POLYDIPSIA INDUCED IN RATS BY SECOND‐ORDER SCHEDULES OF REINFORCEMENT¹

Abstract

Three rats were exposed to a second-order schedule in which fixed-interval components ended either with food or with a brief stimulus that was never paired with food. Food and the brief stimulus occurred in a random sequence (variable-ratio 2 overall schedule). Another three rats were exposed to a similar second-order schedule, the only difference being that the food or the stimulus was presented independently of operant behavior (fixed-time components). The three rats exposed to the fixed-interval components licked at a water spout after each food presentation. These rats also licked in the intervals after the brief stimulus. Although the discriminative properties of food and of the brief stimulus were identical in relation to subsequent reinforcement, licking after the stimulus was less than after food. The three rats exposed to the second-order schedules with fixedtime components also licked at the water spout after food, but these rats did not lick consistently after brief stimulus presentations.Key words: schedule-induced polydipsia, second-order schedules, nonpaired stimuli, fixedinterval components, fixed-time components, licking, lever pressing, ratsIf food-deprived rats are exposed to schedules of intermittent reinforcement, they typically ingest excessive quantities of water after each reinforcer if offered the opportunity to do so (Falk, 1961a). It has been suggested that this excessive drinking is an extreme example of postprandial drinking resulting, for example, from such factors as a dry mouth (e.g., Stein, 1964;Teitelbaum, 1966). Falk (1969), however, argued that this schedule-induced polydipsia is an example of a distinctive class of behavior, which he termed adjunctive. He suggested that adjunctive behavior is "psychogenic", and that one important condition for its occurrence is a temporarily low probability of reinforcement. The delivery of a food reinforcer in many intermittent schedules has discriminative properties resulting from the low probability of further reinforcement for some period of licking at a water spout. In simple schedules, the effects of food reinforcement in producing a dry mouth and in signalling a temporarily low probability of further reinforcement are confounded. The use of second-order schedules of reinforcement, however, may make it possible to isolate the contribution of these factors in inducing licking. Kelleher (1966) defined a second-order schedule as one in which the behavior specified by a sclhedule is treated as a unit that is itself reinforced according to some schedule of primary reinforcement. A second-order schedule in which a fixed-interval (FI) component is reinforced by a fixed-ratio (FR) overall schedule is conventionally designated FR (FI) (Kelleher, 1966). In brief-stimulus second-order schedules, completion of the component schedule is accompanied by delivery of a reinforcer such as food, or by delivery of a brief stimulus such as a flash of light, which may or may not also be delivered when food is presented. In a second-order schedule, as in ...

Factors affecting schedule-induced wood-chewing in rats: Percentage and rate of reinforcement, and operant requirement

“…This prediction has been tested using second-order schedules in which one component terminates in food while another terminates in a nonfood discriminative stimulus. The relevant studies have yielded diverse results, but all agree that drinking is considerably reduced, but not absolutely abolished, by omission of food (see review by Corfield-Sumner, Blackman, & Stainer, 1977). In Experiment 1, we confirmed that omission of food substantially reduces both the probability and the bout duration of drinking, but found that omission had relatively little effect on the probability of induced wood-chewing and no significant effect on its bout duration.…”

Stimulus‐ and Pellet‐induced Drinking During a Successive Discrimination

“…The latter outcome probably is responsible for the absence of stimulus-induced drinking in several studies because postpellet licking was established before exposure to S-(e.g., Dougan et al, 1985;Iversen, 1977;Jacquet, 1972;Porter et al, 1975;Rosenblith, 1970). In contrast, in all successful demonstrations of stimulus-induced drinking (Alferink et al, 1980;Corfield-Sumner et al, 1977;Minor & Coulter, 1982) Swas introduced before stable interim responding had developed.…”

“…Robust stimulus-induced drinking has not been obtained under these conditions. In contrast, Swas introduced at the start of training in all successful demonstrations of the phenomenon (Alferink et al, 1980;Corfield-Sumner et al, 1977;Minor & Coulter, 1982). Because of the tendency of rats to alternate bouts of eating and drinking (Kissileff, 1969), food may be more relevant to drinking than are other events (see Millenson, Allen & Pinker, 1977;Minor & Coulter, 1982, for a thorough discussion).…”

Associative control of schedule-induced drinking

“…They have utilized second-order reinforcement schedules (sometimes referred to as percentage reinforcement schedules) with either fixed-interval components (Allen & Porter, 1977;McCoy & Christian, 1976;Porter, Arazie, Holbrook, Cheek, & Allen, 1975) or fixed-time components (Iversen, 1977), and have consistently failed to fmd schedule-induced polydipsia during periods of nonreinforcement signaled by a brief stimulus paired with food reinforcement (i.e., CS+). Allen and Porter (1977) have shown that those few studies (Corfield-Sumner, Blackman, & Stainer, 1977; The authors' mailing address is: Department of Psychology, Virginia Commonwealth University, Richmond, VA 23284. Porter & Kenshalo, 1974;Rosenblith, 1970) showing polydipsia after presentation of a CS+ probably obtained "spillover" drinking from a previous interval that followed pellet delivery.…”