The Stimulus Properties of Change in Magnitude of Reinforcement

Abstract

Summary The major purpose of the present experiment was to demonstrate the incentive and discriminative stimulus (SD) properties of a change in magnitude of reinforcement. This was accomplished by testing 32 albino female rats in a differential instrumental conditioning paradigm and correlating various shifts in magnitude of reinforcement (and, therefore, incentive) on the discriminative stimulus trial (trial SD) with magnitude of reward on the next trial (trial SD + 1). A 2 × 2 factorial design was utilized with two magnitudes of reward on trial SD (incentive factor) and two magnitudes of reward on trial SD + 1 (discrimination factor). Early in acquisition only significant incentive effects were present. Late in acquisition analyses revealed both incentive effects and the formation of a discrimination with change in magnitude of reward as the SD. Results were discussed in terms of their implications for future analyses of partial and varied reward conditions and incentive contrast effects.