Semester

Summer

Date of Graduation

2009

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Psychology

Committee Chair

Kennon A. Lattal.

Abstract

This experiment assessed effects of jackpotting, defined as the delivery of a larger than usual reinforcer, on responding of pigeons maintained by fixed-interval (FI) schedules. In baseline conditions, reinforcer duration was 1-s and all such reinforcers were delivered from the hopper located on the main work panel. During jackpot conditions, a 1-s reinforcer occasionally was replaced by a 7-s reinforcer (jackpot) delivered from a second hopper located at the rear of the chamber. Sham jackpot conditions also were studied. These sham conditions were identical to the jackpot conditions with one exception: A 1-s, instead of 7-s, reinforcer was delivered from the back hopper. Jackpotting occasionally suppressed rather than enhanced FI responding, which seems to contradict descriptions of its effects in the animal-training literature. While the subjects were not key pecking, however, they were inserting their heads into the back hopper. This result suggests that jackpots reinforce the consummatory response, thereby reducing the rate of operant responding. These findings may be related to incentive contrast, reinforcement omission, the concept of "surprise" in Pavlovian conditioning, response reinstatement, and conditioned emotional responses.

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