The Effects of Manipulating One Requirement of a Conjunctive Schedule on Responding in the Pigeon

Abstract

The problem. The primary purpose of the present study was to examine the effects of systematically increasing the ratio requirement of a conjunctive fixed-interval fixed-ratio schedule on responding during the fixed interval. Procedure. Three experimentally-naive homing pigeons initially trained to peck a red response key on a fixed-interval schedule (FI 180 sec) served as subjects. The inter-reinforcer response range was determined for each subject on the fixed-interval schedule. The ratio values used on the subsequent conjunctive schedules were selected from each subject's baseline response distribution. Findings. The frequency distributions of responses within each fixed interval did not systematically vary in shape as the fixed-ratio requirement was added to the fixed-interval schedule. These results were consistent across all three subjects. Subjects responded in a fixed-interval scallop on all schedules. The overall rate of responding was maintained across conditions. Conclusions. These results suggest that maintenance of responding on a conjunctive fixed-interval fixed-ratio schedule is dependent upon the selection of the ratio values from each subject's range of inter-reinforcer responses on the fixed-interval schedule. Systematic selection of the ratio requirement on this schedule appears to influence the pattern of responding observed per reinforcer. Recommendations. Maintenance of the overall response rate and fixed-interval patterning appear to depend on the manner in which the added response requirement is introduced to the subject. In order to gain an understanding of schedule-controlled behavior, researchers should carefully examine the method of response requirement selection when utilizing schedules with interval and ratio requirements.