Semester

Summer

Date of Graduation

2012

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Psychology

Committee Chair

Michael Perone

Committee Co-Chair

Elizabeth G Kyonka

Committee Member

Kennon A Lattal

Committee Member

Miranda N. Reed

Committee Member

Nathalie Singh-Corcoran Singh-Corcoran.

Abstract

Research on the relative aversiveness of timeout from lean and rich schedules of food delivery has yielded discrepant findings. Some research has shown that a lean schedule maintains higher avoidance response rates than a rich schedule (Thomas, 1964, 1965b; van Haaren & Anderson, 1998)---suggesting that timeout from a lean schedule is more aversive than timeout from a rich schedule---while other research has shown the opposite (D'Andrea, 1971; Richardson & Baron, 2008). The present study was based on the notion that the conflicting results may have arisen from differences in procedural details that influenced the effect of the food schedules on behavior that may compete with avoidance. At issue was whether a limited hold on consumption increases attending to the magazine (i.e., the site of food delivery) and decreases avoidance. When a limited hold is present, behavior directed toward the magazine may compete with avoidance, and thus compromise the validity of avoidance response rates as a measure of the aversiveness of timeout. When a limited hold is absent, competition between magazine-directed behavior and avoidance responding should be reduced, allowing avoidance response rates to serve as a valid measure of the aversiveness of timeout. Sixteen rats pressed a lever to avoid a 30-s timeout from a schedule of free food deliveries. Across conditions, the food deliveries--- either pellets or sucrose water---were arranged on a response-independent basis according to different variable-time (VT) schedules. The VT schedule parameter was 0.5-min, 1-min, 2-min, 4-min, and 8-min. A timeout was programmed whenever 30 s elapsed without a lever press. In Experiment 1, the Limited Hold conditions involved presentation of a dipper of sucrose water for a fixed duration. The Unlimited Hold conditions involved delivery of pellets. Because each pellet remained in the magazine until the rat retrieved it, there was no limited hold on consumption. In Experiment 1, manipulation of the presence or absence of a limited hold was confounded by the item delivered. Experiment 2 was designed to address this confound; sucrose water was delivered in every condition. In some conditions, the sucrose water deliveries incorporated a limited hold as in Experiment 1: The dipper was raised for a fixed duration. In other conditions, the dipper remained in a raised position until the rat's head entered and exited the magazine as detected by a photocell. Regardless of whether a limited hold was present or absent, the rate of avoidance increased as the rate of food delivery was raised. This indicates that the aversiveness of timeout from a schedule of free food delivery is directly related to the richness of the schedule.

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