The effect of varying CS exposure duration on paradoxical enhancement of a conditioned response

Norris, Dena Lynn (1976) The effect of varying CS exposure duration on paradoxical enhancement of a conditioned response. Masters thesis, Memorial University of Newfoundland.

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Abstract

The present study investigated the phenomenon that under certain conditions the presentation of the conditioned stimulus (CS) alone leads to enhancement of the conditioned response (CR) rather than to extinction of the CR. It was further hypothesized that the personality dimensions of neuroticism and introversion were related to enhancement in that those persons high on these dimensions would tend to exhibit enhancement more than persons low on those dimensions. -- Thirty-four male subjects were used, there being eight subjects per group in two groups, and nine subjects per group in the remaining two groups. Three groups received CS (slide presentation)-UCS (a loud burst of white noise) pairings on a 76 per cent irregular reinforcement pattern. The groups differed by the duration of the CS-alone exposure each received one minute after conditioning--either 2, 60 or 300 seconds. The fourth group served as a control and received non-contingent CS and UCS presentations. At two extinction sessions held one and two weeks after conditioning the CR strength (magnitude and latency of the GSR and change in rate of Finger Pulse) was measured. The results showed: (a) that the experimental groups exhibited CR’s on unreinforced CS presentations in the conditioning session with significantly higher SSR magnitudes than the control group (p < .05); (b) that there was no evidence for enhancement since neither of the groups were responding differently on GSR magnitude in the first extinction session (p > .05) nor were they responding differently on change in rate of Finger Pulse (p > .05); (c) significant main effects were found for Sessions and Trials and an interaction effect was found for Sessions x Trials on magnitude of the GSR (p < .05); (d) significant main effects were also found for Sessions x Trials on latency of the GSR (p < .01). These results reflect the well-known extinction effect rather than the desired enhancement effect. Possible explanations of why this study failed to find evidence of enhancement are proposed along with some suggestions for future research.

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