Response-independent food delivery and behavioral resistance to change.

Response-independent food was delivered during a dark-key phase between two multiple-schedule components to explore its disruptive effects on responding. Responding in components was maintained by separate variable-interval 120-s schedules, with a 2-s reinforcer in Component 1 and a 6-s reinforcer in Component 2. Across conditions the rate and duration of response-independent food presentations were manipulated. The results showed that response rates in both components decreased as a function of the duration and the rate of response-independent food presentations; moreover, the decrease in response rate relative to the baseline level was larger in Component 1 than in Component 2. These findings were consistent with expectations from behavioral momentum theory, which predicts that if equal disruption (response-independent food in this case) is applied to responding in two components, then the ratio of response-rate change in Component 1 versus Component 2 should remain constant, irrespective of the magnitude of that disruption.