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 of Psychology, University of 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 Polydipsia 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 with- held 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 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 manipula- tions 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