Demonstration of behavioral contrast with adjunctive drinking

Physiology & Behavior, Vol. 15, pp. 511--515. Pergamon Press and Brain Research Publ., 1975. Printed in the U.S.A.

Demonstration of Behavioral Contrast with Adjunctive Drinking JOSEPH D. ALLEN AND JOSEPH H. PORTER

Department o f Psychology, University o f Georgia, Athens, GA 30602 (Received 3 February 1975) ALLEN, J. D. AND J. H. PORTER. Demonstration of behavioral contrast with adfunctive drinking. PHYSIOL. BEHAV. 15(5) 511-515, 1975. - In 4 food deprived but water sated rats, adjunctive drinking was initially induced and maintained in both components of a multiple FI 1 min FI 1 min food reinforcement schedule. When access to water was prevented in one component, drinking increased substantially above baseline in the other component, demonstrating positive ploydipsia contrast. When access to water was reinstated in the changed component, drinking in the unchanged component decreased again, demonstrating negative contrast. Behavioral contrast

Adjunctive behavior

Schedule-induced drinking

DEMONSTRATIONS of positive behavioral contrast have relied on the use of free operant behaviors, and have, with the recent exception of treadle pressing in pigeons [6,10], achieved a large degree of replicability. The present experiment explores the generality of this phenomenon to schedule-induced drinking or polydipsia which has been classified as an adjunctive behavior. According to Falk [2], adjunctive behavior may be differentiated from operant behavior in that it is "behavior maintained at high probability by stimuli whose reinforcing properties in the situation are derived primarily as a function of schedule parameters governing the availability of another class of reinforcers (p. 586)." For instance, polydipsia can be reliably produced in food deprived but water sated animals which obtain food pellets on an intermittent reinforcement schedule. Typically, the rat consumes about 0.5 ml of water immediately following the delivery and ingestion of each pellet. The standard paradigm used to investigate behavioral contrast employs a multiple schedule in which two independent food reinforcement schedules are presented successively to the organism, each in the presence of a different stimulus [9]. Typically, response rates are first stablized and usually equated by assigning equivalent variable-interval (VI) reinforcement schedules to each component. Subsequently, reinforcers are reduced or withheld altogether in one component while the reinforcement schedule in the other, constant, component remains unchanged. The positive contrast which results from this manipulation is objectively defined as a response rate increase in the constant component which exceeds its baseline rate and in so doing changes in a direction opposite to the response rate change induced by the schedule

Polydipsia

manipulation in the other component. Implicit in this definition, however, is the theoretical assumption that drive maintenance conditions in the constant component have not been systematically affected by the schedule manipulations produced in the altered component. For example, were the reinforcers sufficiently frequent or large in magnitude, their subsequent absence in one component could lead to compensatory changes in drive operating in the unchanged component and thus could account for changes in response rate in that component. Accordingly, reinforcers are typically assigned by schedules which provide infrequent assignment of small amounts of food. This assumption underlying the definition of behavioral contrast has been elaborated here since it bears importantly upon recent reports of contrast-like phenomena with schedule-induced drinking. For example, Jacquet [7] recorded the amount of drinking which occurred at a continuously available water source while lever pressing in rats was maintained by multiple VI VI food reinforcement schedules. She reported that with schedule changes in one component the relative frequency of licking in the unchanged VI 1 min component matched the relative frequency of reinforcement in that component and that all animals exhibited marked positive contrast in drinking in the constant component when the second component was changed from VI 1 rain to extinction. More recently, Allen et al. [ I ] and Porter et al. [8] have reported contrast-like effects with drinking induced by fixed and variable second-order schedules of food reinforcement. Rats shifted from a fixed-interval (FI) 1 min baseline schedule to second-order schedules in which 1 min intervals often terminated without a pellet, exhibited increased drinking following intervals that terminated with

1This study was supported by Contract DADA17-73-3007 from the U. S. Army Medical Research and Development Command to B. N. Bunnell, I. S. Bernstein and J. D. Allen. The authors wish to thank Joseph W. Watson for his assistance in the planning and conduct of this study. 511

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ALLEN AND PORTER

a pellet. Drinking exceeded that induced by the FI 1 min baseline schedule and contrasted with the absence of drinking following intervals in which pellets were omitted. None of these designs, however, has met the implicit assumptions underlying the operational definition of behavioral contrast, and thus increases in drinking could be attributed to factors other than response or reinforcement rate changes in the altered component. For instance, all have permitted food reinforcement frequency to vary between the components, and since the food reinforcement schedule is recognized as a necessary drive operation for adjunctive drinking [2,4], the assumption of constant drive maintenance for the behavior has been violated. Secondly, the primary reinforcer for adjunctive drinking, that is water, has been freely available to the animals throughout the session, whereas in the typical contrast paradigm, access to the reinforcer for the behavior under study is deliberately manipulated. In the present study, these departures from standard procedure were rectified by maintaining a constant schedule of food reinforcement for lever pressing throughout each session while water availability was selectively manipulated in one component of a concurrent multiple schedule of water reinforcement. These alterations thus effected a polydipsia contrast paradigm which is both procedurally and theoretically analogous to the standard paradigm in which behavioral contrast effects with operant behaviors have been observed.

schedule, in which the first lever press, after 1 min had elapsed from the previous reinforcer, delivered a pellet. Sessions were conducted daily and consisted of 60 FI 1 min components. Responses on the water lever were concurrently reinforced according to an FI 0.75 sec schedule. A short FI schedule was used in order to prevent a burst of responses resulting in several very brief dipper presentations. Thus, the number of dipper presentations could be used as an accurate measure of water intake. For convenience, this schedule of water reinforcement is hereafter referred to as continuous reinforcement (CRF). Initially, the water lever was placed on a MULT CRF CRF water reinforcement schedule during which a random 50 percent of the FI 1 min components was associated with the cue light on, the other 50 percent being associated with the cue light off. After drinking in both components was judged to be relatively stable, the water reinforcement schedule was changed to MULT CRF EXT. During EXT components, responses to the water lever were recorded but did not activate the water dipper. For Rats S-1 and S-4, cue light on signalled extinction and cue light off signalled water reinforcement. For Rats S-3 and S-5, the reinforcement contingencies were reversed. Finally, the schedule was returned to MULT CRF CRF in order to recapture baseline performance. Table 1 shows the number of sessions received by each animal under each condition. TABLE 1 NUMBER OF SESSIONS FOR EACH SCHEDULE

METHOD

Animals Three adult male hooded rats (Ss-1,3,4) and one adult female Holtzman rat (S-5) were used. Each animal had a varied experimental history with fixed-interval (FI) food r e i n f o r c e m e n t schedules and with schedule-induced polydipsia. They were housed individually and had free access to water in the home cage throughout the entire study. The animals were maintained at approximately 85 percent of their free-feeding weights by adjusting their daily ration of food (Purina lab chow).

Apparatus A Lehigh Valley Electronics (Model 1417) operant conditioning chamber with a sound attenuated cubicle was used. Levers were mounted in both the left-hand and right-hand positions. On the intelligence panel, the center of the food magazine was located 5.0 cm to the center of the left-hand (food) lever, and a water dipper was located 4.0 cm to the right of the center of the food magazine and 8.5 cm to the left of the center of the right-hand (water) lever. The water dipper initiated each operation from the normally-up position, and each excursion into the water trough delivered 0.1 cc to the animals. A 7 W houselight illuminated the test chamber during each session, and a 7 W white cuelight was mounted above the water lever. Both were powered by 20 V AC. A Ralph Gerbrands (Model D) pellet dispenser delivered 45 mg standard formula Noyes pellets. White noise was present throughout each session. Standard electro-mechanical programming and recording equipment were located in an adjacent room.

Procedure Throughout the entire study, responses on the food lever were reinforced according to a fixed interval (FI) 1 min

Animal

MULTCRF CRF

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RESULTS Positive polydipsia contrast was demonstrated by every rat. Figure 1 presents the mean n u m b e r of responses per interval on the water lever for both light-on and light-off components during each multiple schedule. For all animals except S-l, response rates in the two components were very similar during the initial MULT CRF CFR schedule. When the water reinforcement schedule was changed to MULT CRF EXT, responses on the water lever during the unchanged CRF component systematically increased to and remained at rates which far exceeded the baseline rate, while response rates during the extinction component declined to values below baseline. Control exerted over response cessation by the extinction component was more complete with S-1 and S-4 for which light-on signalled extinction than for S-3 and S-5 for which light-off correlated with extinction. When the MULT CRF CRF schedule was reinstated, response rates for 3 rats returned to levels which approximated those during the original baseline condition. Response rates for S-5 fell substantially but retumed to levels which were higher than those prevailing during the original baseline condition. Drinking rates, based upon the number of water dipper operations in each component, are expressed as mean ml ingested per pellet for the last 5 sessions of each condition

CONTRAST WITH ADJUNCTIVE DRINKING

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SESSIONS FIG. 1. Mean responses per interval on the water lever during light-on (open circles) and light-off (filled circles) components for each stage of the experiment. Occasional breaks in the functions of Ss 4 and 5 indicate sessions where data were lost due to equipment malfunction.

and are presented in Table 2. The water intake data closely parallel the response rate data presented in Fig. 1. In Fig. 2, separate functions relate h o w drinking was distributed a m o n g consecutive I0 sec periods o f the 1 min light-on and light-off intervals during the different stages o f the e x p e r i m e n t . Each data point represents the m e a n n u m b e r o f dipper operations during a 10 sec period averaged over the last 5 sessions o f each condition. During the initial M U L T C R F C R F schedule, drinking was m a x i m a l in the first or second I0 sec period following a pellet and fell rather steeply in a negatively accelerated fashion over the remaining periods of the interval. The effect of r e m o v i n g water availability from one o f the c o m p o n e n t s was to elevate drinking rates p r e d o m i n a n t l y during the first 4 periods o f the u n c h a n g e d c o m p o n e n t . F o r 2 rats, S-4 and S-5, the locus o f m a x i m a l drinking was shifted to a later period in the interval and, in S-5, the drinking distribution was m u c h flatter than that prevailing during the baseline schedule. When r e t u r n e d to the baseline schedule again, drinking distributions were r e c a p t u r e d in b o t h elevation and form for Rats S-1 and S-3. Drinking distributions for S-4 and S-5, although reduced in overall elevation, m o r e

TABLE 2 MEAN ML/PELLET INTAKE FOR THE LAST 5 SESSIONS OF EACH CONDITION IS SHOW_N FOR LIGHT-ON (L) AND LIGHT-OFF (L) INTERVALS Animal

S-1 S-3 S-4 S-5

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0.14 0.45 0.41 0.34

MULT CRF EXT L E 0.69 1.07

0.40 0.58 -

MULT CRF CRF L £ 0.20 0.42 0.38 0.61

0.27 0.43 0.43 0.62

nearly a p p r o x i m a t e d those prevailing during the M U L T C R F E X T schedule in form. DISCUSSION The results of the present study d e m o n s t r a t e that behavioral contrast effects occur with schedule-induced polydipsia, an adjunctive behavior, which are very similar to those r e p o r t e d with free operants, typically k e y pecking in pigeons. When access to water was r e m o v e d from one

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FIG. 2. Intra-interval drinking distributions during light-on (open circles) and light-off (filled circles) components for each stage of the experiment. component of the multiple schedule, drinking rate for each rat increased substantially in the unchanged component and remained elevated, demonstrating sustained positivepolydipsia-contrast. When access to water was reinstated in the changed component, drinking rates fell again in the unchanged component to approximately baseline levels. The latter phenomenon, a decrease in response rate in one

component as a function of a rate increase in the second component, is termed negative contrast and has been typically observed with key pecking in pigeons. It could be argued that the principle of schedule constancy had been violated with regard to the controlling relations in the unchanged component and therefore polydipsia contrast had not been conclusively demonstrated. That is, since the water reinforcement schedule (FI 0.75 sec) permitted the rate of access to water in the constant component to covary with response rate on the water lever, increases in response rate could be explained by the increased frequency of water reinforcement in that component rather than by contrasted conditions in the altered component. Two factors argue against this logic. First, the intent of this experiment was to observe contrast effects in drinking behavior, a response class which must be broadened to include ingestion of the water reinforcer within its boundary. To have artificially separated the bar pressing operant and possibly licking at the dipper from actual water ingestion, so as to maintain the latter constant, would have necessarily altered the response class under study and would have prevented direct comparision with commensurate behavioral processes occurring in other studies reporting contrast-like effects [ 1, 7, 8]. Second, had enhanced drinking rates been controlled by the increased water reinforcement frequency in the constant component, one would strongly suspect that high drinking rates would have been sustained after water reinforcement was returned to the altered component. However, as clearly shown in Fig. 1, drinking rates fell in the constant component and generally returned to levels prevailing during the original baseline condition. It might also be argued that the contrast effect was an artifact of limiting access to water during the interval by delivering it in discrete 0.1 ml amounts through an intermediary operant response. However, there are several factors which indicate that few if any constraints were placed upon the development and maintenance of normal schedule-induced drinking by these arrangements. First, the ml per pellet intakes during the MULT CRF CRF schedules (0.20 to 0.62) were within a range normally obtained by rats receiving water directly through a drinking tube on similar food reinforcement schedules [ 1 ]. Of special significance, however, is that polydipsia contrast was manifested by an elevation and general flattening of the intra-interval drinking distributions as the drinking bout was extended further into the interval. Changes in the drinking distributions were often accompanied by a shift in peak drinking frequency to a later period in the interval. Similar changes in the drinking gradients were found by Allen et al. [ 1] when rats were shifted from a FI 1 min schedule to leaner second-order reinforcement schedules. Therefore, the instances of increased drinking in the former studies reporting contrast-like effects [1, 7, 8] can probably be attributed to the operations which produce behavioral contrast rather than to alterations in the drive maintenance characteristics of the schedules, which also modulate schedule-induced drinking.

REFERENCES 1. Allen, J. D., J. H. Porter and R. Arazie. Schedule-induced drinking as a function of percentage reinforcement. J'. exp. Analysis Behav. 23: 223-232, 1975.

2. Falk, J. L. Theoretical review: the nature and determinants of adjunctive behavior. Physiol. Behav. 6: 577-587, 1971.

C O N T R A S T WITH A D J U N C T I V E D R I N K I N G 3. Flory, R. K. The control of schedule-induced polydipsia: frequency and magnitude of reinforcement. Learn. Motivat. 2: 2 1 5 - 2 2 0 , 1971. 4. Gilbert, R. M. Ubiquity of schedule-induced polydipsia. Z exp. Analysis Behav. 21: 2 7 7 - 2 8 4 , 1974. 5. Hawkins, T. D., J. F. Schrot, S. H. Githens and P. B. Everett. Schedule-induced polydipsia: an analysis of water and alcohol ingestion. In: Schedule Effects: Drugs, Drinking, and Aggression, edited by R. M. Gilbert and J. D. Keehn. Toronto: Univ. of Toronto Press, 1972. 6. Hemmes, N. S. Behavioral contrast in pigeons depends upon the operant. £ comp. physiol. Psychol. 85: 171-178, 1973.

515 7. Jacquet, Y. F. Schedule-induced licking during multiple schedules. £ exp. Analysis Behav. 17: 4 1 3 - 4 2 3 , 1972. 8. Porter, J. H., R. Arazie, J. W. Holbrook, M. S. Cheek and J. D. Allen. The effects of variable and fixed second-order schedules on schedule-induced drinking in the rat. Physiol. Behav. 14: 143-149, 1975. 9. Reynolds, G. S. Behavioral contrast. J. exp. Analysis Behav. 4: 5 7 - 7 1 , 1961. I0. Westbrook, R. F. Failure to obtain positive contrast when pigeons press a bar. £ exp. Analysis Behav. 20: 4 9 9 - 5 1 0 , 1973.