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UBC Theses and Dissertations

Information processing: response complexity and the speed- accuracy tradeoff Rollo, Diana Lynn 1979

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INFORMATION PROCESSING: RESPONSE COMPLEXITY AND THE SPEED-ACCURACY TRADEOFF by DIANA LYNN ROLLQ B.Sc. (P.E.), U n i v e r s i t y of Guelph, 1973 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF PHYSICAL EDUCATION IN THE FACULTY OF GRADUATE STUDIES School of P h y s i c a l Education and Recreation WE ACCEPT THIS THESIS AS CONFORMING TO THE REQUIRED STANDARD. The U n i v e r s i t y of B r i t i s h Columbia March, 1979 © Diana Lynn R o l l o I n 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 t h e r e q u i r e m e n t s f o r a n a d v a n c e d d e g r e e 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 u m b i a , I a g r e e t h a t t h e 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 a n d s t u d y . I f u r t h e r a g r e e 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 D e p a r t m e n t 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 n o t 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 . D e p a r t m e n t o f . 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 2075 W e s b r o o k P l a c e V a n c o u v e r , C a n a d a V6T 1W5 D a t e WltA.rX /cJ XT? abstract The purpose of t h i s investigation was to determine whether stress f o r speed and/or accuracy would d i f f e r e n t i a l l y a f f e c t information processing of tasks of low, versus greater complexity i n a choice reaction time s i t u a t i o n - I t was postulated that a stress for speed would result in the adoption of a response strategy favouring the complex response whereas an accuracy stress would r e s u l t i n the employment of no such strategy. The complex response involved the depression of f i v e keys i n a predetermined seguence. In comparison, the simple response consisted of the depression of only two keys. One co n t r o l (simple reaction time) and four experimental (choice reaction time) condtions were used i n the te s t i n g of four separate hypotheses. The experimental conditions included: accuracy stressed on both, speed stressed on both, accuracy stressed on the simple response and speed stressed on the simple response. Besponse latencies for 500 t r i a l s were obtained from each of the 24 male subjects during f i v e one-half hour testing sessions. Each subject was tested i n a l l f i v e conditions. Subsequent to an analysis of variance, Dunnett*s test was administered to test each hypothesis. The empirical r e s u l t s did not support the predictions from the proposed model. Subjects did not adopt a defensive response strategy by preparing for the more d i f f i c u l t response when stressed f o r speed on both tasks. The difference i n response latency between the two responses when either speed or accuracy was stressed on them both, was equivalent to the difference found in the simple reaction time condition. Thus, no favouritism i n the form of decreased stimulus processing nor selec t i v e attention f o r either response was involved. However, favouritism did appear to be involved when the simple response was stressed for speed or accuracy. This was evidenced by the reduced response latency for the simple response as shown by the difference between the tasks being larger i n these conditions than i n the simple reaction time condition, as well as the greater number of errors for the complex response. In both the simple and choice reaction time conditions the response latency for the complex response was slower than that for the simple response. This supports the contention that complex responses require longer read out time of th e i r motor programs due to the greater number of subroutines involved, i n comparison with simple responses. This r e s u l t i s i n p a r t i a l contrast to previous investigations which found complex responses to have faster response latencies than simple responses in choice reaction time conditions with both s t i m u l i being equally probable. The discrepancy i n findings may be explained by the d i r e c t i o n of the response strategy employed. In the present study, the simple response was favoured when a speed or an accuracy stress was imposed on i t . I t i s suggested that in the previous studies, with the absence of an external reward system that relegated importance to the p a r t i c u l a r responses, subjects favoured the complex response., They favoured i t by putting either a speed or an accuracy stress on i t , thereby reducing i t s response latency. i v Table Of Contents A b s t r a c t i i L i s t Of Tables And Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v i i L i s t of F i g u r e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v i i i Acknowledgements .......................................... x Chapter 1 1 I n t r o d u c t i o n ............................................ 1 Statement Of The Problem .............................. 4 D e f i n i t i o n Of Terms ................................... 4 D e l x m i t a t i o n s .......................................... 6 Assumptions And L i m i t a t i o n s ........................... 6 Hypotheses And R a t i o n a l e .............................. 7 CiiSLjptsr 2 •*• ••••••«•*•••••*••*•••••••••«•»•• •.• 12 Review Of S e l e c t e d L i t e r a t u r e ...........................12 Response Complexity 12 Memory Drum Theory .................................. 12 Movement Ex t e n t . ....................--.-.--.--...« .. 13 Movement R e v e r s a l s . ............................... 15 Temporal Changes In Movement. ..................... 16 Information Theory .................................. 17 Accuracy Of Movement. ............................ - 18 The Speed-Accuracy T r a d e o f f ........................... 20 Two-State Models ................. ..--.....•..---•-.». • ,21 Fas t Guess Model. ................................. 21 Deadline Model. ..................................- 24 Incremental Models. .................................. 26 Random Walk Model- ............................... - 27 Data Accumulation Models. ......................... 31 Runs Model. ..................................... 31 Recruitment Incremental Model. ..................32 Accumulator Model. .............................. 34 Poi s s o n Counting And Timing Models. ............... 35 A d d i t i v e Model .................................... 36 Information Transmission Model. ................... 37 Chapter 3 ...... 40 Methods And Procedures ................................... .40 Sui)j©cfcs • . 40 Apparatus 4 0 Response Tasks. 41 Procedures ....... ,44 Speed-Accuracy Matrix R a t i o n a l e ....................... 46 Experimental C o n d i t i o n s ..,.......---.-......-.--...-..48 Experimental Design .................................... .48 Anal y s i s Of Data ........ ... . 4.9 Chapter 4 .51 R e s u l t s And D i s c u s s i o n .................................. 51 A n a l y s i s Of R e s u l t s ...,,............,.,,..........-.,.51 D i s c u s s i o n Of Hypotheses .............................. 59 Hypothesis one . 59 Hypothesis Two 60 Hypothesis Three .................................... 62 Hypothesis Four .64 Summary «,,,,,,.....,,.,,.,,,....,,.«., — .:,,.,.,,.,,,,,, 66 Chapter 5 ..... 71 v i Summary And Conclus i o n s ................................. 71 Summary- ..•.•....-..»»»-»»»....»••«.»--»»»»•»•-•••-••• 71 ConelusxOAS* • — — — ..72 Suggestions For F u r t h e r Research ...................... 73 B l b l i o g r a p h y «»••»»••»»«.«>•»•••••••••••••••-••»«,<»»,•»••«•»• .74 v i i L i s t Of Tables And Appendices Table 1. Payoff Matrix M o t i v a t i n g Use Of Varying Response S t r a t e g i e s .............................................46 Table 2. C e l l And Marginal Mean flesponse L a t e n c i e s For RCA And RCB. ..................... .......,,...,..-,.-52 Table 3. Response L a t e n c i e s For RCA And RCB Under F i v e Experimental C o n d i t i o n s . ............................... 53 Table 4. ANOVA Of Experimental C o n d i t i o n s And Task Compexity On Response Latency. ......................... 55 Table 5., 3CB-RCA D i f f e r e n c e s In EL Between SfiT And Other C o n d i t i o n s . ............................................59 Table 6. Comparison Of L i t e r a t u r e On Mean BLs For RCA And RCB In SST And CRT C o n d i t i o n s . . . . . . . . . . . . . . . . 6 7 Appendix A. Procedures. ...................................80 Appendix B. R e s u l t s . ......................................35 L i s t Of F i g u r e s F i g u r e 1. P r e d i c t i o n s Of Response Latency For RCA And RCB By Hypotheses- .........................................11 Figu r e 2. P i c t o r a l D e s c r i p t i o n Of Sub j e c t ' s Console (from Leech, 1977). ,43 Figure 3. Response L a t e n c i e s (msec.) For RCA And RCB Under F i v e Experimental C o n d i t i o n s . .......................... 54 F i g u r e 4- Bean Response L a t e n c i e s (msec.) For The order By C o n d i t i o n I n t e r a c t i o n . 58 Acknowledgements I wish t o thank the members of my committee, Dr. G.J. Johnson, Dr. S. Lee, Dr. R.W. Schutz and Dr. G-D. S i n c l a i r f o r t h e i r time, s u g g e s t i o n s and encouragement throughout the study. To my chairman. Dr. Schutz, I wish to express a s p e c i a l thanks f o r h i s p a t i e n c e and guidance i n the p r e p a r a t i o n of t h i s t h e s i s . I would a l s o l i k e to express my a p p r e c i a t i o n to Mr. Hsu f o r being on hand to h e l p with the equipment, when I r e a l l y needed him. To Dave, my husband, whose continued f a i t h i n me has helped to prove t h a t thaumaturgy r e a l l y does e x i s t , thank you. 1 Chapter 1 INTRODUCTION The development of c y b e r n e t i c theory has helped to u n i f y knowledge and experimental evidence f o r a b e t t e r understanding of human l e a r n i n g and behavior-, S p e c i f i c a l l y , the theory emphasizes man's c a p a c i t y to a s s i m i l a t e i n f o r m a t i o n , make d e c i s i o n s , and respond a c c u r a t e l y . Of relevance to the study of l e a r n i n g and performance of perceptual-motor s k i l l s i s how the l e a r n i n g and performance are a f f e c t e d by the s t r e s s f o r speed and/or accuracy. Hany r e s e a r c h e r s have s t u d i e d the e f f e c t of v a r i a t i o n i n s t r e s s f o r speed and/or accuracy on response l a t e n c i e s i n c h o i c e r e a c t i o n time s i t u a t i o n s ( F i t t s , 1966; F i t t s and Radford, 1966; Harm and L a p p i n , 1973; Oilman 1966; Swanson and B r i g g s , 1969; Swensson, 1972; Swensson and Thomas, 1974). I n the t r a d e - o f f a s t r e s s f o r speed produced f a s t e r responses a t the expense o f i n c r e a s e d e r r o r s and, a t the other extreme, improved accuracy was a s s o c i a t e d with slower mean response l a t e n c i e s * E x p l a n a t i o n s f o r t h i s t r a d e - o f f were sought through t h e o r i e s of i n f o r m a t i o n p r o c e s s i n g , p a r t i c u l a r l y a v a r i e t y of "Incremental" models. These models focus on the amount of s t i m u l u s i n f o r m a t i o n used i n r e l a t i o n t o the type of s t r e s s . I t was proposed t h a t p r i o r t o the onset o f the s t i m u l u s the s u b j e c t s e t s c r i t e r i o n boundaries f o r each s t i m u l u s , thereby determining how much of the s t i m u l u s i n p u t i s processed before responding. These models a l s o assume that s t r e s s f o r speed decreases the amount of s t i m u l u s i n f o r m a t i o n processed before responding, whereas an accuracy 2 s t r e s s i n c r e a s e s i t . However, when r e q u i r e d to d e a l with c h o i c e r e a c t i o n time s i t u a t i o n s i n v o l v i n g t a s k s v a r y i n g i n response complexity, these t h e o r i e s are inadequate. Schutz (1972) i n v e s t i g a t e d response l a t e n c y from a response o r i e n t a t i o n r a t h e r than the s t i m u l u s approach of the Incremental models. He proposed a f i v e - s t a g e model of memory r e t r i e v a l to account f o r response l a t e n c y i n a ch o i c e r e a c t i o n time task as f o l l o w s : 1. Stimulus P e r c e p t i o n . The s t i m u l u s i s p e r c e i v e d . 2. Stimulus C a t e g o r i z a t i o n . Neural impulses t r a n s m i t t e d from the s t i m u l u s p e r c e p t i o n stage a r e c l a s s i f i e d as being one of a number of p o s s i b l e s t i m u l i . 3. Response S e l e c t i o n . The name of the s t i m u l u s i s r e c e i v e d i n a form o f n e u r a l code and then matched t o the name of the a p p r o p r i a t e response. 4. Response Search and Release. Memory sto r a g e i s searched f o r the response program and, when l o c a t e d , r e l e a s e s i t to the e f f e c t o r system. 5. Response A c t i o n ^ The response program guides the muscular c o n t r a c t i o n s r e q u i r e d to perform the task. Schutz proposed that r e a c t i o n time was egual t o the sum of the time taken d u r i n g each stage, and t h a t the response search and r e l e a s e stage was the key f a c t o r e x p l a i n i n g v a r i a t i o n o f response l a t e n c i e s . He s t i p u l a t e d t h a t p r i o r to the onset of a st i m u l u s the s u b j e c t prepared h i m s e l f f o r a response. The responses were assumed to be weighted a c c o r d i n g to t h e i r 3 p r o b a b i l i t y o f occurence, t h i s weighting determining the s u b j e c t * s r e a d i n e s s f o r any p a r t i c u l a r response, The s u b j e c t may have; (1) s e l e c t i v e l y attended to a ta s k , (2) s t o r e d the program i n primary memory o r , (3) s t o r e d i t i n secondary memory. I f the a p p r o p r i a t e response program was being s e l e c t i v e l y attended, the s u b j e c t would have a f a s t e r r e a c t i o n time. I f the program was i n primary memory, the s u b j e c t ' s response would have been slower, and t h i s l a t e n c y would be even g r e a t e r i f the program was s t o r e d i n secondary memory. Schutz (1972), r e p l i c a t e d by Byan (1972) demonstrated t h a t a complex response had a f a s t e r response l a t e n c y than d i d a simple response i n a c h o i c e r e a c t i o n time s i t u a t i o n with e q u a l l y probable s t i m u l i . Schutz supposed t h a t s u b j e c t s adopted a d e f e n s i v e response s t r a t e g y - p r e p a r i n g f o r the complex task by s e l e c t i v e l y a t t e n d i n g to i t , and thereby r e d u c i n g search time and response l a t e n c y * However, t h i s model c o u l d not e x p l a i n r e s u l t s o b t a i n e d with unegual p r o b a b i l i t y s i t u a t i o n s (Leech* 1977; Byan, 1972). Thus, n e i t h e r of the above models adequately e x p l a i n s why complex tasks r e q u i r e l e s s p r o c e s s i n g time than simple ones i n a CBT s i t u a t i o n * I t i s the purpose of t h i s study to use the i d e a s c o n t a i n e d i n the Incremental models, combined with Schutz*s theory o f motor memory i n an attempt t o account f o r the s h o r t e r response l a t e n c y of the complex response. I t was p o s t u l a t e d that a s t r e s s f o r speed caused the s u b j e c t to adopt a defensive s t r a t e g y to cou n t e r a c t the longer r e l e a s e time of a complex motor program. T h i s defense might have had two p o s s i b l e forms s 1) l e s s i n f o r m a t i o n was r e q u i r e d b e f o r e the s t i m u l u s probe was 4 c l a s s i f i e d as being the complex r a t h e r than the simple task, and 2) the complex task was s e l e c t i v e l y attended to but the motor program f o r the simple task was s t o r e d i n primary memory. Th e r e f o r e , s e a r c h time and i n t u r n response l a t e n c y was reduced f o r the complex task. I t was f u r t h e r p o s t u l a t e d t h a t a s t r e s s f o r accuracy would not r e s u l t i n a response s t r a t e g y f a v o u r i n g e i t h e r t a s k i An accuracy s t r e s s was expected to cause an i n c r e a s e - e q u a l f o r both tasks - i n the amount of s t i m u l u s i n f o r m a t i o n r e q u i r e d to i d e n t i f y the s t i m u l u s probe as w e l l as s t o r i n g both response programs i n primary memory. STATEMENT OF THE PROBLEM I t i s the purpose of t h i s study to i n v e s t i g a t e whether s t r e s s f o r speed and/or accuracy d i f f e r e n t i a l l y a f f e c t s the i n f o r m a t i o n p r o c e s s i n g of response t a s k s of low, vesus g r e a t e r complexity i n a c h o i c e r e a c t i o n time s i t u a t i o n , as p r e d i c t e d by the d e l i n i a t e d model. DEFINITION OF TERMS 1 Primary Memory (PM). A memory storage area f o r r e c e n t l y p e r c e i v e d s t i m u l i . PM has a l i m i t e d c a p a c i t y r e g a r d i n g the number of items h e l d , and t h e i r r e t e n t i o n time. Primary memory i s analogous t o 'short term, memory {SB) 1, o r •immediate memory (IM)*-JThe f o l l o w i n g d e f i n i t i o n s are as d e f i n e d by Schutz (1972), unless otherwise s p e c i f i e d . 5 Response Latency (RL). The amount of time e l a p s i n g between the p r e s e n t a t i o n of a s t i m u l u s and the f i r s t measurable o v e r t response to t h a t s t i m u l u s . Response l a t e n c y i s d e f i n e d as an i n d i c a t o r of the amount of i n f o r m a t i o n p r o c e s s i n g conducted d u r i n g a stimulus-response (S-R) task. Response l a t e n c y i s synonymous to the term ' r e a c t i o n time*. Simple Reaction Time (SRT). R e f e r s to the time e l a p s i n g from the occurence of a s i n g l e f i x e d s t i m u l u s and the i n i t i a t i o n o f the a p p r o p r i a t e response ( F i t t s and Posner, 1967). Choice R e a c t i o n Time (CRT) . The 81 of a task s e l e c t e d from two or more p o s s i b l e responses. Secondary Memory (SM) . A memory s t o r e c o n t a i n i n g items p r e v i o u s l y p e r c e i v e d and r e i n f o r c e d , and subsequently absent from consciousness f o r a p e r i o d o f time. T h i s s t o r a g e system can c o n t a i n an u n l i m i t e d number of items. Secondary memory i s analogous t o 'long-term memory (LTM) ». Response Complexity (RC). A s u b j e c t i v e measure of the number o f subprograms o r response u n i t s r e t r i e v e d , and the o r g a n i z a t i o n of these u n i t s i n t o an a p p r o p r i a t e temporal sequence (Glencross, 1973). The g r e a t e r the number o f subprograms i n v o l v e d i n a p a r t i c u l a r response program, the more complex the task i s assumed to be. Response complexity i s synonymous to the term 'task complexity'- The two l e v e l s of task complexity used i n t h i s study are; 1- Response Complexity A (RCA). A simple task i n v o l v i n g the d e p r e s s i o n of two response keys. 6 2, Response Complexity B (RCB). A more complex task i n v o l v i n g the depression of f i v e response keys i n a predetermined order. DELIMITATIONS 1. The study i s d e l i m i t e d t o a two-choice r e a c t i o n time task. 2. The study i s d e l i m i t e d to two l e v e l s of response complexity (RCA and £CB) . 3- The study i s d e l i m i t e d to a s t r e s s f o r speed and accuracy as d e f i n e d i n a *paycff * matrix. 4. The study i s d e l i m i t e d t o a d i s c r e t e r e a c t i o n - t i m e response ( s i n c e a s e r i a l , s e l f - p a c e d task might e l i c i t a d i f f e r e n t response s t r a t e g y ) . ASSUMPTIONS AND LIMITATIONS 1. A s t i m u l u s may be a n t i c i p a t e d with an a p p r o p r i a t e response, but only one response can be s e l e c t i v e l y attended at once. 2. Response p r e p a r a t i o n can take the form of one, or both of the f o l l o w i n g : a. C r i t e r i o n boundaries can be s e t by the s u b j e c t to determine how much s t i m u l u s i n f o r m a t i o n i s processed b e f o r e responding. The l e s s s t i m u l u s i n f o r m a t i o n processed, the 7 f a s t e r the EL. b. To reduce time spent i n memory search and r e t r i e v a l , the s u b j e c t can s e l e c t i v e l y attend to a p a r t i c u l a r response program. A response which i s s e l e c t i v e l y attended has a f a s t e r RL than one s t o r e d i n primary memory. 3. A s t r e s s f o r speed or accuracy can d i f f e r e n t i a l l y i n f l u e n c e the amount of time spent i n p r o c e s s i n g i n f o r m a t i o n . L i m i t a t i o n s of the i n v e s t i g a t i o n i n c l u d e ; 1. On s e v e r a l o c c a s i o n s equipment f a i l u r e d i s r u p t e d the sequence of responses. 2. The sample was l i m i t e d t o 24 male s u b j e c t s . HYPOTHESES AND RATION ALE Hypothesis J. I n a c h o i c e r e a c t i o n - t i m e s i t u a t i o n with equal response p r o b a b i l i t i e s , and a payoff matrix s t r e s s i n g accuracy over speed on both. responses, the d i f f e r e n c e i n RL between the complex response (RCB) and the simple response (RCA) i s e q u i v a l e n t t o the d i f f e r e n c e i n the simple r e a c t i o n time c o n d i t i o n . I t i s proposed that when accuracy i s s t r e s s e d , there would be no d i f f e r e n t i a l p r o c essing of i n f o r m a t i o n f o r responses varying i n complexity. The concern o f the s u b j e c t to respond c o r r e c t l y i s suggested to r e s u l t i n the time f o r d i f f e r e n t processing stages being lengthened : 1) s t i m u l u s encoding, owing 8 to a g r e a t e r amount of s t i m u l u s i n f o r m a t i o n being accumulated before the s t i m u l u s probe i s c l a s s i f i e d , and 2) response s e a r c h , owing t o s t o r a g e of both motor programs i n primary memory. I t i s f u r t h e r proposed that d i f f e r e n c e s i n response l a t e n c y between the complex and simple responses i n both the simple and c h o i c e r e a c t i o n time s i t u a t i o n s r e f l e c t the d i f f e r e n c e i n l e n g t h of the response programs. That i s , complex responses are assumed to have more subprograms than simple ones, and t h e r e f o r e they w i l l have l o n g e r r e l e a s e times and consequent l o n g e r response l a t e n c i e s . Hypothesis 2 In a CRT s i t u a t i o n with equal response p r o b a b i l i t i e s and a payoff matrix s t r e s s i n g speed over accuracy on both responses, the d i f f e r e n c e between RCA and RCB i s l e s s than i n the SRT c o n d i t i o n . Schutz's c o n c e p t u a l model provides the r a t i o n a l e f o r the above h y p o t h e s i s i n that s t r e s s f o r speed causes the s u b j e c t t o develop a response s t r a t e g y t h a t compensates f o r the l o n g e r r e l e a s e time of the complex response. E i t h e r one or both of t h e f o l l o w i n g f a c t o r s are proposed to account f o r t h i s compensation: a. The amount of s t i m u l u s i n f o r m a t i o n r e q u i r e d to i d e n t i f y the s t i m u l u s probe a s s o c i a t e d with the complex response i s l e s s than t h a t r e q u i r e d f o r the simple response-b. The complex response proqram i s s e l e c t i v e l y attended, so t h a t search time f o r the complex response i s l e s s than f o r the simple one. The r e s u l t of these processes i s a f a s t e r response l a t e n c y f o r the complex response., 9 Hypothesis 3 I n a CRT s i t u a t i o n with e q u a l response p r o b a b i l i t i e s , and a payoff matrix c r e a t i n g a s m a l l , constant s t r e s s f o r speed and a g r e a t e r s t r e s s f o r accuracy on RCA than on RCB, the d i f f e r e n c e between RCA and RCB i s e q u i v a l e n t to the d i f f e r e n c e i n the SRI c o n d i t i o n * T h i s h y p o t h e s i s p r o v i d e s a s t r o n g e r t e s t f o r the c o n c e p t u a l model. / Since no response s t r a t e g y i s assumed to be i n e f f e c t , n e i t h e r response w i l l be favoured over a l l t r i a l s i n the CRT s i t u a t i o n , with the r e s u l t t h a t the d i f f e r e n c e between RCA and RCB i s due t o the i n c r e a s e d r e l e a s e time of SCB i n both the simple and c h o i c e r e a c t i o n time c o n d i t i o n s . Hypothesis 4 In a CRT s i t u a t i o n with e q u a l response p r o b a b i l i t i e s , and a payoff matrix that p l a c e s a s m a l l s t r e s s f o r accuracy and a g r e a t e r s t r e s s f o r speed on RCA than on RCB, the d i f f e r e n c e between RCA and RCB i s greater than i n the SRT c o n d i t i o n * , 10 T h i s h y p o t h e s i s p r o v i d e s a f a r t h e r t e s t of whether speed causes the s u b j e c t t o adopt a p a r t i c u l a r response s t r a t e g y i n order to reduce response l a t e n c y . In t h i s c a s e , because reward i s given f o r f a s t e r response l a t e n c i e s with the simple response, i t i s p o s t u l a t e d that RCA w i l l be s e l e c t i v e l y a ttended, thereby adding to the d i f f e r e n c e between RCA and RCB. T h i s r e s u l t s from the l o n g e r r e l e a s e time of RCB with s h o r t e r s t i m u l u s encoding and/or s h o r t e r response search f o r RCA. Thus the d i f f e r e n c e between RCA and BCB i s g r e a t e r i n the CRT s i t u a t i o n than i n the SRT condition.: [•• I - Response A \ V J = Response B Q> E c o o o Q : Q : co Qz (0 > Q>(0 o Q : Q) o a QC in o Q. F i g u r e 1 . P r e d i c t i o n s o f r e s p o n s e l a t e n c y f o r RCA a n d RCB by h y p o t h e s e s . 12 Chapter 2 REVIEW OF SELECTED LITERATURE RESPONSE COMPLEXITY The vast r e p e r t o i r e of motor s k i l l s possessed by an i n d i v i d u a l has l e d r e s e a r c h e r s to q u e s t i o n where, and i n what form, such i n f o r m a t i o n i s s t o r e d , and how i t i s r e t r i e v e d . One aspect of t h i s process i s concerned with the complex nature of s k i l l s and whether t h i s i n f l u e n c e s i n f o r m a t i o n p r o c e s s i n g . A s e r i o u s o b s t a c l e i s the d i f f i c u l t y of q u a n t i t a t i v e l y d e f i n i n g complexity. In most i n v e s t i g a t i o n s , complexity has been d e f i n e d e i t h e r i n terms of the mechanical a s p e c t s of the s k i l l o r by the e f f i c i e n c y of i n f o r m a t i o n p r o c e s s i n g . Memory Drum Theory The framework of m e c h a n i c a l l y o r i e n t e d t h e o r i e s was o u t l i n e d by Henry and Rogers (1960) i n t h e i r "Memory Drum Theory." T h i s model a p p l i e d t o d i s c r e t e movements performed a t maximum speed so t h a t there was no o p p o r t u n i t y f o r m o d i f i c a t i o n by feedback. Henry (1961) proposed t h a t w e l l learned motor s k i l l s were s t o r e d as n e u r a l p a t t e r n s which, when r e l e a s e d , c o n t r o l l e d the c i r c u l a t i o n of n e u r a l impulses to execute the movement. These n e u r a l p a t t e r n s were c a l l e d motor programs. On p e r c e i v i n g a s t i m u l u s , the a p p r o p r i a t e motor program was l o c a t e d and then r e l e a s e d from memory. T h i s theory d e f i n e d complexity i n terms of the amount o f i n f o r m a t i o n s t o r e d i n the motor progam. The g r e a t e r amount of 13 i n f o r m a t i o n i n more complex programs r e q u i r e d a longer readout time from memory, with a concomitant i n c r e a s e i n RL- T h i s model proposed t h a t components of complexity i n c l u d e d : the extent o f the movement, the number o f changes of d i r e c t i o n i n the s k i l l (movement r e v e r s a l s ) , temporal a l t e r a t i o n s i n the movement, and accuracy. Movement Extent. Brown and Slatter-Hammel (1949), G l e n c r o s s (1972,1976) and Lagasse and Hayes (1973) dis c o u n t e d movement extent as an aspect of complexity. Brown and Slatter-Hammel (1949) examined the r e l a t i o n s h i p between movement extent and RL using a l i n e a r movement of the hand and arm over a range of 2.5 cm t o 40 cm. RL was independent of the d i s t a n c e moved. Studying g r e a t e r movement ranges, Lagasse and Hayes (1973) compared the r e a c t i o n time f o r r e l e a s i n g a key with t h a t f o r a r a p i d f l e x i o n through a range of 140° . RL was again independent of the ext e n t of the movement. G l e n c r o s s (1972), i n a simple r e a c t i o n time (SET) s i t u a t i o n found that i n c r e a s i n g the d i s t a n c e moved from 15.24 cm to 45.72 cm d i d not change the RL of an elbow f l e x i o n response* S i m i l a r r e s u l t s were obtained with the same s k i l l i n a choice r e a c t i o n time (CRT) s i t u a t i o n i n which the range o f motion v a r i e d from 15.24 cm to 30.48 cm. C o n t r a d i c t o r y r e s u l t s were provided by F i t t s and Peterson (1964), W i l l i a m s (1971), G l e n c r o s s (1973) and S i e g e l (1977). F i t t s and Peterson (1964) arranged p a i r s of t a r g e t s e q u i d i s t a n t to the r i g h t and l e f t of a s t a r t i n g p o s i t i o n . Movement ext e n t was v a r i e d from 7.62 cm to 30.48 cm. CRTs i n c r e a s e d s i g n i f i c a n t l y with i n c r e a s i n g d i s t a n c e . H i l l i a m s (1971) compared the RLs a s s o c i a t e d with a forward arm swing through a 75° a r c 14 with RLs from other s t u d i e s - R e s u l t s o f these comparisons showed th a t movements of g r e a t e r l e n g t h e x h i b i t e d s i g n i f i c a n t l y l o n g e r RLs. H i l l i a m s a t t r i b u t e d the d i s p a r i t y of h i s f i n d i n g s with previous s t u d i e s t o the f a c t t h a t d i f f e r e n t kinds of stu m u l i and i n s t r u c t i o n a l emphases were employed. In a s e r i e s of twO-choice RT experiments, G l e n c r o s s (1973) u t i l i z e d t h r e e d i f f e r e n t movement ranges (key r e l e a s e , 15.24 cm, 45.72 cm movements) . The longer movements had greater RLs- S i e g e l ' s (1977) r e s u l t s supported those of F i t t s and Peterson (1964) and G l e n c r o s s (1973). When the d i s t a n c e to a t a r g e t was v a r i e d from 5 mm to 300mm i n a c h o i c e s i t u a t i o n , t h e r e was a len g t h e n i n g of RL. a major c r i t i c i s m of the memory drum theory was put f o r t h by Klapp et a l . (1974). They observed t h a t the theory s h o u l d p r e d i c t CRT s i t u a t i o n s b e t t e r than SRT ones. I t was suggested that with a SRT paradigm, p r i o r to the onset of the st i m u l u s the s u b j e c t may have undergone processes assumed i n the memory drum theory t o have occurred a f t e r s t i m u l u s onset. Only the s t u d i e s of F i t t s and Peterson (1964), G l e n c r o s s (1973,1976) and S i e g e l (1977) examined CRT s i t u a t i o n s . With the exception of G l e n c r o s s (1976), they found t h a t RL i n c r e a s e d with the exte n t of the movement, su p p o r t i n g the hypothesis t h a t the l a r g e r amount o f i n f o r m a t i o n a s s o c i a t e d with such t a s k s i n c r e a s e d RL and should t h e r e f o r e be co n s i d e r e d a component of complexity, at l e a s t i n CRT t a s k s . 15 Hovement R e v e r s a l s . According to the memory drum theory, •movement r e v e r s a l s * were p r e d i c t e d to be an aspect of response complexity because t a s k s i n c o r p o r a t i n g b a c k t r a c k i n g r e q u i r e more s u b r o u t i n e s and thus i n c r e a s e d p r o c e s s i n g time., S t u d i e s comparing tasks i n c o r p o r a t i n g two movement r e v e r s a l s t o t a s k s l a c k i n g d i r e c t i o n a l changes, support t h i s h y p o t h e s i s (Henry, 1961; Henry and H a r r i s o n , 1960; H o r r i e , 1967). The v a l i d i t y of these s t u d i e s may be questioned, however, s i n c e they employed a SRI paradigm, and a s m a l l number of t r i a l s . N o r r i e (1967) found that the d i f f e r e n c e between t a s k s decreased with p r a c t i c e . In a 5 0 - t r i a l seguence, there was a d i f f e r e n c e of 31 msec. between the t a s k s of the f i r s t ten t r i a l s , but o n l y 11 msec, f o r the l a s t t e n . Henry and H a r r i s o n (1960) used 25 t r i a l s f o r each response, i n c l u d i n g 15 p r a c t i c e t r i a l s . Thus, the r e s u l t s of these s t u d i e s may be d i s t o r t e d due to l e a r n i n g d u r i n g p r a c t i c e . I n c o n t r a s t t o the above r e s u l t s , other i n v e s t i g a t o r s (Glencross 1972,1973; Henry,1961) found s i m i l a r l a t e n c i e s between movements i n c o r p o r a t i n g r e v e r s a l s and those without. G l e n c r o s s (1972,1973), employing a CRT format, d i s c o v e r e d t h a t a s i n g l e d i r e c t i o n a l change i n an elbow f l e x i o n task was i n s u f f i c i e n t to produce any i n c r e a s e i n l a t e n c y . I n summary, the c o n c l u s i o n s of s t u d i e s on movement r e v e r s a l s are confounded by d i f f e r e n c e s i n methodology and numbers o f t r i a l s . However, movement r e v e r s a l s a p p a r e n t l t y a f f e c t RL when more than one d i r e c t i o n a l change oc c u r s . 16 Temporal Changes I n Movement. Another element of response complexity i s the temporal p a t t e r n of the s k i l l . For example, G l e n c r o s s (1972) , using a SRT design, found t h a t movement sequences i n v o l v i n g s e v e r a l pauses or h a l t s (a double or t r i p l e t a pping response) had s i g n i f i c a n t l y g r e a t e r l a t e n c i e s than d i d simple f i n g e r or hand movements. t Sidowski e t a l . (1958) i n v e s t i g a t e d whether t a s k s v a r y i n g i n temporal p a t t e r n i n g had longer response l a t e n c i e s i n s i m p l e and choice c o n d i t i o n s . H i t h the SET, a simple f i n g e r withdrawal was s i g n i f i c a n t l y f a s t e r than when one and two switch movements were r e q u i r e d . However, with a CRT s i t u a t i o n , the t h r e e - s w i t c h response was s i g n i f i c a n t l y f a s t e r than the simple response. Sidowski e t a l . (1958) p o s t u l a t e d t h a t s u b j e c t s prepared themselves i n advance to execute the more d i f f i c u l t response. When a s i m p l e r response was r e q u i r e d , the prepared response had to be i n h i b i t e d b e f o r e the proper response c o u l d be executed, thus the delay. B l a i r (1970) a l s o i n v e s t i g a t e d t h i s problem from a CRT framework. The t a s k s - t u r n i n g o f f one, two or three toggle s w i t c h e s - r e s u l t e d i n RLs t h a t tended to i n c r e a s e with i n c r e a s i n g numbers of temporal d i s r u p t i o n s , although not s i g n i f i c a n t l y . B l a i r suggested that a type I I e r r o r was the reason f o r the l a c k of s i g n i f i c a n c e . B l a i r ' s r e s u l t s , d i d not c o n t r a d i c t r e s u l t s from the p r e c e d i n g two s t u d i e s . SRT was more a f f e c t e d by temporal changes i n movement than was CRT. C o n t r a d i c t o r y r e s u l t s were obtained by Klapp e t a l . (1974) , i n v e s t i g a t i n g the morse code d i t and dah responses., The dah response was assumed to r e f l e c t the hold and wait component. CRT proved to be s i g n i f i c a n t l y l o n g e r f o r the dah reponse. P o s s i b l y 17 the nature of the tasks account f o r the d i s p a r a t e r e s u l t s o f Klapp e t a l . (1974) and those of the p r e v i o u s s t u d i e s . Summarizing, i t must be concluded that the r e l a t i o n s h i p between temporal p a t t e r n i n g of movements and complexity i n CBT s i t u a t i o n s , remains as yet u n c l e a r . I n f o r m a t i o n Theory An a l t e r n a t i v e to the memory drum theory i s i n f o r m a t i o n theory, which d e f i n e s complexity of a motor s k i l l i n terms of how e f f i c i e n t l y i n d i v i d u a l s process i n f o r m a t i o n . To g u a n t i f y the d i f f i c u l t y of movement tasks, F i t t s (1954) devised the * Index of D i f f i c u l t y . ' T h i s measure i s a r a t i o of accuracy to amplitude and i s d e f i n e d as "the amount of i n f o r m a t i o n t h a t a movement i s r e q u i r e d t o generate" ( F i t t s and Hadford, 1966, pg. 475) , thus: ID = l o g 2A/W where ID=index of d i f f i c u l t y , A=amplitude, and W=accuracy. Assuming accuracy and amplitude as the mechanical components of complexity, r e s e a r c h e r s i n i n f o r m a t i o n theory question whether t a s k s of q r e a t e r complexity r e q u i r e l o n g e r motor programs. Furthermore, they attempt t o determine i f the program i s read out i n whole or i n p a r t . In the l a t t e r case, the EL f o r the simple and complex task would be the same s i n c e only a s m a l l p a r t need be read out before e x e c u t i o n . In the former, the time r e q u i r e d t o read out the e n t i r e response program would r e s u l t i n longer EL. 18 ACCURACY OF MOVEMENT. SEVERAL STUDIES CONSIDERED TASKS INVOLVING t a r g e t - o r i e n t e d movements ( F i t t s and Peterson, 1964; F i t t s and Radford, 1966; G l e n c r o s s , 1976). Task d i f f i c u l t y was a l t e r e d by changing t a r g e t diameter and/or d i s t a n c e from the s t a r t i n g p o s i t i o n . F i t t s and Peterson (1964) and F i t t s and Radford (1966) found RL was r e l a t i v e l y independent of t a r g e t s i z e . G l e n c r o s s (1976) found RLs were s h o r t e r f o r l a r g e r t a r g e t s i n two of t h r e e experiments although these r e s u l t s were o n l y m a r g i n a l l y s i g n i f i c a n t . , Klapp (1975) obtained comparable r e s u l t s t o F i t t s and Peterson and F i t t s and Radford using a design s i m i l a r to F i t t s and Radford with movements o f 70 mm l o n g e r . However, with s h o r t e r movements, RL i n c r e a s e d as t a r g e t s i z e decreased. Klapp suggested t h a t longer movements were under feedback c o n t r o l whereas s h o r t e r movements were predominantly programmed d u r i n g the RL i n t e r v a l , with l o n g e r programming r e q u i r e d f o r more p r e c i s e movements. S i m i l a r l y Keele and Posner (1968) found t h a t the minimum amount of time necessary t o process v i s u a l feedback during a movement was between 190 and 260 msec. Movements l e s s than approximately 200 msec. were c o n s i d e r e d to be preprogrammed or open-loop i n nature. Klapp (1975) found t h a t the upper l i m i t f o r preprogrammed responses was 825 msec. These r e s u l t s may e x p l a i n t h e d i s c r e p a n c i e s i n f i n d i n g s , as i n the F i t t s and Peterson (1964) and F i t t s and Radford (1966) s t u d i e s , only a s m a l l p o r t i o n of the movements i n v e s t i g a t e d c o u l d be d e f i n e d as preprogrammed. Furt h e r r e s e a r c h by S i e g e l (1977), u s i n g aiming movements supported Klapp's (1975) c o n t e n t i o n s * From a mechanical p e r s p e c t i v e , L a s z l o and L i v e s e y (1977) v a r i e d accuracy by r e q u i r i n g groups of s u b j e c t s to draw l i n e s 19 through zero,one or two dots from dot p a t t e r n s on a moving paper runway. The zero-dot group had s i g n i f i c a n t l y s h o r t e r fiLs than the other two experimental groups, thus s u p p o r t i n g the c o n c l u s i o n t h a t accuracy was an important element of response complexity* Summarizing, r e s e a r c h e r s from both o r i e n t a t i o n s agree t h a t accuracy c o n t r i b u t e s t o complexity f o r movements l e s s than 70 mm long o r 200 msec, i n d u r a t i o n . I n f o r m a t i o n t h e o r i s t s f u r t h e r conclude t h a t : 1. D i f f i c u l t t a sks (as d e f i n e d by the index of d i f f i c u l t y ) r e q u i r e l o n g e r motor programs than l e s s d i f f i c u l t t a s k s . 2., Motor programs f o r movements s h o r t e r than 70 mm are completely read out before being executed. 3. Programs f o r movements lon g e r than 70 mm may be read out s e r i a l l y so t h a t RL i s independent of co m p l e x i t y . In c o n c l u s i o n t h e r e are three major problems p r e v e n t i n g a more p r e c i s e d e f i n i t i o n of complex i t y : 1. i n apparent f a c t o r of complexity i n a CRT s i t u a t i o n i s not n e c e s s a r i l y e v i d e n t using a SRT paradigm. For example, movement e x t e n t d i d not appear to be a f a c t o r of complexity when analyzed using a SRT paradigm, but was when c o n s i d e r e d under a CRT methodology. 20 2- The apparent r e l a t i o n s h i p between a f a c t o r and complexity may be confounded by the i n c l u s i o n of a p r a c t i c e e f f e c t ( v a r y i n g d i r e c t l y with the number of t r i a l s per subject) -3. When responses are read out s e r i a l l y , BL w i l l be the same as f o r a preprogrammed task and t h e r e f o r e no r e l a t i o n s h i p between com p l e x i t y and the p a r t i c u l a r f a c t o r can be e l u c i d a t e d . Given t h e s e c o n s t r a i n t s , what c o n s t i t u t e s complexity? With movements l e s s than 70 mm i n l e n g t h , and r e q u i r i n g m u l t i p l e b a c k t r a c k i n g , movement extent, movement r e v e r s a l s and accuracy a l l appear t o be components of complexity- In terms of the present study, RCB had i n c l u d e d i n i t s performance two r e v e r s a l s and a g r e a t e r movement extent than RCA, and was t h e r e f o r e c l a s s i f i e d as being of g r e a t e r complexity. Of p a r t i c u l a r r e l e v a n c e t o t h i s study i s the p r e d i c i t i o n of the memory drum theory t h a t movements of g r e a t e r complexity have l o n g e r RLs than movements of l e s s e r complexity. T h i s p r e d i c t i o n forms the b a s i s of the r a t i o n a l e s s u p p o r t i n g the d i f f e r e n t hypotheses. THE SPEED-ACCURACY TRADEOFF The speed-accuracy t r a d e o f f r e f e r s t o RLs performed at f a s t r a t e s a t the expense of accuracy and v i c e v e r s a . T h i s t r a d e o f f i s manipulated through i n s t r u c t i o n a l b i a s e s and p a y o f f s . Wickelgren(1977) argues the importance of employing such an experimental design. He s t a t e s t h a t i t i s so s u p e r i o r to the 21 t r a d i t i o n a l methodology, t h a t many p s y c h o l o g i s t s i n t e r e s t e d i n st u d y i n g the dynamics of i n f o r m a t i o n p r o c e s s i n g i n p e r c e p t i o n , memory, performance, p s y c h o l i n g u i s t i c s , and other c o g n i t i v e tasks, ought to do speed-accuracy t r a d e o f f s t u d i e s i n s t e a d o f r e a c t i o n time s t u d i e s . Numerous i n v e s t i g a t o r s have used speed-accuracy t r a d e o f f s to develop models of i n f o r m a t i o n p r o c e s s i n g . The models considered here i n c l u d e , two-state models {fast guess and d e a d l i n e ) , i n c r e m e n t a l models (random-walk, runs, r e c r u i t m e n t , accumulator, P o i s s o n counting and t i m i n g ) . Two other models may i n f a c t be s u b s i d i a r y models to those noted above but o f f e r d i f f e r e n t d e f i n i t i o n s o f accuracy ( a d d i t i v e and i n f o r m a t i o n t r a n s m i s s i o n ) . Two-State Models According to the ' f a s t guess 1 and 'deadline' models, the speed- accuracy t r a d e o f f r e s u l t s from a mixture of two d i s t i n c t types of responses* F a s t Guess Model. For the f a s t guess model, proposed by Y e l l o t (1967), the s u b j e c t responds i n an a l l - o r - n o n e f a s h i o n u s i n g e i t h e r a f a s t guess or a s t i m u l u s c o n t r o l l e d response. When a f a s t guess response i s used the s t i m u l u s i n f o r m a t i o n i s not c a t e g o r i z e d , r e s u l t i n g i n chance l e v e l accuracy. However, f o r a s t i m u l u s c o n t r o l l e d response, a l l the s t i m u l u s i n f o r m a t i o n i s used r e s u l t i n g i n high accuracy. I t i s assumed t h a t the s u b j e c t decides p r i o r to the onset o f the s t i m u l u s whether to 22 make a f a s t guess or a s t i m u l u s c o n t r o l l e d response- T h i s model p r e d i c t s the mean l a t e n c y f o r s t i m u l u s c o n t r o l l e d responses to be constant and slower than the mean l a t e n c y f o r f a s t guesses which are a l s o assumed to be con s t a n t . Thus, e r r o r l a t e n c i e s are p r e d i c t e d to be f a s t e r than the l a t e n c i e s f o r c o r r e c t responses. Y e l l o t (1971) t e s t e d these hypotheses i n three experiments. In the £irst> speed was s t r e s s e d by va r y i n g the d e a d l i n e b e f o r e which the s u b j e c t must have responded;. The s u b j e c t was rewarded f o r the percentage of responses that beat the d e a d l i n e . Accuracy was s t r e s s e d simply through i n s t r u c t i o n with no reward or d e a d l i n e . In the second experiment accuracy was i n c l u d e d i n the reward system by s u b t r a c t i n g p o i n t s a c c o r d i n g t o the percentage of i n c o r r e c t responses. The t h i r d experiment employed unegual s t i m u l u s p r o b a b i l i t i e s to f u r t h e r t e s t the i n v a r i a n c e o f the l a t e n c y f o r s t i m u l u s c o n t r o l l e d responses. In a l l t h r e e , the two p r e d i c t e d response s t r a t e g i e s emerged., L a t e n c i e s c o u l d be c a t e g o r i z e d as e i t h e r f a s t guesses or s t i m u l u s c o n t r o l l e d responses (SC8) . For SCH, the l a t e n c y d i d not vary a c r o s s a l l c o n d i t i o n s . The mean l a t e n c y f o r guesses was a l s o constant a c r o s s a l l c o n d i t i o n s i n experiments one and t h r e e . T h i s was the case i n experiment two as we l l except when the d e a d l i n e was lowered to l e s s than 150 msec. In a l l o t h e r cases a d i f f e r e n t response s t r a t e g y was n e c e s s a r i l y employed when s u b j e c t s were f o r c e d t o respond a t f a s t e r r a t e s . These f i n d i n g s support the assumptions of the f a s t guess model. Three experiments by Swensson and Edwards (1971) f u r t h e r confirmed the p r e d i c t i o n s of the f a s t guess theory. S u b j e c t s e i t h e r responded a c c u r a t e l y o r made a d e t e c t i o n response when 23 the s t i m u l u s appeared. Depending on the type of s t i m u l i . His were e i t h e r 15-20 msec, ( l i g h t to r i g h t or l e f t of screen) o r 45-70 msec, (angular l i n e t i l t e d t o r i g h t or l e f t ) f a s t e r f o r guesses. These s t u d i e s l e d Swensson (1972) to f u r t h e r i n v e s t i g a t e t h i s model using s t i m u l i which were more d i f f i c u l t to d i s c r i m i n a t e . The s t i m u l i c o n s i s t e d of diamond shapes skewed s l i g h t l y to the l e f t or r i g h t . The c r i t e r i o n used to d i s c r i m i n a t e between preprogrammed guesses and s t i m u l u s c o n t r o l l e d responses was t h a t the s u b j e c t s e l e c t e d h i s response on a block of c o n s e c u t i v e t r i a l s by a c o n s i s t e n t and mechanical r u l e , u n r e l a t e d to the i d e n t i t y of the s t i m u l u s . S u b j e c t s a g a i n used only the two types of s t r a t e g i e s assumed by the f a s t guess model. However, there was an i n c o n s i s t e n c y between the r e s u l t s and the p r e d i c t i o n s of the f a s t guess theory. The f a s t guess theory p r e d i c t e d e r r o r s to be f a s t e r than s t i m u l u s c o n t r o l l e d responses s i n c e they were the r e s u l t of f a s t guesses f o r which the s t i m u l u s i n f o r m a t i o n was not c a t e g o r i z e d . In t h i s case, e r r o r r a t e s of up to 12 percent occurred, even when a l l responses l e s s than 250 msec*, had been removed. T h i s f i n d i n g s e r i o u s l y threatened the assumption of a l l - o r - n o n e d i s c r i m i n a t i o n . To f u r t h e r t e s t t h i s , Swensson, v a r i e d the i n c e n t i v e f o r a c c u r a t e , r e l a t i v e t o f a s t performance i n two experiments. The r e s u l t i n g t r a d e o f f s between speed and accuracy c o u l d not be accounted f o r by a q u a l i t a t i v e change i n the number of f a s t guesses. Thus the f a s t guess model's assumption of a l l -or-none d i s c r i m i n a t i o n was r e j e c t e d . In a r e c o g n i t i o n memory task, i n which the s t i m u l u s was 24 e i t h e r one of a given s e t of consonants or not, Seed (1973) found the lowest accuracy to be a s s o c i a t e d with the l o n g e s t l a t e n c i e s . T h i s i s again i n c o n t r a s t to the f a s t guess p r e d i c t i o n of low response l a t e n c i e s f o r e r r o r s . Green and Luce (1973) i n v e s t i g a t e d the speed-accuracy t r a d e o f f u sing an a u d i t o r y s t i m u l u s . In one c o n d i t i o n the d e a d l i n e b e f o r e which a response had t o be made was v a r i e d between 250 and 2000 msec. In a second c o n d i t i o n the d e a d l i n e was f i x e d a t 600 i s e c . and the payoff matrix t o s t r e s s accuracy v a r i e d . The authors note t h a t the l i n e a r p r e d i c t i o n of the f a s t guess model f o r mean l a t e n c y f o r a c o r r e c t response has been g e n e r a l l y supported f o r easy to d i s c r i m i n a t e s t i m u l i except f o r c o n d i t i o n s of extreme accuray. flnder these c i r c u m s t a n c e s the data p o i n t s are well above the e x t r a p o l a t e d l i n e a r curve. The data from t h e i r study conform to the theory f o r a 50 d e c i b e l s i g n a l but are much more d i s c r e p a n t f o r a 20 d e c i b e l s i g n a l s They concluded t h a t s u b j e c t s may use more than the two s t a t e s o f responding suggested by the f a s t guess model and that perhaps the s u b j e c t e n t e r s i n t o some s o r t of s e g u e n t i a l d e c i s i o n making. Summarizing, the f a s t guess model's p r e d i c t i o n s appear t o be supported when the s t i m u l i are e a s i l y d i s c r i m i n a b l e but f a l l down when more d i f f i c u l t d i s c r i m i n a t i o n t a s k s are employed. Deadline Model. The d e a d l i n e model was proposed by Oilman (1966) and f u r t h e r e l a b o r a t e d on by Oilman and B i l l i n g t o n (1972). fwo types of responses are assumed t o occur, d e a d l i n e and d e t e c t i o n responses with the processes f o r both proceeding s i m u l t a n e o u s l y . I t i s assumed t h a t the s u b j e c t uses a warning s i g n a l to i n i t i a t e a process of time e s t i m a t i o n . At the same 25 time, the s u b j e c t attempts t o e n t e r a d i s c r i m i n a t i o n s t a t e to determine which s t i m u l u s has occurred and t o then i n i t i a t e a response based on t h i s d i s c r i m i n a t i o n . T h i s i s a d e t e c t i o n response. I f a s t i m u l u s - t r i g g e r e d d e t e c t i o n response has not occurred by the time the d e a d l i n e e l a p s e s then a d e a d l i n e response i s made based upon the s u b j e c t ' s a n t i c i p a t i o n o f what response w i l l occur* Thus the s u b j e c t responds e i t h e r when the estimated d e a d l i n e e l a p s e s or when a d e t e c t i o n response has o c c u r r e d , whichever comes f i r s t . The t r a d e o f f between speed and accuracy i s assumed to r e s u l t from v a r i a t i o n s of t h e d e a d l i n e time. «ith a s h o r t e r d e a d l i n e more guesses would occur and with very s h o r t d e a d l i n e s accuracy i s at chance l e v e l * An extended d e a d l i n e would r e s u l t i n more d e t e c t i o n responses but with e r r o r s having a l o n g e r BL than c o r r e c t responses. The l a t t e r case i s p a r t i c u l a r l y t r u e f o r s i t u a t i o n s i n which the s t i m u l i are d i f f i c u l t to d i s c r i m i n a t e . I f a d e t e c t i o n response has not been made by the time the d e a d l i n e e l a p s e s , a guess i s made. Swensson (1974) c r i t i c i z e d the model s t a t i n g t h a t i t r e q u i r e d more complete s p e c i f i c a t i o n of the p r o b a b i l i t y d i s t r i b u t i o n s assumed f o r the d e a d l i n e and d i s c r i m i n a t i o n d e l a y s , as w e l l as needing a demonstration t h a t the two processes c o u l d be c a r r i e d out independentyly a t the same time. However, a n a l y s i s of e r r o r l a t e n c i e s i n the three experiments of Swensson (1972) noted e a r l i e r , which v a r i e d the s t r e s s on speed and accuracy, d i d support the c o n t e n t i o n s of the d e a d l i n e model. Hhen the d e a d l i n e decreased e r r o r s were i n c r e a s i n g l y f a s t e r than c o r r e c t responses whereas under an accuracy s t r e s s , e r r o r s were 2 6 slower than c o r r e c t responses. Wilding (1974) a l s o c r i t i c i z e d the model s t a t i n g that the model does not i n c o r p o r a t e the machinery necessary to produce a longer d i s c r i m i n a t i o n process when the d e c i s i o n i s more d i f f i c u l t . He f u r t h e r a s s e r t e d t h a t only with some p r e l i m i n a r y a n a l y s i s o f the in p u t c o u l d the d e a d l i n e be extended on those t r i a l s when the d e c i s i o n i s more d i f f i c u l t . W i l d i n g then s e t up an experiment t o t e s t the p r e d i c t i o n s of the d e a d l i n e model u s i n g a m u l t i p l e s t i m u l u s s i t u a t i o n i n which the s u b j e c t had to decide on which s i d e o f the ce n t e r a p o i n t of l i g h t f e l l . Of e i g h t p r e d i c t i o n s from the model, one cou l d not be t e s t e d , s i x were r e f u t e d and one accepted* I t was noted t h a t the one p r e d i c t i o n t h a t was accepted c o u l d a l s o be p r e d i c t e d by s e v e r a l o t h e r t h e o r i e s . Thus, the o v e r a l l model was r e j e c t e d by Wilding-Wickelgren (1977), summarized the l i t e r a t u r e , s t a t i n g o f the two models - f a s t guess and de a d l i n e - t h a t , " i t i s now p e r f e c t l y c l e a r t h a t speed-accuracy t r a d e o f f f u n c t i o n s , i n gen e r a l , a re not the r e s u l t of d i f f e r e n t p r o p o r t i o n s of f a s t guesses" (pg. 79). Of the present t h e o r i e s a v a i l a b l e , Wickelgren expressed doubt as to acceptance of any one i n p a r t i c u l a r i n the near f u t u r e . Incremental Models Incremental models i n c l u d e those models which purport to the s t i m u l u s i n f o r m a t i o n being processed by sampling. The speed-accuracy t r a d e o f f i s produced through p a r t i a l p r o c e s s i n g of the st i m u l u s i n f o r m a t i o n . These models i n c l u d e the s t a t i s t i c a l d e c i s i o n or random walk model and the data accumulation models 27 c o n s i s t i n g of the runs, r e c r u i t m e n t and accumulator models. I t should be noted t h a t some au t h o r s , f o r example Swensson and Thomas (1974) view accumulator models as s p e c i a l cases of the random walk model. Poisson counting and t i m i n g models have a l s o been c o n s i d e r e d under t h i s category s i n c e both assume t h a t the s u b j e c t : observes d i f f e r e n t f u n c t i o n s of the v a r i a b l e s t i m u l u s i n p u t . .Random Walk Model. The random walk model was o r i g i n a l l y proposed by Stone i n 1960, extended by Edwards i n 1965 and then taken up by F i t t s i n 1966. I t i s assumed t h a t with the onset o f a warning l i g h t the s u b j e c t s t a r t s t o make repeated but independent o b s e r v a t i o n s of an u n r e l i a b l e p e r c e p t u a l s i g n a l i . e . i t i s n o i s y u n t i l the s t i m u l u s s i g n a l i s added to i t . Observations a r e c o n s i d e r e d to be repeated at a constant r a t e p r o p o r t i o n a l to BL, with the o b s e r v a t i o n s then s t o r e d i n a s i n g l e ' r e g i s t e r * . Each o b s e r v a t i o n a c t s to change the c u r r e n t value i n the r e g i s t e r , adding or s u b t r a c t i n g an amount assumed to depend on which s t i m u l u s was more l i k e l y t o have produced i t - r e f e r r e d to as l i k e l i h o o d t e s t s . One o f two s t o p p i n g r u l e s i s proposed to be employed by the s u b j e c t . With the o p t i o n a l s t o p p i n g r u l e , i n a two c h o i c e task, sampling i s terminated when the l i k e l i h o o d r a t i o exceeds one or the other of two c r i t e r i o n boundaries. The a p p r o p r i a t e response i s then s e l e c t e d and executed* I t i s r e l e v a n t to note t h a t the d e c i s i o n t o respond i s i n f l u e n c e d not by how much time has been spent o b s e r v i n g , as i n the d e a d l i n e model, but r a t h e r when the c u t o f f values have been reached* The l o c a t i o n s of the boundaries are assumed to be under the s u b j e c t ' s c o n t r o l and determined by the r e l a t i v e emphasis on 28 speed versus accuracy. Using the f i x e d s topping r u l e , the s u b j e c t predetermines the l e n g t h of h i s o b s e r v a t i o n sequence so that the number of samples taken i s f i x e d . The s u b j e c t then bases h i s response on whatever evidence these o b s e r v a t i o n s provide. E i t h e r type of s t o p p i n g r u l e can generate a speed-accuracy t r a d e o f f . For o p t i o n a l s t o p p i n g , reduced s t i m u l u s c r i t e r i a l e a d to s h o r t e r l a t e n c i e s , f o r f i x e d s t o p p i n g , a change i n sampling time has the same e f f e c t . Swensson and Thomas (1974) note t h a t the o p t i o n a l stopping r u l e might be deemed more a p p r o p r i a t e f o r experiments i n which the s u b j e c t has u n l i m i t e d access to the s t i m u l u s f o r d i s c r i m i n a t i o n or when he i s motivated to minimize h i s mean RL. The f i x e d s topping r u l e was suggested to be more a p p r o p r i a t e when the s u b j e c t has l i m i t e d a c c e s s to the s t i m u l u s or when the s u b j e c t attempts to minimize h i s RL v a r i a b i l i t y about some s p e c i f i e d v a l u e . Pew (1969) i n v e s t i g a t e d the s t a t i s t i c a l d e c i s i o n model on the b a s i s of the hypothesis that RL should be c o r r e l a t e d with r e l a t i v e c o n f i d e n c e on a l o g a r i t h m i c s c a l e , i . e . the longer the time spent responding, the more c o n f i d e n t the s u b j e c t would be t h a t h i s response was c o r r e c t . He p l o t t e d the log odds ( r a t i o o f c o r r e c t responses to e r r o r s ) versus RL on the data from s e v e r a l d i f f e r e n t s t u d i e s . S i n c e a l i n e a r t r e n d held r e g a r d l e s s of the manner i n which speed or accuracy was manipulated, Pew concluded that the b a s i c concepts of the s t a t i s t i c a l d e c i s i o n model were s t r o n g l y supported. Swensson and Edwards (1971) t e s t e d p r e d i c t i o n s of the random walk model i n comparison with those from the f a s t guess 29 model by d e v i s i n g a system which rewarded s u b j e c t s f o r c o r r e c t responses, but charged a c o s t p r o p o r t i o n a l t o t h e i r response time. Seven of t h e i r e i g h t s u b j e c t s f o l l o w e d the f a s t guess model's p r e d i c t i o n s f o r maximizing p a y o f f s . S u b j e c t s e i t h e r responded a c c u r a t e l y throughout, or they predetermined t h e i r responses by a simple r u l e on a l l 300-450 t r i a l s (eg. l e f t on every t r i a l ) and performed f a s t e r . Thus, the random walk model was not supported. Swensson (1972) i n a f u r t h e r attempt to t e s t the p r e d i c t i o n s of the f a s t guess model, i n comparison with those of the random walk model used s t i m u l i which were more d i f f i c u l t to d i s c r i m i n a t e than those employed by Swensson and Edwards (1971). The data a g a i n c o n t r a d i c t e d the random walk model's p r e d i c t i o n t h a t s u b j e c t s can process i n t e r m e d i a t e amounts of evidence about the i d e n t i t y of the s t i m u l u s befor responding. ,: V i c k e r s e t a l . (1971) used a method i n c o r p o r a t i n g p r o b a b i l i t y to analyze the p r e d i c t i o n of the random walk, runs and r e c r u i t m e n t models. The task f o r each s u b j e c t was t o i n d i c a t e which of two c o l o u r e d l i g h t s was programmed to f l a s h more f r e q u e n t l y . None of the three models gave a good account o f the data, although the r e c r u i t m e n t model was the best of the t h r e e . For the random walk .-. model, a suggestion was made to modify the c r i t e r i o n boundary such t h a t , i n s t e a d of i t being s t e a d f a s t i t a c t u a l l y decreased as the t r i a l progressed. T h i s m o d i f i c a t i o n was r e p o r t e d as r e c e i v i n g some support from p r e v i o u s r e s e a r c h using a s i m i l a r methodology but i t too was s e t a s i d e i n f a v o u r of the accumulator model. Green and Luce (1973) c r i t i c i z e d the random walk model 3 0 s t a t i n g t h a t p r e d i c t i o n s sere simply i n e q u a l i t i e s without any i n d i c a t i o n of the magnitude of the d i f f e r e n c e t h a t should be found. They f u r t h e r s t i p u l a t e d t h at because of the random s t r u c t u r e of the model, i t i s i n h e r e n t l y d i f f i c u l t t o a n a l y z e and t h e r e f o r e a search f o r a s i m p l e r model would be more b e n e f i c i a l . Wilding (1974) analyzed the d e a d l i n e model but a l s o considered whether any of the i n c r e m e n t a l models would p r o v i d e an adequate f i t to the data he c o l l e c t e d . The r e s u l t s from the m u l t i p l e s t i m u l u s dual response s i t u a t i o n confirmed the grounds of V i c k e r s e t a l . (1971) f o r r e j e c t i n g the random walk, runs and r e c r u i t m e n t models. Based on a review of the l i t e r a t u r e , Audley (1973) ev a l u a t e d the s t a t i s t i c a l d e c i s i o n model and found i t to be compatible with the statement t h a t as a RL f o r c o r r e c t responses decreases, the RL f o r e r r o r responses shows a corr e s p o n d i n g decrease. However, the major problem a s s o c i a t e d with the model was r e p o r t e d t o be i t s i n a b i l i t y to account f o r the f i n d i n g t h a t RL f o r e r r o r s i s u s u a l l y s h o r t e r than f o r c o r r e c t responses. M o d i f i c a t i o n s suggested by Laming (1968) and F i t t s (1966) were noted as r e q u i r i n g f u r t h e r e x p l o r a t i o n . Audley concluded though by s t a t i n g t h a t t h i s model " g i v e s the most coherent account o f the phenomena of c h o i c e r e a c t i o n s t h a t I have reviewed" (pg. 504). Thus, although there appears to be a wealth of evidence r e f u t i n g the random walk model, i t c o n t i n u e s to be c o n s i d e r e d as a v i a b l e o p t i o n (eg. Swensson and Green, 1977) i n the search f o r an e x p l a n a t i o n o f the speed- accuracy t r a d e o f f . 31 Data Accumulation Models. Data accumulation models assume the same number o f r e g i s t e r s accumulating evidence as there are s t i m u l i . T h i s f e a t u r e i s i n o p p o s i t i o n to the random walk model which p o s t u l a t e s only one r e g i s t e r . In the data accumulation models the value of each r e g i s t e r can only be i n c r e a s e d by new s t i m u l u s i n f o r m a t i o n - never decreased as a g a i n i s the case f o r the random walk. Thus, each o b s e r v a t i o n i s assumed to a f f e c t o n l y one r e g i s t e r without a f f e c t i n g the o t h e r s . Buns Model. The runs model was proposed by Audley i n 1960 and c o n s i s t s p r i m a r i l y of two assumptions. The f i r s t assumption i s that a s i n g l e parameter i s a s s o c i a t e d with each p o s s i b l e response i n a CBT s i t u a t i o n . T h i s parameter determines the p r o b a b i l i t y of an • i m p l i c i t * response o c c u r r i n g w i t h i n a time i n t e r v a l . I t i s thought t h a t parameters are independent of one another, such that i m p l i c i t responses of each kind may appear a t random u n a f f e c t e d by the appearance of other i m p l i c i t responses. The d i s t r i b u t i o n o f the i n t e r v a l s between s u c c e s s i v e i m p l i c i t responses of a given k i n d i s c o n s i d e r e d to be e x p o n e n t i a l and determined e n t i r e l y by the response parameter. The second assumption i s concerned with when a run of k i m p l i c i t responses of a g i v e n k i n d appears, with t h i s run being u n i n t e r r u p t e d by occurrences of i m p l i c i t responses of other k i n d s . The speed-accuracy t r a d e o f f i s r e f l e c t e d i n the value set f o r k. V i c k e r s (1970) c r i t i c i z e d the runs model s t a t i n g t h at when data from s e v e r a l experiments were analyzed i n the form of l a t e n c y - p r o b a b i l i t y f u n c t i o n s ( i . e . the l a t e n c y of a c o r r e c t 32 response t o the p r o b a b i l i t y of responding c o r r e c t l y ) the r e s u l t s were c l e a r l y i n c o n s i s t e n t with a runs process. The runs model p r e d i c t s t h a t when accuracy i s s t r e s s e d the s u b j e c t waits f o r a longer run of k i m p l i c i t responses before making a d e c i s i o n . Thus, the model c o u l d not account f o r e r r o r s made at l o n g e r l a t e n c i e s , as noted e a r l i e r , both V i c k e r s e t a l * (1971) and Wilding (1974) r e j e c t e d the runs model i n f a v o u r of the accumulator model. Beernitment Incremental Model. The core assumption of the recru i t m e n t i n c r e m e n t a l model, proposed by La Berge (1962), i s that a s u c c e s s i o n of s t i m u l u s sampling events i s necessary t o evoke a p a r t i c u l a r response. The number of elements i n a st i m u l u s p o p u l a t i o n t h a t can be sampled, corresponds to the s t r e n g t h o f the stimulus-response bond i . e . the stronger the bond, the g r e a t e r the number of elements t h a t can be sampled. The . p r o p o r t i o n of these elements needed to evoke a response i s decided on p r i o r t o st i m u l u s onset and i s a f f e c t e d by m o t i v a t i o n a l f a c t o r s such t h a t , when accuracy i s s t r e s s e d the number o f elements to be sampled f o r a p a r t i c u l a r response i n c r e a s e s , whereas i t decreases when speed i s s t r e s s e d . Thus, i n the CHT s i t u a t i o n , the s u b j e c t randomly samples elements one by one, i n any order u n t i l he r e c r u i t s a s u f f i c i e n t number of elements of a p a r t i c u l a r t y p e . The s u b j e c t then emits the corresponding response. Other elements from the d i f f e r e n t response a l t e r n a t i v e s may i n t e r v e n e among the sampled s e r i e s o f elements of the p a r t i c u l a r type. The sampling ends when the number of elements of the p a r t i c u l a r type reaches a l e v e l determined by the s u b j e c t p r i o r t o s t i m u l u s onset. V i c k e r s e t 33 a l . (1971) s t a t e that the c r i t e r i o n (K) f o r a response to occur i s the t o t a l o f e i t h e r K p o s i t i v e or K negative d i f f e r e n c e s . V i c k e r s (1970) found f a u l t with the r e c r u i t m e n t model on two counts. The f i r s t f a c t o r concerned c l a s s i f i c a t i o n of the elements. He noted t h a t the model d i d not c o n s i d e r the d i f f i c u l t y of e s t i m a t i n g v a r i a n c e s i n the s i g n a l s . The v a r i a n c e would determine the amount o f o v e r l a p between s i g n a l s and thus the p r o p o r t i o n o f events c l a s s i f i e d as one or another element would be a f f e c t e d . Tor the second f a c t o r , V i c k e r s commented t h a t , i f the time taken t o accumulate each sample were m u l t i p l i e d by the minimum number of elements r e q u i r e d f o r a d e c i s i o n to be made, the p r e d i c t e d l a t e n c i e s would c o n s i d e r a b l y exceed those a c t u a l l y observed-fts noted i n the previous d i s c u s s i o n r e g a r d i n g the random walk model, both V i c k e r s e t (1971) and Wilding (1974) r e j e c t e d t h e runs and r e c r u i t m e n t models. In the study by V i c k e r s e t ajU (1971) the r e c r u i t m e n t model provided the best account f o r p r e d i c t i n g s m a l l v a r i a t i o n s i n accuracy through v a r i a t i o n s i n the number o f elements r e q u i r e d before responding. I t a l s o provided the best account f o r response p r o b a b i l i t y and mean l a t e n c y but not f o r standard d e v i a t i o n . The p r e d i c t i o n o f the r e c r u i t m e n t model, that a l l d i s t r i b u t i o n s f o r i n c o r r e c t responses should be n e g a t i v e l y skewed (the longer the l a t e n c y , the fewer the e r r o r s ) was a l s o not s u b s t a n t i a t e d s i n c e a s i g n i f i c a n t p r o p o r t i o n was found to be p o s i t i v e f o r each s u b j e c t . A v a r i a b l e recruitment model was suggested as an a l t e r n a t i v e i n order to account f o r the r e s u l t s . With t h i s model the number of elements that have to be r e c r u i t e d f l u c t u a t e from 34 t r i a l t o t r i a l r a t h e r than remaining f i x e d . accumulator Model. V i c k e r s (1970) proposed the accumulator as an a l t e r n a t i v e t o the random walk, runs and r e c r u i t m e n t models. In a two c h o i c e r e a c t i o n time experiment, i t i s proposed t h a t , the s u b j e c t samples i n f o r m a t i o n from each s t i m u l u s p o s s i b i l i t y (a and B) to form an i n t e r n a l r e p r e s e n t a t i o n of each. P e r t u r b a t i o n s i n A and B occur independently. The s u b j e c t i s then supposed to make a s e r i e s of comparisons between the v a l u e s of A and the values o f B. The r e s u l t s of these comparisons a r e a s u c c e s s i o n of B e r n o u i l l i t r i a l s such that success i s met by the value of A being g r e a t e r than the value of B while f a i l u r e i s the r e v e r s e . I t i s f u r t h e r assumed that the s u b j e c t c o n t i n u a l l y samples the outcomes of these t r i a l s and makes two running t o t a l s Ta and Tb of the amounts o f success and f a i l u r e r e s p e c t i v e l y . A response i s made when Ta or Tb reaches some c r i t e r i o n value Ca or Cb. The c r i t e r i o n v a l u e s are assumed to be predetermined by the s u b j e c t and capable of adjustment by him. I t i s i n t e r e s t i n g to note the s i m i l a r i t i e s between t h i s model and the random walk model, the terminology being the major f a c t o r d i f f e r e n t i a t i n g them. Both p o s t u l a t e comparisons of the s t i m u l u s i n p u t based on the number of s t i m u l i , the accumulator by B e r n o u i l l i t r i a l s , the random walk by l i k e l i h o o d t e s t s . As w e l l both assume t h a t the outcome of these t r i a l s w i l l be t o t a l e d , one t o t a l of which w i l l e v e n t u a l l y reach a c r i t e r i o n value or boundary s e t by the s u b j e c t . The response, f o r both, i s then made based on which boundary has been reached. When the random walk, runs and r e c r u i t m e n t models a l l proved to be inadequate, V i c k e r s e t a l . (1971) suggested t h r e e 35 a l t e r n a t e s - a random walk model i n which the c r i t e r i o n boundary decreases as the t r i a l progresses; a v a r i a b l e r e c r u i t m e n t model, i n which the c r i t e r i o n to respond v a r i e s randomly from t r i a l to t r i a l and the accumulator model, of the t h r e e , the accumulator model provided the b e s t accounting of the data., The authors cautioned o u t r i g h t acceptance o f the model as no r a t i o n a l e f o r a s s i g n i n g a value to the v a r i a n c e upon which the whole p a t t e r n of p r e d i c t i o n s depends, had been o f f e r r e d . In W i l d i n g ' s (1974) study, the accumulator model was m a r g i n a l l y b e t t e r i n i t s p r e d i c t i o n s than the v a r i a b l e r e c r u i t m e n t model. F a i l u r e o f the model to p r e d i c t adequate changes i n standard d e v i a t i o n over a wide range of response p r o b a b i l i t y as w e l l as i n a c c u r a t e p r e d i c t i o n of skew and k u r t o s i s f o r high l e v e l s of d i s c r i m i n a b i l i t y were noted. I t appears t h a t o f the c l a s s of data accumulation models, the accumulator model p r o v i d e s the best accounting of the a v a i l a b l e data. Researchers a r e guick to warn though t h a t m o d i f i c a t i o n s as w e l l as f u r t h e r experimental v e r i f i c a t i o n are necessary before acceptance can be a c h i e v e d . Poisson Counting And Timing Models,. The poisson counting and t i m i n g models were proposed by Green and Luce (1973). The counting model assumes t h a t the sensory t r a n s d u c e r c o n v e r t s s i g n a l energy i n t o one or more n e u r a l p u l s e t r a i n s . As s i g n a l i n t e n s i t y i n c r e a s e s the r a t e of pu lses i s expected t o i n c r e a s e c o n c o m i t a n t l y . The s u b j e c t then s e l e c t s a time p e r i o d and counts the number of p u l s e s f o r t h i s 3 6 p e r i o d . I f the number of pulses i s g r e a t e r than some c r i t e r i o n , he responds i n one way, i f the number i s s m a l l e r he responds i n another. The t i m i n g model assumes t h a t a f i x e d number of p u l s e s are c o l l e c t e d and the i n t e r a r r i v a l time i s measured. The s u b j e c t makes response R1 i f the mean of these i n t e r a r r i v a l times i s l e s s than some pr e s e t c r i t e r i o n and responds H2, i f i t i s g r e a t e r . In an a u d i t o r y d e t e c t i o n experiment (Green and Luce, 1973), s u b j e c t s had t o respond e i t h e r yes or no as t o whether or not they had heard a s i g n a l tone. Bhen a d e a d l i n e , before which the s u b j e c t had to respond, was imposed o n l y on s i g n a l t r i a l s the data favoured the t i m i n g model. Khen a f i x e d d e a d l i n e was imposed on both s i g n a l and n o i s e t r i a l s the c o u n t i n g model was favoured. The authors suggest t h a t the order of p r e s e n t a t i o n o f c o n d i t i o n s s t r o n g l y i n f l u e n c e d t h e i r r e s u l t s . Owing to the r e l a t i v e recency of these models, l i t t l e has been p u b l i s h e d t o date e v a l u a t i n g t h e i r v a l i d i t y . A d d i t i v e Model The a d d i t i v e model p o s t u l a t e s a weak p e r c e p t u a l s i g n a l t h a t grows i n s t r e n g t h a t a c o n s t a n t r a t e , such t h a t a p e r c e p t u a l s i g n a l i n the nth o b s e r v a t i o n i n t e r v a l i s n times as s t r o n g as a s i g n a l i n the f i r s t o b s e r v a t i o n i n t e r v a l . G a r r e t t (1922) s t a t e s t h a t a coalescence o f the f a c t o r s i n v o l v e d would g r a d u a l l y occur and i n consequence t h e r e would be an i n c r e a s e i n c o n f i d e n c e with which the judgement would be made. The s i g n a l d e t e c t i o n theory v e r s i o n of t h i s g e n e r a l model. 37 r e p o r t e d by Lappin and Discli (1972) assumes t h a t , i n s e l e c t i n g h i s response at any time, the s u b j e c t must dec i d e whether the c u r r e n t l y a v a i l a b l e p e r c e p t u a l s i g n a l i s a n , i n s t a n c e of one or the other of two random v a r i a b l e s i n a two c h o i c e BT task. These v a r i a b l e s are assumed to be randomly d i s t r i b u t e d with e g u a l v a r i a n c e but d i f f e r i n g i n means by an amount d' - the measure o f d e t e c t a b i l i t y * The s i g n a l s t r e n g t h i s f u r t h e r assumed to i n c r e a s e at a c o n s t a n t amount i n each s u c c e s s i v e time i n t e r v a l . Bhen speed i s s t r e s s e d a response i s made when the p e r c e p t u a l s i g n a l i s s t i l l weak, thus the BL i s s h o r t e r but with a high percentage of e r r o r s . With an accuracy s t r e s s , the s u b j e c t waits u n t i l the p e r c e p t u a l s i g n a l i s s t r o n g e r before r e s p o n d i n g . In t h i s case the BL i s l o n g e r and fewer e r r o r s are recorded. Lappin and D i s c h (1972) r e p o r t t h a t t h i s model d e f i n e s accuracy i n terms of d* whereas the s t a t i s t i c a l , d e c i s i o n model d e f i n e s i t as (d*) .However, Pew (1969) c o n s i d e r s t h i s model to be c o n s i s t e n t with the s t a t i s t i c a l d e c i s i o n model. In f o r m a t i o n T r a n s m i s s i o n Model.. The i n f o r m a t i o n t r a n s m i s s i o n model of BL p o s t u l a t s t h a t BL i s l i n e a r l y r e l a t e d to the u n c e r t a i n t y between s t i m u l u s i n p u t and response output. I t i s based on M H i c k * s Law" - i n CRT s i t u a t i o n s with 1:1 s t i m u l u s response mappings, the average u n c e r t a i n t y of a s e t of s t i m u l i i s l i n e a r l y r e l a t e d t o the average amount of time needed t o respond to a s t i m u l u s from that s e t * The d e f i n i t i o n of s t i m u l u s u n c e r t a i n t y i n c l u d e s v a r i a t i o n of a) the number of s t i m u l u s a l t e r n a t i v e s , b) s t i m u l u s 33 p r o b a b i l i t i e s and c) s e q u e n t i a l dependencies of s t i m u l i upon p r e s e n t a t i o n (Hick, 1952; Hyman, 1953). In t h i s theory RL i s p r e d i c t e d by the equ a t i o n : HT=A*B(Ht) RT=response l a t e n c y , A=total encoding and decoding time, B= c e n t r a l p r o c e s s i n g time, Ht=information t r a n s m i t t e d . P a c h e l l a , F i s h e r and Karsh (1968) f e l t t h a t Hick's Law c o u l d be the key to the speed-accuracy t r a d e o f f . They e s t a b l i s h e d a l i n e a r r e l a t i o n s h i p between i n f o r m a t i o n t r a n s m i t t e d and RL f o r an absolute judgement t a s k which i n c l u d e d 10 p o s s i b l e s t i m u l i * T h i s r e s u l t was r e p l i c a t e d by P a c h e l l a and F i s h e r (1972). Swansson and B r i g g s (1969) argued f o r a response l a t e n c y equation which employed as the b a s i c p r e d i c t o r v a r i a b l e an exp r e s s i o n of c e n t r a l p r o c e s s i n g u n c e r t a i n t y (He) r a t h e r than i n f o r m a t i o n t r a n s m i t t e d i . e . RT|Ht=A*-B (He). For a s t i m u l u s c a t e g o r i z a t i o n task i n which speed and accuracy were s t r e s s e d f o r s e p e r a t e groups, RL was found t o be a l i n e a r f u n c t i o n of c e n t r a l p r o c e s s i n g u n c e r t a i n t y . Swanson and B r i g g s i n t e r p r e t e d t h e i r r e s u l t s as being c o n s i s t e n t with the s t a t i s t i c a l d e c i s i o n model and suggested a f u r t h e r a l t e r a t i o n to the RL equation; RT=C+D(Ht)+B(He) C= i n i t i a l encoding ( c o n s t a n t ) , D= time t o sample encoded s t i m u l u s i n f o r m a t i o n i n u n i t s per second per b i t of i n f o r m a t i o n t r a n s m i t t e d . A l l the models presented i n t h i s s e c t i o n have s t r i k i n g 39 s i m i l a r i t i e s . They a l l p o s t u l a t e : 1. s e q u e n t i a l sampling of the s t i m u l u s i n p u t ; 2. s e t t i n g of c r i t e r i o n values or boundaries; 3- basing the d e c i s i o n t o respond on e i t h e r a set time l i m i t or a s e t amount of i n f o r m a t i o n ; 1. when a speed s t r e s s i s imposed, the s u b j e c t i s f o r c e d to make a d e c i s i o n on a reduced amount of i n f o r m a t i o n and then to respond a c c o r d i n g l y ; 5.., with an accuracy s t r e s s more i n f o r m a t i o n can be compiled before a d e c i s i o n i s made, thereby i n c r e a s i n g the c e r t a i n t y t h a t the s u b j e c t responds c o r r e c t l y . I t i s obvious from the preceeding d i s c u s s i o n that no adequate accounting of the data on the speed-accuracy t r a d e o f f has been p r o v i d e d by any of the p r e s e n t l y a v a i l a b l e models. I t i s not the purpose of t h i s study to determine which of these models p r o v i d e s the best accounting of the d a t a . I t i s s u f f i c i e n t to note t h a t the speed-accuracy t r a d e o f f i s r e l e g a t e d by some form of s t i m u l u s sampling. 40 Chapter 3 METHODS AND PBOCEDUfiES SUBJECTS To ensure that t h e complex task Has more d i f f i c u l t than the simple task, 39 right-handed male v o l u n t e e r s , a t t e n d i n g the U n i v e r s i t y of B r i t i s h Columbia were t e s t e d t o o b t a i n t h e i r simple r e a c t i o n times on both t a s k s . Those 24 p a r t i c i p a n t s who e x h i b i t e d the g r e a t e s t d i f f e r e n c e i n response l a t e n c y between the two t a s k s were then used as s u b j e c t s . T h i s procedure was n e c e s s i t a t e d because ten per cent of the s u b j e c t s from a p r e v i o u s study (Leech,1977) showed the opposite r e a c t i o n with the complex task being f a s t e r than the simple. T h e r e f o r e i n order to ensure t h a t s u b j e c t s were r e s p o n s i v e to the e x p e r i m e n t a l treatments, they were screened p r i o r t o p a r t i c i p a t i n g i n the experiment. A P P a B A T U S The r e a c t i o n - t i m e apparatus i n c l u d e d separate c o n s o l e s f o r the s u b j e c t and the experimenter. The s u b j e c t ' s c o n s o l e c o n s i s t e d of a c e n t r a l l y l o c a t e d warning l i g h t , 6.5 cm above s i x s t i m u l u s l i g h t s placed h o r i z o n t a l l y 7.5 cm above s i x response keys. The s t i m u l u s l i g h t s used i n the study were numbers three and f o u r as i n d i c a t e d i n F i g u r e 2, and the response keys corresponded to the index f i n g e r s of e i t h e r hand. Located at the top of the c o n s o l e , 21.5 cm above the response keys, were three 41 l a r g e r movement-response keys (MRK) 2.5 cm long and 5.0 cm wide, and spaced 6.5 cm apart. When depressed, the MRK stopped a d i g i t a l c l o c k - t i m e r , thereby completing one t r i a l . , The experimenter's console was separated from t h a t of the s u b j e c t by approximately 1.22 m, with a d i v i d e r between them. Included i n the experimenter's c o n s o l e was a programmer, a r e a c t i o n - t i m e i n t e r f a c e , and a d i g i t a l p r i n t e r . The programmer was used t o s e l e c t the f o f e p e r i o d and s t i m u l u s l i g h t s , and to i n i t i a t e a warning and s t i m u l u s l i g h t seguence f o r each t r i a l . Response l a t e n c y and movement time were recorded i n m i l l i s e c o n d s by the r e a c t i o n - t i m e i n t e r f a c e and d i g i t a l p r i n t e r - Recording o f the complete movement time f o r the complex task was not p o s s i b l e because of the equipment* all c o r r e c t responses were recorded i n black and a l l i n c o r r e c t responses were recorded i n red. RESPONSE TASKS. S u b j e c t s were r e q u i r e d t o respond to one o f two p o s s i b l e s t i m u l u s l i g h t s with the a p p r o p r i a t e movement response (MR). When s t i m u l u s * A' o c c u r r e d , the s u b j e c t was r e q u i r e d to depress response key A with h i s index f i n g e r , and then move as q u i c k l y as p o s s i b l e t o depress the c e n t r a l l y l o c a t e d MRK (see F i g u r e 2 ) . T h i s response was r e f e r r e d t o as RCA. RCB r e q u i r e d the s u b j e c t to depress response key B with t h e index f i n g e r when s t i m u l u s 'B* o c c u r r e d , and then depress MRK no. 1-no.2-no. 3-no. 1 i n r a p i d s u c c e s s i o n . For h a l f the s u b j e c t s s t i m u l u s »A' was on the r i g h t , and f o r the other h a l f i t was on the l e f t . BL was measured from the onset of the s t i m u l u s l i g h t u n t i l the response key A or B 42 was depressed. Movement Response Keys o Green Warning Light o 1 O o 2 O o 3 ® Left Index Finger o 4 o 5 Red O Stimulus 6 Lights ® O O Right Index Finger F i g u r e 2 . P i c t o r a l d e s c r i p t i o n o f s u b j e c t ' s c o n s o l e ( f r o m L e e c h , 1 9 7 7 ) . 44 PROCEDURES A t e s t t r i a l was begun with the s u b j e c t s e a t e d . i n f r o n t of the apparatus with h i s index f i n g e r s on the a p p r o p r i a t e response keys. A warning l i g h t appeared, f o l l o w e d by the s t i m u l u s l i g h t a f t e r a v a r i a b l e f o r e p e r i o d o f 1.0, 1.5 # or 2.0 seconds. The sequence of events f o r each t e s t t r i a l was as f o l l o w s : 1) ., Warning l i g h t . 2) . V a r i a b l e f o r e p e r i o d . 3) . Stimulus l i g h t . 4) . S u b j e c t ' s response 5) • RL and MT recorded by d i g i t a l p r i n t e r . 6) . Response checked f o r speed and accuracy. 7) . Auditory feedback g i v e n with regard t o performance as f o l l o w s , a) f a s t and a c c u r a t e b) f a s t and i n a c c u r a t e c) slow and a c c u r a t e d) slow and i n a c c u r a t e 8) . Reset of f o r e p e r i o d and s t i m u l u s l i g h t . 9) . Repeat sequence. Each s u b j e c t came to the l a b o r a t o r y on f i v e separate days at approximately the same time f o r each t e s t i n g s e s s i o n . The i n i t i a l s e s s i o n was used to ensure f a m i l i a r i z a t i o n with the t a s k s , t o o b t a i n response l a t e n c i e s f o r each task i n the simple r e a c t i o n time s i t u a t i o n , and t o compute the c r i t e r i o n times f o r each task. The sequence of t r i a l s was as f o l l o w s : RCA. 15 p r a c t i c e t r i a l s 45 50 SET t r i a l s r e s t 30 seconds RCB. 15 p r a c t i c e t r i a l s 50 SRT t r i a l s r e s t one minute RC& and RCB 15 p r a c t i c e t r i a l s 50 CRT t r i a l s r e s t 30 seconds 50 CRT t r i a l s For the c h o i c e r e a c t i o n - t i m e t r i a l s , the s t i m u l i sere e q u a l l y probable. To compute the c r i t e r i o n times f o r speed used on the subsequent t e s t days, 0.5 times the standard d e v i a t i o n was s u b t r a c t e d from the mean response l a t e n c y f o r each task i n the c h o i c e r e a c t i o n time s i t u a t i o n * The value of 0.5 times the s t a n d a r d d e v i a t i o n was taken as an a r b i t r a r y measure. T h i s measure was designed t o ensure some p o s i t i v e r e inforcement, with approximately 30 per cent o f the responses f a s t e r than the c r i t e r i o n v a l u e , while at the same time c h a l l e n g i n g the s u b j e c t to respond f a s t e r . T h i s was done s e p a r a t e l y f o r each s u b j e c t . One e x p e r i m e n t a l c o n d i t i o n was t e s t e d each day on the remaining f o u r t e s t i n g s e s s i o n s . Immediately p r i o r t o t e s t i n g on these days the two response t a s k s were reviewed and i n s t r u c t i o n s g i v e n with r e s p e c t to the p a r t i c u l a r c o n d i t i o n to be t e s t e d . The a p p r o p r i a t e payoff matrix was shown to the s u b j e c t s and d i s c u s s e d as to which s t r a t e g y would produce the best payoff. , k summary of the p a y o f f matrix i s given i n Table 1. The sequence of t r i a l s and r e s t p e r i o d s f o r the f o u r t e s t s e s s i o n s were as f o l l o w s : 46 6 p r a c t i c e t r i a l s 25 t e s t t r i a l s r e s t 30 seconds 25 t e s t t r i a l s r e s t 1 minute 25 t e s t t r i a l s r e s t 30 seconds 25 t e s t t r i a l s r e s t 5 minutes t o t a l time per s e s s i o n was approximately 20 minutes. Ta b l e 1. Payoff matrix used t o motivate adoption of d i f f e r e n t response s t r a t e g i e s i n a c h o i c e r e a c t i o n time s i t u a t i o n . «l IIIIII IIII IIII H II IIII It II It IIIIII IIIIIIIIII It IIII IIIIIIIIII It It ft IIII IIIIIIII II It It III111 It II It II II It IIII It II It II II It M M II F a s t F a s t Slow Slow a c c u r a t e I n a c curate Accurate I n a c c u r a t e Accuracy ASB RCA 5 -25 1 -25 RCB 5 -25 1 -25 Speed A&B RCA 5 1 -25 -25 RCB 5 1 -25 -25 ACCURACY A RCA 5 -25 1 -25 RCB 2 -2 1 -2 SPEED A RCA 5 1 -25 -25 RCB 2 1 - 2 - 2 SPEED-ACCURACY HATfllX RATIONALE The p o i n t system f o r the matrix was arranged to s e t up a graded system of p e n a l t i e s and rewards. P o i n t s were added t o or subracted from the t o t a l f o r each t r i a l with the t o t a l p o i n t s accumulated r e p o r t e d each day* S u b j e c t s were ranked from h i g h e s t 47 to lowest on the b a s i s of the number of p o i n t s accumulated over the f o u r t e s t i n g s e s s i o n s . Montetary rewards were then given based on the s u b j e c t ' s standing with the s u b j e c t a c h i e v i n g the g r e a t e s t number of p o i n t s r e c e i v i n g f i f t e e n d o l l a r s whereas the one r e c e i v i n g the lowest number o f p o i n t s gained twenty c e n t s . Accuracy A S B Under t h i s c o n d i t i o n i n a c c u r a t e responses were h e a v i l y p e n a l i z e d . Slow, a c c u r a t e responses r e c e i v e d a small reward whereas f a s t , a c c u r a t e responses r e c e i v e d the g r e a t e s t reward. Speed A & B Slow responses were p e n a l i z e d under t h i s c o n d i t i o n * F a s t , a c c u r a t e responses r e c e i v e d the g r e a t e s t reward. , Accuracy A The system of p e n a l t i e s and rewards used i n t h i s c o n d i t i o n were i n the same order as under the c o n d i t i o n that emphasized accuracy on both t a s k s . Task A r e c e i v e d the same value of p o i n t s as occurred i n t h a t c o n d i t i o n , whereas task B r e c e i v e d a l e s s e r reward and p e n a l t y . Speed A In t h i s c o n d i t i o n the rewards and p e n a l t i e s were i n the same order as i n the c o n d i t i o n t h a t emphasized speed f o r both t a s k s . Task A r e c e i v e d the same value of p o i n t s as under t h a t c o n d i t i o n , "but B r e c e i v e d a l e s s e r reward and p e n a l t y . 48 EXPERIMENTAL CONDITIONS Four experimental c o n d i t i o n s were used i n t h i s study, with 100 t e s t t r i a l s per c o n d i t i o n per s u b j e c t . In each experimental c o n d i t i o n two s t i m u l i and two responses were p a i r e d i n 1:1 S-R mapping with the s t i m u l i having egual p r o b a b i l i t y of occurence. The experimental c o n d i t i o n s i n c l u d e d ; 1) . Accuracy s t r e s s e d on RCA and RCB 2) ..Speed s t r e s s e d on RCA and RCB 3) . Accuracy s t r e s s e d on RCA 4) . Speed s t r e s s e d on RCA EXPERIMENTAL DESIGN The experimental design was a one-way f a c t o r i a l experiment with repeated measures on both f a c t o r s . The independent v a r i a b l e s were: (1) c o n d i t i o n s , with one c o n t r o l - the simple r e a c t i o n time s i t u a t i o n ; and f o u r experimental c o n d i t i o n s of speed and/or accuracy s t r e s s i n c h o i c e r e a c t i o n time s i t u a t i o n s ; and (2) response complexity. The dependent v a r i a b l e - RL - was measured i n m i l l i s e c o n d s . A f o u r by f o u r L a t i n Square, r e p l i c a t e d s i x times was used to determine the order i n which each s u b j e c t performed the f o u r experimental c o n d i t i o n s . A t a b l e of random numbers was used to determine the order i n which RCA and RCB were presented f o r each experimental c o n d i t i o n * The order of p r e s e n t a t i o n of responses i n each experimental c o n d i t i o n was the same f o r a l l s u b j e c t s . The experimental design may be c o n c e p t u a l i z e d as f o l l o w s ; EXPEBIMENTAL DESIGN Accuracy ASB Sjaeed MS Accuracy A Speed A SET Subject 1 Subject 24 ANALYSIS OF DATA The computer program * D a t a s n i f f ' (Goodman and Schutz, 1974) was used to check f o r e r r o r s and to compute c e l l and marginal means and standard d e v i a t i o n s . I t a l s o blocked the data such that the 50 SLs of each s u b j e c t were reduced t o f i v e means based on t en BLs each. A 4X2X5 a n a l y s i s of v a r i a n c e was used t o determine i f any l e a r n i n g had occur r e d . The independent v a r i a b l e s i n c l u d e d days (4 l e v e l s ) , response complexity (2 l e v e l s ) , and b l o c k i n g (5 l e v e l s ) . The days e f f e c t , i f s i g n i f i c a n t , would a c t to i n f l a t e the s u b j e c t - b y - c o n d i t i o n s and s u b j e c t - b y - c o n d i t i o n s - b y - r e s p o n s e complexity i n t e r a c t i o n s i n any subsequent a n a l y s i s , and i n so doing, i n c r e a s e the p o s s i b i l i t y of committing a type I I e r r o r . To circumvent t h i s problem, an order of p r e s e n t a t i o n of c o n d i t i o n s term was i n c l u d e d i n the f u r t h e r a n a l y s i s . A 4X5X2X5 a n a l y s i s o f v a r i a n c e was then performed on the data. 50 The independent v a r i a b l e s i n t h i s case i n c l u d e d order of p r e s e n t a t i o n (4 l e v e l s ) , e xperimental c o n d i t i o n s (5 l e v e l s ) , response c o m p l e x i t y (2 l e v e l s ) , and b l o c k i n g (5 l e v e l s ) . 51 Chapter 4 RESULTS AND DISCUSSION ANALYSIS OF RESULTS Twenty-four, of the 39 s u b j e c t s o r i g i n a l l y t e s t e d , were s e l e c t e d f o r f u r t h e r i n v e s t i g a t i o n on the b a s i s of the d i f f e r e n c e i n t h e i r response l a t e n c y between the two t a s k s i n the SRT c o n d i t i o n . I t i s noteworthy t h a t 20.-5$ a c t u a l l y showed f a s t e r l a t e n c i e s f o r the complex than f o r the simple response. A computer program ( D a t a s n i f : Goodman and Schutz, 1975) c a l c u l a t e d s u b j e c t ' s i n d i v i d u a l mean s c o r e s , c e l l means and standard d e v i a t i o n s f o r RCA and RCB under the f i v e e x p e r i m e n t a l c o n d i t i o n s . T h i s i s summarized i n Appendix B. In a d d i t i o n , • D a t a s n i f 1 was used to block i n d i v i d u a l data by reducing the 50 t r i a l s t o f i v e mean s c o r e s . P r e l i m i n a r y a n a l y s i s , to t e s t f o r a l e a r n i n g e f f e c t and to determine i f t h i s l e a r n i n g e f f e c t i n t e r a c t e d with other f a c t o r s , was performed. T h i s was done to ensure no l o s s of power i n subseguent a n a l y s e s . The computer program BMD:P2V {Holm, 1977) c a l c u l a t e d a 4X2X5 a n a l y s i s of v a r i a n c e . The independent v a r i a b l e s i n c l u d e d response complexity (2 l e v e l s ) , days {4 l e v e l s ) , and b l o c k s (5 l e v e l s ) . A s i g n i f i c a n t days e f f e c t was FOUND <F J3,69)=3.11, P <0.033) INDICATING THAT LEARNING probably o c c u r r e d (see c e l l and marginal means i n Table 2 ) . However, the t a s k by days i n t e r a c t i o n was not s i g n i f i c a n t : l e a r n i n g a f f e c t e d both tasks e g u a l l y . 52 Table 2, C e l l and marginal mean response l a t e n c i e s (msec.) f o r RCA and fiCB over the f i v e - d a y p e r i o d . II t l II it It It It II IIIIII It It It IIIIIIIIII It It II IIIIIIIIIIII It II II It IIIIIIII It IIIIII IIIIII II II tl II It 11IIII l l l l IIIIII IIII IIII It IIII Dayl Day2 Day3 Day4 Day5 Mean (SRT) (Day 2-5) RCA 235-9 285.3 267.0 264-9 267.4 271.15 RCB 265.5 325.5 310.5 320.9 317.4 318.58 Mean 250.7 305.4 288.8 292.9 292.4 m i II n m i t u t m i t i n ti n i t n i i tt m i n i l m i t t m i l l t i n it II it it t u t t i n m i i m it t u t it t i n n i l t i n it it t i n t i n ti n it n n A s i g n i f i c a n t task by days by b l o c k i n t e r a c t i o n ( F (12,276)=1.9, £ <O-036) was found , i n d i c a t i n g t h a t s u b j e c t s responded d i f f e r e n t l y t c the two ta s k s over the f i v e b l o c k s each day. Improvement occurred p r i m a r i l y on day one, with RCA showing more c o n s i s t e n t decrements i n performance time on t h i s day than d i d RCB. T h i s i n t e r a c t i o n i s rep r e s e n t e d i n Appendix B. To reduce any s y s t e m a t i c b i a s t h a t t h i s days e f f e c t might have on any task by c o n d i t i o n s i n t e r a c t i o n s , the data were blocked f o r order of p r e s e n t a t i o n of the exp e r i m e n t a l c o n d i t i o n s . The c e l l and marginal mean response l a t e n c i e s and the standard d e v i a t i o n s f o r RCA and RCB under the f i v e e x p e r i m e n t a l c o n d i t i o n s , a r e given i n Table 3. BMD:P2V was then used t o c a l c u l a t e a 4X5X2X5 a n a l y s i s of v a r i a n c e . The independent v a r i a b l e s i n c l u d e d order o f p r e s e n t a t i o n (4 l e v e l s ) , e x perimental c o n d i t i o n s (5 l e v e l s ) , response complexity (2 l e v e l s ) , and b l o c k i n g (5 l e v e l s ) . In b l o c k i n g , the 50 RLs of each s u b j e c t were reduced to f i v e mean s c o r e s of ten responses 53 each. The r e s u l t s of the a n a l y s i s of variance are l i s t e d i n Table 4. The b l o c k i n g f a c t o r has been omitted from the ANOVA t a b l e s i n c e the main e f f e c t of i t , along with i n t e r a c t i o n s with v a r i a b l e s of i n t e r e s t , were a l l n o n - s i g n i f i c a n t . , Table 3. Response l a t e n c i e s (msec.) and t h e i r standard d e v i a t i o n s f o r RCA and RCB under f i v e experimental c o n d i t i o n s . t i n i i i i m t m i u n m i t i n it n m i m i i i i i i i i i u i i t i n m u m i m i i n n n n n n u n n i i i i n n m i II i i i i n i i n t i n n n t i n n Responses EXPESIMENTAL CONDITIONS ACCURACY ASB SPEED A SB ACCURACY A SPEED A SRT MEAN RCA 282.5 2 74.7 270.4 257.4 235.9 264.1 SD 35.4 33.9 33.7 29.4 27.9 JBCB F 310.3 295.5 331.5 337.0 265. 5 308.0 SD 51. 1 51.5 61. 1 62.3 40.7 SEAN 296.4 285.1 300.9 297.0 250.7 i t i i i i n n n t u t n u n n n i t n n n n n n n n n t i n it n n i i t i n n it i i i i n n n n n it m i n i m m i n n nn t i n n i t it it i i t i n it n -n to c - J fD X "C OJ fO • -i —1. 3 fD ro 1/1 3 . -a r r o CD 3 —i (/) ro O o 3 B» a. c-+ —i. fD <-i- 3 — o o —J* 3 fD l/> to • „ Co fD O • - — -h O -5 73 O 3= fti 3 O . - 73 o CO C 3 a. fD • - J - h . < fD RESPONSE LATENCY (msec.) SRT ACCURACY A S B SPEED A S B ACCURACY A SPEED A O J 4\ o o _J L. ro o CO O o o _J L_ L_ OJ o 1 > »»» • • . V . V . ' . V . V . V . I . . . . . . . . . . . . . . . . . . . . . . . . . « o » « » . » . . « « .v.v.| t U I I I I I I I I I I M M I I U I t I < I I • • • • • • • • • • • • • • * • . • • • . . . . . . . « . . • * • . • # « • * * • * . 4 04 O -1 ' • II o I I I J ... . . . • • • • . . . II o CD » » < •• •» • i i i i i I'I i i i i i i n i i i i i m i i i i i i i i i i i i i II 55 T a b l e 4. A n a l y s i s of v a r i a n c e of experimental c o n d i t i o n s and task complexity on response l a t e n c y , with order of p r e s e n t a t i o n c o n t r o l l e d by a l a t i n square design. it m i n ti II m m 11 II t i n t i n it it it m i II II n m i 11 n ti t i n it n n t i n t i n n n t i n m i t i n n i i u i i i i 11 n u it it m i n m i Source df MS F P r o b a b i l i t y F Exceeded Order (0) 3 16544.66 0.31 0.822 SwO 20 54289.00 C o n d i t i o n s (C). 4 102149.88 22-85 <0.001 0 X C 12 95 42.66 2. 14 0.02 SwO X C 80 4470. 15 Response 1 577064.38 44.45 <0.001 Complexity (RC) 0 X RC 3 19055. 10 1.53 0.24 SwO X RC 20 12423.82 C X RC 4 38957.30 20.47 <0.00 1 0 X C X RC 12 2482.65 1.30 0.23 SWO X C X RC 80 1903.54 . i i i i II II II n II n i i ti II n II i i II II II it II II it i i i i it II i i II i i i i i i it i i II n n n n it it n it 11 it t i n n t i u n n n n 1111111111 ti it 11 The response complexity main e f f e c t , measuring whether the mean RL f o r RCa (264.1 msec.) was s i g n i f i c a n t l y d i f f e r e n t from the mean RL f o r RCB (308.0 msec.) when averaged a c r o s s the f i v e e x perimental c o n d i t i o n s , was h i g h l y s i g n i f i c a n t (p<.001). The c o n d i t i o n s main e f f e c t , t e s t i n g whether s u b j e c t s responded d i f f e r e n t l y to the f i v e experimental c o n d i t i o n s was a l s o s i g n i f i c a n t (p<.001). However, an examination of Tab l e 2 suggests t h a t t h i s i s p r i m a r i l y due to the mean RLs (averaged over RCA and RCB) being a p p r e c i a b l y lower i n the SRT c o n d i t i o n than i n the f o u r CRT c o n d i t i o n s . F u r t h e r comparisons among s p e c i f i c c e l l and marginal means, r e l e v a n t to the hypotheses, 56 are d i s c u s s e d below. The i n t e r a c t i o n between c o n d i t i o n s and response complexity was s i g n i f i c a n t as w e l l , i n d i c a t i n g t h a t the experimental c o n d i t i o n s a f f e c t e d the two t a s k s d i f f e r e n t i a l l y (p<.001). The i n t e r a c t i o n e f f e c t i n c l u d e s t h e e f f e c t s s p e c i f i c a l l y r e l a t e d t o the hypotheses of t h i s study. These are analyzed i n subsequent d i s c u s s i o n s of each hypothesis. The order main e f f e c t t e s t e d whether the sequence i n which s u b j e c t s performed the f i v e e xperimental c o n d i t i o n s s i q n i f i c a n t l y a f f e c t e d mean RL. Since a l a t i n Square design was implemented f o r ba l a n c i n g c o n d i t i o n p r e s e n t a t i o n , the order o f the experimental c o n d i t i o n s was not expected to produce a s i g n i f i c a n t ¥ r a t i o , which was a c t u a l l y the case (p=.82). The order by c o n d i t i o n s i n t e r a c t i o n , however, was s i g n i f i c a n t (p=-02), meaning that the i n f l u e n c e o f c o n d i t i o n s d i f f e r e d depending upon the order of p r e s e n t a t i o n . One e x p l a n a t i o n i s that l e a r n i n g c a r r i e d over from one day to the next and e i t h e r s y n e r g i z e d or i n t e r f e r e d with performance* Examining F i g u r e 4, i t can be seen t h a t the l o n g e s t RLs were g e n e r a l l y achieved under order one. However, f o r c o n d i t i o n two the h i g h e s t l a t e n c y was a t t a i n e d under o r d e r f o u r when i t was the f i r s t c o n d i t i o n presented. The lowest RLs f o r c o n d i t i o n s f o u r and one were achieved under order f o u r when they were presented second and t h i r d r e s p e c t i v e l y . The lowest RL f o r c o n d i t i o n s three and two were achieved under order three when they were r e s p e c t i v e l y the second and t h i r d c o n d i t i o n s presented to the s u b j e c t . Although the order by c o n d i t i o n i n t e r a c t i o n was s i g n i f i c a n t , the e f f e c t of major concern i n t h i s study was the c o n d i t i o n by response 57 complexity i n t e r a c t i o n , as no order by c o n d i t i o n by response complexity i n t e r a c t i o n occurred (p=.23), i t was assumed t h a t the order e f f e c t d i d not d i f f e r e n t i a l l y i n f l u e n c e the e f f e c t o f the c o n d i t i o n s on the two responses. Dunnett*s t e s t compared the mean RL o f each e x p e r i m e n t a l c o n d i t i o n to a c o n t r o l (SRT) i n order to t e s t the hypotheses d e l i n e a t e d i n chapter one. a l l hypotheses d e a l t with RCB-RCa d i f f e r e n c e s * These are summarized i n Table 5. F i g u r e 4. Mean r e s p o n s e l a t e n c i e s ( m s e c . ) f o r t h e o r d e r b y c o n d i t i o n i n t e r a c t i o n . 59 T a b l e 5. RCB-ECA d i f f e r e n c e s i n RL (msec.) between SRT and other e xperimental c o n d i t i o n s . n n m i n t i t i n n n n m i it n n n i i i i n 11 it it n m i t t it it t u t it ti t i n m i n it n u n n t i n it it t i n n it n t i n it m i n n n t i n EC 1 EC2 EC3 EC4 EC5 (SRT) RCA 282.5 274.7 270.4 257.0 235-9 RCB 310-3 295.5 331.5 337-0 265.5 RCB—RCA 27.8 20.8 61. 1 80.0 29.6 (ECX -EC5) 1.8 8.8 31.5 50.4 n i t m i n t i n t t n n n i t t i t i n it t i n m i it ti n n ti t i n n t i n n n n n ti n it it n n n u n n m u m t i n n t i it n m i m i n n it n n DISCUSSION OF HYPOTHESES Hypothesis One Hypothesis one l e d to the p r e d i c t i o n that when accuracy over speed was s t r e s s e d on both responses, the d i f f e r e n c e i n RL between RCA and RCB would be e q u i v a l e n t to the d i f f e r e n c e i n the SRT c o n d i t i o n . I t was proposed t h a t when accuracy was s t r e s s e d , no response s t r a t e g y f a v o u r i n g one response over the other would be employed, and thus the i n f o r m a t i o n p r o c e s s i n g s t a g e s of s t i m u l u s encoding and response search would not be a f f e c t e d by v a r i a t i o n s i n response complexity. I t was f u r t h e r assumed t h a t the d i f f e r e n c e i n RL between the two responses i n both the SRT and CRT c o n d i t i o n d s would be made up of the i n c r e a s e d time r e q u i r e d f o r the r e l e a s e of the longer motor program of RCB. The d i f f e r e n c e i n RL between RCA and RCB i n c o n d i t i o n one (27.8msec.) 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 the d i f f e r e n c e i n RL between the two responses i n c o n d i t i o n f i v e (29.6 m s e c ) . 60 Therefore, t h i s h y p o t h e s i s was supported. Hypothesis Two Hypothesis two l e d to the p r e d i c i t i o n t h a t the d i f f e r e n c e i n EL between ECA and RCB, when speed was s t r e s s e d over accuracy, would be l e s s than i n the SET c o n d i t i o n . O r i g i n a l l y i t was proposed that a s t r e s s f o r speed caused the s u b j e c t to u t i l i z e a response s t r a t e g y which compensated f o r the longer r e l e a s e time o f the motor program a s s o c i a t e d with the complex response. I t was assumed that t h i s response s t r a t e g y took the form of e i t h e r decreased time t o i d e n t i f y the s t i m u l u s probe or decreased search time f o r the motor program, the combination of which reduced EL f o r the complex response. The d i f f e r e n c e i n EL between ECA and ECB i n c o n d i t i o n two (20.8 msec.) was compared with the d i f f e r e n c e obtained i n c o n d i t i o n f i v e (29.6 m s e c ) , using Dunhett's t e s t . A non-s i g n i f i c a n t d i f f e r e n c e was found. H h i l e the d i f f e r e n c e of 8.8 msec, was i n the d i r e c t i o n h y p o thesized, i t was l e s s than the 24,6 msec* d i f f e r e n c e r e q u i r e d f o r s i g n i f i c a n c e . Thus t h i s h y p o t hesis was not supported. I t i s r e l e v a n t here to note though, t h a t the p a y o f f matrix d i d s t i m u l a t e s u b j e c t s t o respond f a s t e r i n the speed c o n d i t i o n (285 msec.) than i n the accuracy c o n d i t i o n (296 msec.). I f the c o n t e n t i o n i s t r u e , t h a t a speed s t r e s s does r e s u l t i n the adoption of a response s t r a t e g y f a v o u r i n g the complex response, why was s i g n i f i c a n c e not a t t a i n e d ? The r e s u l t s f o r the c o n t r o l c o n d i t i o n were obtained at the s u b j e c t ' s i n i t i a l s e s s i o n . A n a l y s i s of the l e a r n i n g e f f e c t over the days when the experimental c o n d i t i o n s were presented 61 showed . t h a t the g r e a t e s t percentage of l e a r n i n g took p l a c e on the f i r s t of these days- I t i s obvious then t h a t l e a r n i n g occurred d u r i n g the i n i t i a l s e s s i o n as w e l l . Thus, the d i f f e r e n c e i n RL i n the SET c o n d i t i o n may be i n f l a t e d as a r e s u l t of the l e a r n i n g e f f e c t and consequently mask the e f f e c t of the speed s t r e s s . Klapp e t a l . (1974) p o s t u l a t e d t h a t the RL i n t e r v a l i n a SRT c o n d i t i o n may not be the r e s u l t of the sum of the time taken i n each of the i n f o r m a t i o n p r o c e s s i n g s t a g e s . The p o s s i b i l i t y o f advance p r e p a r a t i o n , p r i o r to stim u l u s onset, thereby r e d u c i n g the BL i n t e r v a l , was noted. Advance p r e p a r a t i o n , was suggested only f o r the SRT c o n d i t i o n as with t h i s paradigm the s u b j e c t knows what response he i s r e q u i r e d t o make on every t r i a l . The p o s s i b i l i t y i s noted here t h a t t h i s t a c t i c - of advance p r e p a r a t i o n - i s employed f o r the complex and not the simple response i n order t h a t speed be maximized. Thus, some s u b j e c t s i n c l u d e d i n the study may have used t h i s p a r t i c u l a r response s t r a t e g y f o r the complex response. T h i s would have the e f f e c t o f f o r e s h o r t e n i n g the RL d i f f e r e n c e between RCA and RCB i n the SET c o n d i t i o n and i n turn c o n c e a l i n g the magnitude of the d i f f e r e n c e obtained i n the CST c o n d i t i o n . On the other hand, i t may a l s o be t h a t the b a s i s on which the s u b j e c t s were chosen f o r the study - those showing a l o n g e r BL f o r BCB than RCA i n the SET c o n d i t i o n - precluded a s t r o n g e r r e l a t i o n s h i p between speed s t r e s s and u t i l i z a t i o n of a response s t r a t e g y f a v o u r i n g RCB, from appearing. I t may be t h a t s u b j e c t s who do not use advance p r e p a r a t i o n f o r the complex response i n the SRT c o n d i t i o n a l s o do not employ a response s t r a t e g y 62 f a v o u r i n g t h i s response i n a CRT c o n d i t i o n . U n f o r t u n a t e l y , the v e r i f i c a t i o n of e i t h e r of these h y p o t h e t i c a l e x p l a n a t i o n s i s not p o s s i b l e based upon the p r e s e n t r e s u l t s . I t t h e r e f o r e remains t h a t s i n c e the d i f f e r e n c e i n BL between RCA and RCB under a s t r e s s f o r speed, was e q u i v a l e n t to the d i f f e r e n c e i n the SRT c o n d i t i o n , then there i s no evidence to t o suggest t h a t a response s t r a t e g y f a v o u r i n g e i t h e r response was employed. Hypothesis Three Hypothesis three l e d to the p r e d i c t i o n t h a t when accuracy was s t r e s s e d more on the simple than on the complex response, the d i f f e r e n c e i n RL between RCA and RCB would be e q u i v a l e n t to the d i f f e r e n c e i n the SRT c o n d i t i o n . I t was hypothesized t h a t when accuracy was s t r e s s e d no response s t r a t e g y i n favour of one response over the other would be e v i d e n t . The concern f o r a c c u r a t e performance was assumed t o precl u d e t h i s from happening. Furthermore, the d i f f e r e n c e i n RL between t h e responses was assumed to r e f l e c t the i n c r e a s e d r e l e a s e time of the motor program f o r RCB. The d i f f e r e n c e between RCA and RCB i n c o n d i t i o n three (61.1 msec.) was s i g n i f i c a n t l y d i f f e r e n t from the d i f f e r e n c e found i n c o n d i t i o n f i v e (29.6 msec.) u s i n g Dunnett's t e s t . S ince Dunn's t e s t b e t t e r accounts f o r dependencies between s c o r e s when a repeated measures design i s used, i t was suggested t h a t Dunn's r a t h e r than Dunnett's t e s t be used to t e s t the s i g n i f i c a n c e o f the hypotheses. Dunn's t e s t was a p p l i e d to the data and the t a b u l a t i o n s were i n agreement with Dunnett's except i n the case 63 of t h i s h y p o t h e s i s . while a d i f f e r e n c e of 32.3 msec. was r e q u i r e d f o r s i g n i f i c a n c e a t the 0.05 l e v e l f o r a two t a i l e d t e s t , the a c t u a l d i f f e r e n c e obtained was 31.5 msec. T h i s d i f f e r e n c e would be s i g n i f i c a n t a t the O.06 l e v e l . Since the importance of making a type two e r r o r i s deemed to be at l e a s t e q u i v a l e n t to t h a t of making a type one, t h i s i n v e s t i g a t o r i s w i l l i n g t o accept the 0.06 l e v e l of s i g n i f i c a n c e with Dunn's two t a i l e d t e s t . Thus, h y p o t h e s i s t h r e e was r e j e c t e d . I t i s obvious t h a t a response s t r a t e g y i n f a v o u r of RCA was empolyed. From the SRT to c o n d i t i o n t h r e e , the RL i n c r e a s e f o r RCA was 34-5 msec., whereas f o r RCB the i n c r e a s e was 66 msec. In terms of t o t a l number of e r r o r s , f i v e o ccurred f o r RCA and 18 f o r RCB- T h i s suggests t h a t s u b j e c t s , i n o r d e r to ensure t h a t they responded c o r r e c t l y f o r RCA, preprogrammed t h i s response and s e l e c t i v e l y attended t o i t . While i t i s e v i d e n t that BCA was s e l e c t i v e l y attended to f o r reasons of e i t h e r decreased s t i m u l u s p r o c e s s i n g time or decreased search time, i t i s a l s o c l e a r t h a t the RL observed f o r RCB (331.5 msec.) was slower than i n the p r e v i o u s two c o n d i t i o n s ( EC 1.,- 310.3 m s e c ; EC2 - 295.5 msec.) . Sidowski e t a l . (1958) p o s t u l a t e d the adoption of a response s t r a t e g y which favoured one response over the other. They , assumed t h a t when the unexpected response was r e q u i r e d , the prepared response s e t had to be i n h i b i t e d t h u s r e s u l t i n g i n a delay p r i o r to the i n i t i a t i o n of the a p p r o p r i a t e response., For the complex response, RL was g r e a t e r than f o r the simple task because of two f a c t o r s : 1) i t s longer readout time f o r the motor program and 2) the delay component caused by the i n h i b i t i o n of the response 64 s e t f o r RCA. Hypothesis Four Hypothesis four l e d to the p r e d i c t i o n that the d i f f e r e n c e i n RL between RCA and RCB would be greater than i n the SRT c o n d i t i o n , when speed was s t r e s s e d more on the simple than on the complex response. A speed s t r e s s was proposed to r e s u l t i n the adoption o f a response s t r a t e g y f a v o u r i n g the simple response i n order f o r RL to be reduced. The response s t r a t e g y was p o s t u l a t e d to take the form of s e l e c t i v e l y a t t e n d i n g to RCA through e i t h e r reduced s t i m u l u s i d e n t i f i c a t i o n time or reduced response search time. The l a g i n RL f o r RCB was assumed to be due t o the l o n g e r r e l e a s e time of i t s motor program as w e l l as the d e l a y caused by s e l e c t i v e l y a t t e n d i n g t o RCA. According to Dunnett's t e s t , the d i f f e r e n c e i n RL between RCA and RCB i n c o n d i t i o n four (80.0 msec.) was s i g n i f i c a n t l y d i f f e r e n t from the d i f f e r e n c e found i n c o n d i t i o n f i v e (29.6 msec.). T h i s h y p o t h e s i s was t h e r e f o r e supported. However, i t i s obvious that the adoption of the p a r t i c u l a r response s t r a t e g y d i d not r e s u l t s o l e l y from a s t r e s s f o r speed s i n c e the r e s u l t s r e l e v a n t to h y p o t h e s i s three suggest that the same s t r a t e g y was employed i n c o n d i t i o n t h r e e , when accuracy was s t r e s s e d on the simple response. Although the s t r e s s f o r speed d i d r e s u l t i n f a s t e r RLs f o r RCA under c o n d i t i o n f o u r (257.4 msec.) than under c o n d i t i o n three (270.4 m s e c ) , the r e s u l t s i n d i c a t e t h a t the response s t r a t e g y adopted was e q u i v a l e n t whether s t r e s s e d f o r speed or accuracy on the simple task. 65 The r e s u l t s obtained and d i s c u s s e d i n regards to the preceeding hypotheses may, i n f a c t be i n d i c a t i v e of a s e l e c t group of s u b j e c t s - The s u b j e c t s from the present study were chosen on the b a s i s o f the complex response showing a longer RL than the simple response i n the SRT c o n d i t i o n . However, the mean RL of the 15 s u b j e c t s not i n c l u d e d i n the study ( RCA - 244-0 msec; RCB - 235.9 msec.) showed an i n v e r s e r e l a t i o n between the two responses i n comparison with the p r e v i o u s 24 s u b j e c t s {RCA -235.9 msec; RCB - 265.5 msec) . S i m i l a r l y , Leech (1977) u s i n g i d e n t i c a l responses and apparatus, found no s i g n i f i c a n t d i f f e r e n c e between the responses i n the SRT c o n d i t i o n . Included i n her sample was one s u b j e c t who e x h i b i t e d the i n v e r s e r e l a t i o n i n RL between the two responses (RCA - 295 m s e c ; RCB - 255 msec.) and s e v e r a l s u b j e c t s showing minor d i f f e r e n c e s i n f a v o u r of the simple response ( l e s s than 4 msec*). I t was expected t h a t the d i f f e r e n c e i n the SRT c o n d i t i o n between the two responses would be i n d i c a t i v e of the l o n g e r r e l e a s e time of the complex response. Why t h i s d i d not occur f o r the 15 s u b j e c t s not i n c l u d e d may be due to one of a number o f f a c t o r s . I n the f i r s t case, i n f o r m a t i o n t h e o r i s t s would argue t h a t s u b j e c t s showing t h i s i n v e r s e r e l a t i o n do not f i n d the complex response to be more d i f f i c u l t than the simple response. Complexity, f o r i n f o r m a t i o n t h e o r i s t s , i s d e f i n e d i n terms of t h e e f f i c i e n c y with which i n f o r m a t i o n i s processed. Thus these s u b j e c t s would be regarded as p r o c e s s i n g i n f o r m a t i o n f o r RCB mor e f f i c i e n t l y than s u b j e c t s showing a longer RL f o r RCB. What i s being d e a l t with then, i s d i f f e r e n t l e v e l s of response complexity f o r the same t a s k . 66 On the other hand, i t may a l s o be the case t h a t s u b j e c t s showing t h i s i n v e r s e r e l a t i o n may read out the motor program f o r the complex response s e r i a l l y , i n a c l o s e d loop system r a t h e r than as a preprogrammed package. This would cause there t o be no s i g n i f i c a n t d i f f e r e n c e i n RL between the two responses. As noted e a r l i e r , Klapp e t a t . (197 4) argued that with a SRT paradigm, s u b j e c t s could prepare f o r the response i n advance of s t i m u l u s onset thereby f o r e s h o r t e n i n g the RL i n t e r v a l . Thus, s u b j e c t s showing t h i s i n v e r s e r e l a t i o n may prepare f o r the complex response i n advance of the s t i m u l u s appearing i n order to c o u n t e r a c t t h e l o n g e r program l e n g t h of the complex response-No response s t r a t e g y was expected t o be u t i l i z e d i n the SRT c o n d i t i o n * However, the l a t t e r two e x p l a n a t i o n s both p o i n t to the p o s s i b i l i t y of a response s t r a t e g y being used by those s u b j e c t s e x h i b i t i n g e i t h e r an i n v e r s e r e l a t i o n o r no s i g n i f i c a n t d i f f e r e n c e between the responses. T h i s f a c t o r poses s e r i o u s q u e s t i o n t o the v a l i d i t y of the s e l e c t i o n c r i t e r i o n - Rather than simply i n s u r i n g that those s u b j e c t s who were chosen found the complex response more d i f f i c u l t , the s e l e c t i o n c r i t e r i o n may have been more d i r e c t e d to s e l e c t i n g s u b j e c t s who d i d not employ a response s t r a t e g y f a v o u r i n g e i t h e r response u n l e s s otherwise i n s t r u c t e d * SUMMARY Schutz (1972) developed a theory of motor response o r g a n i z a t i o n and memory r e t r i e v a l f o r c h o i c e r e a c t i o n time t a s k s . In t h i s theory, he hypothesized t h a t , i n a CRT s i t u a t i o n , f o r two t a s k s , v a r y i n g i n complexity and being e q u a l l y probable. 67 the d i f f e r e n c e i n EL would be made up of the i n c r e a s e d time r e q u i r e d t o read out the motor program of the more complex response. However, i n t e s t i n g t h i s h y p o t h e s i s , no s i g n i f i c a n t d i f f e r e n c e was obtained between the two tasks i n an eguiprobable CBT s i t u a t i o n . Eyan (1972) i n v e s t i g a t e d t h i s problem i n r e l a t i o n to response p r o b a b i l i t y . I t was hypothesized t h a t the more complex the t a s k , the l e s s would be the e f f e c t of response p r o b a b i l i t y on BL. T h i s h y p o t h e s i s was not supported as low p r o b a b i l i t y l e v e l s r a t h e r than task complexity was found to be the most c r i t i c a l f a c t o r i n response r e a d i n e s s . But, when both responses were e g u a l l y probable, the complex task e x h i b i t e d f a s t e r BLs than d i d the simple task* Leech (1977) i n a f u r t h e r attempt t o e l a b o r a t e on the response p r o b a b i l i t y , task complexity i n t e r a c t i o n found no s i g n i f i c a n t d i f f e r e n c e i n BL between two t a s k s of unegual complexity when both tasks were e g u a l l y probable. The same apparatus and tasks were used as those employed i n the present study. ,. Table 6. Mean ELs f o r ECA and ECB i n the SET and CBT c o n d i t i o n s i n experiments by Leech, Byan and Schutz. II i i n i i » II II n i i it i i n it n II II II i i n «i n II II i i II II II II it i i i i it it i i n i i i i II it n II n a n II n it it i i it n ti n n it tt it it it it SET CBT RCA BCB BCA BCB Leech 221 232 296 299 Byan 221 253 330 315 Schutz 159 177 245 243 The present study attempted to e x p l a i n the r e l a t i o n s h i p between BL and task complexity i n the CBT c o n d i t i o n through the use of t h e speed-accuracy t r a d e o f f * A s t r e s s f o r speed on both 68 t a s k s was assumed to r e s u l t i n a response s t r a t e g y which favoured the complex response, whereas a s t r e s s f o r accuracy on both tasks was assumed to cause no such s t r a t e g y . The RLs f o r RCB were longer than those f o r RCA i n the SRT c o n d i t i o n s i n a l l three s t u d i e s noted i n Table 6. The r e s u l t s of the present study a r e i n agreement with t h i s f i n d i n g (RCA - 236 m s e c , RCB - 266 m s e c ) and support the c o n t e n t i o n of the memory drum the o r y t h a t the more complex the response, the longer the RL., The present study, as opposed to the t h r e e p r e v i o u s i n v e s t i g a t i o n s , a l s o supported the memory drum the o r y i n the CRT s i t u a t i o n (EC1 - RCA 283 msec, RCB 310 msec; EC2 - RCA 275 msec.,RCB 296 m s e c ) . Th e r e f o r e , under c h o i c e c o n d i t i o n s , i t i s e v i d e n t t h a t s u b j e c t s from the Leech (1977), Ryan (1972) and Schutz (1972) s t u d i e s g e n e r a l l y employed a d i f f e r e n t response s t r a t e g y from t h a t used by s u b j e c t s i n t h i s experiment. Note that no s t r a t e g y or p a y o f f was imposed on s u b j e c t s i n the o t h e r s t u d i e s . The present r e s u l t s support the c o n t e n t i o n that a speed s t r e s s decreases RL whereas an accuracy s t r e s s i n c r e a s e s i t . However, the p o s t u l a t i o n that a s t r e s s f o r speed as opposed to a s t r e s s f o r accuracy would d i f f e r e n t i a l l y i n f l u e n c e i n f o r m a t i o n p r o c e s s i n g f o r tasks varying i n complexity, was not born out. Thus, s u b j e c t s d i d not favour one response over the other i n the c o n d i t i o n promoting a speed s t r e s s on both t a s k s . Nor was t h i s e v i d e n t when accuracy was s t r e s s e d on both t a s k s . I t i s p o s s i b l e then, t h a t the e x t e r n a l reward system which made both responses e q u a l l y important caused the s u b j e c t s to be c a u t i o u s and t o s e t equal c r i t e r i o n boundaries f o r the p r o c e s s i n g of the s t i m u l u s i n f o r m a t i o n and/or to l e a v e s e l e c t i v e a t t e n t i o n open. 69 Bben the reward system encouraged f a v o u r i t i s m of the simple response f o r reasons o f e i t h e r accuracy or speed s t r e s s e s , EL f o r ECA was a c c o r d i n g l y decreased. Another f a c t o r a s s o c i a t e d with t h i s was the i n c r e a s e d number of e r r o r s f o r ECB r e l a t i v e t o ECA (EC3 - ECA 5, ECB 18;EC& - EGA 3, ECB 6). Both of these f a c t o r s are p o s t u l a t e d to be the r e s u l t o f a response s t r a t e g y which f a v o u r s ECA. T h i s f a v o u r i t i s m i s hypothesized t o take the form of reduced c r i t e r i o n boundaries f o r the c l a s s i f i c a t i o n o f the s t i m u l u s i n f o r m a t i o n and/or s e l e c t i v e a t t e n t i o n to the response program f o r the simple t a s k . S u b j e c t s i n the Leech (1977), Byan (1972) and Schutz (1972) s t u d i e s a l s o showed p a r t i a l i t y of i n f o r m a t i o n p r o c e s s i n g , but i n these cases the p a r t i a l i t y was d i r e c t e d towards the complex r a t h e r than the simple response. The e x p l a i n a t i o n f o r the disc r e p a n c y between the present f i n d i n g s and those j u s t noted i s probably due to the response s t r a t e g y employed. In the present study s u b j e c t s favoured the simple response because the reward system imposed t h i s s t r u c t u r e on them. I t i s proposed here, t h a t i n the absence of t h i s reward system, s u b j e c t s favour the complex response by p u t t i n g e i t h e r a speed or an accuracy s t r e s s on i t . T h i s would account f o r the reduced BL f o r ECB observed i n the p r e v i o u s s t u d i e s i n CBI s i t u a t i o n s . T h e r e f o r e to conclude, a s t r e s s f o r speed and/or accuracy does i n f l u e n c e i n f o r m a t i o n p r o c e s s i n g but not d i f f e r e n t i a l l y f o r ta s k s v a r y i n g i n complexity when both t a s k s are e q u a l l y important. However, a s t r e s s f o r speed or accuracy on one task i n a two-choice r e a c t i o n time s i t u a t i o n does d i f f e r e n t i a l l y i n f l u e n c e the pr o c e s s i n g of i n f o r m a t i o n f o r the responses. I t i s 70 suggested t h a t i n the absence of an e x t e r n a l reward system, s u b j e c t s respond with a speed or an accuracy s t r e s s on the task of g r e a t e s t complexity. 7 1 Chapter 5 SUMMARY AND CONCLUSIONS SUMMARY. The purpose o f t h i s i n v e s t i g a t i o n was to determine whether s t r e s s f o r speed and/or accuracy would d i f f e r e n t i a l l y a f f e c t i n f o r m a t i o n p r o c e s s i n g of t a s k s of low, versus g r e a t e r complexity i n a CRT s i t u a t i o n * I t was p o s t u l a t e d that a s t r e s s f o r speed would r e s u l t i n the adoption of a response s t r a t e g y f a v o u r i n g the complex response whereas an accuracy s t r e s s would r e s u l t i n no such s t r a t e g y . One c o n t r o l (SRT) and f o u r experimental (CRT) c o n d i t i o n s were used i n the t e s t i n g o f f o u r s e p a r a t e hypotheses. Response l a t e n c i e s f o r 500 t r i a l s were obtained form each o f the 24 male s u b j e c t s d u r i n g f i v e one-half hour t e s t i n g s e s s i o n s . Each s u b j e c t was t e s t e d i n a l l f i v e c o n d i t i o n s . There were two l e v e l s of response c o m p l e x i t y . With the onset of one of two stim u l u s l i g h t s , s u b j e c t s responded e i t h e r by p r e s s i n g a response key and then moving to h i t a second key (simple), or by p r e s s i n g a response key and moving to h i t a sequence o f keys (complex). Subsequent to an a n a l y s i s o f v a r i a n c e , Dunnett's t e s t was administered to t e s t each hypothesis. 72 CONCLUSIONS. The c o n c l u s i o n s formulated from t h i s i n v e s t i g a t i o n a re as f o l l o w s ; 1. The complex response, RCB, has a l o n g e r BL than the simple response, BCA, i n the SET and CBT c o n d i t i o n s due to l o n g e r read out time of the complex motor program. 2. In a two-choice r e a c t i o n time s i t u a t i o n , with speed o r accuracy s t r e s s e d on both responses, n e i t h e r response i s favoured i n the form of decreased s t i m u l u s p r o c e s s i n g or s e l e c t i v e a t t e n t i o n * T h i s i s r e f l e c t e d i n the f a c t t h a t the d i f f e r e n c e i n BL between the two t a s k s i n these c o n d i t i o n s i s e q u i v a l e n t to the d i f f e r e n c e obtained i n the SET c o n d i t i o n . 3. In a two-choice r e a c t i o n time s i t u a t i o n , with speed or accuracy s t r e s s e d on the simple t a s k , decreased simulus p r o c e s s i n g and/or s e l e c t i v e a t t e n t i o n t o the response program f o r the simple task, does occur. T h i s r e s u l t i s r e f l e c t e d i n the reduced BL f o r BCA and the i n c r e a s e d number of e r r o r s f o r RCB. 4. The d i s c r e p a n c y o f the r e s u l t s from the present study with p r e v i o u s f i n d i n g s may be ex p l a i n e d by a d i f f e r e n c e i n response s t r a t e g y . Because of the imposed s t r e s s on BCA used i n the present study, the response s t r a t e g y favoured t h i s response, whereas when no such e x t e r n a l s t r e s s was a p p l i e d , ECB was favoured. I t i s suggested t h a t i n the ' 73 Leech (1977), fiyan (1972), and Schutz (1972) s t u d i e s , s u b j e c t s put e i t h e r a speed or an accuracy s t r e s s on the complex response thereby r e d u c i n g the BL f o r BCB r e l a t i v e t o BCA. SUGGESTIONS FOB FUBTHEB BESE&BCH Even though the l e a r n i n g t h a t occurred appeared to be e q u i v a l e n t f o r both t a s k s , the p o s s i b i l i t y e x i s t s that the complex task was not a t the same l e v e l of s k i l l as the simple task i n the i n i t i a l s e s s i o n when SBT s c o r e s were taken. I t i s t h e r e f o r e suggested t h a t s e v e r a l t r a i n i n g s e s s i o n s be administered p r i o r t o t a k i n g BLs f o r experimental a n a l y s i s or f o r s e l e c t i o n of s u b j e c t s . S u b j e c t s t e s t e d , but not in c l u d e d i n the study, showed an i n v e r s e r e l a t i o n i n BL f o r the two t a s k s i n the SBT c o n d i t i o n . I t would be i n t e r e s t i n g t o t e s t these s u b j e c t s i n CBT s i t u a t i o n s i n v o l v i n g v a r i a t i o n of p r o b a b i l i t y or speed/accuracy s t r e s s t o determine whether a p a r t i c u l a r response s t r a t e g y - d i f f e r e n t from t h a t employed by s u b j e c t s i n c l u d e d i n t h i s study - i s used. 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Speed-accuracy t r a d e o f f i n r e a c t i o n time: E f f e c t of d i s c r e t e c r i t e r i o n times- J o u r n a l of Experimental Psychology. 76:19-24, 1968. P a c h e l l a , B. G. Fisher,D-F. and B-Karsh. Absolute judgements i n speeded t a s k s : Q u a n t i f i c a t i o n of the t r a d e - o f f between speed and accuracy. Psychonomic S c i e n c e f 12:225-226, 1968. Pa c h e l l a , f i . G . and Dennis F i s h e r . H i c k * s law and accuracy t r a d e - o f f i n a b s o l u t e judgement. Experimental Psychology. 92:378-384, 1972. Pew,B.W. The speed-accuracy o p e r a t i n g c h a r a c t e r i s t i c s . In if. G. Roster (Ed.), A t t e n t i o n and Performance. I I . Amsterdam:North-Holland, 1969-Babbitt,P.M.A. E r r o r s and e r r o r c o r r e c t i o n i n c h o i c e - response t a s k s . J o u r n a l of Experimental Psychology f f. 71:264-272, 1966. Seed,A.V. , Speed-accuracy t r a d e o f f . i n r e c o g n i t i o n memory. Sc i e n c e . 181:574-576, 1973. Byan,M.W.J. The e f f e c t s of task complexity and response p r o b a b i l i t y on response l a t e n c y . Unpublished Master T h e s i s , U n i v e r s i t y of B r i t i s h Columbia, 1972. S c h i f f r i n , B . M . and B.C.Atkinson* Storage and r e t r i e v a l processes i n long term memory. P s ycholoq i c a 1 Beview, 76:179-183, 1968. Schmitt,J.C. and C . j . S c h e i r e r . E m p i r i c a l approches t o i n f o r m a t i o n p r o c e s s i n g - speed-accuracy t r a d e o f f f u n c t i o n or reaction-rtime. Acta P s y c h o l o g i c a . 41:321-325, 1977. Schutz,H-8. A theory of motor response o r g a n i z a t i o n and r e t r i e v a l i n choice r e a c t i o n time t a s k s . Unpublished D o c t o r a l D i s s e r t a t i o n , U n i v e r s i t y of Wisconsin, 1972, Schouten,J.F. and J.A.fi.Bekker. B e a c t i o n time and accuracy. I n A.F.Sanders (Ed.), A t t e n t i o n and Performance. I.. Amsterdam:North-Holland, 1967. Sidowski,J.B., Morgan,B. and G*Eckstrand. I n f l u e n c e task complexity and i n s t r u c t i o n s upon simple and d i s c r i m i n a t i o n r e a c t i o n times. J o u r n a l of Experimental Psychology, 55:163-166, 1958. Siegel,D.S. E f f e c t of movement amplitude and t a r g e t diameter on r e a c t i o n - t i m e . J o u r n a l of Motor Behavior. 9:257-265,1977. Smith*E.E« Choice r e a c t i o n time : A n a l y s i s o f the major t h e o r e t i c a l p o s i t i o n s * P s y c h o l o g i c a l B u l l e t i n . 69:77-110. 1968. the speed-J o u r n a l o f 78 Stone, M. Models f o r c h o i c e - r e a c t i o n time. Psychometri 25:251-260, 1960. Swanson,J.M. and G.E.Briggs. I n f o r m a t i o n p r o c e s s i n g as a f u n c t i o n of speed versus accuracy. J o u r n a l or Experimental Psychology. 8 1:223-229, 1969. Swensson,R.G. The e l u s i v e t r a d e o f f : Speed versus accuracy i n v i s u a l d i s c r i m i n a t i o n t a s k s . P e r c e p t i o n and Psychophysies. 12:16-32, 1972. Swensson,S.G. T r a d e - o f f bi a s and e f f i c i e n c y e f f e c t s i n s e r i a l c h o i c e r e a c t i o n s . J o u r n a l of Experimental Psychology f 95:397-407,1972. Swensson,H.G. and Hard Edwards. Response s t r a t e g i e s i n a two-c h o i c e r e a c t i o n task with a continuous c o s t f o r time. J o u r n a l of Experimental Psychology. 88:67-81, 1971. Swensson,R-G. and D.M-Green* R e l a t i o n between random-walk models f o r two-choice response-times.. J o u r n a l o f Mathematical Psychology. 15:282-291, 1977. Swensson,R.G. And fi.E.Thomas. F i x e d and o p t i o n a l stopping models f o r two-choice d i s c r i m i n a t i o n times. J o u r n a l o f Mathematical Psychology. 11:213-236, 1974. Thomas,E.A*C. On expectancy and t h e speed and accuracy o f responses. In S.Kornblum (Ed.), A t t e n t i o n and Performance, IV, New Xork: Academic Press, 1973. Thomas,E.A.C. The s e l e c t i v i t y o f p r e p a r a t i o n . P s y c h o l o g i c a l  Review. 81: 442-464. 1974. Vickers,D. Evidence f o r as accumulator model of p s y c h o l o p h y s i c a l d i s c r i m i n a t i o n . Ergonomics. 13:37-58, 1970. Vic k e r s , D . , Caudrey,D. and R.Wilson. D i s c r i m i n a t i n g between the frequency of two a l t e r n a t i v e events. Acta P s y c h o l o g i c a , 35: 151-172, 1971. Wandell,B.A. Speed-accuracy t r a d e o f f i n v i s u a l d e t e c t i o n A p p l i c a t i o n s of neural c o u n t i n g and t i m i n g . V i s i o n  Research. 17:217-225, 1977* Wickelgren,W.A. Speed-accuracy t r a d e o f f and i n f o r m a t i o n p r o c e s s i n g dynamics. Acta Psychologica,, 4:67.-85,1977. Wil d i n g , J.M. The r e l a t i o n between l a t e n c y and accuracy i n the i d e n t i f i c a t i o n of v i s u a l s t i m u l i . , I . The e f f e c t s of task d i f f i c u l t y . Acta P s y c h o l o g i c a . 35:378-398, 1971. 79 Wilding,J.M, E f f e c t s o f s t i m u l u s d i s c r i m i n a b i l i t y on the l a t e n c y d i s t r i b u t i o n of i d e n t i f i c a t i o n responses. Acta P s y c h o l o g i c a , 38:483-500, 3 974. Wi l l i a m s , ! . B . I . Reaction time and l a r g e response movements. New Zealand J o u r n a l of Healthy P h y s i c a l Education and B e e r e a t i o n . 4:46-52, 1971. Wood,C.C. and J.B.Jennings. Speed-accuracy t r a d e o f f f u n c t i o n s i n c h o i c e r e a c t i o n time : Experimental designs and computational procedures. P e r c e p t i o n and Psychophysies. 19^92-101, 1976. Y e l l o t , J , I . , J r . C o r r e c t i o n f o r guessing i n c h o i c e r e a c t i time. Psychonomic S c i e n c e . 8:321-322, 1967. Y e l l o t , J - I - J r . C o r r e c t i o n f o r f a s t f u e s s i n g and the speed-accuracy t r a d e - o f f i n c h o i c e r e a c t i o n time. J o u r n a l o f Mathematical Psychology. 8:159-199. 1971. APPENDIX A Procedures 81 INSTRUCTIONS T h i s experiment measures your response time, that i s , how q u i c k l y you respond to a given s i g n a l - a l i g h t - with a s p e c i f i c movement. There are f o u r t e s t c o n d i t i o n s i n the experiment t h a t you w i l l perform i n subsequent s e s s i o n s . S p e c i f i c d e t a i l s o f these c o n d i t i o n s w i l l be g i v e n immediately before each s e s s i o n * Before you i s a cons o l e with s i x red l i g h t s numbered 1 to 6 from the l e f t . Only l i g h t s 3 and 4, however, w i l l be used as s t i m u l i . D i r e c t l y below these l i g h t s are two white keys. P l a c e your r i g h t index f i n g e r on the white key below l i g h t 4, and your l e f t index f i n g e r on the white key below l i g h t 3. I t i s important to keep both hands l e v e l , and your w r i s t s down. You are r e g u i r e d t o perform two d i f f e r e n t responses, one when l i g h t 3 f l a s h e s , and the other when l i g h t 4 comes on* Notice the three black keys l o c a t e d at the top of the c o n s o l e . These are numbered 1 to 3 from l e f t to r i g h t . RCA: This t a s k r e q u i r e s you t o depress the white key with your r i g h t / l e f t f i n q e r and then t o depress b l a c k key number 2. Now t r y the movement r e q u i r e d f o r RCA - depress the white response key with your index f i n q e r and then depress b l a c k key number 2. Any q u e s t i o n s about RCA? RCB: T h i s task r e q u i r e s you t o depress the white key with your l e f t / r i g h t index f i n g e r and then h i t the b l a c k response keys 2-1-3-2/2-3-1-2 i n r a p i d s u c c e s s i o n . Now t r y t h i s movement. 82 s t a r t i n g with your index f i n g e r on the white response key. Depress i t , and q u i c k l y h i t keys 2-1-3-2/2-3-1-2. Try BCB a g a i n , depressing the white key and then moving to h i t 2-1-3-2/2-3-1-2-Any q u e s t i o n s about RCB? Now t h a t you are f a m i l i a r with the apparatus and the r e q u i r e d responses we p r a c t i s e some t r i a l s of each response. Place your index f i n g e r s on keys 3 and 4 with your w r i s t s down* He w i l l begin with 15 t r i a l s of RCA o n l y . Watch f o r s t i m u l u s l i g h t 3/4 t o f l a s h . As soon as i t l i g h t s , perform RCA as q u i c k l y as p o s s i b l e . Ready... We w i l l now t r y 15 t r i a l s o f RCB. Again watch f o r s t i m u l u s l i g h t 4/3 t c appear, then g u i c k l y perform RCB- Ready... Now you are ready to t r y a c h o i c e s i t u a t i o n i n which e i t h e r l i g h t 3 or 4 may go on. Watch c a r e f u l l y , and when e i t h e r s t i m u l u s l i g h t s up g u i c k l y make the a p p r o p r i a t e response. Ready.,. Now you are ready to begin the a c t u a l experimental. During each o f the next f o u r s e s s i o n s you w i l l perform one experimental c o n d i t i o n c o n s i s t i n g of 100 t r i a l s with s h o r t r e s t p e r i o d s between s e t s of 25. A response to e i t h e r s t i m u l u s l i g h t counts as one t r i a l . Before you s t a r t I w i l l show you a payoff matrix which d e t a i l s how p o i n t s are awarded f o r f a s t and/or a c c u r a t e responses. At the end of the 4 s e s s i o n s a l l the s u b j e c t s w i l l be ranked i n order of the number of p o i n t s they have won. The higher you rank, the more money you w i l l win. The person ranking highest wins 20 d o l l a r s . , A f t e r each t r i a l I w i l l t e l l you whether you responded a c c u r a t e l y , or whether you have responded f a s t e r or slower than 83 your c r i t e r i o n s c o r e . T h i s c r i t e r i o n score i s based on your HLs from the i n i t i a l CBT s e s s i o n . F o l l o w i n g each s e s s i o n you w i l l r e c e i v e your cumulative t o t a l s c o r e . T a b l e 1. Order of P r e s e n t a t i o n of F i v e E x p e r i m e n t a l C o n d i t i o n s Order s u b j e c t s (S) Experimental C o n d i t i o n s EC1 EC2 EC 3 EC 4 EC 5 I S1, S2, S9, S10, S17, S18 2 3 4 5 1 i i S3, S4, S11, S12, S19, S20 3 5 2 4 1 i i i S5, S6 , S13, S14, S21, S22 5 4 3 2 1 i v S7, S8, S15, S16, S23, S24 4 2 5 3 1 APPENDIX B Results 86 Table 1 Mean RL f o r 24 S u b j e c t s over F i v e Experimental C o n d i t i o n s f o r ECA. Subject Accuracy Speed Accuracy Speed SET A&B A&B A A 1 304. 4 295.2 299.8 270. 4 242.6 2 315. 2 271.8 269.6 224. 2 220-8 3 315.4 328. 6 295.8 316.2 232. 4 4 363.0 286.6 308.8 290.6 260.4 5 303. 6 264.6 281.2 277. 2 256.0 6 27 2- 2 252.8 255.0 297.0 234.6 7 302.8 303. 4 325.0 279.6 314. 4 8 280.2 340.6 286.4 285.8 286.8 9 283.0 202.8 258.0 229.2 189-8 10 288. 2 243.3 240.6 239. 2 237. 8 11 244.0 238.2 249.4 240. 2 224.4 12 252.2 240-6 286.4 239-6 242.9 13 298.0 263.8 276.6 292.6 264. 4 14 247. 4 274.2 255.0 247. 0 235.6 15 269.8 286.2 230.8 249.0 233. 8 16 280.0 311.2 298.8 237. 0 205.2 17 354.8 293.2 298.4 245.2 238.8 18 280.0 274.4 252.6 264.0 214.2 19 312-4 316.6 293.4 251.2 211. 8 20 206.8 213.8 199.4 216.2 195.8 21 272.2 298.8 280.6 278.6 260-0 22 255.0 217. 4 235.4 229.2 232- 4 23 240.4 265.6 223.3 219.4 201.0 24 238-6 260.8 230.6 250.4 224.6 282-5 272.7 268.0 257. 0 235. 9 87 Table 2 Mean BL f o r 24 Su b j e c t s over F i v e Experimental C o n d i t i o n s f o r BCD. , Subjects Accuracy Speed Accuracy Speed SBT ASB A&B A A 1 319-4 319.6 437.6 432. 0 323.0 2 37 2.4 356.6 468-4 434.8 289.0 3 398.4 363.6 388.0 424-8 290.4 4 343-8 284.8 355.6 331.0 305.0 5 338. 2 291.6 378.4 438. 4 280.8 6 291-8 268.6 313.8 347.8 268.6 7 350.4 350.4 391.8 363-4 354. 6 8 345.8 381-4 36 0.4 345-6 317.2 9 435.0 326.8 461.4 390. 8 224.0 10 294.8 268.0 288.6 303-0 272-2 11 282.0 247.6 337.4 308.2 252.6 12 277.2 265. 0 308.8 284.8 264.9 13 309.2 272.2 287.2 307. 0 282.0 14 231. 8 299. 2 283.6 328.6 257. 2 15 269.6 285.8 308.2 293.2 256-0 16 286-4 307.2 374.4 371-4 223.2 17 349-8 268.4 332.2 363.2 255-2 18 269.4 260.8 263.4 267.0 229.2 19 351.2 324.6 315.2 372. 8 255.6 20 261.6 243.6 240.8 280.0 212.2 21 30 7. 2 329.6 304.2 305.0 273. 0 22 255.4 226.6 246.4 226.6 239.2 23 264.8 288.0 253. 8 295.2 213.6 24 242.4 260.2 255-2 274.6 232.6 88 F i g u r e 1 . I l l u s t r a t i o n o f t h e t a s k by d a y by b l o c k i n t e r a c t i o n o b s e r v e d f o r RCA a n d RCB. 

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