RESPONSE-INDEPENDENT EVENTS IN THE BEHAVIOR STREAM

The metaphor of the behavior stream provides a framework for studying the effects of response-independent food presentations intruded into a n environment in which operant responding of pigeons was maintained by variable-interval schedules. In the first two experiments, response r ates were reduced when response-independent food was intruded during t he variable-interval schedule according to a concomitantly present fix ed-time schedule. These reductions were not always an orderly function of the percentage of response-dependent food. Negatively accelerated patterns of key pecking across the fixed-time period occurred in Exper iment 1 under the concomitant fixed-time variable-interval schedules. In Experiment 2, positively and negatively accelerated and linear resp onse patterns occurred even though the schedules were similar to those used in Experiment 1. The variable findings in the first two experime nts led to three subsequent experiments that were designed to further illuminate the controlling variables of the effects of intruded respon se-independent events. When the fixed and variable schedules were corr elated with distinct operanda by employing a concurrent fixed-interval variable-interval schedule (Experiment 3) or with distinct discrimina tive stimuli (Experiments 4 and 5), negatively accelerated response pa tterns were obtained. Even in these latter cases, however, the respons e patterns were a joint function of the physical separation of the two schedules and the ratio of fixed-time or fixed-interval to variable-i nterval schedule food presentations. The results of the five experimen ts are discussed in terms of the contributions of both reinforcement v ariables and discriminative stimuli in determining the effects of intr uding response-independent food into a stream of operant behavior.