Reinforcement of schedule-induced drinking in rats by lick-contingent shortening of food delivery

Abstract

Schedule-induced drinking has been a theoretical question of concern ever since it was first described more than 50 years ago. It has been classified as adjunctive behavior; that is, behavior that is induced by an incentive but not reinforced by it. Nevertheless, some authors have argued against this view, claiming that adjunctive drinking is actually a type of operant behavior. If this were true, schedule-induced drinking should be controlled by its consequences, which is the major definition of an operant. The present study tested this hypothesis. In a first experimental phase, a single pellet of food was delivered at regular 90-s intervals, but the interfood interval could be shortened depending on the rat's licking. The degree of contingency between licking the bottle spout and hastening the delivery of the food pellet was 100 %, 50 %, and 0 % for 3 separate groups of animals. Rats that could shorten the interval (100 % and 50 % contingency) drank at a higher rate than those that could not (0 %), and the level of acquisition was positively related to the degree of contingency. In a second phase of the experiment, all groups were exposed to a 100 % contingency, which resulted in all rats developing high levels of schedule-induced drinking. Licking is enhanced if it hastens reinforcement, and can do so at delay characteristics of those present in studies of schedule-induced drinking, thus supporting the view that adjunctive behavior is an operant.Keywords Schedule-induced drinking . Adjunctive vs. operant behavior . Lick-food contingency . Rats Schedule-induced drinking was first described by Falk when he was running an experiment with food-deprived rats on bar pressing under a variable-interval 1-minute food reinforcement schedule in which the animals had continuous access to a bottle of water (Falk, 1961). He observed that rats, despite not being water deprived, consumed large quantities of water (polydipsia) by following the regular pattern of accumulating small quantities after the delivery of each food pellet. As deprivation of food normally leads to a decrease in water intake (e.g., Bolles, 1961), and drinking was not explicitly reinforced, this excessive consumption of water was described by Falk as Babsurd^ (Falk, 1971, p. 577). The main characteristics of schedule-induced drinking are therefore that (a) it takes place after the food pellet has been delivered and (b) in an exaggerated manner. This large consumption of water occurs under an intermittent food schedule and with no apparent reason, as it does not appear to be reinforced during training. Characterization of schedule-induced drinking as an adjunctive behaviorOne of the approaches to explain schedule-induced drinking is to consider this as a phenomenon belonging to a separate category of behavior: adjunctive (Falk, 1971; see a critical analysis by Wetherington, 1982). According to this point of view, adjunctive drinking is induced by the delivery of periodic food but is not reinforced by it (see Baum, 2012, for a recent treatment of ...

Can surprising nonreward and adjunctive behavior influence each other?

“…Thus, the fact that partial reinforcement training only subtly affected the subsequent development of the adjunctive behavior of wheel running (Experiment 1), as well as the absence of transfer obtained in Experiment 2 during extinction, could indicate a lack of a frustration component during the intermittent reinforcement training. The present weak support for a mediational role of frustration counterconditioning to account for transfer to and from adjunctive behavior becomes meaningful if one considers adjunctive behavior as resulting from food reinforcement, in agreement with past (Killeen & Pellón, 2013;Pellón & Killeen, 2015) and current evidence (e.g., Álvarez, Íbias, & Pellón, 2016). Frustration counterconditioning should be expected to play a significant role if one looks at behavior as a stream of organized activities (adjunctive behavior) aiming at reward seeking, rather than considering the reduction of frustration as the source of reinforcement for adjunctive behavior.…”

Effect of Schedule-Induced Behavior on Responses of Spontaneously Hypertensive and Wistar–Kyoto Rats in a Delay-Discounting Task: A Preliminary Report

“…Distribution of licks during the response-reinforcer delay and the ITI exhibits the characteristic inverted U-shape function normally observed for schedule-induced drinking (e.g., López-Crespo et al, 2004; Íbias and Pellón, 2011; Álvarez et al, 2016). Since the delay initiated by the response becomes longer than the ITI, the inverted U-shape form is more defined in that time interval (Íbias and Pellón, 2011).…”

“…In the present study, however, when rats had the opportunity to drink both before and after food reinforcement (LL trials), they allocated licks only during pre-food (the response-reinforcer delay) and not post-food (the ITI) periods, developing licking during the ITI just when there was no response-reinforcer delay (SS trials). These data can be interpreted as if pressing the lever and licking from the spout were part of the same behavioral pattern maintained by intermittent food reinforcement (Ruiz et al, 2016), being reinforcer effective given the systematic presence of behaviors in the context of spread reinforcement in time (Killeen and Pellón, 2013; Álvarez et al, 2016).…”

“…Traditionally, schedule-induced behaviors have been included in a category different than operants (Falk, 1971) because they seem to be induced by a low probability of reinforcement (Staddon, 1977). Nevertheless, Pellón et al (2018) have recently proposed that schedule-induced behaviors are induced by events in the environment and maintained by delayed reinforcement (Killeen and Pellón, 2013; Ruiz et al, 2016; Álvarez et al, 2016).…”

“…The most studied example of schedule-induced behavior is schedule-induced drinking, which consists of a small, regular and persistent drinking after each food pellet is delivered when food-deprived rats are exposed to an intermittent food-presentation schedule (Íbias and Pellón, 2011). After some training, the high pattern of drinking concentrates in the first 15–20 s of the interval (Álvarez et al, 2016), although if access to water is restricted to the last part of the interval, it will develop showing a similar distribution in latter portions of the interval (López-Crespo et al, 2004).…”