Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Dr. Galen Alessi

Second Advisor

Dr. Jack Michael

Third Advisor

Dr. Wayne Fuqua

Fourth Advisor

Dr. Mike Bahr


Concurrent-chain research shows that choice behavior is sensitive to differential delays to reinforcement but apparently insensitive to differential response-requirement factors. To date, however, no studies have directly investigated the effects of differential force requirements on choice behavior under concurrent-chain schedules. This relationship will be the focus of the present study.

In Experiment 1 rats responded on conventional concurrent-chain schedules and were given a choice between different terminal-link force requirements. The force requirement on one terminal-link lever was 0.25 N while the force requirement on the other lever was varied from 0.25 N to 1.51 N across conditions. For comparative purposes, initial-link reinforcement rates and force requirements were also manipulated in certain conditions. The results suggested that choice behavior was sensitive to initial-link reinforcement rates and force requirements, but comparatively insensitive to terminal-link force requirements. These results were confounded, however, by the covariation of terminal-link entries with the manipulation of the independent variable.

The problem of covariation between number of terminal-link entries and manipulation of terminal-link force was further demonstrated in Experiment 2. The design of this experiment involved regular alternations, across conditions, between two modified concurrent-chain procedures. Although the results of Experiment 2 suggested a clear preference for the low force terminal-link alternative with the response-selected initial-link schedules, these data were clearly confounded by covariation in number of terminal-link entries. In contrast, the results from conditions that employed the nonindependent initial-link schedules, which were not confounded by number of terminal-link entries, were comparatively insensitive to terminal-link force requirements. It was therefore concluded that the concurrent-chain procedure with nonindependent schedules was the appropriate procedure for the investigation of force as an independent variable.

Experiment 3 replicated several conditions of Experiment 1, but using the nonindependent procedure. The results showed that choice behavior was sensitive to initial-link force requirements and terminal-link reinforcement rates, but insensitive to terminal-link force requirements. Factors contributing to the insensitivity of choice behavior to terminal-link force requirements with concurrent-chain procedure are discussed.

Access Setting

Dissertation-Open Access

Included in

Psychology Commons