n f o r t h e o t h e r t y p e s of i n t e r v a l . On t h e b a s i s of t h e F r a n k e n h a e u s e r h y p o t h e s i s , t h e weakening o f t h e r i g h t b i a s i m p l i e s t h a t f o r t h e 6 s e c . f i l l e d i n t e r v a l s t h e r e was an a t y p i c a l amount of mental c o n t e n t a s s o c i a t e d w i t h t h e p o s t -c l i c k d u r a t i o n . A p o s s i b l e e x p l a n a t i o n o f t h e i n c r e a s e d p o s t - c l i c k mental c o n t e n t i n 6 second f i l l e d i n t e r v a l s i s t h a t they a r e p e r c e i v e d as l o n g e r i n t o t a l d u r a t i o n t h a n 6 second empty i n t e r v a l s . Schumann (1393) r e p o r t e d a f e e l i n g o f i n t e n s i f i e d e x p e c t a t i o n when th e t e r m i n u s o f an i n t e r v a l was d e l a y e d . Such e x p e c t a t i o n would t e n d t o i n f l a t e t h e p o s t - c l i c k d u r a t i o n and t h u s lower t h e o v e r a l l r i g h t b i a s . I t s h o u l d be noted t h a t t h e h y p o t h e s i z e d d i f f e r e n c e i n p e r c e i v e d d u r a t i o n i s c o n t r a r y t o t h e c o n c l u s i o n o f W a l l a c e and R a b i n (I960) t h a t t h e r e i s no d i f f e r e n c e between d u r a t i o n e s t i m a t e s t o f i l l e d and u n f i l l e d i n t e r v a l s . E x p e r i m e n t II was d e s i g n e d p r i m a r i l y t o t e s t a p r e d i c t i o n from t h e F r a n k e n h a e u s e r h y p o t h e s i s . I t s g e n e r a l v a l i d i t y as an e x p l a n a t i o n of d u r a t i o n e x p e r i e n c e was n o t i n q u e s t i o n but p r e v i o u s r e s u l t s d i d not i n d i c a t e whether i t would be a p p l i c a b l e t o t h e s h o r t d u r a t i o n s o f t h e p r e s e n t e x p e r i m e n t . S u b s i d i a r y i n v e s t i g a t i o n s were of p o s s i b l e a l t e r n a t i v e r e s p o n s e s t r a t e g i e s and of p o s s i b l e d i f f e r e n c e s i n p e r c e i v e d d u r a t i o n between f i l l e d and empty i n t e r v a l s . E x p e r i m e n t I I The p r i m a r y purpose of t h i s e x p e r i m e n t was t o t e s t t h e h y p o t h e s i s t h a t t h e r i g h t b i a s r e p o r t e d i n E x p e r i m e n t I r e s u l t e d from s u b j e c t s d e v o t i n g a r e l a t i v e l y g r e a t e r amount o f c o g n i t i v e a c t i v i t y t o t h e p e r i o d p r e c e d i n g t h e c l i c k . I t was reasoned t h a t i f a h i g h l e v e l o f c o g n i t i v e a c t i v i t y produces a g r e a t e r s u b j e c t i v e d u r a t i o n t h a n a lower l e v e l , t h e n t h e p e r c e i v e d d u r a t i o n o f an i n t e r v a l s h o u l d be a f u n c t i o n of t h e p r o p o r t i o n o f t h e i n t e r v a l t h a t was devoted t o t h e h i g h e r l e v e l of c o g n i t i v e a c t i v i t y . The b a s i c p r e d i c t i o n t h e n , was t h a t i f a r i g h t b i a s ensued, d u r a t i o n e s t i m a t e s f o r i n t e r v a l s w i t h c l i c k s a t p o s i t i o n 5 would be s i g n i f i c a n t l y g r e a t e r than t h e e s t i m a t e s f o r i n t e r v a l s w i t h c l i c k s a t p o s i t i o n I. C l e a r l y t h e r e s h o u l d be a more o r l e s s l i n e a r i n c r e a s e a c r o s s a l l c l i c k p o s i t i o n s b u t because t h e d u r a t i o n s used were s h o r t and t h e v a r i a n c e o f t h e d u r a t i o n e s t i m a t e s was e x p e c t e d t o be l a r g e , a s i g n i f i c a n t d i f f e r e n c e was p r e d i c t e d o n l y between t h e extreme c I i c k pos i t i o n s . T here were two s u b s i d i a r y p r e d i c t i o n s based on an a n a l y s i s o f p o s s i b l e r e s p o n s e s t r a t e g i e s a v a i l a b l e t o a s u b j e c t . Of t h e s t r a t e g i e s t o be d i s c u s s e d below, i t i s assumed t h a t a s i n g l e s u b j e c t may use them a l l a t d i f f e r e n t t i m e s . The s t r a t e g i e s a r e : 1) The S a t t e n d s a t a u n i f o r m h i g h l e v e l t h r o u g h o u t an i n t e r v a l , r e s u l t i n g i n a p p r o x i m a t e l y a c c u r a t e c l i c k l o c a t i o n . 2) The S a n t i c i p a t e s a n d a t t e n d s b e f o r e t h e c l i c k t h e n w a i t s r e l a t i v e l y p a s s i v e l y f o r t h e i n t e r v a l t o end. T h i s s t r a t e g y r e s u l t s i n an o v e r a l l e r r o r t o t h e r i g h t of t h e a c t u a l c l i c k p o s i t i o n . 3) The S w a i t s r e l a t i v e l y p a s s i v e l y f o r t h e c l i c k t h e n a c t i v e l y a t t e n d s f o r t h e end o f t h e i n t e r v a l . T h i s s t r a t e g y r e s u l t s i n an o v e r a l l e r r o r t o t h e l e f t o f t h e a c t u a l c l i c k p o s i t i o n . Use o f s t r a t e g i e s 2 and 3 w i l l r e s u l t i n errors b e c a u s e , w i t h b o t h , t h e r e l a t i v e d u r a t i o n o f some p a r t o f an i n t e r v a l w i l l be u n d e r e s t i m a t e d due t o l a c k o f a t t e n t i o n and t h e co n s e q u e n t drop i n mental c o n t e n t . The f i r s t s u b s i d i a r y p r e d i c t i o n , - t h e n , i s t h a t i n t e r v a l s i n which t h e r e s p o n s e s show a marked l e f t o r r i g h t b i a s w i l l bo judged t o be o f l e s s d u r a t i o n t h a n i n t e r v a l s o f o b j e c t i v e l y equal l e n g t h i n which t h e c l i c k s a r e l o c a t e d more o r l e s s a c c u r a t e l y . The second s u b s i d i a r y p r e d i c t i o n has t h r e e p a r t s : 1) If a s u b j e c t uses s t r a t e g y I , r e s p o n s e s w i l l be c o r r e c t and t h e r e w i l l be no d i f f e r e n c e i n p e r c e i v e d d u r a t i o n as a f u n c t i o n o f c l i c k pos i t i o n s . 2) I f s t r a t e g y 2 i s used, r e s p o n s e s w i l l show a r i g h t b i a s and t h e magnitude of d u r a t i o n e s t i m a t e s w i l l i n c r e a s e a c r o s s t h e f i v e c l i c k pos i t i o n s . 3) If s t r a t e g y 3 i s used, r e s p o n s e s w i l l show a l e f t b i a s and t h e magnitude o f d u r a t i o n e s t i m a t e s w i l l d e c r e a s e a c r o s s t h e f i v e c l i c k pos i t i o n s . There i s , o f c o u r s e , a f o u r t h p o s s i b l e s t r a t e g y i n which a s u b j e c t pays l i t t l e a t t e n t i o n t h r o u g h o u t an i n t e r v a l . I n a t t e n t i o n s h o u l d lead t o u n c e r t a i n t y about t h e a c t u a l l o c a t i o n o f t h e c l i c k and t h u s produce a s t r o n g c e n t r a l tendency f o r l o c a t i o n r e s p o n s e s . How i n a t t e n t i o n w i l l a f f e c t d u r a t i o n e s t i m a t e s , however, i s u n c e r t a i n . There a r e two p o s s i b i l i t i e s . The f i r s t i s t h a t d u r a t i o n e s t i m a t e s w i l l be low, commensurate w i t h t h e low amount of mental c o n t e n t h y p o t h e s i z e d t o accompany low a t t e n t i o n . The second i s t h a t t h e s u b j e c t w i l l respond w i t h an a v e r a g e d u r a t i o n v a l u e , t h a t i s , show a c e n t r a l tendency f o r d u r a t i o n e s t i m a t e s . In e i t h e r c a s e , t h e r e i s no r e a s o n t o e x p e c t s t r a t e g y 4 t o be used w i t h one c o m b i n a t i o n o f f i l l i n g , d u r a t i o n , and c l i c k p o s i t i o n more o f t e n t h a n w i t h any o t h e r , so i t s o v e r a l l e f f e c t s h o u l d be random. The p o s s i b i l i t y was c o n s i d e r e d t h a t a s k i n g f o r a d u r a t i o n e s t i m a t e of t h e t o t a l i n t e r v a l would s e n s i t i z e s u b j e c t s toward p a y i n g a t t e n t i o n t h r o u g h o u t t h e e n t i r e i n t e r v a l . Thus an i n c r e a s e i n the use o f s t r a t e g y I was e x p e c t e d and c o n c o m i t a n t w i t h such an i n c r e a s e , i t was e x p e c t e d t h a t t h e o v e r a l l r i g h t b i a s would be l e s s t h a n i n E x p e r i m e n t I. The t h i r d s u b s i d i a r y p r e d i c t i o n was t h a t 6 second f i l l e d i n t e r v a l s would be judged s i g n i f i c a n t l y l o n g e r t h a n 6 second empty i n t e r v a l s . Method S u b j e c t s . 10 male and 10 f e m a l e g r a d u a t e s and u n d e r g r a d u a t e s a t t h e U n i v e r s i t y of B r i t i s h C o l umbia were r e c r u i t e d from t h o s e a v a i l a b l e d u r i n g t h e i n t e r s e s s i o n a I p e r i o d . Each S was p a i d $2.00 f o r t a k i n g p a r t i n t h e I{ hour e x p e r i m e n t . Ages ranged from 18 t o 29 y e a r s . M a t e r i a I s . The i n t e r v a l s used i n t h i s e x p e r i m e n t were t h e same ones as were used i n E x p e r i m e n t I. F o r t h i s e x p e r i m e n t , however, o n l y t h e f i r s t f o u r b l o c k s o f t r i a l s were p l a c e d on t h e t a p e f o r a t o t a l o f 240 i n t e r v a l s ; e i g h t r e p l i c a t i o n s each o f t h e b a s i c 30. The t i m e between i n t e r v a l s was i n c r e a s e d t o 16 seconds t o accommodate t h e added t a s k o f d u r a t i o n e s t i m a t i o n . The t a o e was p l a y e d on a Sony 630 s t e r e o -p h o n i c t a p e p l a y e r . Response b o o k l e t s were 12 pages long w i t h 20 p a i r s o f r e s p o n s e l i n e s on a page. The f i r s t r e s p o n s e l i n e , f o r t h e c l i c k l o c a t i o n , was 60 m i l l i m e t e r s long w i t h o n l y t h e end p o i n t s marked. The r e s p o n s e l i n e f o r t h e d u r a t i o n e s t i m a t e was b e s i d e t h e f i r s t and was 20 m i l l i m e t e r s l o n g (Appendix C ) . P r o c e d u r e . S u b j e c t s were t e s t e d i n groups o f one t o f o u r . They were s e a t e d a t desks i n a q u i e t room. The f i r s t p a r t o f t h e i n s t r u c t i o n s d e s c r i b i n g t h e c l i c k l o c a t i o n t a s k were e s s e n t i a l l y t h e same as i n E x p e r i m e n t I. The i n s t r u c t i o n s c o n t i n u e d : A f t e r you have l o c a t e d t h e c l i c k by m a r k i n g t h e h o r i z o n t a l l i n e I want you t o g i v e me a v e r y s u b j e c t i v e e s t i m a t e o f row long t h e t o t a l i n t e r v a l seemed t o be. Make y o u r e s t i m a t e t o t h e n e a r e s t t e n t h o f a second and w r i t e i t on t h e l i n e p r o v i d e d . Examples might be 3.4 o r 1.2. In o r d e r t o moderate t h e e x p e c t e d l e s s e n i n g o f t h e r i g h t b i a s because of s e n s i t i z a t i o n t o t h e whole i n t e r v a l , t h e p r i m a r y i m p o r t a n c e of t h e c l i c k l o c a t i o n t a s k was emphasized. S u b j e c t s were asked t o f i r s t l o c a t e and mark t h e p o s i t i o n of t h e c l i c k and t h e n t o " t h i n k back" t o make t h e i r d u r a t i o n e s t i m a t e . I t was f u r t h e r emphasized t h a t t h e a c c u r a c y o f t h e i r d u r a t i o n e s t i m a t e was u n i m p o r t a n t t o t h e i r t a s k and t h a t t h e y were not t o worry about i t . As !n E x p e r i m e n t I, s u b j e c t s l i s t e n e d t o 10 i n t e r v a l s b e f o r e a c t u a l l y b e g i n n i n g t h e e x p e r i m e n t . A t t h e c o n c l u s i o n o f t h e 240 t r i a l s , s u b j e c t s were g i v e n a p o s t -q u e s t i o n n a i r e (Appendix D) i n v e s t i g a t i n g r e s p o n s e s t r a t e g i e s and t h e r e l a t i v e amount of a t t e n t i o n t h e y devoted t o t h e two t a s k s . R e s u I t s Each o f t h e 20 s u b j e c t s made e i g h t l o c a t i o n r e s p o n s e s and e i g h t d u r a t i o n e s t i m a t e s t o each o f t h e 30 b a s i c i n t e r v a l s . C l i c k l o c a t i o n was s c o r e d on t h e same two measures o f magnitude o f e r r o r i n l O t h s o f a second and p r o p o r t i o n o f t o t a l e r r o r s t o t h e r i g h t ( P e , r ) . M a gnitude o f e r r o r . The ANOVA was a t h r e e - f a c t o r c o m p l e t e r e p e a t e d measures d e s i g n . T a b l e 6 p r e s e n t s t h e a n a l y s i s o f v a r i a n c e summary t a b l e f o r t h e magnitude o f e r r o r i n l O t h s o f a sec o n d . I n s e r t T a b l e 6 about h e r e There was a s i g n i f i c a n t main e f f e c t f o r i n t e r v a l f i l l i n g ( F ( I , I 9 ) = 8.38, p < .01 ). The mean e r r o r s were .113 seconds t o t h e r i g h t ( t h a t i s , l a t e i n t i m e ) f o r empty i n t e r v a l s and .200 seconds t o t h e r i g h t f o r f i l l e d i n t e r v a l s . The d u r a t i o n main e f f e c t was n o n s i g n i f i -c a n t (F(2,38) = 1.88, p > . 1 0 ) , b u t d u r a t i o n e n t e r e d i n t o a s i g n i f i c a n t i n t e r a c t i o n w i t h i n t e r v a l f i l l i n g (F(2,38) = 7.37, p < . 0 1 ) . The e r r o r s f o r t h e 2, 4, and 6 second empty i n t e r v a l s and f o r t h e 6 second f i l l e d i n t e r v a l s were a l l v e r y s i m i l a r i n magnitude w i t h v a l u e s o f .091, .133, .113, and .140 seconds r e s p e c t i v e l y . The 2 and 4 second f i l l e d i n t e r v a l s , however, had much l a r g e r e r r o r s o f .215 and .246 seconds r e s p e c t i v e l y . Comparison o f t h e shape o f t h i s i n t e r a c t i o n w i t h t h e same i n t e r a c t i o n i n E x p e r i m e n t I ( F i g u r e 2) shows t h a t w h i l e t h e shapes o f t h e c u r v e s have n o t changed, t h e i r p o s i t i o n w i t h r e s p e c t t o each o t h e r has. In E x p e r i m e n t I t h e 2 and 4 second f i l l e d i n t e r v a l s and t h e t h r e e empty i n t e r v a l s a l l had e r r o r s o f s i m i l a r magnitude, and i t was t h e 6 second f i l l e d i n t e r v a l t h a t s t o o d o u t w i t h an e x c e p t i o n a l l y s m a l l o v e r a l l e r r o r . In t he p r e s e n t e x p e r i m e n t t h e e r r o r s a r e l a r g e r f o r a l l s i x t y p e s o f i n t e r v a l b u t t h e i n c r e a s e i s c o n s i d e r a b l y g r e a t e r f o r t h e f i l l e d i n t e r v a l s so t h a t now t h e 2 and 4 second f i l l e d i n t e r v a l s have e x c e p t i o n a l l y l a r g e e r r o r s . The c l i c k p o s i t i o n main e f f e c t was s i g n i f i c a n t (F(4,76) = 13.74, p < .001 ), showing a l i n e a r d e c r e a s e i n t h e magnitude o f t h e e r r o r f r o m c l i c k p o s i t i o n I t o c l i c k p o s i t i o n 5 b u t i n c o n t r a s t t o E x p e r i m e n t I , t h e r e was no r e a l s h i f t i n t h e d i r e c t i o n o f t h e e r r o r . A t c l i c k p o s i t i o n 5 t h e mean e r r o r was .002 seconds t o t h e l e f t , a t a l l o t h e r c l i c k p o s i t i o n s i t was s t r o n g l y t o t h e r i g h t . In E x p e r i m e n t I, t h e s h i f t t o a l e f t b i a s o c c u r r e d between c l i c k p o s i t i o n s 3 and 4. C l i c k p o s i t i o n e n t e r e d i n s i g n i f i c a n t i n t e r a c t i o n s w i t h i n t e r v a l f i l l i n g (F(4,76) = 3.05, p < .0 5 ) , and w i t h i n t e r v a l d u r a t i o n ( F ( 8 , I 5 2 ) = 4.96, p < .001). F i g u r e 7 shows t h e e f f e c t on t h e magnitude and d i r e c t i o n o f e r r o r o f a) t h e c l i c k p o s i t i o n by i n t e r v a l f i l l i n g i n t e r a c t i o n and b) t h e c l i c k p o s i t i o n by i n t e r v a l d u r a t i o n i n t e r a c t i o n . I n s e r t F i g u r e 7 about h e r e I t i s c l e a r t h a t t h e l i n e a r d e c r e a s e i n t h e magnitude o f t h e r i g h t e r r o r a c r o s s c l i c k p o s i t i o n s i s l e s s f o r f i l l e d i n t e r v a l s t h a n f o r empty ones ( F i g u r e 7 a ) . T h i s r e s u l t i s v e r y s i m i l a r t o t h a t o b s e r v e d i n Ex p e r i m e n t I. From F i g u r e 7b i t i s a p p a r e n t t h a t t h e s l o p e o f t h e d e c r e a s e i n r i g h t e r r o r a c r o s s c l i c k p o s i t i o n s i s l e s s as t h e i n t e r v a l d u r a t i o n i n c r e a s e s . F o r t h e 6 second i n t e r v a l s t h e r e i s l i t t l e o r no d e c r e a s e i n t h e magnitude o f t h e r i g h t e r r o r a c r o s s t h e l a s t t h r e e c I i c k p o s i t i o n s . There was a s i g n i f i c a n t three-way i n t e r a c t i o n between f i l l i n g , d u r a t i o n , and c l i c k p o s i t i o n <F<8,152) = 284, p < .01). T a b l e 7 l i s t s t h e d i r e c t i o n and magnitude i n l O t h s o f a second o f t h e mean e r r o r s t o t h e 30 b a s i c i n t e r v a l s . I n s e r t T a b l e 7 about here I n s p e c t i o n o f T a b l e 7 d e m o n s t r a t e s t h a t t h e d i f f e r e n c e between th e 2 and 4 second f i l l e d i n t e r v a l s and t h e 2 and 4 second empty i n t e r v a l s was r e s t r i c t e d t o t h e l a s t t h r e e c l i c k p o s i t i o n s . T h i s r e s u l t i s v e r y s i m i l a r t o what was o b s e r v e d i n E x p e r i m e n t I , t h e 2 and 4 second f i l l e d i n t e r v a l s m a i n t a i n e d t h e r i g h t b i a s . However, i n t h e p r e s e n t e x p e r i m e n t , th e two 6 second i n t e r v a l s a l s o m a i n t a i n e d a r i g h t b i a s ; i t was o n l y t h e 2 and 4 second empty i n t e r v a l s t h a t showed an a c t u a l c e n t r a l t e n d e n c y . P e , r . The ANOVA was a t h r e e - f a c t o r c o m p l e t e r e p e a t e d measures d e s i g n . T a b l e 3 p r e s e n t s t h e a n a l y s i s o f v a r i a n c e summary t a b l e f o r the P e , r d a t a . I n s e r t T a b l e 8 about here The main e f f e c t s and i n t e r a c t i o n s o f t h e f i l l i n g , d u r a t i o n , and c l i c k p o s i t i o n f a c t o r s each have e s s e n t i a l l y t h e same form and l e v e l o f s i g n i f i c a n c e w i t h t h i s r e s p o n s e measure as w i t h t h e magnitude measure. An e x c e p t i o n i s t h e s i g n i f i c a n t d u r a t i o n e f f e c t (F(2,38) = 6.26, p < .01 ), showing t h e 2 and 4 second i n t e r v a l s w i t h P e , r ' s o f .682 and .539 r e s p e c t i v e l y , d i f f e r i n g from t h e 6 second i n t e r v a l s w i t h a P e , r of .622. A l t h o u g h t h e P e . r ' s a r e h i g h e r , t h e d i f f e r e n c e between t h e 2 and 4 second i n t e r v a l s on t h e one hand and t h e 6 second i n t e r v a l s on the o t h e r , i s i d e n t i c a l t o t h e d i f f e r e n c e o b s e r v e d i n E x p e r i m e n t I. The major d i f f e r e n c e between t h e two response measures i s t h a t P e , r not d e c r e a s e a c r o s s c l i c k p o s i t i o n s t o t h e same e x t e n t as t h e magnitude o f t h e e r r o r s . T a b l e 9 l i s t s t h e P e , r f o r t h e 30 b a s i c i n t e r v a I s . I n s e r t T a b l e 9 a b o u t h e r e The e n t r i e s i n T a b l e 9 a r e t h e means f o r t h e s i g n i f i c a n t f i l l i n g by d u r a t i o n by c l i c k p o s i t i o n i n t e r a c t i o n ( F ( 8 , ! 5 2 ) = 2.80, p < .01). From T a b l e 9 i t i s c l e a r t h a t t h e 2 second empty i n t e r v a l was t h e o n l y one t o show a l e f t b i a s a t any c l i c k p o s i t i o n . The 4 second f i l l e d i n t e r v a l showed v e r y l i t t l e drop i n P e , r a c r o s s c l i c k p o s i t i o n s and both t y p e s o f 6 second i n t e r v a I s s h o w e d a s I i g h t i n c r e a s e i n r i g h t b i a s a t l a t e c l i c k p o s i t i o n s . The c o m p a r i s o n o f t h e s e r e s u l t s w i t h t h e r e s u l t from t h e same r e s p o n s e measure i n E x p e r i m e n t I ( T a b l e 5 ) , i n d i c a t e s t h a t t h e c e n t r a l t endency was much weaker i n t h e p r e s e n t e x p e r i m e n t , i t s e f f e c t s were s t r o n g and o n l y w i t h t h e 2 and 4 second empty i n t e r v a l s . D u r a t i o n . The means of t h e e i g h t d u r a t i o n e s t i m a t e s made by each s u b j e c t t o each o f t h e 30 b a s i c i n t e r v a l s were t h e d a t a f o r a t h r e e f a c t o r , c o m p l e t e r e p e a t e d measures a n a l y s i s of v a r i a n c e . T a b l e 10 p r e s e n t s t h e a n a l y s i s o f v a r i a n c e summary t a b l e f o r t h e d u r a t i o n e s t i m a t e . I n s e r t T a b l e 10 about h e r e The major p r e d i c t i o n o f t h e p r e s e n t e x p e r i m e n t was t h a t t h e r e would be a s i g n i f i c a n t i n c r e a s e i n t h e magnitude o f t h e d u r a t i o n e s t i m a t between c l i c k p o s i t i o n I and c l i c k p o s i t i o n 5. The c l i c k p o s i t i o n main e f f e c t , however, was n o n s i g n i f i c a n t ( F ( 4 , 7 6 ) = 2.09, p < .10). F i g u r e 3 i l l u s t r a t e s t h e e f f e c t o f c l i c k p o s i t i o n on t h e magnitude of t h e d u r a t i o n e s t i m a t e . I n s e r t F i g u r e 8 about here I t i s c l e a r from F i g u r e 8 t h a t a l t h o u g h t h e d u r a t i o n e s t i m a t e s were l a r g e r a t c l i c k p o s i t i o n 5, t h e r e was no l i n e a r i n c r e a s e from c l i c k p o s i t i o n I t o c l i c k p o s i t i o n 5. The o n l y s i g n i f i c a n t d i f f e r e n c e was between c l i c k p o s i t i o n 5 and c l i c k p o s i t i o n 3 (o < .05; Duncan's M u l t i p l e Range T e s t ) . There were s i g n i f i c a n t main e f f e c t s f o r f i l l i n g ( F ( I , I 9 ) = 4.44, p < . 0 5 ) , and d u r a t i o n (F(2,38) = 85.22, p < .001). The s i g n i f i c a n t f i l l i n g by d u r a t i o n i n t e r a c t i o n (F(2,38) = 5.99, D < . 0 1 ) , shows t h a t b o th t h e 4 and 5 second f i l l e d i n t e r v a l s were judged t o be l o n g e r t h a n t h e c o r r e s p o n d i n g empty i n t e r v a l s by t h e a p p r o x i m a t e l y equal amounts o f .19 and .23 seconds r e s p e c t i v e l y . T h i s r e s u l t s u p p o r t s t h e p r e d i c t i o n t h a t t h e 6 second f i l l e d i n t e r v a l s would be j u d g e d l o n g e r t h a n 5 second empty i n t e r v a l s . However, t h e a t y p i c a l l y weak r i g h t b i a s i n 6 second f i l l e d i n t e r v a l s t h a t t h e d i f f e r e n c e i n p e r c e i v e d d u r a t i o n was t o e x p l a i n , d i d not o c c u r i n t h e p r e s e n t e x p e r i m e n t . In c o n t r a s t t o t h e r e s u l t s o f E x p e r i m e n t I, t h e 6 second i n t e r v a l s o f both t y p e s were a l m o s t i d e n t i c a l on both r e s p o n s e measures i n t h e p r e s e n t e x p e r i m e n t . The n o n s i g n i f i c a n t e f f e c t o f c l i c k p o s i t i o n on t h e magnitude o f d u r a t i o n e s t i m a t e s , i n s p i t e o f t h e s t r o n g o v e r a l l r i g h t b i a s shown by t h e c l i c k l o c a t i o n r e s p o n s e s , s u g g e s t e d t h a t any e f f e c t o f e r r o r d i r e c t i o n on d u r a t i o n e s t i m a t e s was a v e r y weak one. T h e r e f o r e , i n o r d e r t o g i v e t h e p r e d i c t e d e f f e c t o f e r r o r d i r e c t i o n on d u r a t i o n e s t i m a t e s t h e g r e a t e s t p o s s i b l e chance t o appe a r , c l i c k l o c a t i o n r e s p o n s e s were not counted as e r r o r s u n l e s s they d e v i a t e d markedly from t h e c o r r e c t c l i c k p o s i t i o n . The c l i c k l o c a t i o n r e s p o n s e s were c a t e g o r i z e d as ERROR LEFT, CORRECT, o r ERROR RIGHT. For 2 second i n t e r v a l s t h e CORRECT c a t e g o r y extended 6 m i l l i m e t e r s t o e i t h e r s i d e o f t h e a c t u a l c l i c k p o s i t i o n so t h a t any r e s p o n s e t h a t d i d n o t d e v i a t e from t h e c o r r e c t c l i c k p o s i t i o n by more t h a n 6 m i l l i m e t e r s was c l a s s e d as a c o r r e c t r e s p o n s e . The CORRECT c a t e g o r y was 3 m i l l i m e t e r s each s i d e o f t h e a c t u a l c l i c k p o s i t i o n f o r 4 second i n t e r v a l s and 2 m i l l i m e t e r s each s i d e f o r 6 second i n t e r v a l s . In o r d e r t o make t h e d u r a t i o n e s t i m a t e s comparable a c r o s s d u r a t i o n s and between s u b j e c t s , t h e y were c o n v e r t e d t o z - s c o r e s . F o r each s u b j e c t , z - s c o r e s were c a l c u l a t e d f o r t h e 80 d u r a t i o n e s t i m a t e s o f each o f t h e t h r e e d u r a t i o n s . Thus, f o r each s u b j e c t , t h e r e were t h r e e s e t s o f d u r a t i o n e s t i m a t e z - s c o r e s . Each d u r a t i o n z - s c o r e was a s s i g n e d t o t h e same c a t e g o r y as i t s a s s o c i a t e d c l i c k l o c a t i o n r e s p o n s e . The d u r a t i o n z - s c o r e - c l i c k l o c a t i o n r e s p o n s e p a i r s were s t i l l d i f f e r e n t i a t e d on t h e b a s i s o f t h e a c t u a l p o s i t i o n o f t h e c l i c k t o which they were made. The r e s u l t was a 3 ( c a t e g o r i e s ) by 5 ( c l i c k p o s i t i o n s ) m a t r i x f o r each s u b j e c t . The median d u r a t i o n z - s c o r e was t a k e n as t h e r e p r e s e n t a t i v e v a l u e f o r each c e l l o f t h e m a t r i x . The v a l u e s f o r each s u b j e c t were p l o t t e d a c r o s s t h e f i v e c i i c k p o s i t i o n s s e p a r a t e l y f o r each c a t e g o r y . F i g u r e 9 shows t h e d u r a t i o n e s t i m a t e z - s c o r e s averaged a c r o s s s u b j e c t s a t each c l i c k p o s i t i o n s e p a r a t e l y f o r each o f t h r e e c a t e g o r i e s o f c l i c k l o c a t i o n r e s p o n s e : ERROR LEFT, CORRECT, and ERROR RIGHT. I n s e r t F i g u r e 9 about h e r e F i g u r e 9 shows t h a t when e r r o r s were t o t h e l e f t t h e r e was a tendency f o r d u r a t i o n e s t i m a t e s t o d e c r e a s e from c l i c k p o s i t i o n I t o c l i c k p o s i t i o n 4. When t h e e r r o r s were t o t h e r i g h t , however, t h e d u r a t i o n e s t i m a t e s d i d not show any i n c r e a s e a c r o s s c l i c k p o s i t i o n s . F u r t h e r m o r e , t h e r e was no a p p a r e n t d i f f e r e n c e between d u r a t i o n e s t i m a t e s when c l i c k l o c a t i o n r e s p o n s e s were c o r r e c t and when they were e r r o r s t o t h e r i g h t . The o v e r a l l means f o r t h e t h r e e c a t e g o r i e s were c a l c u l a t e d t o t e s t t h e f i n a l s u b s i d i a r y h y p o t h e s i s t h a t d u r a t i o n e s t i m a t e s would be g r e a t e s t when t h e c l i c k s were c o r r e c t l y l o c a t e d . As was e x p e c t e d from t h e p r e v i o u s r e s u l t ( F i g u r e 9), d u r a t i o n e s t i m a t e s were o f t h e same magnitude f o r both a c c u r a t e c l i c k l o c a t i o n r e s p o n s e s and e r r o r s t o t h e r i g h t . P o s t - q u e s t i onna i r e . To q u e s t i o n I, i n v e s t i g a t i n g c l i c k l o c a t i o n s t r a t e g i e s , t h i r t e e n o f t h e twenty s u b j e c t s s t a t e d t h a t t h e y compared t h e d u r a t i o n s b e f o r e and a f t e r t h e c l i c k . Nine s u b j e c t s used c o u n t i n g s t r a t e g i e s , f i v e c o u n t e d r i g h t t h r o u g h and remembered t h e number where t h e c l i c k f e l l and f o u r s t a r t e d a new c o u n t when t h e c l i c k o c c u r r e d . One s u b j e c t r o t a t e d h e r f o o t and remembered t h e p o i n t i n t h e r o t a t i o n where t h e c l i c k f e l l . O t h e r s t r a t e g i e s were: h o l d i n g b r e a t h , p u t t i n g f i n g e r down t o mark c l i c k , two s u b j e c t s mentioned c l o s i n g t h e i r eyes and v i s u a l i z i n g t h e i n t e r v a l as s p a c e . Q u e s t i o n 2 i n v e s t i g a t e d d u r a t i o n r e s p o n s e s t r a t e g i e s . Seven s u b j e c t s based t h e i r d u r a t i o n e s t i m a t e on t h e t o t a l c o u n t o f t h e i n t e r v a l . I t i s p r o b a b l e t h a t t h e c o u n t i n g method e n t a i l s c o m p a r i s o n between i n t e r v a l s . Three s u b j e c t s s t a t e d t h a t t h e y d e r i v e d t h e i r e s t i m a t e by com p a r i s o n w i t h p r e v i o u s i n t e r v a l s . The o t h e r t e n s u b j e c t s " guessed." Q u e s t i o n 3 i n v e s t i g a t e d t h e a t t e n t i o n devoted t o t h e two t a s k s . T h i r t e e n s u b j e c t s d e voted more a t t e n t i o n t o c l i c k l o c a t i o n . F i v e s a i d t h a t t h e y c o n s i d e r e d t h e t a s k s t o be o f equal i m p o r t a n c e and one s a i d t h a t he p a i d more a t t e n t i o n t o t h e d u r a t i o n from s t a r t t o c l i c k t h a n from c l i c k t o f i n i sh. To q u e s t i o n 4, seven s u b j e c t s responded t h a t c l i c k l o c a t i o n became e a s i e r as t r i a l s p r o g r e s s e d and f o u r found d u r a t i o n s e a s i e r t o j u d g e as t r i a l s p r o g r e s s e d . To q u e s t i o n 5, t e n s u b j e c t s r e p o r t e d t h a t both c l i c k l o c a t i o n and d u r a t i o n e s t i m a t i o n were e a s i e r w i t h w h i t e n o i s e ; f o u r found both t a s k s e a s i e r w i t h empty i n t e r v a l s ; f o u r o t h e r s r e p o r t e d c l i c k s e a s i e r t o l o c a t e i n empty i n t e r v a l s b u t found d u r a t i o n e s t i m a t e s e a s i e r w i t h w h i t e n o i s e ; two s u b j e c t s found no d i f f e r e n c e between f i l l i n g s f o r e i t h e r t a s k . D i s c u s s i o n I t i s c l e a r t h a t t h e p r e d i c t i o n s based upon t h e F r a n k e n h a e u s e r h y p o t h e s i s were not s u p p o r t e d . The major p r e d i c t i o n o f a d i f f e r e n c e between t h e d u r a t i o n e s t i m a t e s a t c l i c k p o s i t i o n s 5 and I was i n t h e r i g h t d i r e c t i o n and c l o s e t o s i g n i f i c a n c e (p < . 1 0 ) . O t h e r a s p e c t s o f t h e d a t a , however, s u g g e s t t h a t t h e d i f f e r e n c e may be s a f e l y a c c e p t e d as a chance o c c u r r e n c e , and n o t c o n s t r u e d as weak s u p p o r t f o r a d i f f e r e n t i a l mental c o n t e n t e x p l a n a t i o n o f re s p o n s e b i a s e s . In t h e f i r s t p l a c e , d u r a t i o n e s t i m a t e s t o c l i c k s a t p o s i t i o n s 2, 3, and 4 were l e s s t h a n o r equal t o t h e e s t i m a t e s a t p o s i t i o n I. A l t h o u g h t h e i r r e l a t i v e m agnitudes w i t h r e s p e c t t o c l i c k p o s i t i o n s I and 5 were n o t p r e d i c t e d , on the b a s i s o f t h e h y p o t h e s i s they would be e x p e c t e d t o have magnitudes i n t e r m e d i a t e between t h o s e f o r c l i c k s I and 5. Second, t h e i n c r e a s e i n t h e magnitude o f d u r a t i o n e s t i m a t e s a c r o s s c l i c k p o s i t i o n s s h o u l d have been g r e a t e s t when o n l y t h o s e r e s p o n s e s w i t h a marked r i g h t e r r o r were c o u n t e d . As F i g u r e 9 i l l u s t r a t e s , t h e r e were no l a r g e d i f f e r e n c e s between c l i c k p o s i t i o n s even f o r t h e d a t a most l i k e l y t o show them. The t h i r d p i e c e o f e v i d e n c e c o u n t e r t o t h e h y p o t h e s i s was t h e o v e r a l l e f f e c t on r e s p o n s e b i a s e s o f a s k i n g s u b j e c t s t o make d u r a t i o n e s t i m a t e s . If t h e r i g h t b i a s of E x p e r i m e n t I r e s u l t e d from s u b j e c t s p a y i n g g r e a t e r a t t e n t i o n t o t h e p e r i o d b e f o r e t h e c l i c k , d i r e c t i n g t h e i r a t t e n t i o n toward t h e t o t a l i n t e r v a l , as was done i n E x p e r i m e n t I I , s h o u l d have l e d t o a d e c r e a s e i n t h e o v e r a l l r i g h t b i a s . The o v e r a l l magnitude o f t h e r i g h t e r r o r was .156 seconds f o r E x p e r i m e n t II and .075 seconds f o r E x p e r i m e n t I. E x p e r i m e n t II had an o v e r a l l P e , r of .665 compared t o a P e , r o f .595 f o r E x p e r i m e n t I. C l e a r l y , i n s t e a d o f showing t h e e x p e c t e d d e c r e a s e i n r i g h t b i a s , E x p e r i m e n t II showed a marked i n c r e a s e compared t o E x p e r i m e n t I. F i g u r e 10 shows t h e average p e r c e i v e d c l i c k p o s i t i o n s f o r a l l 30 b a s i c i n t e r v a l s f o r E x p e r i m e n t l ( ibove t h e l i n e ) and E x p e r i m e n t II (below t h e l i n e ) . I t i l l u s t r a t e s t h e s t r o n g e r r i g h t b i a s o f t h e E x p e r i m e n t II r e s p o n s e s . I n s e r t F i g u r e 10 a b o u t here F i g u r e 10 a l s o d e m o n s t r a t e s t h e d i s c r e p a n c y between t h e p a t t e r n s o f r e s p o n s e s t o t h e l o n g e r i n t e r v a l s i n t h e two e x p e r i m e n t s . The a v e r a g e r e s p o n s e s t o t h e 6 second i n t e r v a l s i n E x p e r i m e n t II show an a p p a r e n t c o n s t a n t d e v i a t i o n from t h e a c t u a l c l i c k p o s i t i o n r e g a r d l e s s o f where i t i s i n t h e i n t e r v a l . I t i s reasoned t h a t t h e l o n g e r t i m e between t r i a l s (16 v s . 6 seconds) and t h e i n t e r p o l a t e d a c t i v i t y o f d u r a t i o n e s t i m a t i o n , l e s s e n e d t h e c o m p a r i s o n of c l i c k l o c a t i o n s a c r o s s t r i a l s and t h u s c o n s i d e r a b l y weakened t h e c e n t r a l t e n d e n c y . I f t h i s r e a s o n i n g i s c o r r e c t , t h e r i g h t b i a s i n i t s unconfounded form i s an e r r o r of c o n s t a n t magnitude between t h e o b j e c t i v e and t h e s u b j e c t i v e p o s i t i o n s o f t h e c l i c k . I t i s p o s s i b l e t o e x p l a i n such a c o n s t a n t orror by h y p o t h e s i z i n g a d e l a y between t h e o c c u r r e n c e and t h e p e r c e p t i o n of t h e c l i c k . Reber and Anderson's (1970) N e o - T i t c h e n e r i a n h y p o t h e s i s proposed j u s t such a d e l a y and a t t r i b u t e d i t t o t h e t i m e r e q u i r e d t o s w i t c h p e r c e p t u a l c h a n n e l s . However, i n a d d i t i o n t o t h e r e s e r v a t i o n s about a c h annel s w i t c h i n g h y p o t h e s i s mentioned e a r l i e r , t h e r e i s r e a s o n t o s u s p e c t t h a t i t c a n n o t a d e q u a t e l y a c c o u n t f o r a c o n s t a n t e r r o r . In t h e d e v e l o p -ment o f t h e i r h y p o t h e s i s , Reber and Anderson mention t h a t as an i n t e r v a l p r o g r e s s e s , t h e o c c u r r e n c e of t h e c l i c k becomes i n c r e a s i n g l y more p r o b a b l e . They a c c o u n t f o r t h e a p p a r e n t l e f t b i a s p r e s e n t a t l a t e r c l i c k p o s i t i o n s i n t h e i r d a t a by s u g g e s t i n g t h a t as t h e p r o b a b i l i t y o f t h e c l i c k i n c r e a s e s , s u b j e c t s s w i t c h t h e i r a t t e n t i o n t o t h e c l i c k channel s p o n t a n e o u s l y and t h u s when t h e c l i c k o c c u r s , i t i s p e r c e i v e d e a r l i e r than t h e accompanying p r i m a r y message. Even i f o r e - c l i c k channel s w i t c h i n g i s d i s c o u n t e d , channel s w i t c h i n g s h o u l d n o t produce a c o n s t a n t e r r o r . Mowrer (1940) o b s e r v e d t h a t , i f an e v e n t o c c u r s when i t i s h i g h l y p r o b a b l e , r e a c t i o n t i m e i s l e s s than i f t h e e v e n t o c c u r s a t a t i m e when i t i s l e s s p r o b a b l e . A channel s w i t c h i n g h y p o t h e s i s , t h e r e f o r e , would p r e d i c t a d e c r e a s e i n s w i t c h i n g t i m e and a c o n s e q u e n t d e c r e a s e i n t h e magnitude o f t h e e r r o r f o r c l i c k s a t l a t e r p o s i t i o n s i n an i n t e r v a l . In E x p e r i m e n t I I , t h e d e c r e a s e a c r o s s c l i c k p o s i t i o n s s h o u l d o c c u r i n t h e l o n g e s t i n t e r v a l s b u t be n e g l i g i b l e i n s h o r t e r ones. An a l t e r n a t e p o s s i b i l i t y i s t h a t , r a t h e r t h a n t h e c l i c k b e i n g p e r c e i v e d l a t e r i n t i m e , t h e p o r t i o n o f t h e i n t e r v a l f o l l o w i n g t h e c l i c k i s u n d e r e s t i m a t e d by a c o n s t a n t amount. The p o s t - c l i c k d u r a t i o n would be u n d e r e s t i m a t e d i f t h e c l i c k was p e r c e i v e d t o occupy an a p p r e c i a b l e d u r a t i o n which was n o t c o u n t e d as p a r t of e i t h e r t h e p r e - o r p o s t - c l i c k d u r a t i o n s , o r was p e r c e i v e d as p a r t o f t h e p r e - c l i c k d u r a t i o n . In E x p e r i m e n t I, f o u r o f t h e t e n s u b j e c t s r e p o r t e d t h a t t h e c l i c k l a s t e d an a p p r e c i a b l e l e n g t h o f t i m e . F u r t h e r m o r e , something a n a l o g o u s t o G a s t a u t ' s (1949) c o r t i c a l p o t e n t i a l c o u l d d e l a y t h e p e r c e i v e d o n s e t o f t h e p o s t - c l i c k d u r a t i o n w i t h o u t a s u b j e c t n e c e s s a r i l y b e i n g c o n s c i o u s l y aware o f i t . U n f o r t u n a t e l y , a h y p o t h e s i s i n v o l v i n g a c l i c k o f p e r c e p t i b l e d u r a t i o n o r an e n d u r i n g c o r t i c a l p o t e n t i a l would be u n a b l e t o a c c o u n t f o r t h e o c c u r r e n c e of a r i g h t b i a s o r p o s i t i v e t i m e - e r r o r when two d u r a t i o n s t o be compared a r e s e p a r a t e d by more t h a n a few t e n t h s o f a s econd. I t may be t h a t t h e t i m e - e r r o r when two i n t e r v a l s have a common l i m i t i s q u a l i t a t i v e l y d i f f e r e n t from t h e t i m e - e r r o r when two i n t e r v a l s a r e s e p a r a t e d by a t h i r d i n t e r v a l . As P l u t c h i k and S c h w a r t z (1968) c o n c l u d e d , t h e t i m e - e r r o r i s p r o b a b l y not an u n i t a r y phenomenon. In c o n c l u s i o n , i t has been shown t h a t i n d i v i d u a l s l o c a t e a c l i c k i n an i n t e r v a l o f t i m e by comparing t h e d u r a t i o n between t h e c l i c k and the l i m i t s o f the i n t e r v a l . A c c u r a c y o f c o m p a r i s o n i s a p p a r e n t l y a f f e c t e d by two r e s p o n s e b i a s e s , a c e n t r a l tendency and a r i g h t b i a s . The c e n t r a l t endency i s g r e a t e s t when t h e r e i s o p p o r t u n i t y f o r c o m p a r i s o n between i n t e r v a l s . Whether c o m p a r i s o n i s f a c i l i t a t e d o r n o t , s h o r t i n t e r v a l s show a s t r o n g e r c e n t r a l tendency t h a n l o n g e r i n t e r v a l s and empty i n t e r v a l s show a s t r o n g e r c e n t r a l tendency t h a n f i l l e d i n t e r v a l s . An e x p l a n a t i o n o r t h e r i g h t b i a s based upon d i f f e r e n t i a l amounts o f mental c o n t e n t b e f o r e and a f t e r t h e c l i c k was n o t s u p p o r t e d by t h e d a t a . F i n a l l y , f o r 6 second i n t e r v a l s a t l e a s t , t h e r i g h t b i a s has t h e a ppearance o f a c o n s t a n t e r r o r . R e f e r e n c e s A n s t o t l e . In J . T. F r a s e r , The v o i c e s o f t i m e . New Yor k : G. B r a z i I l e r , 1966. B e l l , C. R. Time e s t i m a t i o n and i n c r e a s e i n body t e m p e r a t u r e . J o u r n a I of E x p e r i m e n t a l P s y c h o l o g y , 1965, 70, 232-234. S e v e r , T. G., & L a c k n e r , J . R. T r a n s i t i o n a l p r o b a b i l i t y i s not a g e n e r a l mechanism f o r t h e s e g m e n t a t i o n o f s p e e c h . J o u r n a l o f E x p e r i m e n t a l P s y c h o l o g y , 1969, 79, 387-394. B i n d r a , D., & Waksberg, H. 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V i e r o r d t , K. Der Z e i t s i n n nach V e r s u c h e n . Tubingen: H. Laupp, 1868. Von S t u r m e r , G. S t i m u l u s v a r i a t i o n and s e q u e n t i a l judgements o f d u r a t i o n . Q u a r t e r l y J o u r n a l o f E x p e r i m e n t a l P s y c h o l o g y , 1966, l_8, 354-357. Von S t u r m e r , G., Wong, T., & C o l t h e a r t , M. D i s t r a c t i o n and t i m e e s t i m a t i o n . Q u a r t e r l y J o u r n a l o f E x p e r i m e n t a l P s y c h o l o g y , 1968, 20, 380-384. W a l l a c e , M . , & R a b i n , A. Temporal e x p e r i e n c e . P s y c h o l o g i c a l B u l l e t i n , I960, 51_, 213-236. Woodrow, H. The r e p r o d u c t i o n o f temporal i n t e r v a l s . J o u r n a l o f E x p e r i m e n t a l P s y c h o l o g y , 1930, J_3, 473-499. Woodrow, H. Time p e r c e p t i o n . In S. S. St e v e n s ( e d . ) , Handbook of e x p e r i m e n t a l p s y c h o l o g y . New Y o r k : W i l e y , 1951, 1224-1236. Wundt, W. Grundzllge d e r p h y s i o l o g i schen p s y c h o l o q i e . L e i p z i g , 1903. P o s s i b l e C l i c k P o s i t i o n s f o r Each o f Three D u r a t i o n s C I i c k Pos i t i o n 2 s e c , 4 sec. 6 s e c . .33 s e c . .67 I .00 " 1.33 " 1.67 11 .67 s e c . 1.33 " 2.00 " 2.67 " 3.33 " I .00 s e c . 2.00 " 3.00 " 4.00 " 5.00 " E x p e r i m e n t I Source d_f Mean Square E r r o r Term F P r o b . Mean 1 517.3081 P 1 .8276 P 9 283.0564 Sess i o n s 2 71.9110 SP 4.9640 <.025 SP 18 14.4364 F i l l i n g 1 1.3489 FP 0.3594 >.20 FP 9 3.7529 D u r a t i o n 2 21.8515 DP 0.6635 >.20 DP 13 32.9323 CI i c k A 896.7576 CP 12.7250 < .00 1 CP 36 70.4722 S x F 9 6.6284 SFP 4.6298 <.025 SFP 18 1.4317 S x D 4 9.8406 SDP 2.2645 <. 10 SDP 36 4.3455 F x D 2 15.3608 FDP 6.31 1 1 <.0I FDP 18 2.4339 S x C 8 27.0120 SCP 3.7326 <.005 SCP 72 7.2367 F x C 4 69.6467 FCP 15.2172 < .00 i FCP 36 4.5763 D x C 8 5.0115 DCP 0.6175 > .20 DCP 72 8. 1156 S x F x D 4 1.4944 SFDP 0.6529 >.20 SFDP 36 2.2889 S x F x C 3 2.5936 SFCP 1 .1773 >.20 SFCP 72 2.2023 S x D x C 16 7.4853 SDCP 3.0557 <.00l SDCP 144 2.4496 M x D x C 8 10.1859 MDCP 4.6344 <.00l MDCP 72 2.1979 S x F x D x C 16 4.5649 SMDCP 2.0730 <.025 D i r e c t i o n and Magnitude i n lOth s o f a Second of t h e Mean E r r o r s t o t h e 30 B a s i c I n t e r v a l s E x p e r i m e n t I F i I I i n g D u r a t i o n CI i c k P o s i t i o n _!_ 2 3 4 5 2 s e c . 3.994 2.732 0.316 -1.281 -2.315 Empty A '-t s e c . 4.579 2.965 1 . 166 - ! .479 -2.604 6 s e c . 4. 122 2.494 1 .090 -1.396 -2.610 2 s e c . 2.675 i .794 1 .638 0.194 -1.262 Fi 1 l e d 4 s e c . 1 .663 2.749 1 .462 0.543 -1 .515 6 s e c . 2.748 1 .592 0.269 -1.527 -2.236 A n a l y s i s o f V a r i a n c e Summary T a b l e : P e , r Ex p e r i m e n t I Source d_f_ Mean Square E r r o r Term F P r o b . Mean 1 2973.535 P 213.393 P 9 13.935 Sess i o n s 2 6.053 SP 5.500 <.025 SP 18 1 . 101 F i 1 1 i ng 1 0.278 FP 0.785 >.20 FP 9 0.354 D u r a t i o n 2 5.680 DP 5.937 <.025 DP 18 0.956 CI i c k 4 32.051 CP 3.341 < .001 CP 36 3.842 S x F ? 0.483 SFP 4.274 <.05 SFP 18 0.113 S x D 4 0.259 SDP 0.940 >.20 SDP 36 0.275 F x D 2 3.386 FDP 24.322 <. 00! FDP 18 0. 139 S x C 8 0.96S SCP 2.337 <.05 SCP 72 0.41 4 F x C 4 5.088 FCP 15.377 < .00 i FCP 36 0.320 D x C 8 2.121 DCP 3.958 < .00 1 DCP 72 0.536 S x F x D /i '4 0.204 SFDP 1 . 195 >. 10 SFDP 36 0. 1 70 S x F x C 8 0. 1 49 SFCP 0.856 >.20 SFCP 72 0. 174 S x D x C 16 0.084 SDCP 0.420 >.20 SDCP 1 44 0. 199 F x D x C 8 1 .517 FDCP 10.320 < .00 1 FDCP 72 0. 147 S x F x D x C 16 0. 1 38 SFDCP 0.999 >.20 SFDCP 144 0. 133 P e , r f o r t h e 30 B a s i c I n t e r v a l s E x p e r i m e n t I F i l l i n g D u r a t i o n C J j c k P o s r M o n Empty 4 s e c . 6 s e c . 2 s e c . F i M e d 4 s e c . 6 sec. 2 s e c . .899 .931 .487 .354 .265 331 .731 .573 .478 .359 7?q .643 .544 .480 .496 .303 .741 .719 .630 .439 695 .732 .600 .646 .463 1606 .591 .464 .440 .415 E x p e r i m e n t I I Sourc e df i Mean Square E r r o r Term F P r o b . Mea n 1 1 469.349 P 26.181 P 19 56.123 F i11 i ng 1 115.676 FP 8.334 <.0I FP 19 13.797 D u r a t i o n 2 20.222 DP 1 .382 >. 10 DP 33 10.746 CI i c k 4 165.934 CP 13.736 <.00l CP 76 12.084 F x D 2 14.022 FDP 7.366 <.0I FDP 38 1 .903 F x C 4 13.624 FCP 3.048 <.05 FCP 76 4.47 1 D x C 3 19.230 DCP 4.965 <.00l DCP 152 3.373 F x D x C 8 6.379 FDCP 2.344 <.0I FDCP 152 2.419 D i r e c t i o n and Magnitude i n lOt h s of a Second of t h e Mean E r r o r s t o t h e 30 .Basic I n t e r v a l s E x p e r i m e n t I I F i 1 1 i ng D u r a t i o n CI i c k P o s i t i o n 1 2 3 4 5 2 s e c . 3.53 2.78 0.33 -0.36 -1 .72 Empty 4 s e c . 3.32 2.40 1 .62 0.09 -0.75 6 s e c . 2.28 0.91 1 .23 0.64 0.59 2 s e c . 2.86 3.32 2.99 1 .55 0.02 Fi1 l e d 4 s e c . 3.30 2.97 3.18 2.14 0.71 6 s e c . 2..42 1 .72 0.57 1 .28 1 .02 A n a l y s i s o f V a r i a n c e Summary T a b l e : P e , r Ex p e r i m e n t I I Source df_ Mean Square E r r o r Term F P r o b . Mean 1 265.119 P 497.320 P 19 0.533 Fi11 i nq 1 .604 FP 9.044 <.0I FP 19 .067 D u r a t i o n 2 .271 DP 6.255 <.0I DP 38 .043 CI i c k 4 .798 CP 6. 102 <.00l CP 76 .131 F x D 2 . 245 FDP 11.631 •c.OOl FDP 38 .021 F x C 4 .160 FCP 3.671 <.0I FCP 76 .044 D x C Q .389 DCP 3.625 <. 001 DCP 152 .045 F x D x C 3 .081 FDCP 2.802 <.0I FDCP 152 .029 P e . r f o r t h e 30 B a s i c I n t e r v a l s E x p e r i m e n t I I F i 1 1 i nq D u r a t i o n CI i c k Pos i t i o n 1 2 3 4 5 2 s e c . .864 .846 .575 .470 .319 Empty 4 s e c . .805 .720 .692 .572 .508 6 s e c . .632 . 54 1 .607 .633 .662 2 s e c . .796 .853 .834 .725 .539 F i11ed 4 s e c . .797 .702 .738 .728 .637 6 s e c . .647 . 604 .557 .659 .633 E x p e r i m e n t I I Source df_ Mean Square E r r o r Term f_ P r o b . Mea n 1 658176.8 P 121.503 P 19 5416.711 Fi11 i ng 1 289.315 FP 4.441 <.05 FP 19 55.263 D u r a t i o n 2 35036.34 DP 86.215 < - 001 DP 38 406.333 CI i c k 4 59.797 CP 2.036 <• 10 CP 76 28.665 F x D 2 36.469 FDP 5.989 <.0I FDP 38 14.438 F x C 4 20.502 FCP 2.027 >. 10 FCP 76 10.115 D x C 8 ' 13.649 DCP 0.817 >.20 DCP 152 16.707 F x D x C 8 11.249 FDCP 1 .576 >. 10 FDCP 152 7. 137 I F i g u r e ' I i Ef f ec't o f ; e l i c k •'pos i t i o n on 11 p e a t ion o f : t h e c l i c k . ' ;. •i •( (a) Average p e r c e i v e d c I i c k ! p o s i t i o n ' i n :reI a t i o n ; t o | Y •! a c t u a l c l i c k p o s i t i o n . - '. (p.). M a g n i t u d e of.. e r r o r i n '.j j -: i <••'••:••:••: l O t h s o f a se c o n d . • - ,.;..<.'...•..;.? • J . - . ' . j . LLI to 7 0 0 -z 2 6 0 0 -00 UJ. ^ 5 0 0 -LL. : 0 4 0 0 " >-z 3 0 0 -LU § 2 0 0 -LU u. 1 00-2 3 4 5 6. : 7 8 ; 9 1 0 , 11 R E S P O N S E C A T E G O R Y : . ; : ]..) ' V';.'' F i g u r e 5.'; Response te n d e n c y o f ' " s u b l.im.ina i " ; s u b j e c t s . '. ' I . i , i. i .1. j. ; .:: i. i. !, 1.... ; ! ; [•'..[,.[ .... i '. CLICK POSITION; F i g u r e 7.; M a g n i t u d e o f e r r o r , (a) F i I I iing ;by.cl i c k ' p o s i t i o n ' s ; ; (b) D u r a t i o n / b y c l i c k p o s i t i o n s . •;,,';."[ .', ';, ; 3-451 oo 3<40 .O U UJ 00 < or Z) •3.35-O 3-30-3-25-2 3: j V A CL ICK , POS IT ION ; 5 \ .Figure,,8/ Ef.f.ect !.of c l i c k j ; p o s i , t i o n ! o n jmagnitu.de. o f j u r a t i o n e s t i m a t e s , •> i i 00 LU o o LO I N < .5-§ o-- 5 -ERROR L E F T o-C O R R E C T : ' ERROR RIGHT b--© . ; .1.. CL ICK POS IT ION F i g u r e . 9. -"Duration e s t i m a t e z - s c o r e s .averaged a c r o s s s u b j e c t s ;!•.;•; ' ' y a t each c l i c k p o s i t i o n , f o r Jeach.of' t h r e e c a t e g o r i e s o f c l i c k I o c a t i o n r e s p o n s e . . ••. ; ;.. ^. ••;..'. j •.!;;;. j. ! ' I •I ; "t 2 SEC-E M P T Y , 1 2,3 1 ^A i A 2 3 A 4 5 A 5 2 SEC-' F ILLED; 4 S E C : E M P T Y 1 V A^ 1 2 _2_ A 1. 1 3 "4" 3V. 4 5 2 V A 2 . A : 3 4 r 5 _2_ "A" 5 ; i 4 S E C . F I LLED 6 SEC-.. E M P T Y 1 A A T 1 JSL 2 V A ! 2 ! 3 2 V AT 2 3 A ^ 4 5 ; . 3 Iv AT 3 5 V 6 SEC-F I L L E D Figure; '10. ' ,'1 ; » I v 2: /.. V v i " 9 , : ; A : 1 : ' .2. , , 2 I X ; 3 ' ' 4 •...-.5.. :L; C L I C K ; P O S I T I O N Average p e r c e i v e d 'cI i c k ' p o s i t i o n s f o r 3 0 \ b a s i c i n t e r v a l s . E x p e r i m e n t I , above t h e r e s p o n s e l i n e ; - E x p e r i m e n t • U , , • below t h e r e s p o n s e I i n e . (.Response ' l i n e 2x a c t u a l ••: , l e n g t h . ) : !'. : :- • i. : ' -; • •', '•• ]-••'•.' ;. ; -, [•*' ,• j • Appendix A Response Sheet (Condensed): Experiment I 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. IL. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29.-30. 31. 32. 33. 34. 35. 36. 37. 38. 3.9. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. Appendix 3 P o s t Q u e s t i o n n a i r e : E x p e r i m e n t i 1) On t h e a v e r a g e , were t h e c l i c k s e v e n l y d i s t r i b u t e d t h r o u g h o u t t h e i n t e r v a l s o r d i d t h e y seem t o o c c u r more i n some p o s i t i o n s t h a n i n o t h e r s ? 2) I f you do not t h i n k t h a t t h e c l i c k s were e v e n l y d i s t r i b u t e d , p l e a s e i n d i c a t e on t h e f o l l o w i n g l i n e s : I) t h e a r e a o r a r e a s t h a t seemed t o have a h i g h e r t h a n a v e r a g e d e n s i t y o f c l i c k s ; and 2) t h e a r e a o r a r e a s t h a t had a lower t h a n average d e n s i t y o f c l i c k s i f i t seems t o you t h a t such a r e a s a l s o o c c u r r e d . P l e a s e i n d i c a t e t h e l o c a t i o n and e x t e n t o f each a r e a by d r a w i n g two v e r t i c a l l i n e s and s h a d i n g between them. 1) High D e n s i t y 2) Low D e n s i t y 3) Was t h e c l i c k i n s t a n t a n e o u s o r d i d i t seem t o l a s t an a p p r e c i a b l e l e n g t h o f time? G i v e n t h a t t h e l i n e below r e p r e s e n t s an i n t e r v a l o f 5 seconds i n l e n g t h , mark o f f t h e l e n g t h of t i m e t h a t seems t o you t o be e q u i v a l e n t t o t h e d u r a t i o n o f t h e c l i c k . A s i n g l e v e r t i c a l l i n e w i l l mean t h a t you p e r c e i v e t h e c l i c k s t o have been i n s t a n t a n e o u s . 4) P l e a s e t e l l me i f you have any i d e a s as t o how you d e t e r m i n e d t h e p o s i t i o n s of t h e c l i c k s . ( E l a b o r a t e as much as p o s s i b l e . ) Appendix C Response Sheet (Condensed): Experiment II Location Of The Click Within The Interval. Total Interval To Nearest .1 Sec. 2 -> 6.1-7 ' r . 9- r-10. |_ 11. |_ 12. ^ 13. L. 14. , 15. 16. 17. 18. 19,,. Appendix D P o s t Q u e s t i o n n a i r e : E x p e r i m e n t II 1) D e s c r i b e , i n as much d e t a i l as p o s s i b l e , how you d e t e r m i n e d t h e c l i c k l o c a t i o n . 2) D e s c r i b e , i n as much d e t a i l as p o s s i b l e , how you e s t i m a t e d t h e d u r a t i o n of t h e i n t e r v a I . 3) D i d you d e v o t e more a t t e n t i o n t o one t a s k t h a n t o t h e o t h e r ? If s o , wh i ch? 4) a) D i d l o c a t i n g t h e c l i c k become e a s i e r as t i m e p r o g r e s s e d ? I f i t d i d , can you e x p l a i n why? b) D id e s t i m a t i n g t h e d u r a t i o n become e a s i e r as t i m e p r o g r e s s e d ? If i t d i d , can you e x p l a i n why? 5) a) Was i t e a s i e r t o l o c a t e t h e c l i c k s i n t h e w h i t e n o i s e o r i n t h e s i l e n t i n t e r v a l s ? Why? b) Was i t e a s i e r t o e s t i m a t e t h e d u r a t i o n i n t h e w h i t e n o i s e o r i n th e s i l e n t i n t e r v a l s ? Why? 

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