Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Michael Perone.


Simple schedules of reinforcement typically are preferred to chained schedules of equal duration. In the current study, pigeons served in six experiments designed to test whether the juxtaposition of simple and chained schedules would engender the disruption in behavior typically observed in the transition from favorable to unfavorable conditions of reinforcement. In one set of experiments, a multiple schedule was employed in which a simple schedule alternated irregularly with a chained schedule. Whether fixed-ratio or fixed-interval schedules were employed, only half the subjects paused for an extended duration in the simple-to-chain transition, and this occurred only when the first segment of the chained schedule was short. When the option to turn off the stimuli correlated with the schedule in effect (escape) was available at the start of each component, escape occurred infrequently and inconsistently across pigeons. In another set of experiments, a (rich) schedule ending in a large reinforcer was juxtaposed with a (lean) schedule ending in a small reinforcer. In addition, either the rich or lean schedule was segmented across conditions. Inconsistent results were obtained when fixed-ratio schedules were employed; however, when fixed-interval schedules were employed, pausing was extended in the rich-to-lean transition and this effect was attenuated by segmenting the rich schedule and enhanced by segmenting the lean schedule. When the option to escape was available, escape was more frequent (or constituted a larger percentage of the session) in the rich-to-lean transition when simple schedules operated. Segmenting the lean schedule had inconsistent effects on escape. The fact that the predicted results were obtained only when fixed-interval schedules differed in reinforcer magnitude and schedule segmentation is attributed to two factors. First, perhaps it was only in this experiment that the difference in favorability across schedules was sufficient to produce noticeable disruptions in behavior. Second, response patterns suggest that the pigeons failed to respond differentially across the simple and chained fixed-ratio schedules. The results of the present study together with previous findings suggest the potential for basic research to contribute to the identification and manipulation of variables that control problem behavior in institutional settings and in everyday situations.