BEHAVIORAL-CONTRAST USING A PERCENTAGE REINFORCEMENT PROCEDURE

Behavioral contrast can be defined as an inverse relation between rate of responding in one component of a multiple schedule and the conditi ons of reinforcement in the other component. The present study was an attempt to produce contrast by changing the probability of reinforceme nt. Four pigeons pecked a key for mixed-grain reinforcers delivered by a two-component multiple schedule. In each component, reinforcers wer e scheduled by a variable-interval schedule and were delivered at a ce rtain probability (i.e., a percentage reinforcement procedure). In con trast conditions, the probability of reinforcement in the second compo nent was either increased or decreased. In some contrast conditions, n onreinforcement in the second component was signaled and in other cond itions it was not. Nonreinforcement was always signaled in the first c omponent. The changes in probability of reinforcement produced contras t. However, the contrast produced by changes in probability of reinfor cement could not be differentiated from the contrast produced by chang es in the rate at which reinforcers were delivered. The present result s demonstrate that behavioral contrast can occur when a percentage rei nforcement procedure is employed. Furthermore, although the results do not suggest that probability of reinforcement can be varied independe ntly, they do extend the generality of contrast and its potential prac tical implications. (C) 1997 Academic Press.