Psychology ETDs

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The major purpose of the present experiment was to demonstrate the incentive and discriminative stimulus (SD) properties of a change in magnitude of reinforcement. This was accomplished in a differential instrumental conditioning setting by correlating carious shifts in magnitude of reinforcement (and, therefore, incentive) on the discriminative stimulus trial (trial SD) with magnitude of reward on the next trial (trials SD+1). In condition LL a large reinforcement on trial SD was perfectly correlated with large reward on trial SD+1. Thus, incentive and the discrimination worked together to increase rate of responding on trials SE+1 relative to trial SD. In condition SS a small incentive on trial SD was correlated with a small reinforcement on trial SD+1 so that incentive and the discrimination worked together to decrease rate of responding on SD+1. Completing the factorial design, two conditions (LS and SL) determined the net effect on behavior when incentive worked against the discrimination. In condition LS a large inventive was a perfect predictor of small reward on the next trial while in condition SL a small incentive predicted a large reward on trial SD+1. The trial on which Ss received the SD was randomly received for all Ss to one of three trial positions. This was done so that change in magnitude of reward rather than temporal or ordinal position of trial cues would function as the SD. Results of major interest were the final acquisition data where the effects of the discrimination were present. Analyses indicated that both the effects of incentive and a discrimination were present. In the start and goal sections of the runway, condition LL increased response rate on trial SD+1 relative to condition LS and SL. This difference did not reach significance in the run section of the alley. Similarly, condition SS decreased in response rate on trial SD+1 relative to condition SL and LS in all section of the runway. The net effects of opposing incentive and SD properties of change in magnitude of reward after 45 experiences with the reward contingencies were neither a significant increase nor decrease in response rate for conditions SL and LS. The results revealed both rapid “one trial” incentive effects throughout the experiment as well as the formation of a discrimination with change in magnitude of reward as the SD. Results were discussed in terms of their implications for future analyses of partial and varied reward conditions. Finally, distinctions were made between the results of the present experimental procedure and the double runway paradigm where inverse incentive effects have been commonly found.

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First Committee Member (Chair)

Frank Anderson Logan

Second Committee Member

G. Robert Grice

Third Committee Member

Douglas Peter Ferraro



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Psychology Commons