Date of Graduation

1996

Document Type

Thesis

Abstract

Rats and pigeons responded under schedules of delayed reinforcement in three experiments. Two operanda were available but only one was correlated with reinforcement. In Experiment 1, either operandum could be correlated with reinforcement depending on which was pressed first. Due to this procedure the source of reinforcement varied irregularly between sessions. In Experiment 2, the operandum correlated with reinforcement was pre-determined and remained consistent within conditions. In Experiment 3, the source of reinforcement was pre-determined and varied semi-randomly. Responses were acquired without prior response shaping in the first two experiments and maintained in all three using unsignalled, resetting delays to reinforcement. Response rates were higher on the relevant operandum when it was the same as in previous sessions, and higher response rates were exhibited on the irrelevant operandum when it was relevant in the previous sessions. These results indicate that induction does not account for responding under delayed reinforcement, and the control of responding by the delayed reinforcement contingencies is affected by the subjects' history of responding on each operandum.

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