On the Reliability of Blocking Effects in Response Acquisition with Delayed Reinforcement

Background: Stimuli perfectly correlated with impending access to food have been shown to both attenuate response rates and to prevent response acquisition when they occur during delays to reinforcement. One explanation of these findings is that the stimulus better predicts food than the operant response itself, and therefore, “blocks” learning of the response-reinforcer association. That such stimuli can abolish operant learning implies a breakdown in an organism’s ability to detect causality between its own behavior and effects on the environment.

Method: Two response acquisition experiments in which a stimulus preceded food delivery were conducted. In one experiment, an attempt was made to replicate the prevention of response acquisition using a non-resetting delay procedure that parallels those that result in overshadowing. In a second experiment, stimulus-food pretraining was given to provide a better parallel to typical respondent-conditioning blocking procedures.

Results: Under neither circumstance was response acquisition prevented.

Discussion: The generality and robustness of blocking the response-reinforcer association in operant response acquisition is questioned.