BEHAVIORAL AND NEURAL BIOLOGY
27, 558-563 (1979)
BRIEF REPORT Inappropriate Ingestive Behaviors Arising from Autoshaping Procedures L . D. DEVENPORT 1 Department of Psychiatry and Behavioral Sciences, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190 An apparatus was especially designed to present rats with discrete portions of ingestible substances (food pellets, water drops, oil drops) that were predictive of intermittent reinforcement, but irrelevant to physiological need. This arrangement resulted in a rapid and frequent consumption of irrelevant substances with a probability of consumption, in most cases, equal to that of consuming the reinforcer itself. Response topographies depended upon the nature of the predictive stimulus, not that of the reinforcer. The effect observed was dependent on reinforcement as nonreinforced controls engaged in no irrelevant ingestive behavior; but temporal locus of reinforcement was not critical. This phenomenon was shown by a specific aversion experiment not to depend on any possible indiscriminability of the stimuli employed. It is hypothesized that the important associative process operating in these experiments was spatial classical conditioning. A u t o s h a p i n g ( B r o w n & J e n k i n s , 1968; S c h w a r t z & G a m z u , 1977) r e f e r s to a p r o c e d u r e w h i c h y i e l d s a c l a s s o f v i g o r o u s d i r e c t e d b e h a v i o r m o s t e a s i l y o b s e r v e d in a n i m a l s r e c e i v i n g r e s p o n s e - i n d e p e n d e n t , s i g n a l e d reinf o r c e m e n t . S u b j e c t s for w h i c h a signal ( e . g . , r e t r a c t a b l e l e v e r , l i g h t e d k e y ) is p r e d i c t i v e e v e n t u a l l y b e g i n to c o n t a c t it. This b e h a v i o r u s u a l l y r e s e m bles t h a t d i s p l a y e d t o w a r d t h e r e i n f o r c e r itself, s u g g e s t i n g a c l a s s i c a l c o n d i t i o n i n g i n t e r p r e t a t i o n ( M o o r e , 1973). N e a r l y all a u t o s h a p i n g e x p e r i m e n t s e m p l o y c o n d i t i o n e d stimuli (CSs) w h i c h , if n o t c o m p l e t e l y n e u t r a l , a r e n e v e r t h e l e s s stimuli f o r w h i c h t h e s u b j e c t h a s n o e x a c t l y a d e q u a t e r e s p o n s e . P e r h a p s this n e u t r a l i t y p r o m o t e s the t e n d e n c y for stimulus substitution. T h e e x p e r i m e n t s w h i c h follow t e s t this p o s s i b i l i t y b y e m p l o y i n g n o n n e u t r a l C S s . M o r e o v e r , t h e C S s 1 This research was conducted at the State University of New York, College of Arts and Science, Geneseo, N.Y. A portion of the work was presented at the Annual Meeting of the Midwestern Psychological Association in Chicago, May, 1976. J. Devenport collaborated in all phases of the study. 558 0163-1047/79/120558-06502.00/0 Copyright © 1979 by Academic Press, Inc. All fights of reproduction in any form reserved.
CONDITIONED INGESTIVE BEHAVIOR
559
chosen are ingestible substances which possess certain physiological actions different from, and somewhat opposed to, those of the reinforcers (USs). It is of importance to know if by force of a conditioning procedure substances are consumed regardless, or in spite, of their postingestional consequences. Thirsty (water-deprived, 48 hr) or hungry (food-deprived, 60 hr) Sprague-Dawley rats (male, 50 days old) were presented with stimuli delivered by liquid and pellet dispensers onto a 25.4-cm rotating steel disk (Fig. 1), a portion of which coursed through the corner of a soundattenuated Lafayette operant chamber. This arrangement resulted, from the subject's point of view, in a wedge-shaped ledge on which stimuli would appear for 5 sec. Stimuli which were not consumed by the animal were automatically removed by a brush and cleansing sponge immediately upon their exit from the chamber. The experiments were conducted in a
TOP
. j ~ - CHAM BER
STEEL DISK
.r M° °R
|
FEEDER~
S IDE
....~j S~
~ LIQUID DISPENSERS
c---
FIc. 1. Top and side views of the apparatus used to present discrete portions of oil, water, or dry food. Disk turns in direction indicated at 0.94 rpm. Dispensed pellets were prevented from rolling by the shallow groove in which they rested. The stimulus-removal device, which is not depicted, was situated near the disk's exit from the chamber. Free stimuli (Si) were available from the recessed food cup or from an inverted water bottle fitted into the cup as illustrated.
560
L.D. DEVENPORT
darkened room and the chamber was lighted from within to permit observation through aluminized film installed on one wall. Groups receiving forward C S - U S pairings were familiarized with the chamber and source of stimuli for one session during which USs only were available. These stimuli (45 mg food pellets or 0.03 ml water drops for hungry and thirsty animals, respectively) were at first available on a stationary disk. When the US was taken the disk was advanced to expose another until three USs had been ingested. At this point the disk began to rotate and a variable-time 100 sec (VT 100-sec) schedule of US delivery continued for the rest of the session (100 US deliveries). Conditioned stimuli were paired with USs on the following 2 days. These training sessions began with 10 US-only presentations in order to ensure that the animal was responding efficiently, followed by 90 C S - U S pairings presented on a VT 100-sec schedule. For hungry animals 0.03-ml water drops served as CSs; for thirsty animals, food pellets or 0.03-ml vegetable oil drops. Thus, three groups were run and are identified as W - P * , P - W * , and O - W * (n = three per group). The CSs were dispensed 15 sec before USs. As each stimulus was exposed in the chamber for 5 sec, the interstimulus interval was 10 sec. Testing was terminated by an extinction session which consisted of 10 C S - U S pairings followed by 10 CS-only presentations. Three other groups served as CS-only controls (n = three per group). These animals were deprived and received presentations of P, W, or O; at first on the stationary disk, and later, according to the VT 100-sec schedule, on a rotating disk for the same number of sessions as C S - U S groups. The control and forward conditioning groups were provided with constant access within the chamber to stimuli which served as CSs (see Fig. 1) in order to ensure that any need for these substances was met. Although photocells and contact sensors provided reliable estimates of ingestive activities across each session, the data presented here are restricted to behavior directly observed and scored by the experimenter. This includes the 10 preliminary US-only trials, and the first and last 10 C S - U S (or CS-only) trials. TABLE 1 Mean C S s C o n s u m e d i n S e s s i o n s 2 a n d 3 Session 2
Session 3
Group
Aa
B
A
B
P-W* W-P* O-W*
8.67 10.00 10.00
5.00 10.00 10.00
8.00 10.00 10.00
7.33 9.67 10.00
a A and B, first and last 10 presentations, respectively.
561
CONDITIONED INGESTIVE BEHAVIOR
The CS-only groups thoroughly sniffed and sometimes pawed the CS. Ingestion, however, was never observed across any session. As Table 1 indicates, CS-US pairings produced quite immediate and strong effects on CS ingestion compared to the control groups [F(I,12) = 25946.84, p < .01]. In most cases the probability of CS ingestion was the same as that of the US. Ratios of CSs to USs consumed across both training sessions were: W-P*, 1.02; P-W*, 0.83; 0-W*, 1.00. The slightly lower P-W* ratio seemed to be owing to the interference of "dry mouth" with pellet consumption and was responsible for a significant effect of CS employed IF(2,12) = 361.26, p < .01]. The O-W* group was included in anticipation of this result. During extinction trials the CS-US groups ingested the following mean number of CSs (in 10 opportunities): W, 9.67; P, 4; O, 10. Control groups in a comparable session refused all stimuli IF(l,12) = 1261.51, p < .01]. Response topographies were noted for each instance of stimulus ingestion. Pellets were usually taken with the forepaws where they were held and gnawed in the common rodent posture. Ocassionally the pellet was simply scooped into the mouth and chewed. Liquids were always sniffed prior to consumption. Contact of the forepaws with these liquids seemed to be carefully avoided and ingestion, which was very thorough, was always accomplished by licking. Thus, the topography of the CR was entirely attributable to the nature of the CS, not the US; i.e., stimulus substitution was not observed. Interpretation of these results in terms of simple classical conditioning could be more easily accomplished were it not for the findings of a backward and random pairing experiment. In all details this experiment was identical to the first except that a backward (US-CS) pairing procedure was employed during session 2, and a random (Rescorla, 1967) procedure in which CS and US presentations were uncorrelated was employed in session 3. Table 2 contains the CS consumption data for each of these sessions. It is apparent that the temporal position of the CS is of no great importance; this suggests that some nonassociative factor might be responsible for the results of the experiments. TABLE 2 M e a n CSs C o n s u m e d a s a F u n c t i o n o f T e m p o r a l
Nacement
Backward
Random
Group
A~
B
A
B
P-W* W-P* O-W*
7.67 9.33 10.00
7.33 10.00 10.00
7.33 9.67 9.67
5.67 9.67 10.00
A and B, first and last 10 presentations, respectively.
562
L. D. DEVENPORT
Perhaps the animals were simply manifesting eat-then-drink or drinkthen-eat tendencies. Such an explanation, however, cannot account for the persistence of CS ingestion during extinction. Similarly, the findings might be explained in terms of adjunctive behavior (Falk, 1971), except that this class of responses also abruptly ceases with termination of reinforcement (Devenport, 1978). An adjunctive hypothesis would more properly describe the behavior directed toward the freely available sources of substances within the chamber. Visits to the foodcup or tube, although quite erratic and infrequent, seemed to vary as a function of the interval separating successive pairs of disk stimuli. The longer the interval, the more likely the visit. No more than one visit was observed in any animal during extinction. A final nonassociative explanation concerns the rat's ability to differentiate CSs from USs. Although the difference between water and food is great, the similarity of oil and water drops might lead to indiscriminate lapping of these stimuli. This hypothesis was tested by establishing an aversion to oil in four rats. They were food deprived and offered oil to drink in their home cages. After one bout of drinking, oil tubes were removed and each rat was injected (ip) with 6 cc of a 0.15 M solution of LiC1. Toxicosis was obvious within 15 min. Eight hours later laboratory chow and water were provided and the animals were permitted to recover for 48 hr. Water deprivation was instituted and procedures exactly like those applied to O-W* animals of the first experiment were followed. Animals were observed throughout the O-W* training session until O was consumed with moderate consistency. While nonpoisoned rats (experiments 1 and 2) met the 70% criterion within the first 10 trials (see Tables 1 and 2), criterion was not achieved by the poisoned animals until between the 38th and 79th CS-US pairing (U = O, p < .01). If rats were unable to differentiate O from W*, then they should have either accepted or rejected all stimuli on the disk. Because they selected W* exclusively for the first half of the session, it is concluded that the stimuli were discriminable and therefore the results of experiments 1 and 2 cannot be explained in these terms. In two respects the findings reported here are contrary to associative theory; yet, they can be assimilated. First, stimulus substitution was not observed. This finding partially confirms the hypothesis that nonneutral CSs elicit unique CR topographies, a result which does not stand alone. Timberlake and Grant (1975) employed the presentation of another rat as a CS correlated with food delivery. They found the procedure to greatly increase the amount of behavior elicited by the food-predictive rat. Importantly, the CRs were common social responses and were unrelated to feeding. Thus, the present experiments are congruent with the only other comparable study in which USs were found to provide the impetus for,
CONDITIONED INGESTIVE BEHAVIOR
563
but not the form of, responses elicited by nonneutral CSs. Uniquely they show that CRs can include ingestive behavior. Second, the present experiments diverge from ordinary classical conditioning on temporal grounds as the results obtained did not depend upon forward pairing. However, temporal factors may be most important in the formation of associations between spatially disparate stimuli; a close spatial relationship as in the present case may have allowed great temporal latitude in association formation. It is relevant to note that autoshaping (Wasserman & McCracken, 1974) and classical conditioning generally (Rescorla & Cunningham, 1979) proceed much more rapidly when the CS is situated near the source of reinforcement. It has been speculated that spatial contiguity alone might be sufficient for conditioning (Rescorla & Cunningham, 1979). The present results are in accordance with this view. REFERENCES Brown, P. L., & Jenkins, H. M. (1968). Autoshaping of the pigeon's keypeck. Journal of the Experimental Analysis of Behavior, 11, 1-8. Devenport, L. D. (1978). Schedule-induced polydipsia in rats: Adrenocortical and hippocampal modulation. Journal of Comparative and Physiological Psychology, 92, 651-660. Falk, J. L. (1971). The nature and determinants of adjunctive behavior. Physiology and Behavior, 6, 577-588. Moore, B. R. (1973). The role of directed Pavlovian reactions in simple instrumental learning in the pigeon. In R. A. Hinde & J. Stevenson-Hinde (Eds.), Constraints on Learning, pp. 159-188. New York: Academic Press. Rescorla, R. A. (1967). Pavlovian conditioning and its proper control procedures. Psychological Review, 74, 71-80. Rescorla, R. A., & Cunningham, C. L. (1979). Spatial contiguity facilitates Pavlovian second-order conditioning. Journal of Experimental Psychology: Animal Behavior Processes, 5, 152-161. Schwartz, B., & Gamzu, E. (1977). Pavlovian control of operant behavior. In W. K. Honig & J. E. R. Staddon (Eds.), Handbook of Operant Behavior, pp. 53-97. Englewood Cliffs, N.J.: Prentice-Hall. Timberlake, W., & Grant, D. L. (1975). Auto-shaping in rats to the presentation of another rat predicting food. Science, 190, 690-692. Wasserman, E. A., & McCracken, S. G. (1974). The disruption of autoshaped key pecking in the pigeon by food-tray illumination. Journal of the Experimental Analysis of Behavior, 22, 39-45.
27, 558-563 (1979)
BRIEF REPORT Inappropriate Ingestive Behaviors Arising from Autoshaping Procedures L . D. DEVENPORT 1 Department of Psychiatry and Behavioral Sciences, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190 An apparatus was especially designed to present rats with discrete portions of ingestible substances (food pellets, water drops, oil drops) that were predictive of intermittent reinforcement, but irrelevant to physiological need. This arrangement resulted in a rapid and frequent consumption of irrelevant substances with a probability of consumption, in most cases, equal to that of consuming the reinforcer itself. Response topographies depended upon the nature of the predictive stimulus, not that of the reinforcer. The effect observed was dependent on reinforcement as nonreinforced controls engaged in no irrelevant ingestive behavior; but temporal locus of reinforcement was not critical. This phenomenon was shown by a specific aversion experiment not to depend on any possible indiscriminability of the stimuli employed. It is hypothesized that the important associative process operating in these experiments was spatial classical conditioning. A u t o s h a p i n g ( B r o w n & J e n k i n s , 1968; S c h w a r t z & G a m z u , 1977) r e f e r s to a p r o c e d u r e w h i c h y i e l d s a c l a s s o f v i g o r o u s d i r e c t e d b e h a v i o r m o s t e a s i l y o b s e r v e d in a n i m a l s r e c e i v i n g r e s p o n s e - i n d e p e n d e n t , s i g n a l e d reinf o r c e m e n t . S u b j e c t s for w h i c h a signal ( e . g . , r e t r a c t a b l e l e v e r , l i g h t e d k e y ) is p r e d i c t i v e e v e n t u a l l y b e g i n to c o n t a c t it. This b e h a v i o r u s u a l l y r e s e m bles t h a t d i s p l a y e d t o w a r d t h e r e i n f o r c e r itself, s u g g e s t i n g a c l a s s i c a l c o n d i t i o n i n g i n t e r p r e t a t i o n ( M o o r e , 1973). N e a r l y all a u t o s h a p i n g e x p e r i m e n t s e m p l o y c o n d i t i o n e d stimuli (CSs) w h i c h , if n o t c o m p l e t e l y n e u t r a l , a r e n e v e r t h e l e s s stimuli f o r w h i c h t h e s u b j e c t h a s n o e x a c t l y a d e q u a t e r e s p o n s e . P e r h a p s this n e u t r a l i t y p r o m o t e s the t e n d e n c y for stimulus substitution. T h e e x p e r i m e n t s w h i c h follow t e s t this p o s s i b i l i t y b y e m p l o y i n g n o n n e u t r a l C S s . M o r e o v e r , t h e C S s 1 This research was conducted at the State University of New York, College of Arts and Science, Geneseo, N.Y. A portion of the work was presented at the Annual Meeting of the Midwestern Psychological Association in Chicago, May, 1976. J. Devenport collaborated in all phases of the study. 558 0163-1047/79/120558-06502.00/0 Copyright © 1979 by Academic Press, Inc. All fights of reproduction in any form reserved.
CONDITIONED INGESTIVE BEHAVIOR
559
chosen are ingestible substances which possess certain physiological actions different from, and somewhat opposed to, those of the reinforcers (USs). It is of importance to know if by force of a conditioning procedure substances are consumed regardless, or in spite, of their postingestional consequences. Thirsty (water-deprived, 48 hr) or hungry (food-deprived, 60 hr) Sprague-Dawley rats (male, 50 days old) were presented with stimuli delivered by liquid and pellet dispensers onto a 25.4-cm rotating steel disk (Fig. 1), a portion of which coursed through the corner of a soundattenuated Lafayette operant chamber. This arrangement resulted, from the subject's point of view, in a wedge-shaped ledge on which stimuli would appear for 5 sec. Stimuli which were not consumed by the animal were automatically removed by a brush and cleansing sponge immediately upon their exit from the chamber. The experiments were conducted in a
TOP
. j ~ - CHAM BER
STEEL DISK
.r M° °R
|
FEEDER~
S IDE
....~j S~
~ LIQUID DISPENSERS
c---
FIc. 1. Top and side views of the apparatus used to present discrete portions of oil, water, or dry food. Disk turns in direction indicated at 0.94 rpm. Dispensed pellets were prevented from rolling by the shallow groove in which they rested. The stimulus-removal device, which is not depicted, was situated near the disk's exit from the chamber. Free stimuli (Si) were available from the recessed food cup or from an inverted water bottle fitted into the cup as illustrated.
560
L.D. DEVENPORT
darkened room and the chamber was lighted from within to permit observation through aluminized film installed on one wall. Groups receiving forward C S - U S pairings were familiarized with the chamber and source of stimuli for one session during which USs only were available. These stimuli (45 mg food pellets or 0.03 ml water drops for hungry and thirsty animals, respectively) were at first available on a stationary disk. When the US was taken the disk was advanced to expose another until three USs had been ingested. At this point the disk began to rotate and a variable-time 100 sec (VT 100-sec) schedule of US delivery continued for the rest of the session (100 US deliveries). Conditioned stimuli were paired with USs on the following 2 days. These training sessions began with 10 US-only presentations in order to ensure that the animal was responding efficiently, followed by 90 C S - U S pairings presented on a VT 100-sec schedule. For hungry animals 0.03-ml water drops served as CSs; for thirsty animals, food pellets or 0.03-ml vegetable oil drops. Thus, three groups were run and are identified as W - P * , P - W * , and O - W * (n = three per group). The CSs were dispensed 15 sec before USs. As each stimulus was exposed in the chamber for 5 sec, the interstimulus interval was 10 sec. Testing was terminated by an extinction session which consisted of 10 C S - U S pairings followed by 10 CS-only presentations. Three other groups served as CS-only controls (n = three per group). These animals were deprived and received presentations of P, W, or O; at first on the stationary disk, and later, according to the VT 100-sec schedule, on a rotating disk for the same number of sessions as C S - U S groups. The control and forward conditioning groups were provided with constant access within the chamber to stimuli which served as CSs (see Fig. 1) in order to ensure that any need for these substances was met. Although photocells and contact sensors provided reliable estimates of ingestive activities across each session, the data presented here are restricted to behavior directly observed and scored by the experimenter. This includes the 10 preliminary US-only trials, and the first and last 10 C S - U S (or CS-only) trials. TABLE 1 Mean C S s C o n s u m e d i n S e s s i o n s 2 a n d 3 Session 2
Session 3
Group
Aa
B
A
B
P-W* W-P* O-W*
8.67 10.00 10.00
5.00 10.00 10.00
8.00 10.00 10.00
7.33 9.67 10.00
a A and B, first and last 10 presentations, respectively.
561
CONDITIONED INGESTIVE BEHAVIOR
The CS-only groups thoroughly sniffed and sometimes pawed the CS. Ingestion, however, was never observed across any session. As Table 1 indicates, CS-US pairings produced quite immediate and strong effects on CS ingestion compared to the control groups [F(I,12) = 25946.84, p < .01]. In most cases the probability of CS ingestion was the same as that of the US. Ratios of CSs to USs consumed across both training sessions were: W-P*, 1.02; P-W*, 0.83; 0-W*, 1.00. The slightly lower P-W* ratio seemed to be owing to the interference of "dry mouth" with pellet consumption and was responsible for a significant effect of CS employed IF(2,12) = 361.26, p < .01]. The O-W* group was included in anticipation of this result. During extinction trials the CS-US groups ingested the following mean number of CSs (in 10 opportunities): W, 9.67; P, 4; O, 10. Control groups in a comparable session refused all stimuli IF(l,12) = 1261.51, p < .01]. Response topographies were noted for each instance of stimulus ingestion. Pellets were usually taken with the forepaws where they were held and gnawed in the common rodent posture. Ocassionally the pellet was simply scooped into the mouth and chewed. Liquids were always sniffed prior to consumption. Contact of the forepaws with these liquids seemed to be carefully avoided and ingestion, which was very thorough, was always accomplished by licking. Thus, the topography of the CR was entirely attributable to the nature of the CS, not the US; i.e., stimulus substitution was not observed. Interpretation of these results in terms of simple classical conditioning could be more easily accomplished were it not for the findings of a backward and random pairing experiment. In all details this experiment was identical to the first except that a backward (US-CS) pairing procedure was employed during session 2, and a random (Rescorla, 1967) procedure in which CS and US presentations were uncorrelated was employed in session 3. Table 2 contains the CS consumption data for each of these sessions. It is apparent that the temporal position of the CS is of no great importance; this suggests that some nonassociative factor might be responsible for the results of the experiments. TABLE 2 M e a n CSs C o n s u m e d a s a F u n c t i o n o f T e m p o r a l
Nacement
Backward
Random
Group
A~
B
A
B
P-W* W-P* O-W*
7.67 9.33 10.00
7.33 10.00 10.00
7.33 9.67 9.67
5.67 9.67 10.00
A and B, first and last 10 presentations, respectively.
562
L. D. DEVENPORT
Perhaps the animals were simply manifesting eat-then-drink or drinkthen-eat tendencies. Such an explanation, however, cannot account for the persistence of CS ingestion during extinction. Similarly, the findings might be explained in terms of adjunctive behavior (Falk, 1971), except that this class of responses also abruptly ceases with termination of reinforcement (Devenport, 1978). An adjunctive hypothesis would more properly describe the behavior directed toward the freely available sources of substances within the chamber. Visits to the foodcup or tube, although quite erratic and infrequent, seemed to vary as a function of the interval separating successive pairs of disk stimuli. The longer the interval, the more likely the visit. No more than one visit was observed in any animal during extinction. A final nonassociative explanation concerns the rat's ability to differentiate CSs from USs. Although the difference between water and food is great, the similarity of oil and water drops might lead to indiscriminate lapping of these stimuli. This hypothesis was tested by establishing an aversion to oil in four rats. They were food deprived and offered oil to drink in their home cages. After one bout of drinking, oil tubes were removed and each rat was injected (ip) with 6 cc of a 0.15 M solution of LiC1. Toxicosis was obvious within 15 min. Eight hours later laboratory chow and water were provided and the animals were permitted to recover for 48 hr. Water deprivation was instituted and procedures exactly like those applied to O-W* animals of the first experiment were followed. Animals were observed throughout the O-W* training session until O was consumed with moderate consistency. While nonpoisoned rats (experiments 1 and 2) met the 70% criterion within the first 10 trials (see Tables 1 and 2), criterion was not achieved by the poisoned animals until between the 38th and 79th CS-US pairing (U = O, p < .01). If rats were unable to differentiate O from W*, then they should have either accepted or rejected all stimuli on the disk. Because they selected W* exclusively for the first half of the session, it is concluded that the stimuli were discriminable and therefore the results of experiments 1 and 2 cannot be explained in these terms. In two respects the findings reported here are contrary to associative theory; yet, they can be assimilated. First, stimulus substitution was not observed. This finding partially confirms the hypothesis that nonneutral CSs elicit unique CR topographies, a result which does not stand alone. Timberlake and Grant (1975) employed the presentation of another rat as a CS correlated with food delivery. They found the procedure to greatly increase the amount of behavior elicited by the food-predictive rat. Importantly, the CRs were common social responses and were unrelated to feeding. Thus, the present experiments are congruent with the only other comparable study in which USs were found to provide the impetus for,
CONDITIONED INGESTIVE BEHAVIOR
563
but not the form of, responses elicited by nonneutral CSs. Uniquely they show that CRs can include ingestive behavior. Second, the present experiments diverge from ordinary classical conditioning on temporal grounds as the results obtained did not depend upon forward pairing. However, temporal factors may be most important in the formation of associations between spatially disparate stimuli; a close spatial relationship as in the present case may have allowed great temporal latitude in association formation. It is relevant to note that autoshaping (Wasserman & McCracken, 1974) and classical conditioning generally (Rescorla & Cunningham, 1979) proceed much more rapidly when the CS is situated near the source of reinforcement. It has been speculated that spatial contiguity alone might be sufficient for conditioning (Rescorla & Cunningham, 1979). The present results are in accordance with this view. REFERENCES Brown, P. L., & Jenkins, H. M. (1968). Autoshaping of the pigeon's keypeck. Journal of the Experimental Analysis of Behavior, 11, 1-8. Devenport, L. D. (1978). Schedule-induced polydipsia in rats: Adrenocortical and hippocampal modulation. Journal of Comparative and Physiological Psychology, 92, 651-660. Falk, J. L. (1971). The nature and determinants of adjunctive behavior. Physiology and Behavior, 6, 577-588. Moore, B. R. (1973). The role of directed Pavlovian reactions in simple instrumental learning in the pigeon. In R. A. Hinde & J. Stevenson-Hinde (Eds.), Constraints on Learning, pp. 159-188. New York: Academic Press. Rescorla, R. A. (1967). Pavlovian conditioning and its proper control procedures. Psychological Review, 74, 71-80. Rescorla, R. A., & Cunningham, C. L. (1979). Spatial contiguity facilitates Pavlovian second-order conditioning. Journal of Experimental Psychology: Animal Behavior Processes, 5, 152-161. Schwartz, B., & Gamzu, E. (1977). Pavlovian control of operant behavior. In W. K. Honig & J. E. R. Staddon (Eds.), Handbook of Operant Behavior, pp. 53-97. Englewood Cliffs, N.J.: Prentice-Hall. Timberlake, W., & Grant, D. L. (1975). Auto-shaping in rats to the presentation of another rat predicting food. Science, 190, 690-692. Wasserman, E. A., & McCracken, S. G. (1974). The disruption of autoshaped key pecking in the pigeon by food-tray illumination. Journal of the Experimental Analysis of Behavior, 22, 39-45.
