The interaction of deprivation and delay of reinforcement under a fixed-ratio schedule of responding

Abstract

Interaction of deprivation and delay of reinforcement was studied in an operant framework in this experiment. Four male Sprague-Dawley rats at approximately 250 days of age served as subjects. They were exposed to a series of conditions within a counterbalanced design. The four conditions represented the orthogonal combinations of amount of delay (0 and 10 sec) and levels of deprivation (75% and 85%). Conclusions from the study concerned the finding that the effect of a delay in reinforcement is magnified by an increase in deprivation and the value of searching for such interactive effects in operant research.Delay of reinforcement has a long history of experimentation with a great variety of apparatus. Most studies have found that an increase in delay is followed by a decrease in performance. Recent research in the operant framework, however, has indicated the specificity of the effects of the delay procedure. For example, Morgan (1972) found that, in the case of fixed-ratio schedules, as the delay in reinforcement increased so did the pause after the reinforcement and before the organism begins responding for the next reinforcer (the postreinforcement pause).The effects of delay of reinforcement have also been found to interact with other variables. The relationships between sucrose concentration (McCloskey & Tombaugh, 1971), reward magnitude (Shanab, Rouse, & Cavallaro, 1973), secondary and partial reinforcement (Tombaugh, 1973), and contingency descriptions using fixed-ratio schedules (Frazier, 1973) have all been studied in recent experiments. The purpose of the present experiment is to search for an interaction between delay of reinforcement and level of deprivation. Although the effects of each have been thoroughly documented, their interactive effects in the operant setting have not been reported. METHOD SubjectsTen naive male albino rats of Sprague-Dawley stock were obtained from Harlan, Inc., Cumberland, Indiana, at approximately 100 days of age, and served as subjects. The rats were fed ad lib for 150 days, after which time six of the rats were allowed to continue ad lib and the other four rats were deprived to 80% of their weight. Deprived weights were adjusted according to the weight gain of the six rats that were fed ad lib throughout the experiment (Capaldi, 1972).This experiment is based on a portion of a thesis submitted by Larry D. Hilgert in partial fulfillment of the requirements of a masters degree at Ball State University. The study was partially supported by a grant to Gary F. Meunier by the Ball State University Office of Research. ApparatusThe test cage was a LVE Model 142-28 in a sound-attenuated chamber programmed by standard relay-type equipment located in an adjacent room. Reinforcers consisted of Noyes 45-mg food pellets_ A supply of water was maintained in the home cage. ProcedureThe four experimental rats were shaped to leverpress in the test cage and then placed on a schedule of continuous reinforcement for one session (100 reinforcers). The schedule was then gradually increased ...