Psychology ETDs

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Previous within-subject manipulations of the CS-US interval (ISI) in classical conditioning have shown that if two ISIs are randomly presented, conditioning rates will be directly related to the proportion of trials during which the more optimal ISI is presented. The present study was designed to extend this finding to sensory preconditioning (SPC). Ten groups of rats were trained to bar press on a Variable­Interval 30 sec. schedule prior to the introduction of a three phase SPC paradigm. The first phase consisted of 16 pairings of light and tone, while Phase 2 established a conditioned emotional response to the tone through pairings with foot shock. Phase 3 assessed SPC by the amount of reduction in bar pressing during presentations of the light alone. In Phase 1 two distinct time intervals between light onset and tone onset (ISI) were used with the relative proportion of the more optimal ISI varied across groups at either 16/16, 12/16, 8/16, 4/16, or 0/16. Since this proportion manipulation affected overall mean ISI, three additional groups received fixed ISIs of either 11.5, 17, or 23.5 sec., which corresponded to the mean ISI of Groups 12/16, 8/16, and 4/16 respectively. Two control groups received explicitly unpaired Phase 1 and Phase 2 trials, respectively, so as to assess the contributions of pseudoconditioning. The absence of SPC in the two control groups indicated that nonassociative influences were minimal. The magnitude of SPC was linearly and quadratically related to proportion of the more optimal ISI. However, no differences were observed between each proportion group and its fixed ISI counterpart. Since SPC was assessed with an extinction procedure, each group received its original Phase 1 pairings on the day following extinction in an attempt to recover suppression. All groups showed significant suppression to the light. Thus, reinstatement of the original light-tone pairings both maintained suppression in the groups originally showing SPC and established suppression in the groups with longer ISIs.

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First Committee Member (Chair)

Douglas Peter Ferraro

Second Committee Member

G. Robert Grice

Third Committee Member

Frank Anderson Logan

Fourth Committee Member

John Paul Gluck Jr.



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Psychology Commons