UCS Intensity and Number of CS-UCS Pairings as Determiners of Conditioned Fear r

Abstract

Thirty-six albino rats, 92 to 97 days old, were used to investigate some of the determiners of classically conditioned fear R. Three shock intensities, 0, 50, and 90 μamp., were paired with a 4-cps blinking light either 2, 6, or 12 times. The strength of the conditioned fear R was tested on 4 successive days at one trial/day and measured in terms of running speeds in an alley in which the CS was present as an obstruction. Following are the findings and conclusions: (a) The stronger the shock, within the limits of the experiment, the stronger the conditioned fear R. (b) Variations in the number of CS-UCS pairings did not yield significant differences. (c) The data strongly suggest that classically conditioned fear Rs extinguish rapidly. (d) Finally, the technique for measuring conditioned fear R strength proved to be very sensitive. It was indicated that its versatility might render it appropriate in studies of fear as well as other acquired drives.

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