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Evidence that pigeons are not lost in space : pigeons perform well at long retention intervals on a modified… Willson, Robert James 1988

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EVIDENCE THAT PIGEONS ARE NOT LOST IN SPACE: PIGEONS PERFORM WELL AT LONG RETENTION INTERVALS ON MODIFIED DELAYED MATCHING OF KEY LOCATION TASK by ROBERT JAMES WILLSON B . S c , D a l h o u s i e U n i v e r s i t y , 1982 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF PSYCHOLOGY We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA October 1988 (5) R o b e r t James W i l l s o n , 1988 In p r e s e n t i n g this thesis in part ia l f u l f i lmen t o f t h e requ i remen ts fo r an a d v a n c e d d e g r e e at t h e Univers i ty o f Bri t ish C o l u m b i a , I agree that t h e Library shall m a k e it f ree ly avai lable fo r re fe rence and s t u d y . I f u r the r agree tha t permiss ion fo r ex tens ive c o p y i n g o f th is thesis fo r scholar ly p u r p o s e s may be g r a n t e d b y the h e a d o f m y d e p a r t m e n t o r b y his o r her representa t ives . It is u n d e r s t o o d that c o p y i n g o r pub l i ca t i on o f th is thesis fo r f inancia l ga in shall n o t b e a l l o w e d w i t h o u t m y w r i t t e n pe rm iss ion . D e p a r t m e n t o f f$ucMo)°< T h e Un ivers i ty o f Brit ish C o l u m b i a 1956 M a i n M a l l Vancouver , Canada V 6 T 1Y3 D a t e Qtl. 11, MM DE-6(3/81) 1 1 ABSTRACT The p r e s e n t s e r i e s of experiments examined p i g e o n s ' s p a t i a l w o r k i n g memory u s i n g two v a r i a n t s of the d e l a y e d matching of key l o c a t i o n paradigm ( W i l k i e & Summer, 1982). Exposure t o the sample l o c a t i o n was extended t o 15 min and pecks t o t h i s s t i m u l u s (S+) produced g r a i n on a v a r i a b l e i n t e r v a l 30-s s c h e d u l e (the 1 Cue g r o u p ) . For some s u b j e c t s (the 2 Cues group) b o t h the p o s i t i v e and n e g a t i v e (S-) s t i m u l i were p r e s e n t e d d u r i n g the sample p e r i o d . I n a subsequent t e s t phase s u b j e c t s were exposed t o b o t h the S+ and S- f o r 1 min. I f the s u b j e c t made more res p o n s e s t o the S+ an a d d i t i o n a l 15 min of acc e s s t o the S+ o c c u r r e d , w i t h g r a i n a v a i l a b l e on the p r e v i o u s s c h e d u l e . I f more res p o n s e s were made t o the S- the t r i a l t e r m i n a t e d and the s u b j e c t was i m m e d i a t e l y removed from the a p p a r a t u s . I n the f i r s t e x p e r i m e n t a l l s u b j e c t s performed w e l l w i t h r e t e n t i o n i n t e r v a l s of up t o 30 s, a l e v e l of performance b e t t e r than p r e v i o u s l y demonstrated i n the d e l a y e d matching of key l o c a t i o n ( W i l k i e & Summers, 1982). However, s u b j e c t s ' performance was d i s r u p t e d when they were removed from the a p p a r a t u s d u r i n g the r e t e n t i o n i n t e r v a l . S u b j e c t s i n the 1 Cue group were more s e v e r e l y d i s r u p t e d t h a n the s u b j e c t s i n the 2 Cues group. Performance improved d r a m a t i c a l l y when the s e s u b j e c t s were s u b s e q u e n t l y t r a i n e d and t e s t e d on the 2 cues c o n d i t i o n . Experiment 2 examined the d i f f e r e n c e s between the 1 cue and 2 cues t a s k s f u r t h e r . A l l s u b j e c t s were r u n f o r 30 i i i t r i a l s on each t a s k and removed from the apparatus d u r i n g the r e t e n t i o n i n t e r v a l . Performance on the 2 cues t a s k was s i g n i f i c a n t l y h i g h e r f o r a l l s u b j e c t s . When s u b j e c t s were s w i t c h e d t o the 1 cue t a s k , performance i m m e d i a t e l y dropped and remained a t a low l e v e l f o r a l l b l o c k s t e s t e d . The obs e r v e d d i f f e r e n c e s p r o b a b l y r e f l e c t the o p e r a t i o n of t r a n s f e r a p p r o p r i a t e p r o c e s s i n g ( c f . M o r r i s , B r a n s f o r d , & F r a n k s , 1977), g i v e n the s i m i l a r i t y between t r a i n i n g and t e s t i n g on the 2 cues t a s k . E x p e r i m e n t 3 used the 2 cues t a s k t o examine the performance of pi g e o n s when r e t e n t i o n i n t e r v a l s l o n g e r than 30 s were imposed between t r a i n i n g and t e s t i n g . The r e t e n t i o n i n t e r v a l was inc r e m e n t e d i n the f o l l o w i n g s t a g e s : 5 min, 15 min, 30 min, 1 h r , 2 h r , 4 h r , 8 h r , 12 hr and 24 h r . S u b j e c t s were r u n u n t i l t h e i r performance f e l l below a c r i t e r i o n (70% a c c u r a c y o r b e t t e r f o r a b l o c k of 10 t r i a l s ) . When a s u b j e c t f a i l e d t o a t t a i n c r i t e r i o n w i t h i n 3 b l o c k s , no f u r t h e r d a t a were c o l l e c t e d from t h a t s u b j e c t . S u b j e c t s ' upper r e t e n t i o n l i m i t v a r i e d somewhat, r a n g i n g from a minimum of 30 min t o a maximum of 24 h r , but the performance of most s u b j e c t s began t o d e t e r i o r a t e a t about 4 h r , a l e v e l c o n s i d e r a b l y above the upper l i m i t p r e v i o u s l y d emonstrated i n o t h e r paradigms (30 min-Spetch & Honig, 1988). Experiment 4 was a s y s t e m a t i c r e p l i c a t i o n of Experiment 3, u s i n g a mixed, r a t h e r t h a n an i n c r e m e n t a l , s c h e d u l e of r e t e n t i o n i n t e r v a l s . Performance was not q u i t e i v as good. For most s u b j e c t s performance began to d e t e r i o r a t e a t about 2 h r , somewhat sooner than i n Experiment 3, but n e v e r t h e l e s s h i g h e r than the l e v e l of performance seen i n o t h e r paradigms. The r e s u l t s of the p r e s e n t experiments are i n t e r p r e t e d i n terms of the e c o l o g i c a l v a l i d i t y of the p r o c e d u r e s employed. The i m p l i c a t i o n s of the p r e s e n t s t u d i e s f o r the s t u d y of " a d a p t i v e s p e c i a l i z a t i o n s i n c o g n i t i o n " ( S h e r r y , 1984; S h e r r y & S c h a c t e r , 1987), are a l s o d i s c u s s e d , as are the i m p l i c a t i o n s f o r the d i s t i n c t i o n between r e f e r e n c e and w o r k i n g memory. V TABLE OF CONTENTS A b s t r a c t . ./ i i T a b l e of C o n t e n t s v L i s t of T a b l e s v i i L i s t of F i g u r e s i x Acknowledgements x i i I n t r o d u c t i o n 1 A B r i e f H i s t o r y of Research on A n i m a l s ' S p a t i a l Memory 3 Two Types of S p a t i a l Memory 5 S p a t i a l Memory i n the P i g e o n 6 G e n e r a l Purpose and R a t i o n a l e 17 Experiment 1 20 Method 21 S u b j e c t s . . 21 Appa r a t u s 22 Proce d u r e 25 R e s u l t s 29 D i s c u s s i o n 36 Experiment 2 42 Method 43 S u b j e c t s and Apparatus 43 Pro c e d u r e 43 R e s u l t s 44 D i s c u s s i o n 49 Experiment 3 50 Method 50 S u b j e c t s and Apparatus 50 Procedure 51 R e s u l t s 52 D i s c u s s i o n 65 v i Experiment 4 66 Method 67 S u b j e c t s and A p p a r a t u s 67 Procedure 67 R e s u l t s 68 D i s c u s s i o n 79 G e n e r a l D i s c u s s i o n 79 C o n c l u s i o n s and F u t u r e D i r e c t i o n s 83 R e f e r e n c e s 87 v i i LIST OF TABLES T a b l e I . Data from each b l o c k of Experiment 1. Mean d a i l y d i s c r i m i n a t i o n r a t i o s a re i n the f i r s t row f o r each s u b j e c t , c u m u l a t i v e d i s c r i m i n a t i o n r a t i o s are i n the second row, and t o t a l c o r r e c t f i r s t c h o i c e s a re i n the t h i r d row. An a s t e r i s k denotes t h a t the 1 Cue group was r u n on the 2 cues c o n d i t i o n 30 Tab l e I I . Data from each b l o c k of Experiment 2. Mean d a i l y d i s c r i m i n a t i o n r a t i o s a re i n the f i r s t row f o r each s u b j e c t , c u m u l a t i v e d i s c r i m i n a t i o n r a t i o s are i n the second row, and t o t a l c o r r e c t f i r s t c h o i c e s a r e i n the Ta b l e I I I . Data from each b l o c k of Experiment 3. Mean d a i l y d i s c r i o m i n a t i o n r a t i o s a re i n the f i r s t row of each b l o c k , c u m u l a t i v e d i s c r i m i n a t i o n r a t i o s a r e i n the second row, t o t a l c o r r e c t f i r s t c h o i c e s a r e i n the row 3, and the t h i r d row 45 r e t e n t i o n i n t e r v a l i s i n the f o u r t h row 53-55 v i i i Table IV. Data from each block of Experiment 4. The f i r s t row of each r e t e n t i o n i n t e r v a l shows the mean d a i l y d i s c r i m i n a t i o n r a t i o s , the second row shows the cumulative d i s c r i m i n a t i o n r a t i o s , and the t h i r d row shows the t o t a l c o r r e c t f i r s t c h o i c e s 69 1 X LIST OF FIGURES F i g u r e 1. An overhead, s c h e m a t i c diagram o f the a p p a r a t u s and s u r r o u n d i n g room used i n the p r e s e n t e x p e r i m e n t s 23-24 F i g u r e 2. A comparison of the mean d i s c r i m i n a t i o n r a t i o s from the 1 and 2 Cues groups a t the t h r e e r e t e n t i o n i n t e r v a l s t e s t e d i n Experiment 1. Data p o i n t s are based on b l o c k s of 10 t r i a l s and r e p r e s e n t an average of the cummulative and mean d a i l y d i s c r i m i n a t i o n r a t i o f o r each b l o c k 31 F i g u r e 3. A comparison of the mean p e r c e n t a g e of c o r r e c t f i r s t r e s ponses from the 1 and 2 Cues groups a t the t h r e e r e t e n t i o n i n t e r v a l s t e s t e d i n Experiment 1. Data p o i n t s are based on b l o c k s of 10 t r i a l s 33 F i g u r e 4. A comparison of the mean d i s c r i m i n a t i o n r a t i o s a t the 30 s r e t e n t i o n i n t e r v a l as a f u n c t i o n of whether the r e t e n t i o n i n t e r v a l was spent i n or out of the t e s t chamber 34 F i g u r e 5. A comparison of the mean p e r c e n t a g e of c o r r e c t f i r s t r esponses a t the 30 s r e t e n t i o n i n t e r v a l as a f u n c t i o n of whether the r e t e n t i o n i n t e r v a l was spent i n o r out of the t e s t chamber 35 X F i g u r e 6. A comparison of the mean d i s c r i m i n a t i o n r a t i o s f o r the 1 cue group a t the 30 s r e t e n t i o n i n t e r v a l as a f u n c t i o n of whether they were r u n on the 1 or 2 cues c o n d i t i o n . The r e t e n t i o n i n t e r v a l was spent out of the t e s t chamber 37 F i g u r e 7. A comparison of the mean p e r c e n t a g e of c o r r e c t f i r s t r e s p o n s e s f o r the 1 cue group a t the 30 s r e t e n t i o n i n t e r v a l as a f u n c t i o n of whether they were r u n on the 1. or 2 cues c o n d i t i o n . The r e t e n t i o n i n t e r v a l was spent out of the t e s t chamber 38 F i g u r e 8. A comparison of t h e mean d i s c r i m i n a t i o n r a t i o s from Experiment 2 f o r the l->2 Cues and 2->l Cue gro u p s . The r e t e n t i o n i n t e r v a l was 30 s and spent o u t s i d e of the t e s t chamber 45 F i g u r e 9. A comparison of the mean pe r c e n t a g e of c o r r e c t f i r s t r e s p o n s e s from Experiment 2 f o r the l->2 Cues and 2->l Cue groups. The r e t e n t i o n i n t e r v a l was 30 s and spent o u t s i d e of the t e s t chamber 47 X 1 F i g u r e 10. The f i n a l d i s c r i m i n a t i o n r a t i o f o r each r e t e n t i o n i n t e r v a l t e s t e d i n Experiment 3. Each p a n e l c o n t a i n s the d a t a from one s u b j e c t . A l l d a t a p o i n t s , e x c e p t f o r the l o n g e s t r e t e n t i o n i n t e r v a l s , r e p r e s e n t b l o c k s i n which c r i t e r i o n (.70) was met. Note t h a t The s c a l e of the X a x i s d i f f e r s from p a n e l t o p a n e l 56-59 F i g u r e 11. The d i s c r i m i n a t i o n r a t i o s from Experiment 3. A r e g r e s s i o n l i n e t h a t b e s t f i t s the d a t a i s a l s o shown. Each p a n e l shows the d a t a from one s u b j e c t . Note t h a t the s c a l e of the X a x i s v a r i e s from p a n e l t o p a n e l 61-64 F i g u r e 12. The mean d i s c r i m i n a t i o n r a t i o s from Experiment 4 as a f u n c t i o n of r e t e n t i o n i n t e r v a l . Each p a n e l shows the d a t a from one s u b j e c t 70-73 F i g u r e 13. The d i s c r i m i n a t i o n r a t i o s from Experiment 4. Data f o r i n d i v i d u a l s u b j e c t s a re p r e s e n t e d i n s e p a r a t e p a n e l s . The r e g r e s s i o n l i n e t h a t b e s t f i t s the d a t a i s a l s o i n c l u d e d 75-78 Acknowledgements Many thanks t o Don W i l k i e f o r h i s p a t i e n c e and su p p o r t t h r o u g h o u t the c o u r s e of t h i s p r o j e c t , e s p e c i a l l y i n the l a t e r s t a g e s . Thanks a l s o t o Lee Gass and P e t e r Graf who put t h i n g s i n a d i f f e r e n t p e r s p e c t i v e , and i n so d o i n g , had a tremendous impact on the way I t h i n k about many of the i s s u e s p r e s e n t e d h e r e . Thanks a l s o t o Shayne K a r d a l who h e l p e d w i t h many a s p e c t s of the r e s e a r c h p r e s e n t e d here. F i n a l l y , thanks t o my b e s t f r i e n d , K r i s t a , who a l s o happens t o be my w i f e , f o r r e c o g n i z i n g what I had t o do and l e t t i n g me do i t . T h i s r e s e a r c h was s u p p o r t e d by the N a t i o n a l S c i e n c e s and E n g i n e e r i n g C o u n c i l of Canada. 1 INTRODUCTION For mobile animals, the a b i l i t y to process and remember s p a t i a l information (e.g. the location of a nest, burrow or a good food source) i s extremely important. Consequently, this a b i l i t y has received much attention from researchers studying both the cognitive and physiological processes of the brain. Comparative studies have revealed that many organisms possess excellent s p a t i a l memory a b i l i t i e s . For example, the Clark's Nutcracker caches food i n the season of abundance, and then relocates and excavates these caches during the winter months, even though they are often snow-covered (Tomback, 1980). Good s p a t i a l memory has been shown for several other species, including the commonly-studied laboratory rat (see Roberts, 1979, for example). Another commonly studied animal, the pigeon, however, has t y p i c a l l y shown rather limited s p a t i a l memory a b i l i t i e s when tested i n laboratory experiments (e.g. Bond, Cook, & Lamb, 1981). Given that the s p a t i a l a b i l i t i e s of some types of pigeons are renowned ( i . e . the homing pigeon's a b i l i t y to f i n d i t s way home even when released from novel, distant s i t e s ) , this f a i l u r e to perform well on s p a t i a l memory tasks i s somewhat paradoxical. This apparent paradox i s the major focus of this thesis. Some authors have argued that differences i n a cognitive a b i l i t y across species may r e f l e c t the existence of "adaptive s p e c i a l i z a t i o n s " (Sherry, 1984; Sherry & Schacter, 1987). Certain species, because of the pressures 2 of n a t u r a l s e l e c t i o n , have e v o l v e d s p e c i a l i z e d c o g n i t i v e a b i l i t i e s f o r c o p i n g w i t h the unique problems p r e s e n t e d by t h e i r n i c h e s . The phenomenal memory performance of f o o d -s t o r i n g b i r d s , mentioned above, i s an example. Because t h i s type of b i r d l i v e s i n a h a b i t a t where the a v a i l a b i l i t y of fo o d undergoes extreme s e a s o n a l f l u c t u a t i o n , an a b i l i t y f o r r e o r g a n i z i n g the s e a s o n a l d i s t r i b u t i o n of food items may have e v o l o v e d . They cache f o o d i n times of abundance and then f i n d and e x c a v a t e t h e s e caches d u r i n g the w i n t e r . F i e l d s t u d i e s suggest t h a t they can remember the l o c a t i o n of hundreds of d i f f e r e n t c a c h e - s i t e s (Tomback, 1980). T h i s phenomenal memory performance, argue S h e r r y and S c h a c t e r , i s a s p e c i a l i z e d c o g n i t i v e a b i l i t y . However, a d a p t i v e s p e c i a l i z a t i o n s can be shown o n l y when s u b j e c t s are t e s t e d on s p e c i e s - a p p r o p r i a t e t a s k s . The im p o r t a n c e of a p p r o p r i a t e t r a i n i n g and t e s t i n g p r o c e d u r e s has been w e l l e s t a b l i s h e d i n human c o g n i t i o n r e s e a r c h ( c f . M o r r i s , B r a n s f o r d , & F r a n k s , 1977). I n t h i s t h e s i s I w i l l argue t h a t i n a p p r o p r i a t e t r a i n i n g and t e s t i n g p r o c e d u r e s have l e a d t o i n v a l i d c o n c l u s i o n s about the c o g n i t i v e a b i l i t i e s of the p i g e o n and t h a t the a f o r e m e n t i o n e d paradox c o n c e r n i n g the p i g e o n s ' s p a t i a l memory a b i l i t i e s i s a d i r e c t r e s u l t of t h i s problem. The i m p l i c a t i o n s of t h i s problem f o r the modern s t u d y of c o m p a r a t i v e p s y c h o l o g y w i l l a l s o be d i s c u s s e d . I n the f i r s t s e c t i o n of the I n t r o d u c t i o n a b r i e f h i s t o r i c a l o v e r v i e w of the s t u d y of s p a t i a l memory i s 3 presented and the terms r e f e r e n c e and working memory are d e f i n e d . The second s e c t i o n i s a review o f 0 t h e e x i s t i n g work i n the study of s p a t i a l memory i n the pigeon and a d i s c u s s i o n of the r e l a t i v e m e r i t s and d i f f i c u l t i e s of the procedures t h a t have been used to study i t so f a r . The f i n a l s e c t i o n of the I n t r o d u c t i o n d e s c r i b e s the r a t i o n a l e f o r the procedures and experiments i n c l u d e d i n t h i s t h e s i s . A B r i e f H i s t o r y o f R e s e a r c h o n A n i m a l s ' S p a t i a l M e m o r y In some of the e a r l i e s t work i n v o l v i n g s p a t i a l memory, Tolman and h i s a s s o c i a t e s (e.g. Tolman, R i t c h i e & K a l i s h , 1946a,b) used s p a t i a l tasks to show t h a t l e a r n i n g was more than j u s t the simple a c q u i s i t i o n of stimulus-response (S-R) a s s o c i a t i o n s , a view that was predominant at the time ( c f . H u l l , 1943). Tolman used mazes of v a r i o u s c o n f i g u r a t i o n s to demonstrate such d i v e r s e phenomena as l a t e n t l e a r n i n g , s h o r t cut l e a r n i n g , and place l e a r n i n g . U n f o r t u n a t e l y h i s work f a i l e d to convince the m a j o r i t y of h i s contemporaries and S-R dominated theory and r e s e a r c h p e r s i s t e d f o r many y e a r s . Furthermore, with the advent of the automated Skinner box, maze and s p a t i a l l e a r n i n g tasks f e l l out of vogue. Beginning i n the 1960's, r e s e a r c h e r s i n the area of human l e a r n i n g and memory began to abandon S-R theory i n f a v o r of a more c o g n i t i v e o r i e n t a t i o n . J u s t as theory from animal l e a r n i n g had s t r o n g l y i n f l u e n c e d human l e a r n i n g theory i n the preceding decades, t h i s more c o g n i t i v e approach i n human l e a r n i n g r e s e a r c h s t a r t e d to i n f l u e n c e 4 work i n animal l e a r n i n g . Researchers began to use tasks, such as delayed matching to sample (Blough, 1959), that p e r m i t t e d the study of animals' c o g n i t i v e a b i l i t i e s . Many of the tasks developed at t h i s time were designed as animal l e a r n i n g analogs of tasks used to study human l e a r n i n g and memory. In a seminal paper i n the resurgence of the study of s p a t i a l memory, O l t o n and Samuelson (1976) d e s c r i b e d an apparatus, the wagon-wheel shaped r a d i a l - a r m maze, f o r st u d y i n g s h o r t - t e r m memory f o r l o c a t i o n i n the r a t . In t h e i r procedure a r a t was allowed to expl o r e the maze f r e e l y u n t i l i t had found the food l o c a t e d at the d i s t a l end of each maze arm. A l l arms were b a i t e d at the s t a r t of a t r i a l . The o r i g i n a l maze c o n s i s t e d of e i g h t arms and the task was i n i t i a l l y viewed as a s p a t i a l analog to the l e a r n i n g of word l i s t s i n human c o g n i t i v e psychology. Rats proved to be very p r o f i c i e n t at the task, q u i c k l y l e a r n i n g to v i s i t each arm once without r e p e t i t i o n . V arious c o n t r o l m a nipulations ensured t h a t the r a t s 1 performance was based on memory, not non-memorial s t r a t e g i e s such as response algor i t h m s or the use of odor t r a i l s . Since t h i s f i r s t paper the r a d i a l arm maze and many v a r i a n t s of i t have been used to i n v e s t i g a t e the s p a t i a l memory a b i l i t i e s of s e v e r a l s p e c i e s (human a d u l t s and c h i l d r e n - A a d l a n d , Beatty & Maki, 1985; C l a r k ' s n u t c r a c k e r s - B a l d a , 1980; honeybees-Gould, 1984; chimpanzees-Menzel, 1978; Siamese f i g h t i n g f i s h -R o i t b l a t , Tham & Golub, 1982; black-capped chickadees-5 S h e r r y , 1984; g e r b i l s - W i l k i e & S l o b i n , 1981; r i n g doves-W i l k i e , Spetch & Chew, 1981; r a t s - M o r r i s , 1981; R o b e r t s , 1979; r a t s & pigeons-Bond, Cook & Lamb, 1981; p i g e o n s -Spetch & Edwards, 1986; Spetch & Honig, 1988; W i l k i e & Summers, 1982 ;R o b e r t s , 1988; Rob e r t s & Van V e l d h u i z e n , 1985; D a l e , 1988) . T w o T y p e s o f S p a t i a l M e m o r y S h o r t l y a f t e r O l t o n and Samuelson's (1976) paper Honig (1978) and O l t o n (1978) i n d e p e n d e n t l y proposed a d i s t i n c t i o n between two types of memory. Refer e n c e memory can most e a s i l y be thought of as a p r o c e s s f o r the s t o r a g e and r e t r i e v a l of r e l a t i v e l y i n v a r i a n t i n f o r m a t i o n . Permanent f e a t u r e s of the environment (e.g. f i x e d landmarks) and response r u l e s (e.g. "peck an i l l u m i n a t e d p e c k i n g key i n a S k i n n e r box t o r e c e i v e g r a i n " ) a re good examples of the ty p e s of i n f o r m a t i o n t h a t a re thought t o be r e p r e s e n t e d i n r e f e r e n c e memory. Working memory i s b e s t thought of as a p r o c e s s f o r the temporary s t o r a g e and subsequent r e t r i e v a l of t r a n s i e n t i n f o r m a t i o n . P r e v i o u s l y v i s i t e d arms i n a r a d i a l maze and the c u r r e n t sample f e a t u r e s i n a matching t o sample t a s k a re good examples of the type of i n f o r m a t i o n t h a t may be r e p r e s e n t e d i n w o r k i n g memory. Many t a s k s have b o t h a w o r k i n g and r e f e r e n c e memory component. For example, d e l a y e d matching t o sample (DMTS) i n v o l v e s b o t h w o r k i n g and r e f e r e n c e memory. The s u b j e c t must not o n l y remember the f e a t u r e s of the c u r r e n t l y 6 r e l e v a n t sample (a working memory t a s k ) , but must a l s o remember to peck the ch o i c e s t i m u l u s t h a t matches the sample (a r e f e r e n c e memory t a s k ) . Remembering the i n f o r m a t i o n r e l e v a n t to the task at hand i s a working memory problem whereas remembering what to do with that i n f o r m a t i o n i s a r e f e r e n c e memory problem. A r e c e n t paper by Roberts and Van Veldhuizen (1985) i l l u s t r a t e s the d i s t i n c t i o n between r e f e r e n c e and working memory q u i t e n i c e l y . In separate experiments, they t r a i n e d pigeons to search f o r food i n a r a d i a l arm maze under two d i f f e r e n t c o n d i t i o n s . In one experiment a l l arms were b a i t e d and the pigeons' task was to c o l l e c t a l l food items i n an e f f i c i e n t manner. S u c c e s s f u l performance r e q u i r e d t h a t the s u b j e c t keep t r a c k of the l o c a t i o n s that i t had p r e v i o u s l y v i s i t e d to av o i d r e - e n t e r i n g food d e p l e t e d arms. T h i s i s a working memory task because the p a t t e r n of empty arms v a r i e d from day-to-day, depending upon the s u b j e c t s ' own beh a v i o r . In a second experiment, only four of the e i g h t arms were b a i t e d and the l o c a t i o n of the b a i t e d arms remained constant from day-to-day. S u c c e s s f u l performance r e q u i r e d t h a t the pigeons l e a r n which four of the e i g h t arms were b a i t e d . T h i s i s a r e f e r e n c e memory task because the p a t t e r n of empty arms remained constant from day-to-day. S p a t i a l M e m o r y i n t h e P i g e o n The f i r s t systematic attempt to examine pigeons' s p a t i a l memory appeared i n a 1981 paper by Bond, Cook and 7 Lamb. They compared t h e w o r k i n g memory p e r f o r m a n c e o f p i g e o n s and r a t s i n t h e r a d i a l maze. I n t h a t i n i t i a l e x p e r i m e n t p i g e o n s p e r f o r m e d a t a l e v e l f a r below t h a t o f r a t s . P e r f o r m a n c e was so p o o r t h a t t h e a u t h o r s s p e c u l a t e d t h a t t h e f o r a g i n g e c o l o g y o f p i g e o n s may n o t have been c o n d u c i v e f o r t h e e v o l u t i o n o f a p r o f i c i e n t s p a t i a l w o r k i n g memory. Bond e t a l s u g g e s t e d t h a t b e c a u s e p i g e o n s t e n d t o f e e d i n l o c a t i o n s t h a t a r e n o t t y p i c a l l y d e p l e t e d i n a s i n g l e f e e d i n g b o u t , t h e y may have d e v e l o p e d b o t h a p r o f i c i e n t r e f e r e n c e memory i n w h i c h f e e d i n g s i t e l o c a t i o n was s t o r e d and a t e n d e n c y t o use a w i n - s t a y f o r a g i n g s t r a t e g y t o v i s i t t h e s e s i t e s , two a b i l i t i e s t h a t r e s p e c t i v e l y p l a y a m i n o r r o l e s i n o r a c t i v e l y i n h i b i t t h e s u c c e s s f u l p e r f o r m a n c e o f t h e r a d i a l arm maze t a s k . A l t h o u g h a rguments a b o u t c o g n i t i v e a b i l i t i e s b a s e d on s p e c u l a t i o n a b o u t t h e c o u r s e o f e v o l u t i o n a r e o f n e c e s s i t y t e n u o u s , t h e e x i s t i n g e v i d e n c e p e r t a i n i n g t o t h e p r o f i c i e n c y o f p i g e o n s ' r e f e r e n c e memory s u p p o r t a t l e a s t some a s p e c t s o f Bond e t a l 's a s s e r t i o n . W i l k i e and W i l l s o n ( i n p r e s s ) have r e c e n t l y shown t h a t p i g e o n s do have a p r o f i c i e n t r e f e r e n c e memory f o r l o c a t i o n . U s i n g a key l o c a t i o n d i s c r i m i n a t i o n p r o c e d u r e t h e y r e w a r d e d p i g e o n s f o r r e s p o n d i n g t o one key i n a 3 by 3 m a t r i x o f p e c k i n g k e y s . The l o c a t i o n o f t h e key r e m a i n e d c o n s t a n t a c r o s s s e s s i o n s and t h e s u b j e c t s q u i c k l y l e a r n e d t o r e s p o n d o n l y t o t h a t k e y . V a r i o u s r e t e n t i o n t e s t s showed t h a t t h e p i g e o n s ' 8 memory f o r the l o c a t i o n of a f o r m e r l y rewarded pecking key was s t a b l e and i n t a c t a f t e r as long as 30 days. Roberts and Van Veldhuizen (1985) have a l s o found evidence of good r e f e r e n c e memory i n pigeons t e s t e d on the r a d i a l maze. Pigeons e a s i l y l e a r n e d the l o c a t i o n of four d i f f e r e n t i a l l y b a i t e d arms w i t h i n an e i g h t arm maze when the l o c a t i o n of those f o u r arms remained constant across days. They p l a c e d a d i f f e r e n t q u a n t i t y of food i n each of the four b a i t e d arms and found that t h e i r s u b j e c t s q u i c k l y l e a r n e d to v i s i t the f o u r arms i n descending order of reward magnitude. Pigeons a l s o e x h i b i t e d a r e l a t i v e l y p r o f i c i e n t working memory i n the r a d i a l maze f o l l o w i n g e x t e n s i v e shaping and t r a i n i n g , a f i n d i n g i n c o n s i s t e n t with Bond e t a 1 ' s h y p o t h e s i s . However, although performance was i n i t i a l l y q u i t e good on the working memory task i t dropped to chance l e v e l s when r e t e n t i o n i n t e r v a l s of o n l y 3 min were imposed between the f i r s t and l a s t four c h o i c e s . Dale (1988) has r e c e n t l y r e p l i c a t e d Roberts and Van Veldhuizen's f i n d i n g s u s i n g a four ( r a t h e r than the usual e i g h t ) arm r a d i a l maze. The maze was c o n s t r u c t e d of chicken wire and o f f e r e d the pigeons an unobstructed view of the e n t i r e apparatus and surrounding environment. Dale presented two f i n d i n g s of i n t e r e s t . F i r s t , working memory performance was w e l l above chance even without e x t e n s i v e t r a i n i n g and remained high with delays of up to 5 min. Dale a t t r i b u t e d the improved performance to the b e t t e r v i s i b i l i t y p r o v i d e d w i t h i n h i s apparatus and to the s m a l l e r number of 9 p o s s i b l e c h o i c e s a v a i l a b l e t o the p i g e o n s . Second, he found t h a t p i g e o n s made a b e t t e r t h a n chance number of c o r r e c t r e s p o n s e s f o l l o w i n g an i n i t i a l i n c o r r e c t c h o i c e . He sug g e s t e d t h a t pigeons c o u l d re-examine working memory f o l l o w i n g a m i s t a k e and th e n respond c o r r e c t l y . Other a u t h o r s have a l s o found e v i d e n c e of s p a t i a l w o r k i n g memory i n the p i g e o n . For example, W i l k i e and Summers (1982) used a v a r i a t i o n of the DMTS pr o c e d u r e . In t h e i r p r o c e d u r e , c a l l e d d e l a y e d matching of key l o c a t i o n , the p i g e o n f a c e s a 3 by 3 m a t r i x of p e c k i n g keys. On each t r i a l a randomly s e l e c t e d key i s i l l u m i n a t e d as the sample. A f t e r a b r i e f p r e s e n t a t i o n the key i s t u r n e d o f f and a r e t e n t i o n i n t e r v a l (RI) b e g i n s . F o l l o w i n g the RI the sample i s r e - i l l u m i n a t e d t o g e t h e r w i t h a randomly d e t e r m i n e d d i s t r a c t o r s t i m u l u s . A response t o the sample produces r e i n f o r c e m e n t whereas a response t o the d i s t r a c t o r key l e a d s d i r e c t l y i n t o the i n t e r t r i a l i n t e r v a l . Pigeons r e a d i l y a c q u i r e the t a s k but t h e i r performance t y p i c a l l y drops t o chance l e v e l s w i t h r e t e n t i o n i n t e r v a l s of o n l y 8 s. O l s e n and Maki (1983) a l s o found e v i d e n c e of s p a t i a l w o r k i n g memory. T h e i r p i g e o n s performed w e l l on a d e l a y e d -a l t e r n a t i o n t a s k i n a T-maze. S u b j e c t s were p l a c e d i n the s t a r t box and a l l o w e d t o choose and consume the r e i n f o r c e r i n one arm of the T-maze and the n were removed from the a p p a r a t u s . A f t e r a r e t e n t i o n i n t e r v a l the pigeons were r e p l a c e d i n the s t a r t box and a l l o w e d t o choose one of the two arms. C h o s i n g the n o v e l o r u n v i s i t e d arm was rewarded. P i g e o n s performed q u i t e w e l l on the t a s k w i t h s h o r t r e t e n t i o n i n t e r v a l s but t h e i r performance dropped t o chance w i t h r e t e n t i o n i n t e r v a l s of 16 min. W i l k i e , Spetch and Chew (1981) t e s t e d s p a t i a l memory i n r i n g doves u s i n g a v a r i a t i o n of the r a d i a l maze. T h e i r a p p a r a t u s , the " f l i g h t maze", c o n s i s t e d of 14 c a r d b o a r d tubes r a d i a t i n g from a c y l i n d r i c a l c e n t r a l area i n two p a r a l l e l rows of seven arms, one row above the o t h e r . I n d i v i d u a l tubes were 30 cm a p a r t , b o t h w i t h i n and between l e v e l s . The bottom row was a p p r o x i m a t e l y 15 cm above the f l o o r o f the chamber. The p r o x i m a l end of each tube c o n t a i n e d a p e r c h , w h i l e the d i s t a l end c o n t a i n e d a f o o d cup. W i l k i e e t a l found t h a t t h e i r s u b j e c t s were q u i t e p r o f i c i e n t a t t h i s t a s k , r e s p o n d i n g a t a l e v e l w e l l above chance i n terms of b o t h p e r c e n t c o r r e c t c h o i c e s and the e x p e c t e d p r o b a b i l i t y of making a c o r r e c t c h o i c e as a f u n c t i o n of the number of p o s s i b l e c o r r e c t c h o i c e s . However, a l t h o u g h not e x p l i c i t l y s t a t e d by the a u t h o r s , i n i t i a l t r a i n i n g was e x t e n s i v e (100 s e s s i o n s ) . A c o n s i d e r a t i o n e v i d e n t i n W i l k i e e t a l ' s paper, a l t h o u g h not e x p l i c i t l y d i s c u s s e d , i s the importance of u s i n g a p p r o p r i a t e a p p a r a t i t o t e s t c o g n i t i v e a b i l i t i e s . I n r e t r o s p e c t i t seems f a i r l y c e r t a i n t h a t the a u t h o r s c o n s i d e r e d the b e h a v i o r a l c h a r a c t e r i s t i c s of t h e i r s u b j e c t s b e f o r e b u i l d i n g t h e i r a p p a r a t u s . The l a t e r work of the second a u t h o r , Spetch, d e s c r i b e d below, i l l u s t r a t e s t h i s p o i n t more e x p l i c i t l y . Perhaps the most c o n v i n c i n g d e m o n s t r a t i o n of s p a t i a l w o r k i n g memory i n the p i g e o n has come from the work of Spetch and her c o l l e a g u e s (Spetch & Edwards, 1986; Spetch & Honig, 1988) , who have used a n o v e l t e s t i n g p r o c e d u r e . They reasoned t h a t because pigeons f o r a g e i n open f i e l d e n vironments the c o n s t r a i n i n g n a t u r e of r a d i a l mazes, T-mazes and s i m i l a r a p p a r a t i might be i n a p p r o p r i a t e f o r t e s t i n g s p a t i a l w o r k i n g memory a b i l i t i e s , and t h a t p i g e o n s ' apparent poor performance might be an a r t i f a c t of i n a p p r o p r i a t e t e s t i n g p r o c e d u r e s r a t h e r than a p o o r l y d e v e l o p e d s p a t i a l w o r k i n g memory. The ap p a r a t u s t h a t Spetch and Edwards d e v e l o p e d , the " w a l k i n g maze" (an open f i e l d a n a l o g t o the r a d i a l arm maze), c o n s i s t e d of e i g h t f e e d i n g s t a t i o n s t h a t c o u l d be ar r a n g e d i n any c o n f i g u r a t i o n on the f l o o r of a l a r g e t e s t i n g room. Each s t a t i o n i n i t i a l l y c o n t a i n e d s e v e r a l p i e c e s of g r a i n . The p i g e o n was a l l o w e d t o walk f r e e l y between the s t a t i o n s w i t h o u t h a v i n g t o r e t u r n t o a c e n t r a l a r e a between v i s i t s , as i s r e q u i r e d i n a r a d i a l - a r m maze. The pigeons c l e a r l y demonstrated p r o f i c i e n t w o r k i n g memory, w i t h o u t e x t e n s i v e o r s p e c i a l p r e t r a i n i n g ( c f . R o b e r t s & Van V e l d h u i z e n , 1985). However, even w i t h t h i s t a s k p i g e o n s ' r e t e n t i o n of s p a t i a l i n f o r m a t i o n decayed q u i c k l y . Performance began t o decrease a f t e r a r e t e n t i o n i n t e r v a l of 5 min, was s t i l l r e a s o n a b l y good a f t e r 30 min., but had f a l l e n t o chance l e v e l s a f t e r 2 hr ( S p e t c h & Honig, 1988). 1 2 R o b e r t s (1988) extended the work of Spetch and her c o l l e a g u e s by u s i n g the w a l k i n g maze a p p a r a t u s t o examine p i g e o n s p a t i a l memory i n a s i m u l a t e d p a t c h y environment. He s e t up f o u r " p a t c h e s " w i t h i n a l a r g e room and a l l o w e d h i s s u b j e c t s t o e x p l o r e f r e e l y . A p a t c h c o n s i s t e d of a c i r c u l a r arrangement of e i g h t f e e d i n g s t a t i o n s . P a t c h e s were d i f f e r e n t i a t e d b o t h by t h e i r l o c a t i o n w i t h i n the room and by the d e n s i t y of f o o d a v a i l a b l e w i t h i n them a t the s t a r t of a s e s s i o n . Food d e n s i t y was v a r i e d by m a n i p u l a t i n g the number of f o o d i t e m s p e r f e e d i n g s t a t i o n or by v a r y i n g the p r o p o r t i o n of b a i t e d s t a t i o n s w i t h i n p a t c h e s . The c h a r a c t e r i s t i c s of i n d i v i d u a l p atches were h e l d c o n s t a n t t h r o u g h o u t h i s e x p e r i m e n t s . R o b e r t s found good ev i d e n c e of s p a t i a l memory f o r p a t c h c h a r a c t e r i s t i c s , but l i t t l e e v i d e n c e of w o r k i n g memory w i t h i n p a t c h e s . The pigeons made more f i r s t v i s i t s t o r i c h e r p a t c h e s and spent more time t h e r e . They a l s o v i s i t e d a l l p a t c h e s b e f o r e making r e p e a t v i s i t s , a f i n d i n g which s u g g e s t s t h a t the p i g e o n s were u s i n g w o r k i n g memory t o keep t r a c k of p a t c h e s p r e v i o u s l y v i s i t e d . However, h i s s u b j e c t s showed l i t t l e a b i l i t y t o remember which f e e d i n g s t a t i o n s had p r e v i o u s l y been v i s i t e d w i t h i n a p a t c h . H i s s u b j e c t s d i d not t y p i c a l l y d e p l e t e each p a t c h on t h e i r f i r s t v i s i t and on subsequent v i s i t s chose an a l r e a d y empty f e e d i n g s t a t i o n as o f t e n as t h e y d i d a f u l l one. In summary, s p a t i a l memory r e s e a r c h w i t h pigeons has produced a p p a r e n t l y c o n t r a d i c t o r y f i n d i n g s . E a r l y work suggested that pigeons had excellent reference memory, but l i t t l e or no working memory for location (Bond e t a l , 1981). More recently various researchers have presented data ind i c a t i n g that pigeons have working memory for location (Wilkie & Summers, 1982; Spetch & Edwards, 1986) but have also concluded that i t decays more rapidly than i n other species. For example, rats have demonstrated durable retention of the location of previously v i s i t e d arms i n a r a d i a l maze for int e r v a l s of up to 4 hr (Beatty & Shavalia, 1980). Food caching birds l i k e the Clark's Nutcracker or the black-capped chickadee have demonstrated retention of the location of t h e i r caches on the order of months (Tomback, 1980, and Sherry, 1984, respectively) A major difference between early and l a t e r work i n the study of pigeon s p a t i a l memory has been the type of task used to assess performance. Experiments that have used the radial-arm maze, an apparatus designed for burrowing rodents l i k e the rat, have t y p i c a l l y yielded poor results when used with pigeons (Bond e t a l , 1981). Other studies that have used open f i e l d apparati l i k e the " f l i g h t maze" (Wilkie, Spetch, & Chew, 1981) or the "walking maze" (Spetch & Edwards, 1986), which model the type of environments that pigeons t y p i c a l l y forage i n , have provided better performances, while experiments employing other apparati l i k e the chicken wire r a d i a l maze (Dale, 1988) have provided intermediate r e s u l t s . Pigeons do best on problems similar 14 t o t hose t h a t they would f a c e i n the w o r l d o u t s i d e the l a b o r a t o r y , a f i n d i n g t h a t i s h a r d l y s u r p r i s i n g . But what e x a c t l y i s a " p i g e o n - l i k e " problem? A l t h o u g h a f a i r l y e x t e n s i v e b i o l o g i c a l l i t e r a t u r e on the p i g e o n f o r a g i n g e c o l o g y e x i s t s (Goodwin, 1983; Whitman, 1919), p s y c h o l o g i s t s have shown a s u r p r i s i n g l a c k of awareness of the e x i s t e n c e of t h i s l i t e r a t u r e . A l t h o u g h some c o n t r o l l e d r e s e a r c h has been conducted (see f o r example, G i r a l d e a u , 1984; G i r a l d e a u & L e f e b v r e , 1984,1987) most of what p s y c h o l o g i s t s p r o f e s s t o know i s based on c a s u a l o b s e r v a t i o n (Levy, 1941) o r has c o n s i d e r e d o n l y l i m i t e d a s p e c t s of the p i g e o n f o r a g i n g e c o l o g y (Bond e t a l , 1981; S p e t c h & Edwards, 1986). G i v e n the amount of r e s e a r c h t h a t employs p i g e o n s as s u b j e c t s , t h i s apparent l a c k of awareness of an e x i s t i n g l i t e r a t u r e i s somewhat s u r p r i s i n g . Some a s p e c t s of the p i g e o n f o r a g i n g e c o l o g y have been c o n s i d e r e d i n p r e v i o u s s p a t i a l memory work, as i l l u s t r a t e d by the work of S p e t c h and her c o l l e a g u e s . An open f i e l d e nvironment, the type of environment i n which p i g e o n s g e n e r a l l y f o r a g e , has p r o v i d e d some e v i d e n c e of a p r o f i c i e n t w o r k i n g memory f o r l o c a t i o n i n t h i s s p e c i e s . However, o t h e r r e s e a r c h u s i n g a s i m i l a r s t y l e of a p p a r a t u s ( R o b e r t s , 1988) has found e v i d e n c e t h a t a l t h o u g h pigeons remember p r e v i o u s p a t c h v i s i t s , t h ey a p p a r e n t l y do not remember v i s i t s t o f e e d i n g s i t e s w i t h i n a p a t c h . R o b e r t s ' s u b j e c t s tended t o v i s i t a l l p a t c h e s b e f o r e making r e p e a t v i s i t s , but showed no tendency t o a v o i d r e v i s i t i n g d e p l e t e d f e e d i n g s i t e s w i t h i n a g i v e n p a t c h . R o b e r t s o f f e r s a p l a u s i b l e e x p l a n a t i o n f o r the apparent c o n t r a d i c t i o n between h i s f i n d i n g s and those of Sp e t c h . He used 32 d i f f e r e n t f e e d i n g s i t e s , a r r a n g e d i n f o u r c i r c u l a r g r o u p i n g s . Spetch and Edwards (1986) used o n l y a s i n g l e g r o u p i n g ( i n v a r i o u s c o n f i g u r a t i o n s ) of e i g h t f e e d i n g s i t e s . R o b e r t s suggested t h a t perhaps 32 f e e d i n g s i t e s was too many f o r p i g e o n s t o a c c u r a t e l y remember, e s p e c i a l l y i n l i g h t of the s i m i l a r i t y of the f e e d i n g s i t e s t h a t he employed i n h i s s t u d y . A l t h o u g h p l a u s i b l e , R o b e r t s ' e x p l a n a t i o n f a i l s t o add r e s s an i m p o r t a n t q u e s t i o n : Should p i g e o n s remember the d i s t r i b u t i o n of foo d w i t h i n a p a t c h ? The work of Spetch and her c o l l e a g u e s s u g g e s t s t h a t p i g e o n s can do so, a t l e a s t w i t h i n a l i m i t e d c o n t e x t , but the answer, i n g e n e r a l , would seem t o be no. Pigeons a r e g e n e r a l l y group f e e d e r s and the ty p e s of f o o d items t h a t they consume are h i g h l y s u s c e p t i b l e t o r e d i s t r i b u t i o n by the n a t u r a l elements (Inman, LeFebvre, & G i r a l d e a u , 1987). A l t h o u g h the l o c a t i o n of p a t c h e s may be f a i r l y c o n s t a n t and w e l l d e f i n e d by permanent g e o g r a p h i c f e a t u r e s of the ar e a ( c f . Levesque & M c N e i l , 1985), the d i s p e r s i o n of food w i t h i n t h a t area v a r i e s . T h e r e f o r e remembering the d i s t r i b u t i o n of f o o d items w i t h i n a p a t c h would not be of much use, g i v e n t h a t t h i s d i s t r i b u t i o n w i l l be d i f f e r e n t a t a l a t e r time due t o n a t u r a l f o r c e s and the f o r a g i n g of f l o c k - m a t e s . From the p r e c e d i n g d i s c u s s i o n i t f o l l o w s t h a t a t a s k used t o examine w o r k i n g memory f o r f o o d w i t h i n a p a t c h i s u n l i k e l y t o y i e l d r e s u l t s r e f l e c t i n g t he t r u e e x t e n t of p i g e o n s ' s p a t i a l memory a b i l i t i e s . P i g e o n s g e n e r a l l y f o r a g e i n f a i r l y l i m i t e d g e o g r a p h i c a r e a s and e x p l o i t the same pa t c h e s on a day-to-day b a s i s (Levesque & M c N e i l , 1986). The n a t u r e of the p i g e o n f o r a g i n g e c o l o g y has i m p o r t a n t i m p l i c a t i o n s f o r s p a t i a l memory r e s e a r c h i n t h i s s p e c i e s . F i r s t , p i g e o n s s h o u l d demonstrate p r o f i c i e n t r e f e r e n c e memory f o r s p a t i a l i n f o r m a t i o n , an i d e a f i r s t s uggested by Bond e t a l (1981), and s u b s e q u e n t l y c o n f i r m e d i n the l i t e r a t u r e ( R oberts & Van V e l d h u i z e n , 1985; R o b e r t s , 1988; W i l k i e & W i l l s o n , i n p r e s s ) . Second, p i g e o n s s h o u l d demonstrate p r o f i c i e n t w o r k i n g memory f o r p a t c h l o c a t i o n and c h a r a c t e r i s t i c s , g i v e n t h a t the p r o f i t a b i l i t y of patc h e s v a r i e s from day-to-day and the f a c t t h a t pigeons are o f t e n f o r c e d t o t e m p o r a r i l y abandon p r o f i t a b l e p a t c h e s due t o the i n t r u s i o n of humans or o t h e r a n i m a l s (Levesque & M c N e i l , 1985). R o b e r t s (1988) has take'n a s i g n i f i c a n t s t e p i n a d d r e s s i n g b o t h of these i m p l i c a t i o n s . H i s r e c e n t r e s e a r c h , d i s c u s s e d p r e v i o u s l y , has demonstrated c o n c l u s i v e l y t h a t p i g e o n s p o s s e s s a p r o f i c i e n t r e f e r e n c e memory f o r p a t c h l o c a t i o n and c h a r a c t e r i s t i c s . He has a l s o p r e s e n t e d d a t a s u g g e s t i n g t h a t pigeons use w o r k i n g memory t o remember the l o c a t i o n and c h a r a c t e r i s t i c s of p a t c h e s c u r r e n t l y b e i n g e x p l o i t e d . U n f o r t u n a t e l y , h i s e v i d e n c e c o n c e r n i n g w o r k i n g memory i s somewhat i n d i r e c t . He d i d not v a r y the r e l a t i v e p r o f i t a b i l i t y of h i s patc h e s from s e s s i o n t o s e s s i o n and h i s s u b j e c t s may t h e r e f o r e have used a r e f e r e n c e memory s t r a t e g y t o f o r a g e e f f i c i e n t l y . G i v e n t h a t h i s s u b j e c t s l e a r n e d t o v i s i t t he p a t c h e s i n o r d e r of t h e i r r e l a t i v e p r o f i t a b i l i t y , t h e y may w e l l have f o r a g e d s t r i c t l y on the b a s i s of a resp o n s e r u l e (e.g. v i s i t p a t c h A, then p a t c h B, e t c . ) . G e n e r a l P u r p o s e a n d R a t i o n a l e The r a t i o n a l e f o r the p r e s e n t r e s e a r c h i s founded on two key i d e a s . The f i r s t and most i m p o r t a n t one i s t h a t the p r e v i o u s l y d emonstrated d u r a b i l i t y of p i g e o n ' s s p a t i a l w o r k i n g memory i s too low ( i . e . 30 min-Spetch & Honig, 1988). An i n a b i l i t y t o remember c u r r e n t p a t c h c h a r a c t e r i s t i c s ( i . e . the l o c a t i o n o f the c u r r e n t l y most p r o f i t a b l e patch) beyond the l i m i t p r e v i o u s l y demonstrated seems, i n t u i t i v e l y , t o be too c o s t l y i n terms of a d a p t i v e f i t n e s s . G e n e r a l p a t c h c h a r a c t e r i s t i c s , such as r e l a t i v e p r o f i t a b i l i t y s h o u l d not change over the c o u r s e of a few minutes and an i n a b i l i t y t o remember and l a t e r e x p l o i t t h i s type of i n f o r m a t i o n c o u l d have p o t e n t i a l l y s e r i o u s consequences f o r an i n d i v i d u a l . The second and more c o n t r o v e r s i a l i d e a i s t h a t the most i m p o r t a n t c h a r a c t e r i s t i c of a p a t c h i s the f a c t t h a t i t i s a l o c a t i o n t h a t p r o v i d e s m u l t i p l e f o o d i t e m s . P a t c h s i z e ( i . e . g e o g r a p h i c e x t e n t ) i s r e l a t i v e l y u n i m p o r t a n t . W i t h i n the l i m i t e d c o n f i n e s of t h i s d e f i n i t i o n , an i l l u m i n a t e d p e c k i n g key t h a t p r o v i d e s a c c e s s t o f o o d on a v a r i a b l e s c h e d u l e can be used t o s i m u l a t e a p a t c h . A l t h o u g h the v a l i d i t y of u s i n g r e i n f o r c e m e n t s c h e d u l e s t o s i m u l a t e f o r a g i n g has been q u e s t i o n e d (see F a n t i n o & Aba r c a , 1985, and the accompanying commentaries) the r e s u l t s p r e s e n t e d below o f f e r some s u p p o r t f o r t h i s n o t i o n . Two main purposes u n d e r l i e the p r e s e n t r e s e a r c h . The f i r s t i s t o compare the e f f e c t i v e n e s s of s e v e r a l n o v e l p r o c e d u r a l m o d i f i c a t i o n s i n a s s e s s i n g s p a t i a l w o r k i n g memory i n the p i g e o n . T h i s t a s k i s un d e r t a k e n i n the f i r s t two ex p e r i m e n t s p r e s e n t e d below. Delayed m a t c h i n g of key l o c a t i o n has been used w i t h some s u c c e s s t o examine s p a t i a l memory ( W i l k i e & Summers, 1982). The comparisons i n the f i r s t two e x p e r i m e n t s a re between two m o d i f i e d v e r s i o n s of t h i s p r o c e d u r e . The new p r o c e d u r e s d i f f e r i n t h e s e ways. F i r s t , the d u r a t i o n of exposure t o the to-be-remembered l o c a t i o n has been extended, t h e r e b y i n c r e a s i n g the amount of time a v a i l a b l e t o the s u b j e c t f o r p r o c e s s i n g the r e l e v a n t i n f o r m a t i o n ( i . e . l o c a t i o n , p a t c h c h a r a c t e r i s t i c s ) . Second, the amount of r e i n f o r c e m e n t a v a i l a b l e t h r o u g h r e s p o n d i n g a t the to-be-remembered l o c a t i o n has a l s o been i n c r e a s e d . T r a d i t i o n a l p r o c e d u r e s have used non-rewarded cues or cues a s s o c i a t e d w i t h a s i n g l e r e i n f o r c e r (see W i l k i e , 1983, f o r an e x c e p t i o n ) . These m o d i f i c a t i o n s s h o u l d make the i n i t i a l t r a i n i n g a t the to-be-remembered l o c a t i o n more l i k e a p a t c h v i s i t (see r a t i o n a l e p r e s e n t e d above). T h i r d , the method used t o a s s e s s r e c a l l has been changed from a s i n g l e r e s p o n s e , yes-no f o r m a t , t o a 1 min i n t e r v a l d u r i n g which the s u b j e c t i s a l l o w e d t o respond f r e e l y a t e i t h e r the p r e v i o u s l y v i s i t e d , rewarded s i t e o r n o v e l l o c a t i o n . F i r s t c h o i c e s a re a l s o r e c o r d e d . I n l i g h t of the t r a i n i n g p r o c e d u r e s used, an extended t e s t p e r i o d , because of i t s s i m i l a r i t y t o the t r a i n i n g p r o t o c o l , i s more a p p r o p r i a t e ( c f . M o r r i s , B r a n s f o r d & F r a n k s , 1977). F o u r t h , s u b j e c t s are g i v e n o n l y a s i n g l e t r i a l per day t o reduce the p o s s i b i l i t y of p r o a c t i v e i n t e r f e r e n c e between s e s s i o n s ( R o i t b l a t 1980; R o b e r t s & Van V e l d h u i z e n , 1985; W r i g h t , U r c u i o l i , fi Sands, 1986). F i f t h , the amount of r e i n f o r c e m e n t f o r c o r r e c t l y remembering l o c a t i o n i s i n c r e a s e d . Most p r o c e d u r e s t y p i c a l l y p r o v i d e a s i n g l e r e i n f o r c e m e n t f o r s u c c e s s f u l r e c a l l ( W i l k i e & Summers, 1982). S i x t h , s e p a r a t e groups of pi g e o n s are exposed t o e i t h e r a s i n g l e l o c a t i o n (the S+) or t o b o t h the rewarded and non-rewarded l o c a t i o n s (the S+ and S-) d u r i n g t r a i n i n g , i n some e x p e r i m e n t s . Adding the S- d u r i n g t r a i n i n g s h o u l d make t r a i n i n g c o n d i t i o n s more s i m i l a r t o t e s t i n g c o n d i t i o n s and make t r a i n i n g more s i m i l a r t o the type of problem t h a t p i g e o n s would e n c o u n t e r i n the r e a l w o r l d . F i n a l l y , d u r i n g the r e t e n t i o n i n t e r v a l between t r a i n i n g and t e s t i n g the s u b j e c t w i l l e i t h e r remain i n the ap p a r a t u s (the IN c o n d i t i o n ) as i s t y p i c a l l y the cas e , o r i n a s m a l l h o l d i n g cage o u t s i d e of the t e s t i n g room (the OUT c o n d i t i o n ) . Removing the s u b j e c t s d u r i n g the r e t e n t i o n i n t e r v a l s h o u l d 2 0 make the t a s k more s i m i l a r t o the type of s i t u a t i o n e n c o u n t e r e d i n t h e i r n a t u r a l environment, g i v e n t h a t pigeons don't need t o r e t u r n t o an i m p o r t a n t l o c a t i o n u n l e s s they l e a v e i t . T h i s m a n i p u l a t i o n w i l l a l s o e l i m i n a t e the p o s s i b i l i t y of u s i n g a non-memorial s t r a t e g y , such as r e m a i n i n g i n f r o n t of the to-be-remembered l o c a t i o n d u r i n g the R I , t o p e r f o r m s u c c e s s f u l l y . The second main purpose of the p r e s e n t r e s e a r c h i s t o s e a r c h f o r the r e a l upper l i m i t t o the p i g e o n s ' w o r k i n g memory f o r l o c a t i o n . The f i n a l two experiments of t h i s t h e s i s address t h a t i s s u e . A l t h o u g h t h e r e i s almost c e r t a i n l y some v a r i a t i o n i n the p r o f i c i e n c y of w o r k i n g memory a c r o s s s p e c i e s , I b e l i e v e t h a t p r e v i o u s e x p e r i m e n t s have not demonstrated p i g e o n s ' t r u e c a p a b i l i t i e s . Because b o t h the v a r i o u s p r o c e d u r a l d i f f i c u l t i e s d i s c u s s e d above and the f o r a g i n g e c o l o g y of f e r a l p i g e ons have been c o n s i d e r e d i n d e s i g n i n g the new p r o c e d u r e s p r e s e n t e d below, they are much more l i k e l y t o measure the t r u e e x t e n t of p i g e o n s ' s p a t i a l memory c h a r a c t e r i s t i c s than p r e v i o u s work. E x p e r i m e n t 1 I n t h i s e x periment one group of f o o d - d e p r i v e d pigeons was exposed t o a s i n g l e i l l u m i n a t e d p e c k i n g key (the S+) d u r i n g each day's t r a i n i n g phase (the 1 Cue g r o u p ) . Another group was exposed t o two keys (the S+ and S-) d u r i n g the t r a i n i n g phase (the 2 Cues g r o u p ) . Responses t o the S+ p r o v i d e d r e i n f o r c e m e n t on a v a r i a b l e s c h e d u l e . A f t e r 15 min 2 1 a response t o S+ produced a f i n a l r e i n f o r c e r and the p e c k i n g keys and room l i g h t went o u t . A f t e r a r e t e n t i o n i n t e r v a l the room l i g h t s came back on and a t e s t phase i n which the s u b j e c t was exposed t o the S+ and S- f o r 1 min began. For b i r d s i n the 1 Cue group the S- was n o v e l . For b i r d s i n the 2 Cues group the S- was the same as i n t r a i n i n g . I f a s u b j e c t responded more t o t h e S+ d u r i n g the 1 min p e r i o d , the S- went o f f and pecks t o the S+ produced r e i n f o r c e m e n t on the same s c h e d u l e as p r e v i o u s l y f o r an a d d i t i o n a l 15 min. Making more res p o n s e s t o the S- ended the s e s s i o n . The d u r a t i o n of the i n i t i a l r e t e n t i o n i n t e r v a l was 10 s, but i t was s u b s e q u e n t l y i n c r e a s e d t o 20 and 30 s. At the 30-s RI s u b j e c t s were e i t h e r l e f t i n the a p p a r a t u s d u r i n g the RI or were removed t o a s m a l l h o l d i n g cage. The 1 Cue group was a l s o r u n on the 2 cues c o n d i t i o n f o r one b l o c k of 10 t r i a l s w i t h a 30 s R I . They spent the r e t e n t i o n i n t e r v a l i n the h o l d i n g cage d u r i n g t h i s b l o c k . Method S u b j e c t s S i x pigeons s e r v e d as s u b j e c t s . Four b i r d s were of the White K i n g s t r a i n and were e x p e r i m e n t a l l y n a i v e a t the s t a r t of the e x p e r i m e n t s d e s c r i b e d below ( b i r d s 1,2,3,4). The o t h e r two p i g e o n s were of the S i l v e r K i n g s t r a i n and had v a r i e d e x p e r i m e n t a l h i s t o r i e s ( b i r d s 5,6) i n a s t a n d a r d S k i n n e r box, but no o t h e r e x p e r i m e n t a l h i s t o r y . A l l s u b j e c t s were m a i n t a i n e d a t a p p r o x i m a t e l y 90% of t h e i r f r e e f e e d i n g w e i g h t . D a i l y f o o d was p r o v i d e d d u r i n g the e x p e r i m e n t a l s e s s i o n s w i t h o c c a s i o n a l p o s t - s e s s i o n a l supplements when n e c e s s a r y . Water, h e a l t h g r i t and c r u s h e d o y s t e r s h e l l was a v a i l a b l e a d l i b i t u m i n the home cage but was not a v a i l a b l e d u r i n g the e x p e r i m e n t a l s e s s i o n s . A l l s u b j e c t s were run s i x days per week. Appa r a t u s The a p p a r a t u s f o r the p r e s e n t s t u d i e s was an 1 1 - s i d e d S k i n n e r box. The chamber and s u r r o u n d i n g room are shown s c h e m a t i c a l l y i n F i g u r e 1. I n d i v i d u a l s i d e s of the box were 20 cm X 30 cm X 7 mm c l e a r P l e x i g l a s s h e e t s , r e i n f o r c e d w i t h 2.5 cm wide s t r i p s of sheet metal on each v e r t i c a l s i d e and i n d i v i d u a l l y anchored t o a l a r g e wooden base (95 cm X 90 cm X 30 cm). The a n g l e between a d j a c e n t s i d e s was a p p r o x i m a t e l y 32.7 d e g r e e s . Ten of the 11 s i d e s had a 2.5 cm i n d i a m e t e r c l e a r P l e x i g l a s p e c k i n g key, c e n t e r e d 15 cm above the f l o o r of the chamber. Each of the keys c o u l d be i l l u m i n a t e d by a s m a l l s t i m u l u s p r o j e c t o r mounted on i t s ' p o s t e r i o r s i d e . The keys r e q u i r e d a f o r c e of a p p r o x i m a t e l y 0.2 N t o r e g i s t e r a r e s p o n s e . A s t a n d a r d g r a i n d i s p e n s e r was mounted on the 11th s i d e and a s m a l l opening (6.25 cm X 7.5 cm) f o r f o o d a c c e s s was c e n t e r e d on the w a l l of the chamber 7.5 cm above the chamber f l o o r . The a p p a r a t u s was c o v e r e d by a l a r g e removable p l a s t i c mesh l i d (90 cm X 90 cm). The gauge of the mesh was 2.5 cm X 5 cm and d i d not o b s t r u c t the s u b j e c t s ' view of the s u r r o u n d i n g room. The wooden base of the chamber was c o v e r e d w i t h brown 23 Figure 1. An overhead, schematic diagram of the experimental apparatus and surrounding room used in the present experiments. Numbers indicate the pecking key positions. 150 cm ley A. Hendecagonal Skinner box E. Door B. Grain Dispenser F. Two-way mirror C. Wooden base G. Cement column D. Table H. Connector box 25 wax paper ( t o f a c i l i t a t e c l e a n i n g ) and was i n t u r n o v e r l a i d w i t h p l a s t i c mesh of the type d e s c r i b e d above. The a p p a r a t u s was housed i n a s m a l l room w i t h dimensions of 150 cm X 180 cm X 270 cm. There were s e v e r a l prominent landmarks w i t h i n the room a l l of which were c l e a r l y v i s i b l e from the chamber (see F i g u r e 1 ) . The l o c a t i o n of t h e s e landmarks remained c o n s t a n t throughout the ex p e r i m e n t s . I n some phases of the p r e s e n t r e s e a r c h the s u b j e c t s were removed from the app a r a t u s d u r i n g the r e t e n t i o n i n t e r v a l and were housed i n a s m a l l h o l d i n g cage (40 cm X 25. cm X 30 cm). The h o l d i n g cage was l o c a t e d i n e i t h e r a s m a l l d a r k room a d j a c e n t t o the room h o u s i n g the e x p e r i m e n t a l a p p a r a t u s o r i n the h a l l w a y near the t e s t i n g room. Data c o l l e c t i o n and e x p e r i m e n t a l c o n t r o l were c a r r i e d out on a Data G e n e r a l NOVA 3 computer o p e r a t i n g under RDOS and the MANX programming language ( G i l b e r t and R i c e , 1979). Procedure-^P T r a i n i n g A l l b i r d s were h a b i t u a t e d t o the e x p e r i m e n t a l a p p a r a t u s and t r a i n e d t o e a t from the g r a i n d i s p e n s e r . They were then autoshaped ( c f . Brown and J e n k i n s , 1968) t o peck a t the two keys c l o s e s t t o the g r a i n d i s p e n s e r . Once p e c k i n g was w e l l e s t a b l i s h e d on a CRF s c h e d u l e , the s u b j e c t s were s l o w l y exposed t o a l a r g e r s u b s e t of the keys u n t i l t h ey were r e s p o n d i n g e q u a l l y o f t e n on a l l 10 keys . The r i c h n e s s of the r e i n f o r c e m e n t s c h e d u l e was then s l o w l y d e c r e a s e d over a 5 day p e r i o d u n t i l a l l s u b j e c t s were r e s p o n d i n g a t a s t a b l e r a t e on a v a r i a b l e 26 i n t e r v a l (VI) 30-s s c h e d u l e . P r e l i m i n a r y t r a i n i n g took no more than 10 days f o r any p i g e o n (7,8,7,9,8 and 10 days f o r b i r d s 1-6 r e s p e c t i v e l y ) . S u b j e c t s were then a s s i g n e d t o one of two groups (the 1 Cue group or the 2 Cues g r o u p ) . The p r o p o r t i o n of n a i v e t o e x p e r i e n c e d b i r d s (2:1) was b a l a n c e d , but w i t h i n each sub-group i n d i v i d u a l s were a s s i g n e d a t random. I n i t i a l S t i m u l u s P h a s e One of the f i v e k e y - p a i r s was s e l e c t e d q u a s i - r a n d o m l y f o r each s u b j e c t d a i l y . The key-p a i r s c o m p r i sed keys t h a t were e q u i d i s t a n t from the g r a i n d i s p e n s e r . F o r example, keys 1 and 10, which b r a c k e t e d the g r a i n d i s p e n s e r , made up k e y - p a i r 1, and keys 5 and 6, the keys f u r t h e s t away from the g r a i n d i s p e n s e r and a d j a c e n t t o one a n o t h e r , made up k e y - p a i r 5. Each k e y - p a i r was used o n l y once d u r i n g each b l o c k of 10 s e s s i o n s and each member of the p a i r was used as the p o s i t i v e o r n e g a t i v e s t i m u l u s o n l y once p e r b l o c k . F or b i r d s i n the 1 Cue group ( b i r d s 1,2,3) o n l y the p o s i t i v e key (S+) was i l l u m i n a t e d d u r i n g t h i s phase. Pecks t o t h i s key produced 8-s of acc e s s t o mixed g r a i n on a VI 30-s s c h e d u l e . For b i r d s i n the 2 Cues group ( b i r d s 4,5,6) b o t h the p o s i t i v e and n e g a t i v e (S-) key were i l l u m i n a t e d d u r i n g t h i s phase. For these s u b j e c t s , pecks t o the S+ key produced a c c e s s t o g r a i n on the s c h e d u l e d e s c r i b e d p r e v i o u s l y . Pecks t o the S- key had no e f f e c t . A l l resp o n s e s were r e c o r d e d , as was the number of r e i n f o r c e m e n t s r e c e i v e d . Pecks d u r i n g the f i n a l minute of t h i s phase were r e c o r d e d s e p a r a t e l y . A f t e r 15 min, a peck t o the S+ i n i t i a t e d a f i n a l r e i n f o r c e r and the key l i g h t s were e x t i n g u i s h e d . A f t e r the 8-s of a c c e s s t o g r a i n the room l i g h t s were t u r n e d o f f and remained o f f f o r the d u r a t i o n of the r e t e n t i o n i n t e r v a l ( R I ) . The i n i t i a l t r a i n i n g v a l u e of the RI was 10 s (8 s of r e i n f o r c e m e n t f o l l o w e d by 2 s of d a r k n e s s ) . T e s t P h a s e F o l l o w i n g the RI the room l i g h t s came back on and the S+ and S- keys were l i t . Responses t o b o t h s t i m u l i were r e c o r d e d s e p a r a t e l y i n 3 b l o c k s of 20 s. The l o c a t i o n o f the i n i t i a l c h o i c e ( e i t h e r the S+ or S-) was a l s o r e c o r d e d . I f the s u b j e c t made more responses t o the S+ key d u r i n g t h i s 1 min p e r i o d , the S- key was e x t i n g u i s h e d and pecks t o the S+ key produced a c c e s s t o g r a i n on the same s c h e d u l e as d e s c r i b e d p r e v i o u s l y . Access t o the p o s i t i v e key l a s t e d f o r 15 minutes a f t e r which the s u b j e c t was removed from the a p p a r a t u s . I f the s u b j e c t responded more to the S- key d u r i n g the 1 min t e s t p e r i o d b oth keys were e x t i n g u i s h e d and the s u b j e c t was i m m e d i a t e l y removed from the a p p a r a t u s . R e t e n t i o n I n t e r v a l M a n i p u 1 a t i o n s The i n i t i a l d u r a t i o n of the r e t e n t i o n i n t e r v a l was 10 s. Both groups of s u b j e c t s were g i v e n 30 t r i a l s a t t h i s R I . The RI d u r a t i o n was then i n c r e m e n t e d by 10 s a t the end of each b l o c k of 10 s e s s i o n s u n t i l i t reached a maximum of 30 s. For one b l o c k of t r i a l s w i t h the RI a t 30 s, the s u b j e c t s remained i n the e x p e r i m e n t a l chamber (the IN c o n d i t i o n ) . D u r i n g a second 28 b l o c k , they were removed from the ap p a r a t u s a t the end of the i n i t i a l phase and spent the d u r a t i o n of the RI i n a s m a l l h o l d i n g cage a d j a c e n t t o the t e s t i n g room (the OUT c o n d i t i o n ) . D u r i n g the f i n a l b l o c k of 10 s e s s i o n s a l l s u b j e c t s were r u n on the 2 Cues c o n d i t i o n and were removed t o the h o l d i n g cage d u r i n g the 30 s R I . Data. A n a l y s i s S e v e r a l measures of performance were computed f o r each s u b j e c t . Two t y p e s of d i s c r i m i n a t i o n r a t i o s (DR) were computed. A DR i s a r a t i o of p o s i t i v e t o t o t a l r e s p o n s e s and i s computed by d i v i d i n g the t o t a l number of re s p o n s e s t o the S+ key by the t o t a l number of r e s p o n s e s . Thus i f a s u b j e c t responds o n l y t o the S+ key, the DR w i l l be 1.0. I f the s u b j e c t responds e q u a l l y o f t e n t o the S+ and S- the DR w i l l be .50, and so f o r t h . A d a i l y DR was computed based on the t o t a l number of p o s i t i v e and n e g a t i v e r e s p o n s e s made d u r i n g the 1 min t e s t p e r i o d from t h a t s e s s i o n . A mean DR was then computed by a v e r a g i n g the d a i l y DR's a c r o s s b l o c k s of 10 d a i l y s e s s i o n s . A c u m u l a t i v e DR was a l s o computed by summing p o s i t i v e and n e g a t i v e r esponses w i t h i n each b l o c k of 10 s e s s i o n s . The r a t i o n a l e f o r computing b o t h types of d i s c r i m i n a t i o n r a t i o i s based on the f a c t t h a t DR's can be i n f l a t e d or d e f l a t e d by f l u c t u a t i o n s i n response r a t e . T h i s i s g e n e r a l l y not a problem f o r m u l t i p l e d a i l y t r i a l p r o c e d u r e s , s i n c e response r a t e s t e n d t o remain s t a b l e w i t h i n a s e s s i o n , however, because the p r e s e n t r e s e a r c h employs a s i n g l e t r i a l p er day p r o c e d u r e , t r i a l t o t r i a l f l u c t u a t i o n s i n response r a t e a re 29 much more l i k e l y . These d i s c r i m i n a t i o n r a t i o s were i n i t i a l l y c a l c u l a t e d f o r each 20 s segment of the t e s t p e r i o d , but because the r e s u l t s were s i m i l a r among segments the measures were c o l l a p s e d a c r o s s the e n t i r e 1 min t e s t p e r i o d . The p e r c e n t a g e of c o r r e c t f i r s t c h o i c e s was a l s o c a l c u l a t e d f o r each b l o c k of 10 s e s s i o n s . Between group comparisons were made u s i n g a Group by R e t e n t i o n I n t e r v a l a n a l y s i s of v a r i a n c e and p o s t h o c c o m p a r i s o n s . D i f f e r e n c e s i n the d i s c r i m i n a b i l i t y of the 5 k e y - p a i r s d u r i n g the t e s t phase were a s s e s s e d w i t h a Group by K e y - p a i r a n a l y s i s of v a r i a n c e . R e s u l t s No d i f f e r e n c e s were found between the 1 Cue and 2 Cues groups d u r i n g the f i r s t 5 b l o c k s o f t r i a l s . Both groups performed w e l l a t a l l r e t e n t i o n i n t e r v a l s . However, when the s u b j e c t s were removed from the a p p a r a t u s d u r i n g the RI performance dropped. The drop i n performance was l a r g e r f o r the s u b j e c t s i n the 1 Cue group. When they were s w i t c h e d t o the 2 cues c o n d i t i o n performance rebounded d r a m a t i c a l l y . Data from the p r e s e n t experiment are p r e s e n t e d i n T a b l e I . The mean d i s c r i m i n a t i o n r a t i o s f o r the f i r s t 5 b l o c k s of s e s s i o n s are shown i n F i g u r e 2. Because the p a t t e r n of r e s u l t s from b o t h the c u m u l a t i v e and mean d a i l y d i s c r i m i n a t i o n r a t i o s was the same, the d a t a p r e s e n t e d here are an average of these two measures. The f i l l e d squares show the d a t a from the 1 Cue group and the open c i r c l e s show 3 0 T a b l e I . Data from each b l o c k of Experiment 1. Mean d a i l y d i s c r i m i n a t i o n r a t i o s a r e i n the f i r s t row f o r each s u b j e c t , c u m u l a t i v e d i s c r i m i n a t i o n r a t i o s a r e i n the second row, and t o t a l c o r r e c t f i r s t c h o i c e s a r e i n the t h i r d row. A s t e r i s k denotes t h a t Group 1 Cue was r u n on the 2 cues c o n d i t i o n . Group 1 R e t e n t i o n I n t e r v a l a n d C o n d i t i o n Cue 10"-IN 10"-IN 10"-IN 20"-IN 30"-IN 30"-OUT 30"-OUT .777 .633 .719 .767 .561 .482 .863* 1 .918 .817 .908 .777 .588 .550 .860* 9 8 9 9 5 . 4 9* .607 .662 .714 .847 .961 .677 .867* 2 .711 .726 .732 .829 .961 .750 .939* 4 6 8 9 9 7 8* .964 .963 .831 .684 .899 .295 .794* 3 .976 .979 .836 .702 .924 .223 .900* 9 10 8 6 10 3 7 Group Cues 2 . 882 .903 .836 .818 .964 .799 .899 4 .903 .902 .924 . 817 .927 .875 .920 9 9 7 7 8 8 8 .676 .840 . 805 .734 .754 .605 .682 5 .758 .863 . 855 .733 .751 .569 .500 6 7 9 4 6 7 6 .737 .915 .918 .964 .720 .782 .782 6 .682 .924 .903 .965 .851 .571 .724 5 9 9 9 9 9 9 31 < o r z o 1-1 0 . 9 -0 . 8 -0 . 7 -< Z 2 0 . 6 -o r o Q 0.5-1 0.4 0 . 3 Legend • 1 CUE • 2 CUES 10 20 30 RETENTION INTERVAL (SEC.) Figure 2. A comparison of the mean discrimination ratios from the 1 Cue and 2 Cues groups at the three retention int e r v a l s tested i n Experiment 1. Data points are based on blocks of 10 t r i a l s and represent an average of the cumulative and mean d a i l y discrimination r a t i o for each block. the d a t a from the 2 Cues group. There was no s i g n i f i c a n t d i f f e r e n c e between the two groups [F (1,4)=.1104, p>.74] or between any of the r e t e n t i o n i n t e r v a l s [F (4,16)=1.6826, p>.20]. The Group by R e t e n t i o n I n t e r v a l i n t e r a c t i o n was a l s o n o n - s i g n i f i c a n t [F (4,16)=.2950, p>.87]. F i g u r e 3 shows the p e r c e n t c o r r e c t f i r s t c h o i c e s p l o t t e d as a f u n c t i o n of R I . The f i l l e d s quares show the performance of the 1 Cue group and the open c i r c l e s show the performance o f the 2 Cues group. The 1 Cue group showed a h i g h , f a i r l y s t a b l e matching performance ( g r e a t e r than 8 0 % ) . The 2 Cues group showed somewhat more v a r i a b l e r e s u l t s , but t h e i r performance d i d not d i f f e r s i g n i f i c a n t l y from the 1 Cue group [F (1,4)=.3273, p>.60]. Both the main e f f e c t of r e t e n t i o n i n t e r v a l and the group by r e t e n t i o n i n t e r v a l i n t e r a c t i o n were n o n s i g n i f i c a n t [F (4,16)=.4860, p>.74, and F (4,16)=.1591, p>.95, r e s p e c t i v e l y ] . The mean d i s c r i m i n a t i o n r a t i o d a t a from the IN vs OUT c o n d i t i o n s are p r e s e n t e d i n F i g u r e 4. Performance dropped f o r b o t h groups when they were removed from the apparatus d u r i n g the r e t e n t i o n i n t e r v a l . A r e p e a t e d measures t - t e s t performed on t h e s e d a t a ( c o l l a p s e d a c r o s s cue c o n d i t i o n s ) r e v e a l e d a m a r g i n a l l y s i g n i f i c a n t drop i n performance on the OUT c o n d i t i o n [ t (5)=2.46, p=.057]. The p e r c e n t c o r r e c t f i r s t c h o i c e s d a t a from the IN and OUT c o n d i t i o n s a r e p r e s e n t e d i n F i g u r e 5. Performance dropped i n b o t h groups, but the drop ( c o l l a p s e d a c r o s s cue 33 100-90-80-O UJ £ 70-o o g 60-or 50-40-30-10 2 0 3 0 RETENTION INTERVAL (SEC.) Legend • 1 CUE • 2 CUES F i g u r e 3. A c o m p a r i s o n o f t h e mean p e r c e n t a g e o f c o r r e c t f i r s t r e s p o n s e s f r o m t h e 1 Cue and 2 Cues g r o u p s a t t h e t h r e e r e t e n t i o n i n t e r v a l s t e s t e d i n E x p e r i m e n t 1. D a t a p o i n t s a r e b a s e d on b l o c k s o f 10 s e s s i o n s . 34 Figure 4 . A comparison of the mean discrimination r a t i o s at the 30 s retention i n t e r v a l as a function of whether the retention interval was spent i n or out of the test chamber. 35 100-1 90-Legend mi 1 CUE 2 CUES IN OUT RETENTION INTERVAL CONDITION F i g u r e 5. A comparison of the mean percentage of c o r r e c t f i r s t r e s p o n s e s as a f u n c t i o n of whether the r e t e n t i o n i n t e r v a l was spent i n or out of the t e s t chamber. c o n d i t i o n ) d i d not approach s i g n i f i c a n c e [ t (5)=1.83, p=.13]. F i g u r e 6 shows a comparison of the mean d i s c r i m i n a t i o n r a t i o d a t a from the 1 Cue group on the 1 and 2 cues c o n d i t i o n s . A f t e r an i n i t i a l b l o c k of 10 t r i a l s w i t h the r e t e n t i o n i n t e r v a l a t 30 s and the OUT c o n d i t i o n i n e f f e c t , s u b j e c t s i n the 1 Cue group were t r a n s f e r r e d t o the 2 cues c o n d i t i o n . Performance was b e t t e r on the l a t t e r c o n d i t i o n , but t h i s d i f f e r e n c e d i d not approach s i g n i f i c a n c e [ t (2)=2.65, p=.12]. A n a l y s i s of the p e r c e n t c o r r e c t f i r s t c h o i c e s d a t a , shown i n F i g u r e 7, r e v e a l e d a s i g n i f i c a n t d i f f e r e n c e between the 1 and 2 cues c o n d i t i o n s [ t (2)=4.91, p<.04] . A comparison of the r e l a t i v e d i s c r i m i n a b i l i t y of the f i v e k e y - p a i r s d u r i n g the t e s t phase a c r o s s the f i r s t 5 b l o c k s showed no d i f f e r e n c e s between the k e y - p a i r s [F (4,16)=1.1454, p>.37]. The Group by K e y - p a i r i n t e r a c t i o n was a l s o n o n - s i g n i f i c a n t [F (4,16)=2.1771, p > . l l ] . p i s c u s s i o n A l l s u b j e c t s showed h i g h l e v e l s of performance a t r e t e n t i o n i n t e r v a l s up t o 30 s, much l o n g e r than p r e v i o u s l y found w i t h S k i n n e r box p r o c e d u r e s ( c f . W i l k i e & Summers, 1982). However, when the s u b j e c t s were removed from the a p p a r a t u s d u r i n g the R I , performance l e v e l s dropped. T h i s decrement i n performance was l a r g e r i n the 1 cue c o n d i t i o n 1 CUE 2 CUES TRAINING CONDITION F i g u r e 6. A comparison of the mean d i s c r i m i n a t i o n r a t i o s f o r the 1 Cue group at the 30 s r e t e n t i o n i n t e r v a l as a f u n c t i o n of whether they were run on the 1 or 2 cues c o n d i t i o n . The r e t e n t i o n i n t e r v a l was spent out of the t e s t chamber. 38 lOO-, 90-1 CUE 2 CUES TRAINING CONDITION Figure 7. A comparison of the mean percentage of correct f i r s t responses for the 1 Cue Group at the 30 s retention i n t e r v a l as a function of whether they were run on the 1 or 2 cues condition. The retention i n t e r v a l was spent out of the test chamber. 39 and d i s a p p e a r e d when t h a t group was t r a n s f e r r e d t o the 2 cues c o n d i t i o n . There a re s e v e r a l p l a u s i b l e e x p l a n a t i o n s f o r the obs e r v e d drop i n performance. The f i r s t , and most p o t e n t i a l l y damaging i d e a , i s t h a t n e i t h e r group of s u b j e c t s was u s i n g a memorial s t r a t e g y t o s o l v e t h e i r r e s p e c t i v e t a s k . Because i t was i m p o s s i b l e t o o b s e r v e the s u b j e c t s d u r i n g the R I , which was spent i n d a r k n e s s , they may have remained i n f r o n t of the c o r r e c t s t i m u l u s w h i l e w a i t i n g t o be t e s t e d . S u b s e q u e n t l y , when the o p p o r t u n i t y t o use t h i s non-memorial based s t r a t e g y was e l i m i n a t e d , by removing the s u b j e c t from the ap p a r a t u s d u r i n g the R I , performance l e v e l s dropped. T h i s e x p l a n a t i o n , however, o f f e r s no i n s i g h t as t o why t h e r e was a d i f f e r e n c e between the two groups, o r why the performance l e v e l of the 1 Cue group rebounded when they were t r a n s f e r r e d t o the 2 cues c o n d i t i o n . More i m p o r t a n t l y , the p r o c e d u r a l arrangement of h a v i n g the i n i t i a l s t i m u l i t e r m i n a t e w i t h a r e i n f o r c e r makes t h i s e x p l a n a t i o n u n l i k e l y . A n other p l a u s i b l e e x p l a n a t i o n f o r the obser v e d performance decrement i s s i m p l y t h a t b e i n g h a n d l e d d u r i n g the RI d i s r u p t e d performance. Pigeons do not l i k e b e i n g h a n d l e d , but i t i s a g a i n u n c l e a r why t h i s would have a d i f f e r e n t i a l e f f e c t on the two groups. H a n d l i n g may have accounted f o r some of the performance decrement, but i t seems l i k e l y t h a t the sh a r p drop i n performance shown by the 1 Cue group was a r e s u l t of some o t h e r f a c t o r s as w e l l , e s p e c i a l l y i n l i g h t of t h e i r improved performance when t r a n s f e r r e d t o the 2 cues c o n d i t i o n . The apparent d i f f e r e n c e s between the two groups may a l s o r e f l e c t the im p o r t a n c e of u s i n g a p p r o p r i a t e t e s t i n g p r o c e d u r e s . The r e l a t i o n s h i p between t r a i n i n g and t e s t i n g p r o c e d u r e s has been w e l l documented i n the human c o g n i t i v e l i t e r a t u r e ( c f . M o r r i s e t a l , 1977). I n a p p r o p r i a t e or l e s s a p p r o p r i a t e t e s t s can i n h i b i t performance. I t may be t h a t the p a r t i c u l a r t e s t i n g p r o c e d u r e s used i n the p r e s e n t s t u d y are more a p p r o p r i a t e f o r t e s t i n g performance i n the 2 cues c o n d i t i o n . Perhaps s u c c e s s i v e matching t o sample (Wasserman,1976 ), a p r o c e d u r e i n which o n l y a s i n g l e s t i m u l u s (the S+ o r an S-) i s p r e s e n t e d f o l l o w i n g the RI would be more a p p r o p r i a t e f o r t e s t i n g the 1 cue c o n d i t i o n . I n t h i s type of p r o c e d u r e the s u b j e c t must d e c i d e whether o r not t o respond based on whether or not the t e s t s t i m u l u s was p r e s e n t e d p r e v i o u s l y . The apparent s u p e r i o r i t y of the d i s c r i m i n a t i o n r a t i o measure, as opposed t o a measure of p e r c e n t c o r r e c t f i r s t c h o i c e s , i n measuring s p a t i a l memory performance i s a l s o i n t e r e s t i n g . A l t h o u g h the g e n e r a l p a t t e r n of r e s u l t s was the same w i t h b o t h measures, the observed d i f f e r e n c e s were l a r g e r and o v e r a l l performance b e t t e r when based oh the DR. The s u p e r i o r i t y of the DR measure may be because pigeons o c c a s i o n a l l y make e r r o r s due t o f a c t o r s o t h e r than f o r g e t t i n g . For example, W i l k i e and Spetc h (1981) have shown t h a t p i g e o n s respond more s l o w l y f o l l o w i n g an i n c o r r e c t c h o i c e than f o l l o w i n g a c o r r e c t c h o i c e . I n t h e i r p r o c e d u r e , a m o d i f i c a t i o n of DMTS, p i g e o n s were r e q u i r e d t o make a d d i t i o n a l responses f o l l o w i n g the i n i t i a l c h o i c e t o complete a t r i a l . I f a s u b j e c t made a c o r r e c t i n i t i a l c h o i c e , the d i s t r a c t o r was t u r n e d o f f . The s u b j e c t then had to make an a d d i t i o n a l 30 r e s p o n s e s t o r e c e i v e r e i n f o r c e m e n t . I f the s u b j e c t made an i n c o r r e c t i n i t i a l c h o i c e the sample was t u r n e d o f f and the s u b j e c t had t o make an a d d i t i o n a l 30 re s p o n s e s t o end the t r i a l . W i l k i e and Spetch found t h a t s u b j e c t s responded s i g n i f i c a n t l y s l o w e r f o l l o w i n g an i n c o r r e c t response compared t o t h e i r response r a t e f o l l o w i n g a c o r r e c t c h o i c e , s u g g e s t i n g t h a t the p i g e o n r e c o g n i z e d t h a t the s t i m u l u s i n f r o n t of them was not c o r r e c t . Dale (1988) has found a s i m i l a r e f f e c t i n a v a r i a t i o n of the r a d i a l arm maze. He found t h a t p i g e o n s made s i g n i f i c a n t l y more c o r r e c t c h o i c e s , f o l l o w i n g an i n i t i a l i n c o r r e c t c h o i c e , than would be e x p e c t e d by chance. He s u g g e s t e d t h a t h i s s u b j e c t s were a b l e t o re-examine w o r k i n g memory f o l l o w i n g an i n c o r r e c t c h o i c e and then respond a c c o r d i n g l y . Because the t e s t p e r i o d employed i n the p r e s e n t r e s e a r c h l a s t s f o r a f u l l m inute, pigeons may be a b l e t o r e c o g n i z e i n c o r r e c t i n i t i a l c h o i c e s and c o r r e c t t h e i r performance a c c o r d i n g l y . E x p e r i 2 A l t h o u g h the r e s u l t s of Experiment 1 suggested t h a t the 2 cues c o n d i t i o n might produce b e t t e r performance, the e f f e c t was not s t a t i s t i c a l l y r e l i a b l e . The p r e s e n t experiment f u r t h e r examined the r e l a t i v e e f f e c t i v e n e s s of the 1 and 2 cues c o n d i t i o n s i n d e m o n s t r a t i n g a c c u r a t e r e c a l l of l o c a t i o n u s i n g a w i t h i n , r a t h e r than between, s u b j e c t d e s i g n . The improved performance of the 1 Cue group i n the p r e v i o u s e x p e r i m e n t , when they were s w i t c h e d t o the 2 cues c o n d i t i o n , s u g g e s t e d t h a t t h i s t y pe of d e s i g n might be more s u c c e s s f u l i n showing a r e l i a b l e d i f f e r e n c e between t h e s e two c o n d i t i o n s . I n the p r e s e n t experiment the two groups of p i g e o n s from Experiment 1 were r e - e x p o s e d t o the t a s k s used i n the p r e v i o u s e x p e r i m e n t . They were p r e v e n t e d from u s i n g non-memorial s t r a t e g i e s by removing them from the a p p a r a t u s d u r i n g the R I . The RI remained c o n s t a n t a t 30 s t h r o u g h o u t the e x p e r i m e n t and b o t h groups r e c e i v e d 3 c o n s e c u t i v e b l o c k s of t r i a l s on each c o n d i t i o n . One group ( b i r d s 1,2,3; 2->l Cue group) s t a r t e d on the 2 cues c o n d i t i o n and was t r a n s f e r r e d t o the 1 cue c o n d i t i o n a f t e r 30 t r i a l s . The o t h e r group ( b i r d s 4,5,6; l->2 Cues group) s t a r t e d on the 1 cue c o n d i t i o n and was t r a n s f e r r e d t o the 2 cues c o n d i t i o n a f t e r 30 t r i a l s . The main purpose of the p r e s e n t experiment was t o see i f the d i s r u p t i o n i n performance o b s e r v e d i n the p r e v i o u s e x p e r i m e n t was s p e c i f i c t o the 1 cue c o n d i t i o n o r t o the 43 s u b j e c t s i n t h a t group. The r e l a t i v e p e r s i s t e n c e of the d i s r u p t i o n was a l s o of i n t e r e s t . Method S u b j e c t s a n d A p p a r a t u s The p i g e o n s from Experiment 1 a l s o s e r v e d as t h e s u b j e c t s i n the p r e s e n t s t u d y . A l l h o u s i n g c o n d i t i o n s remained the same. The a p p a r a t u s from Experiment 1 was a l s o used i n the p r e s e n t s t u d y . P r o c e d u r e The same b a s i c p r o c e d u r e used i n Experiment 1 was used i n the p r e s e n t s t u d y , e x c e p t t h a t no i n i t i a l t r a i n i n g was n e c e s s a r y . The r e t e n t i o n i n t e r v a l remained a t 30 s t h r o u g h o u t the experiment and a l l s u b j e c t s were removed from the a p p a r a t u s d u r i n g the R I . F o l l o w i n g the RI a l l s u b j e c t s were r e t u r n e d t o the a p p a r a t u s and c a r e f u l l y p l a c e d f a c i n g the g r a i n d i s p e n s e r . T h i r t y seconds l a t e r the t e s t phase began. The l->2 Cues group was g i v e n 30 t r i a l s on the 1 cue c o n d i t i o n and then t r a n s f e r r e d t o the 2 cues c o n d i t i o n f o r a f u r t h e r 30 t r i a l s . The 2->l Cue group r e c e i v e d the same number of t r i a l s but was exposed t o the 2 cues c o n d i t i o n f i r s t and t h e n t r a n s f e r r e d t o the 1 cue c o n d i t i o n . D a t a A n a l y s i s The measures of performance c a l c u l a t e d i n the p r e v i o u s e xperiment were a l s o used i n the p r e s e n t s t u d y . Both a mean d a i l y DR and a c u m u l a t i v e DR were computed f o r each s u b j e c t i n each b l o c k of 10 s e s s i o n s . Data were i n i t i a l l y a n a l y z e d i n t h r e e 20 s segments d u r i n g the 1 min t e s t p e r i o d but because no d i f f e r e n c e s were found a c r o s s 4 4 segments the d a t a were c o l l a p s e d a c r o s s the e n t i r e t e s t p e r i o d . Data a re p r e s e n t e d i n T a b l e I I . Group comparisons were made u s i n g a Group by B l o c k a n a l y s i s of v a r i a n c e and p o s t hoc t e s t s . D i f f e r e n c e s i n the d i s c r i m i n a b i l i t y of the f i v e key p a i r s were a s s e s s e d u s i n g a Group by B l o c k by K e y - p a i r a n a l y s i s of v a r i a n c e . R e s u l t s A l l b i r d s performed a t a lower l e v e l when r u n on the 1 cue c o n d i t i o n . Group l->2 Cues, which s t a r t e d on the 1 cue c o n d i t i o n , was e s s e n t i a l l y a t chance d u r i n g the f i r s t phase of the e x p e r i m e n t , a l t h o u g h t h e i r performance d i d improve i n the 3 r d b l o c k . When they were t r a n s f e r r e d t o the 2 cues c o n d i t i o n performance i m m e d i a t e l y r o s e . The performance of the 2->l Cue Group showed an o p p o s i t e p a t t e r n . Performance was i n i t i a l l y v e r y h i g h when they were r u n on the 2 cues c o n d i t i o n , but f e l l t o chance l e v e l s i m m e d i a t e l y a f t e r t hey were t r a n s f e r r e d t o the 1 cue c o n d i t i o n . The mean d i s c r i m i n a t i o n r a t i o s from each b l o c k of the p r e s e n t experiment are shown i n F i g u r e 8. Because the p a t t e r n of r e s u l t s from b o t h the c u m u l a t i v e and mean d a i l y d i s c r i m i n a t i o n r a t i o s was the same, the d a t a p r e s e n t e d here are an average of those two measures. The f i l l e d s quares show the d a t a from the 2->l Cue group and the open squares show the d a t a from the l->2 Cues group. There was no o v e r a l l d i f f e r e n c e between the two groups [F (1,4)=.2601, p>.6]]. However, the f i g u r e c l e a r l y shows a T a b l e I I . Data from each b l o c k of Experiment 2. Mean d a i l y d i s c r i m i n a t i o n r a t i o s a r e i n the f i r s t row f o r each s u b j e c t , c u m u l a t i v e d i s c r i m i n a t i o n r a t i o s a r e i n the second row, and t o t a l c o r r e c t f i r s t c h o i c e s a r e i n the t h i r d row. Group B l o c k s 2->l Cues 1 2 3 SWITCH 4 5 6 1 .859 .891 8 .615 .719 6 .726 .910 8 .691 .748 6 .585 .513 5 .477 .154 4 2 .782 . 848 6 .954 .954 9 .972 .966 9 .659 .657 8 .561 .446 3 .565 .579 4 3 .974 .97 8 9 .828 .914 8 .922 .934 8 .628 .599 8 .560 .587 5 .662 .673 5 Group l->2 Cues 4 .668 .806 7 .702 .748 6 .681 .732 7 .882 .955 9 .984 .963 10 .651 .726 6 5 .722 .735 7 .599 .528 4 .793 .779 9 .932 .962 10 .659 .899 7 .638 .767 7 6 .485 .415 4 .490 .500 4 .646 .824 5 . 829 .914 7 . 909 .964 10 .772 .652 8 4 6 < Oct z o 1-1 0.9-0.8-0.7 3 0.6 OC O to Q 0.5 0.4-0.3 Legend • 2 CUES — > 1 CUE • 1 CUE — > 2 CUES 3 4 BLOCKS OF 1 0 SESSIONS F i g u r e 8. A comparison of the mean d i s c r i m i n a t i o n r a t i o s from Experiment 2 f o r the l->2 Cues and 2->l Cue groups. The r e t e n t i o n i n t e r v a l was 30 s and spent o u t s i d e the t e s t chamber. s t r o n g Group by B l o c k i n t e r a c t i o n [F (5,20)=14.7995, p<.001]. Both groups show i n f e r i o r performance on the 1 cue c o n d i t i o n (Newman-Keuls, a l l p's<.05). There was a l s o a s i g n i f i c a n t e f f e c t of B l o c k s . O v e r a l l performance, c o l l a p s e d a c r o s s groups, was b e t t e r i n the 3 r d b l o c k and w o r s t i n the f i n a l b l o c k [F (5,20)=3.6386, p<.02, Newman-K e u l s , p<.05] F i g u r e 9 shows a comparison of the p e r c e n t c o r r e c t f i r s t c h o i c e s . F i l l e d s quares show the d a t a from the 2->l Cue group and the open c i r c l e s show d a t a from the l->2 Cues' group. The p a t t e r n of r e s u l t s i s e s s e n t i a l l y the same as w i t h the DR measure, but the main e f f e c t o f b l o c k s i s not s i g n i f i c a n t [F (5,20) =2.0026-, p>.12]. There i s s t i l l a c l e a r i n t e r a c t i o n e f f e c t however [F (5,20)=5.4763, p<.003]. Both groups show s t r o n g decrements i n performance i n the 1 cue c o n d i t i o n . However, p o s t hoc t e s t s d i d not c o n f i r m t h i s d i f f e r e n c e (Newman-Keuls, a l l p's>.05). There was no d i f f e r e n c e i n performance between the f i v e key p a i r s d u r i n g the t e s t phase [F (4,16)=.3006, p>.87]. A l l s u b j e c t s performed e q u a l l y w e l l on a l l key p a i r s . The Group by K e y - p a i r , B l o c k by K e y - p a i r , and Group by B l o c k by K e y - p a i r i n t e r a c t i o n s were a l l n o n - s i g n i f i c a n t [F (4,16)=.5677, p>.69, F (20,80)=1.8375, p>.10, and F (20,80)=1.4040, p>.23, r e s p e c t i v e l y ] . 4 8 100 90-80-O UJ £ 70 O o U l o 60-50-40 30 Legend • 2 CUES —> t CUE • 1 CUE —> 2 CUES 1 BLOCKS OF 10 SESSIONS Figure 9. A comparison of the mean percentage of correct f i r s t responses from Experiment 2 for the l->2 Cues and 2->l Cue groups. The retention i n t e r v a l was 30 s and spent outside the test chamber. D i s c u s s i o n The r e s u l t s of the p r e s e n t experiment c l e a r l y i l l u s t r a t e s e v e r a l i m p o r t a n t p o i n t s . F i r s t , the d i s c r i m i n a t i o n r a t i o measure i s a much b e t t e r m e t r i c w i t h which t o a s s e s s s p a t i a l w o r k i n g memory i n the p i g e o n , a t l e a s t w i t h i n the c o n f i n e s of the p r o c e d u r e s used h e r e . A n a l y z e s based s o l e l y on the l a t t e r measure would have su g g e s t e d a much lower l e v e l of performance. Performance measures based on f i r s t c h o i c e responses a re a c o n s e r v a t i v e measure of r e t e n t i o n because they p r o v i d e the s u b j e c t w i t h no o p p o r t u n i t y t o c o r r e c t f o r e r r o r s t h a t a r e not due t o f o r g e t t i n g ( W i l k i e & Sp e t c h , 1981). Second, p i g e o n s p e r f o r m much b e t t e r on the 2 cues t a s k t h a n they do on the 1 cue t a s k . The performance decrement o b s e r v e d i n the 1 cue c o n d i t i o n i n Experiment 1 was r e p l i c a t e d i n the p r e s e n t e x p e r i m e n t . F u r t h e r m o r e , t h i s decrement p e r s i s t e d a c r o s s s e v e r a l b l o c k s of s e s s i o n s and was i m m e d i a t e l y e v i d e n t when s u b j e c t s were s w i t c h e d from the 2 cues c o n d i t i o n t o the 1 cue c o n d i t i o n . The decrement was a b o l i s h e d when the s w i t c h proceeded i n the o p p o s i t e d i r e c t i o n . Because performance on the 1 cue t a s k was e s s e n t i a l l y a t chance w i t h RI's of 30 s, when the s u b j e c t was removed from the a p p a r a t u s , f u r t h e r i n c r e m e n t s i n the RI would p r o v i d e no new d a t a . The 2 cues t a s k , on the o t h e r hand, p r o v i d e s the o p p o r t u n i t y f o r f u r t h e r r e t e n t i o n i n t e r v a l m a n i p u l a t i o n s because performance i s s t i l l a t a h i g h l e v e l . 5 0 E x p e r i m e n t 3 I t i s e v i d e n t from the p r e v i o u s two e x p e r i m e n t s t h a t the 2 cues t a s k i s b e t t e r s u i t e d f o r the s t u d y of s p a t i a l w o r k i n g memory than i t s 1 cue c o u n t e r p a r t . P i g e o n s p e r f o r m w e l l w i t h RI's of up t o 30 s, a l e v e l f a r above the p r e v i o u s l y demonstrated l i m i t i n a d e l a y e d matching of key l o c a t i o n paradigm ( 8 - s , W i l k i e & Summers, 1982) The purpose of the p r e s e n t experiment was t o examine how w e l l p i g e o n s r e t a i n s p a t i a l i n f o r m a t i o n i n the 2 cues c o n d i t i o n when the r e t e n t i o n i n t e r v a l between t r a i n i n g and t e s t i n g was extended f u r t h e r . P r e v i o u s work has s u g g e s t e d t h a t p i g e o n s ' upper r e t e n t i o n l i m i t f o r s p a t i a l i n f o r m a t i o n i n w o r k i n g memory i s a p p r o x i m a t e l y 30 min (Spetch & Honig, 1988) . Other work has su g g e s t e d an even lower l i m i t ( c f . O l s e n & M a k i , 1983; R o b e r t s & Van V e l d h u i z e n , 1985; W i l k i e & Summers, 1982), r a n g i n g from o n l y a few seconds t o as l o n g as 16 minut e s . T h e r e f o r e the approach t a k e n i n the p r e s e n t experiment was to s y s t e m a t i c a l l y r e p l i c a t e the p r e v i o u s f i n d i n g s and then e x t e n d the a n a l y s i s t o l o n g e r r e t e n t i o n i n t e r v a l s . Method S u b j e c t s a n d A p p a r a t u s Three randomly s e l e c t e d s u b j e c t s ( b i r d s 1,5,6) from Experiment 1 and 2 were used i n the p r e s e n t r e s e a r c h . An a d d i t i o n a l t h r e e S i l v e r K i n g p i g e o n s ( b i r d s 7,8,9) were a l s o used. The a d d i t i o n a l b i r d s had been used i n numerous s t u d i e s , but were n a i v e w i t h r e s p e c t t o the p r o c e d u r e s used i n the p r e s e n t r e s e a r c h . Housing c o n d i t i o n s were the same as i n the p r e v i o u s e x p e r i m e n t s r e p o r t e d above. The a p p a r a t u s used i n the p r e v i o u s e x p e r i m e n t s was a l s o used i n the p r e s e n t r e s e a r c h . P r o c e d u r e The b a s i c p r o c e d u r e s used p r e v i o u s l y were a l s o used h e r e . However, a l l s u b j e c t s were r u n e x c l u s i v e l y on the 2 cues t a s k . A l l b i r d s responded t o i l l u m i n a t e d p e c k i n g keys so no p r e l i m i n a r y t r a i n i n g was n e c e s s a r y . A l l s u b j e c t s were r u n f o r 30 s e s s i o n s w i t h an RI of 30 s t o e s t a b l i s h a b a s e l i n e f o r performance. R I I n c r e m e n t s The r e t e n t i o n i n t e r v a l was in c r e m e n t e d i n the f o l l o w i n g sequence: 5 min, 15 min, 30 min, 60 min, 2 h r , 4 h r , 8 h r , 12 h r , 24 h r . The RI was incremented o n l y i f a s u b j e c t ' s c u m u l a t i v e and mean d a i l y DR's were above .70 a t the end of a b l o c k of 10 s e s s i o n s . I n d i v i d u a l s u b j e c t s were g i v e n a maximum of t h r e e b l o c k s t o a t t a i n t h i s l e v e l of performance. I f a s u b j e c t f a i l e d t o a c h i e v e a DR of over .70 w i t h i n 3 b l o c k s , no f u r t h e r d a t a were c o l l e c t e d from t h a t s u b j e c t . A DR of .70 was chosen as the c r i t e r i o n n e c e s s a r y f o r subsequent r e t e n t i o n i n t e r v a l m a n i p u l a t i o n s because a c o n s e r v a t i v e measure of performance seemed more a p p r o p r i a t e g i v e n the n o v e l p r o c e d u r e s employed i n the p r e s e n t r e s e a r c h . Some s u b j e c t s ( b i r d s 7,8 & 9) were g i v e n an e x t r a b l o c k of b a s e l i n e s e s s i o n s due t o a break a t C h r i s t m a s . S u b j e c t 7 was a l s o g i v e n a d d i t i o n a l b l o c k s of s e s s i o n s a t the l o n g e r RI's t o a s s e s s the s t a b i l i t y of h i s performance. D a t a A n a l y s i s Data from each s u b j e c t were c o n s i d e r e d i n d e p e n d e n t l y . The same measures of performance used p r e v i o u s l y were c o l l e c t e d i n the p r e s e n t r e s e a r c h . However, because i t was c l e a r from the p r e v i o u s e x p e r i m e n t s t h a t the DR measure of performance was b e t t e r t h a n the p e r c e n t c o r r e c t f i r s t c h o i c e s measure, o n l y the former measure i s a n a l y z e d h e r e . A l l d a t a c o l l e c t e d , however, are shown i n T a b l e I I I . A l e a s t - s q u a r e s l i n e a r r e g r e s s i o n a n a l y s i s was-was used t o f i n d the l i n e t h a t b e s t d e s c r i b e d the f o r g e t t i n g f u n c t i o n f o r each s u b j e c t . S e v e r a l a d d i t i o n a l a n a l y s e s were conducted. The r e l a t i v e d i s c r i m i n a b i l i t y of the k e y - p a i r s was a s s e s s e d i n b o t h the I n i t i a l S t i m u l u s Phase and the T e s t Phase u s i n g a n a l y s i s of v a r i a n c e t e c h n i q u e s . R e s u l t s A l l s u b j e c t s , w i t h the e x c e p t i o n of B i r d 9, showed good r e t e n t i o n a t i n t e r v a l s of a t l e a s t 4 h r . B i r d 7 performed w e l l w i t h RI*s of up t o 24 h r , but most b i r d s f a i l e d t o r e a c h c r i t e r i o n a t 4 or 8 h r . Performance was o f t e n d i s r u p t e d when the RI was i n c r e m e n t e d but r e c o v e r e d i n subsequent b l o c k s . S i m i l a r p a t t e r n s of r e s u l t s were found w i t h b o t h the d i s c r i m i n a t i o n r a t i o measures and the p e r c e n t c o r r e c t f i r s t c h o i c e s , a l t h o u g h the DR*s p r o v i d e d a h i g h e r , more s t a b l e measure of performance. F i g u r e 10 shows the mean DR d a t a . Only the f i n a l b l o c k a t each RI i s p r e s e n t e d . Because a s i m i l a r p a t t e r n of 53 T a b l e I I I . D a t a f r o m e a c h b l o c k o f E x p e r i m e n t 3. Mean d a i l y d i s c r i m i n a t i o n r a t i o s a r e i n t h e f i r s t row o f e a c h b l o c k , c u m u l a t i v e a r e i n t h e s e c o n d row, t o t a l c o r r e c t f i r s t c h o i c e s a r e i n row 3, and t h e r e t e n t i o n i n t e r v a l l e n g t h i s i n t h e f o u r t h row. Bird Block 1 5 6 7 8 9 .863 .682 .782 .817 .954 .843 1 .860 . 500 .724 .876 .962 .865 9 6 9 7 8 8 30" 30" 30" 30" 30" 30" .789 .852 .712 .699 .953 .933 2 .754 .904 .856 .708 .914 .939 6 8 7 10 10 10 30" 30" 30" 30" 30" 30" .705 .573 .794 .750 .889 .836 3 .862 .543 .774 .855 .984 .888 5 8 7 4 10 10 30" 30" 30" 30" 30" 30" .871 .796 .776 .922 .762 .521 4 .857 .825 .805 .931 .828 .579 8 8 8 7 8 6 5 ' 5 ' 5 ' 5 ' 5 ' 5 ' . 518 .841 .855 .758 .786 .521 5 .720 746 .911 .808 .869 .841 5 6 8 8 6 5 15 ' 15 • 15 ' 15 ' 15 ' 5 ' .704 .786 .835 .763 .743 .863 6 .737 .804 . 871 .733 .814 .962 5 6 7 7 8 7 15 ' 30 ' 30 ' 30 ' 30 ' 15 ' .623 .567 .571 .731 .526 .613 7 .643 . 495 .574 .717 .555 .626 5 8 4 7 6 9 30 ' 1 hr 1 hr 1 hr 1 hr 30 ' .670 .686 .773 .782 .693 .680 8 .795 .742 .827 .812 .637 .605 7 5 8 6 8 3 30 1 1 hr 1 hr 2 hr 1 hr 30 ' .614 . 553 .773 .802 .646 .779 9 .577 .601 . 824 .817 .770 .841 7 5 6 9 6 4 1 hr 2 hr 2 hr 30" 30" 30" .739 .738 .719 .763 .607 .684 10 .787 :77l .730 .838 .516 .665 5 7 9 9 5 7 1 hr 2 hr 4 hr 2 hr 1 hr 30 ' .637 .559 .618 .760 .771 .623 11 .610 .603 .677 .719 .840 .743 6 7 6 8 8 6 2 hr 4 hr 8 hr 4 hr 1 hr 30 ' Table 3. continued. Bird Block 1 5 6 7 8 9 .800 .643 .712 .802 .826 .866 12 .824 .640 .684 .638 .794 .860 6 7 8 7 7 8 2 hr 4 hr 8 hr 8 hr 2 hr 30 ' .658 .587 .710 .522 .497 13 .637 .585 .685 .591 .484 6 6 5 5 5 4 hr 4 hr 8 hr 4 hr 1 hr .667 .267 .430 14 .667 .285 .515 6 2 6 8 hr 4 hr 1 hr .693 .532 .438 15 .748 .531 .351 8 7 5 8 hr 4 hr 1 hr .700 16 .746 7 12 hr .718 17 .709 8 12 hr .728 18 .793 8 12 hr .671 19 .681 5 24 hr .714 20 .713 6 24 hr . 825 21 .823 7 24 hr 5 6 F i g u r e 10. The f i n a l d i s c r i m i n a t i o n r a t i o f o r each r e t e n t i o n i n t e r v a l t e s t e d i n Experiment 3. Each p a n e l c o n t a i n s the d a t a from one s u b j e c t . A l l d a t a p o i n t s e x c e p t f o r the those at the l o n g e s t r e t e n t i o n i n t e r v a l s r e p r e s e n t b l o c k s i n which c r i t e r i o n (.70) was met. Note t h a t the s c a l e of the X a x i s v a r i e s from p a n e l t o p a n e l . 1 BIRD 1 5 7 0 .9 A Q 0 . 6 A 0 .5 —1 I - I 1 , , j— °-5 1 1.5 2 2 .5 3 3 .5 RETENTION INTERVAL (HRS.) 1 BIRD 6 0.9 H o r a t o Q 0 . 6 -0 . 5 -0.4 J 1 1 , —r— 1 , , — , r 0 1 2 3 4 5 6 7 8 BIRD 7 i - i 1 1 I I I I I I 1 1 1 1 1 1 1 1 1 1 1 j - — i 1 1 1 p-0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0 21 22 2 3 24 RETENTION INTERVAL (HRS.) 5 9 r e s u l t s was o b t a i n e d w i t h b o t h the c u m u l a t i v e and mean d a i l y DR, the r e s u l t s p r e s e n t e d here are an average of those two measures. I n d i v i d u a l s u b j e c t s are p r e s e n t e d i n s e p a r a t e p a n e l s . N o t i c e t h a t the X axes have d i f f e r e n t s c a l e s i n each p a n e l . B i r d s 1, 5 and 8 performed w e l l w i t h RI's of up 4 h r , a l t h o u g h a l l t h r e e f a i l e d t o r e a c h c r i t e r i o n (.70) a t t h a t l e v e l . B i r d 6 performed w e l l a t RI's of up t o 8 h r . A l t h o u g h he f a i l e d t o r e a c h c r i t e r i o n , the combined DR f o r h i s f i n a l b l o c k was .698 (mean d a i l y = . 6 8 4 , c u m u l a t i v e = . 7 1 4 ) . B i r d 7 performed w e l l a t a l l RI's t e s t e d , up t o 24 h r . A d d i t i o n a l s e s s i o n s r u n a t the 8, 12, and 24 hr r e t e n t i o n i n t e r v a l s r e v e a l e d t h a t h i s performance was s t a b l e (see T a b l e I I I ) . B i r d 9 performed w e l l w i t h RI's of 30 min, but f a i l e d t o r e a c h c r i t e r i o n a t 1 h r . Data from a l l b l o c k s a t each r e t e n t i o n i n t e r v a l a re shown i n F i g u r e 11. I n a d d i t i o n , the b e s t f i t t i n g r e g r e s s i o n l i n e i s shown. I n d i v i d u a l s u b j e c t s are p r e s e n t e d s e p a r a t e l y and the s c a l e of the X a x i s v a r i e s from p a n e l t o p a n e l . With the e x c e p t i o n of B i r d s 8 and 9, the r e g r e s s i o n a n a l y s i s s u g g e s t s t h a t a l l s u b j e c t s were p e r f o r m i n g a t a h i g h l e v e l w i t h RI's of up t o 4 h. A comparison of the DR's from the i n i t i a l phase r e v e a l e d t h a t the d i s c r i m i n a t i o n r a t i o s from k e y - p a i r s 4 and 5 were s i g n i f i c a n t l y lower than f o r the o t h e r 3 k e y - p a i r s . K e y - p a i r 5 c o n s i s t e d of keys 5 and 6. They were a d j a c e n t t o each o t h e r and a l s o the f u r t h e s t from the g r a i n d i s p e n s e r . K e y - p a i r 4 c o n s i s t e d of keys 4 and 7. They were s e p a r a t e d 61 F i g u r e 11. The d i s c r i m i n a t i o n r a t i o s f r o m E x p e r i m e n t 3. A r e g r e s s i o n l i n e t h a t b e s t f i t s t h e d a t a i s a l s o shown. E a c h p a n e l shows t h e d a t a f r o m one s u b j e c t . N ote t h a t t h e s c a l e o f t h e X a x i s v a r i e s f r o m p a n e l t o p a n e l . BIRD 1 62 BIRD 6 63 BIRD 8 by keys 5 and 6, but formed the 2nd f u r t h e s t s e t from the g r a i n d i s p e n s e r . An a n a l y s i s of v a r i a n c e and subsequent p o s t hoc t e s t s c o n f i r m e d t h i s d i f f e r e n c e [F (4,20)=4.02730, p<.015, Newman-Keuls p<.05]. However, a comparison of the DR's from the t e s t phase r e v e a l e d no d i f f e r e n c e s among the f i v e k e y - p a i r s . A l l k e y - p a i r s were remembered e q u a l l y w e l l . A B l o c k by K e y - p a i r a n a l y s i s of v a r i a n c e c o n f i r m e d t h i s f i n d i n g [F (4,20)=2.0681, p>.12]. The B l o c k by K e y - p a i r i n t e r a c t i o n was a l s o not s i g n i f i c a n t [F (16,20) = .8337 , p>.64] . p i s c u s s i o n The r e s u l t s of the p r e s e n t s t u d y c l e a r l y i l l u s t r a t e s e v e r a l i m p o r t a n t p o i n t s . Most i m p o r t a n t l y , they show t h a t p i g e o n s can r e t a i n s p a t i a l i n f o r m a t i o n i n w o r k i n g memory f o r 4 o r more h o u r s , a t l e a s t w i t h i n the c o n f i n e s of the p r e s e n t p r o c e d u r e . A l t h o u g h i n d i v i d u a l a b i l i t i e s v a r y , r a n g i n g from a maximum of 24 h (the l o n g e s t RI t e s t e d ) t o a minimum of 30 min, the performance of most b i r d s t e s t e d began t o d e t e r i o r a t e around 4 h, a l e v e l f a r above the p r e v i o u s l y d e m onstrated l i m i t (30 min-Spetch & Honig, 1988). A l t h o u g h d i r e c t comparisons are i m p o s s i b l e because of p r o c e d u r a l d i f f e r e n c e s , i t i s i n t e r e s t i n g t o note t h a t p i g e o n s ' performance on the 2 cues c o n d i t i o n d e t e r i o r a t e s a t about the same p o i n t t h a t r a t s ' performance d e t e r i o r a t e s on a r a d i a l - a r m maze t a s k ( B e a t t y & S h a v a l i a , 1980). 66 The d i f f e r e n c e s between the i n i t i a l DR's f o r the 5 k e y - p a i r s were not s u r p r i s i n g . The c l o s e p r o x i m i t y of the keys t h a t made up k e y - p a i r s 4 (keys 4 and 7) and 5 (keys 5 and 6) most l i k e l y a c c o u n t s f o r the lower DR's. Sampling both keys would n ot r e q u i r e much e f f o r t . A l t h o u g h the keys of k e y - p a i r 1 (keys 1 and 10) were c l o s e r t o g e t h e r than those of k e y - p a i r 4, the presence of an e x t r e m e l y s a l i e n t i n t r a m a z e cue, the g r a i n d i s p e n s e r , between them p r o b a b l y i n h i b i t e d t h i s t y pe of s a m p l i n g b e h a v i o u r . The t r e n d i l l u s t r a t e d i n the t a b l e of DR's (Table I I I ) s u g g e s t s t h a t the s u b j e c t s were " l e a r n i n g t o remember". For many s u b j e c t s i n i t i a l i n c r e m e n t s i n the d u r a t i o n of the r e t e n t i o n i n t e r v a l caused f a i r l y s e v e r e decrements i n performance. However, i n subsequent b l o c k s performance improved, but g e n e r a l l y o n l y t o a l e v e l below t h a t of e a r l i e r , e a s i e r R I ' s . O l s e n and Maki (1983) found a s i m i l a r e f f e c t when t h e y t e s t e d p i g e ons i n a T-maze. Increments i n the RI.between c h o i c e and t e s t i n i t i a l l y d i s r u p t e d p e rformance, but performance s l o w l y r e c o v e r e d . E x p e r i m e n t 4 In E x periment 3 the r e s u l t s showed t h a t pigeons c o u l d r e t a i n the l o c a t i o n of a p r e v i o u s l y rewarded p e c k i n g key i n w o r k i n g memory f o r up t o 4 h. However, i n c r e m e n t s i n the RI i n i t i a l l y tended t o d i s r u p t performance, which then g r a d u a l l y r e c o v e r e d i n subsequent b l o c k s . L e a r n i n g t o remember a p p a r e n t l y p l a y e d a s i g n i f i c a n t r o l e i n the 67 s u c c e s s f u l performance of the t a s k . However, g i v e n t h a t RI's i n the w o r l d o u t s i d e the l a b o r a t o r y v a r y depending on c i r c u m s t a n c e s (e.g. how l o n g p a t c h e s are u n a v a i l a b l e due t o the i n t r u s i o n of humans or o t h e r a n i m a l s ) , i t i s u n c l e a r what r o l e l e a r n i n g t o remember would p l a y i n the n a t u r a l e nvironment. The q u e s t i o n u n d e r l y i n g the p r e s e n t r e s e a r c h i s : How w e l l do p i g e o n s remember the l o c a t i o n of a p r e v i o u s l y rewarded p e c k i n g key when the r e t e n t i o n i n t e r v a l between i n i t i a l t r a i n i n g and t e s t i n g v a r i e s ? Thus the p r e s e n t r e s e a r c h i s a s y s t e m a t i c r e p l i c a t i o n of the p r e v i o u s e x p e r i m e n t and i n d i r e c t l y i n v e s t i g a t e s the importance of " l e a r n i n g t o remember", by e l i m i n a t i n g t h e o p p o r t u n i t y t o do so. Method S u b j e c t s a n d A p p a r a t u s F i v e p i g e o n s s e r v e d as s u b j e c t s i n the p r e s e n t r e s e a r c h . Three s u b j e c t s ( b i r d s 2,3 & 4) p r e v i o u s l y used i n Ex p e r i m e n t s 1 and 2 were randomly s e l e c t e d f o r use i n the p r e s e n t s t u d y . The o t h e r two s u b j e c t s ( b i r d s 8 & 9) were p r e v i o u s l y used i n Experiment 3. A l l h o u s i n g c o n d i t i o n s were the same as i n the p r e v i o u s e x p e r i m e n t s . The a p p a r a t u s used i n the p r e v i o u s s t u d i e s was a l s o used i n the p r e s e n t r e s e a r c h . P r o c e d u r e The same b a s i c p r o c e d u r e s used p r e v i o u s l y were a l s o used i n the p r e s e n t r e s e a r c h . A l l pigeons were f a m i l i a r w i t h the a p p a r a t u s and b a s i c p r o c e d u r e s so no 68 p r e l i m i n a r y t r a i n i n g was necessary. However, a l l s u b j e c t s r e c e i v e d 30 s e s s i o n s of b a s e l i n e t r a i n i n g (RI=30 s) p r i o r to the s t a r t of the experiment proper. F o l l o w i n g b a s e l i n e t r a i n i n g a l l s u b j e c t s r e c e i v e d 60 s e s s i o n s at fo u r r e t e n t i o n i n t e r v a l s presented i n a random orde r . The r e t e n t i o n i n t e r v a l s were 30 s, 30 min, 2 hr and 4 h. A l l s u b j e c t s r e c e i v e d 30 s e s s i o n s at the s h o r t e s t RI and 10 s e s s i o n s at each of the other R I 1 s , i n a random order D a t a A n a l y s i s The same measures of performance c o l l e c t e d i n Experiment 3 were a l s o c o l l e c t e d here. The same analyses were a l s o conducted. Only the DR data are presented below. A l l data c o l l e c t e d are presented i n Table IV. R e s u l t s A p a t t e r n of r e s u l t s s i m i l a r to that of Experiment 3 was obtained i n the present experiment. Three out of f i v e s u b j e c t s showed good r e t e n t i o n of the l o c a t i o n of the p r e v i o u s l y rewarded key at the lo n g e s t RI. B i r d s 2 and 4 performed w e l l at a l l r e t e n t i o n i n t e r v a l s . B i r d 8 performed w e l l at only the s h o r t e s t and lo n g e s t RI. B i r d s 3 and 9 performed w e l l o n l y on the s h o r t e s t RI. F i g u r e 12 shows the DR's from the present r e s e a r c h . Because a s i m i l a r p a t t e r n of r e s u l t s was obtained from both the mean d a i l y and cumulative DR's the data presented here are an average of those two measures. Subjects' data are presented i n d i v i d u a l l y . B i r d 2 performed w e l l at a l l RI's. His DR's remained at .75 or b e t t e r throughout the 69 Table IV. Data from each block of Experiment 4. The f i r s t row of each r e t e n t i o n i n t e r v a l shows the mean d a i l y d i s c r i m i n a t i o n r a t i o s , the second row shows the cumulative d i s c r i m i n a t i o n r a t i o s and the t h i r d row shows the t o t a l c o r r e c t f i r s t c h o i c e s . R e t e n t i o n B i r d I n t e r v a l 2 3 4 8 9 . 867 .794 .899 .958 .621 30 sec .939 .900 .920 .961 .635 8 8 8 10 6 .752 .943 .817 .877 .809 30 sec .737 .963 .899 .900 .820 5 8 8 9 9 .830 .933 .811 .956 .645 30 sec .790 .940 .543 .958 .642 7 7 8 10 7 .669 .724 .944 .944 .695 30 sec .605 .842 .952 .942 .695 7 8 9 8 6 .813 .900 .865 . 892 .885 30 sec . 863 .929 .718 .908 .992 9 7 9 7 7 . 842 .718 .980 .996 .736 30 sec .869 .755 .958 .995 .837 . 9 9 10 10 6 . 856 .628 .756 .624 .531 30 min .851 .572 .784 .624 .334 10 4 9 4 7 .755 .634 .727 .369 .544 2 hours .785 .621 .727 .268 .383 9 5 9 5 5 .756 . 382 .649 .699 . 408 4 hours .744 .362 .650 .726 . 312 7 6 6 5 5 70 F i g u r e 12. The mean d i s c r i m i n a t i o n r a t i o s from Experiment 4 as a f u n c t i o n of R e t e n t i o n I n t e r v a l . Each panel shows the data from one s u b j e c t . BIRD 4 D I S C R I M I N A T I O N R A T I O o in I ~4 I C D O CO 74 experiment. B i r d 3 performed w e l l only at the s h o r t e s t RI. His DR's had dropped to chance l e v e l s at 30 min. B i r d 4 performed w e l l at a l l r e t e n t i o n i n t e r v a l s . His DR's remained above .70 f o r the s h o r t e r r e t e n t i o n i n t e r v a l s , but f e l l to .65 at 4 hr. B i r d 8 performed w e l l (above .70) at on l y the s h o r t e s t and l o n g e s t RI. His performance was at chance at the three i n t e r m e d i a t e RI's. B i r d 9 performed w e l l on only the s h o r t e s t RI. The DR's from a l l b l o c k s at each r e t e n t i o n i n t e r v a l are shown i n Fi g u r e 13. The r e g r e s s i o n l i n e t h a t best f i t s the data i s a l s o shown. Data from i n d i v i d u a l s u b j e c t s are shown s e p a r a t e l y . The r e s u l t s are somewhat mixed. B i r d s 2 and 4 perform above chance l e v e l s with RI's of up to approximately 4 h. B i r d 8 performs at a l e v e l above chance with RI's of up to 2 h. B i r d s 3 and 9 performed above chance l e v e l s o n l y at the s h o r t e s t RI. A comparison of the DR's from the i n i t i a l phase r e v e a l e d that the DR's from k e y - p a i r s 1 (keys 1 and 10) and 5 (keys 5 and 6) were s i g n i f i c a n t l y d i f f e r e n t from the other three p a i r s . An a n a l y s i s of v a r i a n c e and subsequent post hoc comparisons confirmed t h i s d i f f e r e n c e (F (4,16)=4.0226, p<.02, Newman-Keuls, p<.05). T h i s d i f f e r e n c e was a l s o apparent d u r i n g the t e s t phase [F (4,16)=4.1983, p<.02, Newman-Keuls, p<.05). The Key-pair by R e t e n t i o n i n t e r v a l i n t e r a c t i o n was not s i g n i f i c a n t [F (12,16)=1.0509, p>.42]. 7 5 F i g u r e 13. The d i s c r i m i n a t i o n r a t i o s from Experiment 4. Data f o r i n d i v i d u a l s u b j e c t s are presented i n separate p a n e l s . The r e g r e s s i o n l i n e t h a t best f i t s the data i s a l s o i n c l u d e d . BIRD 4 DISCRIMINATION RATIO 79 p i s c u s s i o n The r e s u l t s from Experiment 4 , a l t h o u g h somewhat more v a r i a b l e , r e p l i c a t e the f i n d i n g from Experiment 3 t h a t p i g e o n s can remember the l o c a t i o n of a p r e v i o u s l y rewarded p e c k i n g key f o r a p p r o x i m a t e l y 4 h r . Three of f i v e s u b j e c t s p erformed w e l l a t t h i s r e t e n t i o n i n t e r v a l . O v e r a l l performance on the p r e s e n t t a s k was l o w e r , s u g g e s t i n g t h a t " l e a r n i n g t o remember" may p l a y an i m p o r t a n t p a r t i n the s u c c e s s f u l performance of d e l a y e d m a tching w i t h l o n g r e t e n t i o n i n t e r v a l s . B i r d s i n the p r e s e n t r e s e a r c h performed p o o r l y on key-p a i r s 1 and 5. The d i s t a n c e between the members of these k e y - p a i r s was the l e a s t of a l l k e y - p a i r s . The d i f f e r e n c e i n performance p r o b a b l y r e f l e c t s t h i s c l o s e p r o x i m i t y between the members o f the s e t s . I t i s u n c e r t a i n why these d i f f e r e n c e s f a i l e d t o m a n i f e s t i n the p r e v i o u s s t u d i e s , but the most p l a u s i b l e e x p l a n a t i o n i s t h a t the mixed sc h e d u l e of RI's makes the matching t a s k more d i f f i c u l t , and t h e r e f o r e more s e n s i t i v e i n d e t e c t i n g the d i f f e r e n c e s between the key-p a i r s . G e n e r a l D i s c u s s i o n The r a t i o n a l e f o r the p r e s e n t r e s e a r c h was based on two key i d e a s . F i r s t , the p r e v i o u s l y demonstrated upper l i m i t f o r r e t e n t i o n of l o c a t i o n i n w o r k i n g memory by pigeons was, i n t u i t i v e l y , t oo low (30 min-Spetch & Honig, 1988). I t was argued t h a t t h i s poor r e t e n t i o n was a r e s u l t of i n a p p r o p r i a t e t r a i n i n g and t e s t i n g p r o c e d u r e s . Most p r e v i o u s s t u d i e s have examined p i g e o n s ' s p a t i a l memory w i t h t a s k s o r i g i n a l l y d e s i g n e d f o r o t h e r s p e c i e s , l i k e r a t s (Bond e t a l , 1981; R o b e r t s & Van V e l d h u i z e n , 1985). Tasks d e s i g n e d e s p e c i a l l y f o r pigeons have produced b e t t e r r e s u l t s (Spetch & Edwards, 1986; Spetch & Honig, 1988) but have g e n e r a l l y l o o k e d a t s p a t i a l memory a t the l e v e l of food d i s t r i b u t i o n w i t h i n a p a t c h . That i s , they have t y p i c a l l y examined memory f o r l o c a t i o n s t h a t have p r o v i d e d s i n g l e r e i n f o r c e m e n t s . An e x a m i n a t i o n of p i g e o n f o r a g i n g e c o l o g y s u g g e s t s t h a t t e s t s of r e c a l l f o r food d i s t r i b u t i o n w i t h i n a p a t c h may a l s o be i n a p p r o p r i a t e , because p i g e o n s a re group f e e d e r s and the type of f o o d items t h a t they consume are v u l n e r a b l e t o r e d i s t r i b u t i o n w i t h i n the p a t c h by n a t u r a l elements, l i k e wind and r a i n , and by the f o r a g i n g of c o n s p e c i f i c s . T h e r e f o r e the d i s t r i b u t i o n of food w i t h i n p a t c h e s i s l i k e l y t o between v i s i t s . T h e r e f o r e , i t was argued, the most a p p r o p r i a t e t a s k f o r examining s p a t i a l memory i n t h i s s p e c i e s i s one t h a t examines s p a t i a l memory a t the l e v e l of p a t c h c h a r a c t e r i s t i c s , l i k e r e l a t i v e p r o f i t a b i l i t y . R o b e r t s (1988) examined t h i s l e v e l of r e c a l l u s i n g a s i m u l a t e d p a t c h y environment and found t h a t pigeons show e x c e l l e n t r e f e r e n c e memory f o r p a t c h c h a r a c t e r i s t i c s . He a l s o s u g g e s t e d t h a t p i g e o n s were u s i n g w o r k i n g memory t o remember p r e v i o u s p a t c h v i s i t s , but u n f o r t u n a t e l y he d i d not e x p l i c i t l y t e s t w o r k i n g memory and h i s r e s u l t s were t h e r e f o r e open t o o t h e r i n t e r p r e t a t i o n s . The p r e s e n t r e s e a r c h was d e s i g n e d t o examine w o r k i n g memory f o r p a t c h c h a r a c t e r i s t i c s e x p l i c i t l y . The second main i d e a upon which the p r e s e n t r e s e a r c h was founded was t h a t a p a t c h c o u l d be s i m u l a t e d t h rough the use of an i l l u m i n a t e d p e c k i n g key and a VI s c h e d u l e of r e i n f o r c e m e n t . P a t c h s i z e , ( i . e g e o g r a p h i c e x t e n t ) was assumed t o be u n i m p o r t a n t . The r e s u l t s of the p r e s e n t s t u d y u n e q u i v o c a l l y s u p p o r t b o t h of t h e s e i d e a s . P i g e o n s demonstrated e x c e l l e n t r e t e n t i o n of the l o c a t i o n of a p r o f i t a b l e key f o r as l o n g as 4 h r . I n d i v i d u a l performance on the t a s k v a r i e d . One b i r d p e r f o rmed p o o r l y w i t h r e t e n t i o n i n t e r v a l s of o n l y 30 min ( B i r d 9 ) , whereas a n o t h e r ( B i r d 7) performed w e l l a t 24 h r , the l o n g e s t r e t e n t i o n i n t e r v a l t e s t e d . However, most b i r d s p erformed w e l l w i t h r e t e n t i o n i n t e r v a l s of up t o 4 h r . S e v e r a l o t h e r i n t e r e s t i n g f i n d i n g s were n o t i c e d . S u b j e c t s exposed t o b o t h the S+ and S- (the " p r o f i t a b l e " and " n o n - p r o f i t a b l e " p a t c h e s , r e s p e c t i v e l y ) performed b e t t e r t h a n a group of s u b j e c t s exposed t o the o n l y the S+. A p l a u s i b l e e x p l a n a t i o n f o r t h i s d i f f e r e n c e comes from human memory r e s e a r c h . The importance of t r a n s f e r a p p r o p r i a t e p r o c e s s i n g i n memory r e s e a r c h has been w e l l e s t a b l i s h e d ( M o r r i s e t a l , 1977). For example, M o r r i s e t a l (1977) showed t h a t human s u b j e c t s t r a i n e d t o p r o c e s s the semantic c o n t e n t of a word l i s t d i d w e l l on a subsequent word r e c o g n i t i o n t e s t . However, t h e y d i d p o o r l y on a rhyme r e c o g n i t i o n t e s t . S u b j e c t s t r a i n e d t o p r o c e s s the r y t h m i c r e l a t i o n s h i p s between words d i d w e l l on a subsequent rhyme r e c o g n i t i o n t e s t , but p o o r l y on a word r e c o g n i t i o n t e s t . They a t t r i b u t e d the d i f f e r e n t i a l performances t o t r a n s f e r a p p r o p r i a t e p r o c e s s i n g . A h i g h degree of s i m i l a r i t y between t r a i n i n g and t e s t i n g p r o c e d u r e s l e a d s t o b e t t e r performance on the t e s t . I t may be t h a t the type of t e s t i n g p r o c e d u r e used i n the p r e s e n t r e s e a r c h was more a p p r o p r i a t e f o r the s u b j e c t s t r a i n e d on the 2 cues c o n d i t i o n . T e s t i n g and t r a i n i n g seem t o be much more s i m i l a r i n t h a t c o n d i t i o n . However, the s u p e r i o r i t y of the 2 cues c o n d i t i o n may be as much due t o e c o l o g i c a l c o n s i d e r a t i o n s . The r e l a t i v e p r o f i t a b i l i t y of p a t c h e s can o n l y be d e t e r m i n e d by s a m p l i n g and i t may be t h a t the performance decrement obse r v e d i n the 1 cue c o n d i t i o n was due t o s a m p l i n g of b o t h the S+ and S- d u r i n g the r e t e n t i o n t e s t . Improved performance on the t e s t would be e x p e c t e d as the p i g e o n s l e a r n e d t h a t r e s p o n d i n g t o the non-rewarded l o c a t i o n was never r e i n f o r c e d . The improved performance of the s u b j e c t s on the 1 cue t a s k i n the t h i r d b l o c k of Experiment 2 o f f e r s some s u p p o r t f o r t h i s e x p l a n a t i o n , but more c o n c l u s i v e e v i d e n c e must a w a i t f u r t h e r r e s e a r c h . The s u p e r i o r i t y of the d i s c r i m i n a t i o n r a t i o measure of performance r e l a t i v e t o the p e r c e n t c o r r e c t f i r s t c h o i c e s measure i s a l s o i n t e r e s t i n g . There are s e v e r a l p l a u s i b l e e x p l a n a t i o n s . The i m p o r t a n c e of a p p r o p r i a t e t r a i n i n g and 83 testing procedures has been discussed previously and i t may be that the extended test period was a more appropriate testing procedure for the type of t r a i n i n g procedures employed i n the present research. The improved performance as measured by the discrimination r a t i o may also be a r e s u l t of the pigeons' a b i l i t y to recognize that i t has made an incorrect response (Wilkie fi Spetch, 1981) and to subsequently respond co r r e c t l y (Dale, 1988; Roitblat, 1980). It seems l i k e l y that both the appropriateness of the testing procedures and the fact that the subjects were given an opportunity to correct i n i t i a l errors contributed to the better performance observed with the discrimination r a t i o measure. C o n c l u s i o n s a n d F u t u r e D i r e c t i o n It i s int e r e s t i n g to note that the l e v e l of performance observed i n the present research i s similar to the l e v e l of performance of rats on the r a d i a l maze. Although d i r e c t comparisons between species are impossible because of procedural differences i n pigeon and rat research, the present findings have important implications for the study of comparative psychology. Most importantly, they demonstrate the importance of using species-appropriate t r a i n i n g and testing procedures when examining the cognitive a b i l i t i e s of a given species. I n i t i a l l y , cognitive a b i l i t i e s are best studied within the context of the subjects' habitat. Comparisons of species which inhabit 84 s i m i l a r n i c h e s can t e l l us much about the r e l a t i v e s t r e n g t h s and weaknesses of an a n i m a l ' s c o g n i t i v e a b i l i t i e s . Once the l i m i t s of a g i v e n s p e c i e s ' c o g n i t i v e a b i l i t i e s have been d e t e r m i n e d w i t h i n t h e i r a p p r o p r i a t e c o n t e x t , we can l o o k f o r p o t e n t i a l i n s t a n c e s of " a d a p t i v e s p e c i a l i z a t i o n " ( S h e r r y , 1984; S h e r r y & S c h a c t e r , 1987). I t s h o u l d then be p o s s i b l e t o d e s i g n t a s k s f o r d e t e r m i n i n g the e x t e n t t o which such s e e m i n g l y s p e c i a l i z e d a b i l i t i e s a re i n f a c t s p e c i a l i z e d . The p r e s e n t r e s e a r c h has d emonstrated c o n c l u s i v e l y t h a t the upper l i m i t f o r r e t e n t i o n of l o c a t i o n i s much g r e a t e r than p r e v i o u s l y shown (Spetch & Honig, 1988; Bond et a l , 1981; W i l k i e & Summers, 1982). However, much a d d i t i o n a l work remains t o be done, some of w h i c h i s c u r r e n t l y under way i n our l a b o r a t o r y . The c u r r e n t approach i s s i m i l a r i n many r e s p e c t s t o the p o s i t i o n o u t l i n e d by Domjan and G a l e f , 1983, e m p h a s i z i n g the importance of e c o l o g i c a l v a r i a b l e s i n the modern s t u d y of c o m p a r a t i v e p s y c h o l o g y . The importance of the p i g e o n f o r a g i n g e c o l o g y i n h e l p i n g t o p r e d i c t what p i g e o n s s h o u l d and s h o u l d not be a b l e t o do has been emphasized on numerous o c c a s i o n s t h r o u g h o u t the c u r r e n t d i s c o u r s e . Many of the c o n c l u s i o n s and i d e a s p r e s e n t e d here have, by n e c e s s i t y , been founded on a s t r i c t l y l o g i c a l a n a l y s i s of p i g e o n f o r a g i n g e c o l o g y , due t o a s p a r s i t y of c o n t r o l l e d f i e l d r e s e a r c h d i r e c t l y r e l e v a n t t o the i s s u e s under c o n s i d e r a t i o n . A l t h o u g h the r e s u l t s p r e s e n t e d here s u p p o r t the v a l i d i t y of the i d e a s d i s c u s s e d above, more c o n c l u s i v e e v i d e n c e must a w a i t the outcome of some c a r e f u l l y c o n t r o l l e d f i e l d r e s e a r c h aimed d i r e c t l y a t t e s t i n g t h e s e i s s u e s . The p r e s e n t f i n d i n g s are a l s o r e l e v a n t t o the common d i s t i n c t i o n between r e f e r e n c e memory and w o r k i n g memory. Re f e r e n c e memory has t y p i c a l l y been thought of as a p r o c e s s f o r the permanent s t o r a g e and subsequent r e t r i e v a l of i n v a r i a n t i n f o r m a t i o n ( i . e . permanent g e o g r a p h i c f e a t u r e s ) . Working memory has t y p i c a l l y been thought of as a p r o c e s s f o r the temporary s t o r a g e and r e t r i e v a l of v a r i a b l e i n f o r m a t i o n ( i . e . p r e v i o u s l y v i s i t e d arms i n a r a d i a l maze). However, the p r o c e d u r e s used i n the p r e s e n t r e s e a r c h b l u r t h i s d i s t i n c t i o n . Throughout t h i s t h e s i s , the t a s k s employed t o examine s p a t i a l memory have been d e s c r i b e d , e i t h e r d i r e c t l y o r i n d i r e c t l y , as t a s k s t h a t r e q u i r e the use of w o r k i n g memory and the r e s u l t s have been i n t e r p r e t e d w i t h i n t h a t framework. However, the p r o c e d u r e s employed i n the p r e s e n t t h e s i s a re not e a s i l y c l a s s i f i e d as w o r k i n g or r e f e r e n c e memory t a s k s . Working memory has t y p i c a l l y been examined as a w i t h i n t r i a l o r w i t h i n s e s s i o n phenomenon. That i s , the i n f o r m a t i o n t o be remembered i s u s e f u l f o r o n l y a s i n g l e t r i a l or s e s s i o n . F u r t h e r m o r e , the d e l a y s between o r w i t h i n t r i a l s have g e n e r a l l y been s h o r t . R e f e r e n c e memory has t y p i c a l l y been examined as a between s e s s i o n phenomenon. The i n f o r m a t i o n t o be remembered i s u s e f u l from day-to-day. The d e l a y between s e s s i o n s has t y p i c a l l y been q u i t e l o n g , u s u a l l y 24 h r or more. However, the p r o c e d u r e s used i n the p r e s e n t r e s e a r c h f a l l s somewhere between the t r a d i t i o n a l views of wo r k i n g and r e f e r e n c e memory. The l o n g d e l a y s between t r a i n i n g and t e s t i n g make the d i s t i n c t i o n between a t r i a l and a s e s s i o n somewhat c l o u d y . The f a c t t h a t s u b j e c t s were g i v e n o n l y a s i n g l e t r i a l p er day a l s o c l o u d s the i s s u e . A c o r r e c t c l a s s i f i c a t i o n of the new p r o c e d u r e s p r e s e n t e d here as e i t h e r w o r k i n g o r r e f e r e n c e memory t a s k s , i f t h a t i s p o s s i b l e , w i l l have t o a w a i t answers t o two i m p o r t a n t q u e s t i o n s : How permanent must i n f o r m a t i o n be t o f a l l i n t o the domain of r e f e r e n c e memory? and How v a r i a b l e must i n f o r m a t i o n be t o f a l l i n t o the domain of w o r k i n g memory? At the p r e s e n t time n e i t h e r q u e s t i o n i s answerable. I t may not be p o s s i b l e t o answer them. I t i s c l e a r from the p r e s e n t r e s u l t s t h a t the dichotomy between r e f e r e n c e and wo r k i n g memory i s not a t a l l c l e a r c u t and as such may need to be r e f o r m u l a t e d o r even d i s c a r d e d as a framework f o r s t u d y i n g memory. 87 Ref erenc.es A a d l a n d , J . , B e a t t y , W.M., & Maki , R.H. (1985) S p a t i a l memory of c h i l d r e n and a d u l t s a s s e s s e d i n the r a d i a l - a r m maze. Developmental P s y c h o b i o l o g y , 18, 163-172. B a l d a , R.P. (1980) Recovery of cached seeds by a c a p t i v e N u c i f r a g a ca^crca^ctes^. Z. T i e r p s y c h o l . , 52, 331-346. B e a t t y , W.W.& S h a v a l i a , D.A. (1980) S p a t i a l memory i n r a t s : Time c o u r s e of w o r k i n g memory and e f f e c t of a n e s t h e t i c s . B e h a v i o r a l and N e u r a l B i o l o g y , 28, 454-462. B l o u g h , D.S. (1959) D e l a y e d matching i n the p i g e o n . J o u r n a l of the E x p e r i m e n t a l A n a l y s i s of B e h a v i o r , 2, 151-160. Bond, A.B., Cook, R.G., & Lamb, M.R. (1981) S p a t i a l memory and performance of r a t s and pi g e o n s i n the r a d i a l - a r m maze. Animal L e a r n i n g & B e h a v i o r , 9, 575-580. Brown, P., & J e n k i n s , H.M. (1968) A u t o s h a p i n g of the pi g e o n ' s keypeck. J o u r n a l of the E x p e r i m e n t a l A n a l y s i s of B e h a v i o r , 11, 1-8. D a l e , R.H.I. (1988) P i g e o n s p a t i a l memory on a fou r - a r m r a d i a l maze. The Canadian J o u r n a l of P s y c h o l o g y , 42, 78-83. Domjan, M, & G a l e f , B.G. (1983) B i o l o g i c a l c o n s t r a i n t s on i n s t r u m e n t a l and c l a s s i c a l c o n d i t i o n i n g : R e t r o s p e c t and p r o s p e c t . Animal L e a r n i n g & B e h a v i o r , 11, 151-161. F a n t i n o , E. & Abarca, N (1985) C h o i c e , o p t i m a l f o r a g i n g , and the d e l a y - r e d u c t i o n h y p o t h e s i s . The B e h a v i o r a l and B r a i n S c i e n c e s , 8, 315-330. G i l b e r t , S.G., & R i c e , D.C. (1979) NOVA SKED I I : A b e h a v i o r a l n o t a t i o n language u t i l i z i n g the Data G e n e r a l r e a l - t i m e d i s k - o p e r a t i n g system. B e h a v i o r Research Methods & I n s t r u m e n t a t i o n , 11, 71-7 3. G i r a l d e a u , L.A. (1984) Group f o r a g i n g : the s k i l l p o o l e f f e c t and fr e q u e n c y dependant l e a r n i n g . American N a t u r a l i s t , 124, 72-79. G i r a l d e a u , L.A., & L e f e b v r e , L. (1987) S c r o u n g i n g p r e v e n t s c u l t u r a l t r a n s m i s s i o n of f o o d - f i n d i n g b e h a v i o r i n p i g e o n s . A n i m a l B e h a v i o r , 35, 387-394. Goodwin, D. (1983) P i g e o n s and doves of the w o r l d . B r i t i s h Museum ( N a t u r a l H i s t o r y ) , I t h i c a : New York: C o r n e l l U n i v e r s i t y P r e s s . 8 8 Honig, W.K. (1978) S t u d i e s of w o r k i n g memory i n the p i g e o n . I n S.H. H u l s e , H. F o w l e r , & W.K. Honig (Eds.) C o g n i t i v e p r o c e s s e s i n a n i m a l b e h a v i o r (pp. 211-248). H i l l s d a l e , N.J.:Erlbaum. H u l l , C . L . (1943) P r i n c i p l e s of b e h a v i o r . New York: A p p l e t o n - C e n t u r y - C r o f t . Inman, A . J . , LeFebvre, L., & G i r a l d e a u , L.A. (1987) I n d i v i d u a l d i e t d i f f e r e n c e s i n f e r a l p i g e o n s : E v i d e n c e f o r r e s o u r c e p a r t i t i o n i n g . A n i m a l B e h a v i o u r , 35, 1902-1903. L e f e b v r e , L., & G i r a l d e a u , L.A. (1984) D a i l y f e e d i n g s i t e use by urban p i g e o n s . Canadian J o u r n a l of Zoology, 62, 1425-1428. Levesque, H. & M c N e i l , R. (1985) Abundance and a c t i v i t i e s of the r o c k dove ( C o l u m b a l i v i a ) i n the. p o r t of M o n t r e a l , Quebec, Canada. Canadian F i e l d - N a t u r a l i s t , 99, 343-355. Levesque, H. & M c N e i l , R. (1986) L o c a l movements o f the r o c k dove ( C p l u m b a l i v i a ) i n the o l d s e c t i o n of M o n t r e a l , Canada. N a t u r a l i s t e Canadien, 113, 47-54. Levy, W.M. (1974) The p i g e o n . Sumpter, S.C.: L e v i . M e n z e l , E.W. (1978) C o g n i t i v e mapping i n chimpanzees. I n S.H. H u l s e , H. F o w l e r , & W.K. Honig (Eds.) C o g n i t i v e p r o c e s s e s i n a n i m a l b e h a v i o r (pp. 375-422). H i l l s d a l e , N.J.:Erlbaum. M o r r i s , R.G.M. (1981) S p a t i a l l o c a l i z a t i o n does not r e q u i r e the p r e s e n c e of l o c a l cues. L e a r n i n g & M o t i v a t i o n , 12, 239-260. M o r r i s , C D . B r a n s f o r d , J.D & F r a n k s , J . J . (1977) L e v e l s of p r o c e s s i n g v e r s u s t r a n s f e r a p p r o p r i a t e p r o c e s s i n g . J o u r n a l of V e r b a l L e a r n i n g and V e r b a l B e h a v i o r , 16, 519-533 O l s e n , D.J., & Maki , W.S. (1983) C h a r a c t e r i s t i c s of s p a t i a l memory i n p i g e o n s . J o u r n a l of E x p e r i m e n t a l P s y c h o l o g y : A n i m a l B e h a v i o r P r o c e s s e s , 2, 266-280. O l t e n , D.S. (1978) C h a r a c t e r i s t i c s of s p a t i a l memory. I n S.H. H u l s e , H. F o w l e r , & W.K. Honig (Eds.) C o g n i t i v e p r o c e s s e s i n a n i m a l b e h a v i o r (pp• 341-373). H i l l s d a l e , N.J.:Erlbaum. O l t e n , D. & Samuelason, R.J. (1976) Remembrance of p l a c e s p a s s e d : S p a t i a l memory i n r a t s . J o u r n a l of E x p e r i m e n t a l P s y c h o l o g y : A n i m a l B e h a v i o r P r o c e s s e s , 2, 97-116. 89 R o b e r t s , W.A. (1979) S p a t i a l memory i n the r a t on a h i e r a r c h i a l maze. L e a r n i n g & M o t i v a t i o n , 10, 117-140. R o b e r t s , W.A. (1988) F o r a g i n g and s p a t i a l memory i n pigeons (Columba l i v i a ) . J o u r n a l of Comparative P s y c h o l o g y , 102, 108-117. R o b e r t s , W.A., & Van V e l d h u i z e n , N. (1985) S p a t i a l memory i n p i g e o n s on the r a d i a l - a r m maze. J o u r n a l of E x p e r i m e n t a l P s y c h o l o g y : A n i m a l B e h a v i o r P r o c e s s e s , 11, 241-260. R o i t b l a t , H.L. (1980) Codes and c o d i n g p r o c e s s e s i n p i g e o n s h o r t - t e r m memory. Animal L e a r n i n g & B e h a v i o r , 8, 341-351. R o i t b l a t , H.L., Tham, W. & Golub, L. (1982) Performance of B e t t a s p l e n d e n s i n a r a d i a l - a r m maze. A n i m a l L e a r n i n g & B e h a v i o r , 10, 108-114. S h e r r y , D.F. (1984) What food s t o r i n g b i r d s remember. Canadian J o u r n a l of P s y c h o l o g y , 38, 304-321. S h e r r y , D.F., & S c h a c t e r , D.L. (1987) The e v o l u t i o n of m u l t i p l e memory systems. P s y c h o l o g i c a l Review, 94, 439-454. S p e t c h , M.L. & Edwards, C.A. (1986) S p a t i a l memory i n pi g e o n s ( C o l u m b a l i v i a ) i n an o p e n - f i e l d f e d i n g e n v i r o n m e n t . J o u r n a l of Comparative P s y c h o l o g y , 100, 266-278. S p e t c h , M.L., & Honig, W.K. (1988) C h a r a c t e r i s t i c s of p i g e o n s ' s p a t i a l w o r k i n g memory i n an o p e n - f i e l d t a s k . A n i m a l L e a r n i n g & B e h a v i o r , 16, 123-131. Tolman, E.C, R i t c h i e , B.F., & K a l i s h , D. (1946a) S t u d i e s of s p a t i a l l e a r n i n g . I . O r i e n t a t i o n and the s h o r t c u t . J o u r n a l of E x p e r i m e n t a l P s y c h o l o g y , 36, 13-24. Tolman, E.C, R i t c h i e , B.F., & K a l i s h , D. (1946b) S t u d i e s of s p a t i a l l e a r n i n g . I I . P l a c e l e a r n i n g vs response l e a r n i n g . J o u r n a l of E x p e r i m e n t a l P s y c h o l o g y , 36, 221-229. Tomback, D.F. (1980) How n u t c r a c k e r s f i n d t h e i r seed s t o r e . Condor, 82, 10-19. Wasserman,E.A. (1976) S u c c e s s i v e matching-to-sample i n the p i g e o n : V a r i a t i o n s on a theme by K o n o r s k i . B e h a v i o r R e s e a r c h methods and I n s t r u m e n t a t i o n , 8, 278-282. 90 Whitman, C O . (1919) Posthumous works of C h a r l e s O t i s Whitman. (0. R i d d l e , E d . ) , Washington: The C a r n e g i e I n s t i t u t e of Washington. W i l k i e , D.M. (1983a) P i g e o n s ' s p a t i a l memory: I I . A c q u i s i t i o n of d e l a y e d matching of key l o c a t i o n and t r a n s f e r t o new l o c a t i o n s . J o u r n a l of the E x p e r i m e n t a l A n a l y s i s of B e h a v i o r , 39, 69-76. W i l k i e , D.M. (1983b) P i g e o n s ' s p a t i a l memory: I I I . E f f e c t s of d i s t r a c t o r s on d e l a y e d amtching of key l o c a t i o n . J o u r n a l of the E x p e r i m e n t a l A n a l y s i s of B e h a v i o r , 40, 143-151. W i l k i e , D.M. (1983c) R e i n f o r c e m e n t f o r p e c k i n g the sample f a c i l i t a t e s p i g e o n s ' d e l a y e d m a t c h i n g t o sample. B e h a v i o u r A n a l y s i s L e t t e r s , 3, 311-316. W i l k i e , D.M. (1984) P i g e o n s ' s p a t i a l memory: IV. E f f e c t s of i n t e r t r i a l i n t e r v a l m a n i p u l a t i o n s on d e l a y e d matching of key l o c a t i o n . Canadian J o u r n a l of P s y c h o l o g y , 38, 178-195. W i l k i e , D.M. (1986a) Some f a c t o r s a f f e c t i n g p i g e o n s ' v i s u a l t r a c k i n g b e h a v i o r . B e h a v i o u r a l P r o c e s s e s , 12, 287-297. W i l k i e , D.M. (1986b) P i g e o n s ' s p a t i a l memory: V. P r o a c t i v e i n t e r f e r e n c e i n the d e l a y e d amtching o f key l o c a t i o n paradigm o c c u r s o n l y under l i m i t e d c o n d i t i o n s . Animal L e a r n i n g & B e h a v i o r , 14, 257-266. W i l k i e , D.M., & Kennedy, D.J. (1987) Computer s i m u l a t i o n of pi g e o n s performance on a s p a t i a l m a tching t a s k . B e h a v i o u r a l P r o c e s s e s , 14, 105-122. W i l k i e , D.M., & S l o b i n , P. (1983) G e r b i l s i n space: Performance on the 17-arm r a d i a l maze. J o u r n a l of the E x p e r i m e n t a l A n a l y s i s of B e h a v i o r , 40, 301-312. W i l k i e , D.M., & Sp e t c h , M.L. (1981) P i g e o n s ' d e l a y e d matching t o sample e r r o r s are not always due t o f o r g e t t i n g . B e h a v i o u r A n a l y s i s L e t t e r s , 1, 317-323. W i l k i e , D.M., Sp e t c h , M.L., & Chew, L. (1981) The r i n g doves s h o r t - t e r m c a p a c i t y f o r s p a t i a l i n f o r m a t i o n . A n i m a l B e h a v i o r , 29, 639-641. W i l k i e , D.M., & Summers, R.J. (1982) Pigeo n s s p a t i a l memory: F a c t o r s a f f e c t i n g d e l a y e d matching of key l o c a t i o n . J o u r n a l of the E x p e r i m e n t a l A n a l y s i s of B e h a v i o r , 37, 45-56. 91 W i l k i e , D.M., & W i l l s o n , R.J. ( i n p r e s s ) P i g e o n s ' (Columba l i v i a ) s p a t i a l r e f e r e n c e memory i s s t a b l e over l o n g r e t e n t i o n i n t e r v a l s . B u l l e t i n of the Psychonomic S o c i e t y . W r i g h t , A.A., U r c u i o l i , P . J . , & Sands, S.F. (1986) P r o a c t i v e i n t e r f e r e n c e i n an i m a l memory. I n D.F. K e n d r i c k , M.E. R i l l i n g , & M.R. Denny ( E d s . ) , T h e o r i e s of a n i m a l memory (pp.101-125). H i l l s d a l e , NJ: Erlbaum. 

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