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When interreinforcement intervals were equated, pigeons demonstrated little or no preference between reinforcement after a delay interval and reinforcement presented on a fixed‐interval schedule. The small preferences sometimes found for the fixed interval (a) were considerably smaller than when the delay and fixed intervals differed in duration, and (b) were caused by the absence of light during the delay. These results suggest that the effects of delayed reinforcement on prior responding can be reproduced by imposing a temporally equal fixed‐interval schedule in place of the delay; and, therefore, that the time between a response and reinforcement controls the probability of that response, whether other responses intervene or not.

In two experiments, the free‐operant shock‐avoidance behavior of rats was punished by electric shock. Two aspects of the schedule of response‐produced shock were varied: the frequency of punishment over time (punishment density) and the temporal interval between the punished response and the punishment (punishment delay). The general finding was that response‐produced shock suppressed avoidance responding under most of the density‐delay combinations studied, and suppression increased as a function of increases in density and decreases in delay. Rate increases of small magnitude also were observed, usually as an initial reaction to the lesser densities and longer delays. Response suppression, while decreasing the number of punishment shocks received, also increased the number of avoidance shocks, so that the total number of shocks received usually was greater than the minimal number possible. The results were discussed from the standpoint of similarities between the effects of punishing positively and negatively reinforced behavior. The finding that subjects did not minimize the total number of shocks suggested that when avoidance behavior is punished, responding is controlled more by the local consequences of responding than by overall shock frequencies during the course of the session.

This study was addressed to the problem of applying behavior modification techniques on a group basis to a class of retarded students with “attentional deficits”. Seven boys, age 8 to 15 yr, characterized as showing severe “attentional” problems or disruptive behavior in their respective classrooms, participated daily for 30‐min sessions in a special class over a 1.5‐month period. In each session, verbal instructions were given to the class as a whole. In control sessions, each appropriate instruction‐following response by a child produced praise for that child. In experimental sessions, appropriate responses also produced tokens exchangeable for tangible reinforcers after the session. Token reinforcement differentially maintained instruction‐following behavior in four children while one responded appropriately to most instructions and a second improved continuously during the study. While the data suggest that the present approach can be successfully applied to the alteration of instruction‐following behavior in retarded children, its major contribution may be that of providing objective quantitative information about such behavior.