Local constraint of the contingent response controls rates of wheel-running and lever-pressing on an interval schedule of wheel-running reinforcement

Abstract

Three experiments assessed whether changes in rates of wheel running and lever pressing on a schedule of wheel-running reinforcement were controlled by local or overall constraint of the contingent response. In Experiment 1 rats responded on a response-initiated variable interval 15-s schedule with wheel running as reinforcement. Overall constraint (total revolutions by session) was held constant at 600 revolutions while local constraint (revolutions per reinforcement) varied from 5 to 60 revolutions. Results showed that rates of wheel running and lever pressing decreased as local constraint decreased. In Experiment 2, rats responded on the same schedule, but local constraint (revolutions per reinforcement) was held constant at 10 revolutions. Overall constraint (total revolutions) was varied from 100 to 800 revolutions. Results showed no systematic changes in rates of wheel running and lever pressing with variation in overall constraint. In Experiment 3, rats responded on the same VI schedule for 30 revolutions as reinforcement. A 4.5-s interruption during the wheel-running reinforcement (30 revolutions) occurred after 2, 5, 10, and 15 revolutions as a manipulation of local constraint. Results showed that with overall constraint (total revolutions) and total reinforcement held constant, rates of wheel running before the interruption and overall lever-pressing rates varied in a bitonic relationship with local constraint. Comparison of the results across experiments demonstrates that local constraint of contingent wheel running controls the rate of wheel running and the rate of instrumental responding for wheel-running reinforcement.