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This study addressed the question of whether or not a stimulus paired with the termination of shock would acquire a positive conditioned reinforcing function. Previous investigators have suggested that a stimulus paired with shock termination must increase the frequency of a response upon which it is made contingent. This test for conditioned reinforcement is incomplete because multiple stimulus functions will be established during conditioning trials that can influence the rate of responding. The solution to this multiple stimulus control problem involved the effects of reinforcement upon events antecedent to the criterion response. Reinforcement results in the establishment of discriminative stimulus control. The test for conditioned reinforcement from shock termination, therefore, would involve using the presumed conditioned reinforcer to establish discriminative control for a response. Subjects were four male albino rats of the Wistar strain. The experimental procedure was divided into three phases. The initial phase involved consecutive trials in which a tone was paired with shock offset. The next phase continued tone/shock offset pairings and, in addition, the tone alone was presented sometimes for establishment of a lever press. In the third phase an attempt was made to bring the lever press under the discriminative stimulus control of a light. A successful response shaping effect was obtained for two of the four rats. There was no establishment of discriminative stimulus control for level pressing for the two rats who proceeded to the discrimination test for conditioned reinforcement. Conditioned reinforcement from shock termination was not revealed in this study. The establishment of stable discriminative control over the criterion response would require a strong reinforcer relative to the other established stimulus functions. Future research should concentrate on developing procedures to maximize the conditioned reinforcing properties while minimizing the control from competing stimulus functions.

No description available.

The experiments described in this thesis examined post-extinction recovery phenomena following classical conditioning in the rabbit. The first series of experiments examined the rate of reacquisition to the original conditioned stimulus (CS) and to a cross-modal CS following various amounts of extinction. In both the rabbit nictitating membrane (NM) preparation and rabbit heart rate (HR) conditioning, there was a graded reduction in the rate of reacquisition as a direct function of the number of extinction trials. In the rabbit NM preparation, there was also a graded reduction in the rate of acquisition to a cross-modal stimulus (CSB, e.g., light). However, concurrent recovery of responding to the original, extinguished stimulus (CSA, e.g., tone) during training with a novel, cross-modal stimulus (CSB, e.g., light), appeared uniformly robust even following extensive extinction. The second series of experiments examined the conditions necessary for concurrent recovery to occur in the rabbit NM preparation. The introduction of CSB-US pairings resulted in strong recovery of responding to CSA, while the reintroduction of the US alone failed to result in any discernable reinstatement of responding to CSA. Concurrent recovery was specific to the trained and extinguished CSA, with virtually no generalized responding to a novel cross-modal test stimulus (CSC). However, pretraining with CSB-US pairings significantly reduced the amount of recovery to CSA during subsequent CSB???US pairings. The third series of experiments revealed that concurrent recovery was specific to the extinguished stimulus (CSA) with only moderate generalization to other familiar but untrained stimuli in the same modality as CSA. Together these results indicate that concurrent recovery is not primarily the result of the unmasking of the original CSA-US association. Rather, concurrent recovery appears to be at least partially the result of learning-dependent generalization. However, in order for responding to CSB, to generalize to CSA, CSA must have been paired with the same US which is subsequently paired with CSB. Thus, the CSA-US association must be partially intact for concurrent recovery to occur. A layered network model with multiple hidden units is able to simulate rapid reacquisition, facilitated cross-modal acquisition and concurrent recovery.

Thesis (M.S.)--Northern Michigan University, 2009. / Bibliography: leaves 101-114.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 65-69). Also available on the Internet.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Psychology." Includes bibliographical references (p. 55-61).