Reinforcer Efficacy, Response Persistence, and Delay of Reinforcement

In an evaluation of the effects of delayed reinforcement on response persistence, two pigeons were exposed to a series of conditions in which reinforcement that either immediately followed or was delayed from the response that produced it alternated across blocks of sessions. Responding was maintained by a progressive-ratio schedule in which the response requirements incremented for successive reinforcers. The effects of signaled and unsignaled delay values of 1, 5, 10, and 20 s were investigated. In general, responding was more persistent, as measured as the point at which responding ceased for 300 s, with shorter delays, regardless of whether the delays were correlated with a distinct stimulus (that is signaled) or not. The results complement earlier findings showing that reinforcement delays affect reinforcer efficacy or response persistence by showing similar effects using an index of response strength that is independent of response rate. They also extend the general effects of delay of reinforcement to a schedule in which they previously have not been demonstrated.