Effects of extinction on wheel running and lever pressing as operant behaviors within a multiple schedule of reinforcement

Rats were exposed to a multiple schedule in which they pressed a lever on a variable-ratio schedule for wheel-running reinforcement in one component and pressed a lever or completed wheel revolutions on a fixed-ratio schedule for 15% sucrose solution reinforcement in the changed component. After 20 sessions, sucrose reinforcement was replaced with water (0% sucrose) and operant behavior (lever pressing or wheel running) placed on extinction in the changed component. Extinction markedly reduced lever-pressing rate and lengthened postreinforcement pause (PRP) duration in the changed component, but only modestly reduced wheel-running rate and actually shortened PRP duration. In the unchanged component, when either lever pressing or wheel running were placed on extinction in the changed component, wheel-running rate, lever-pressing rate, and wheel-running reinforcers decreased while PRP duration increased in the changed component. The effect of extinction differed in the changed component as a function of the type of operant, but not in the unchanged component. This ruled out the automatic reinforcement effect of wheel running as a bridge for transferring the extinction effect between components. Arousal, negative induction, and a shift from high to low valued reinforcement were considered as potential accounts for the effects in the unchanged component.