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This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Graduation

Summer 5-7-2010

Document Type


Degree Name

Master of Arts (MA)


Department of Graduate Psychology


Some researchers have suggested that the discrepancy in findings between studies of resistance-to-extinction that use single-schedules and those that use multiple-schedules is the result of increased discriminability between training and extinction conditions in the single-schedule preparation, masking the true relation between reinforcer density and resistance to extinction. Because d-amphetamine has been shown to interfere with stimulus control in a number of preparations, the current study examined the effects of d-amphetamine on rats’ lever-pressing in the context of a single-schedule resistance-to-extinction preparation. During training, doses of d-amphetamine or vehicle were administered 15 min prior to sessions in which the delivery of reinforcers occurred according to variable-interval 10-s, 90-s, or 240-s schedules. A 2-hr extinction session followed the 50-min training sessions, which occurred 5-7 days per week for each rat for at least 15 sessions. Pre-session injections of d-amphetamine resulted in higher resistance to extinction across all training schedules than pre-session injections of vehicle did, but d-amphetamine did not change the direction of the relation between reinforcer density and resistance to extinction. I discuss the results in a context that emphasizes the commonalities between resistance to extinction procedures completed in discrete trials and free-operant contexts with the hope of bridging the gap between these two bodies of literature.

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