Sources of control over schedule-induced drinking produced by second-order schedules of reinforcement

Abstract

In Experiment 1, schedule-induced polydipsia was studied in rats reinforced by both simple and second-order fixed-interval 1 min schedules while session length, position of the drinking tube, and magnitude of the pellet reward were varied. Pellet-induced drinking decreased with successive transitions from simple to second-order schdules; however, drinking did not follow stimuli associated with pellet delivery until the reward magnitude was raised from 1 to 5 pellets. Neither session length nor tube position affected drinking. Poststimulus drinking received closer analysis in Experiment 2, where tandem, nonpaired and delayed or simultaneous paired brief stimulus second-order schedules, which were either fixed or variable, assigned large pellet magnitudes to rats. No evidence of adjunctive, stimulus-induced drinking was found. Occasions of drinking during poststimulus intervals were classified as either resumption of postpellet drinking or as low-rate terminal behavior which was unaffected by pairing relations between stimuli and pellets or by schedule class. No support was found for either discriminative or conditioned stimulus interpretations of schedule-induced polydipsia.