Response strength and conditioned stimulus intensity.

Abstract

Two experiments were run to test the hypothesis that conditioned stimulus (CS) intensity is directly related to response strength. In expt. 10 albino rats were trained to avoid electric shock by responding to 1 of a series of 6 lights of different intensities. Every light was used as CS, in a balanced order, for every subject. Three measures of response strength (probability of occurrence, speed of response, and response amplitude) during training were significantly related to CS intensity (p=0.05 or better). In expt. 32 rats were run in the same avoidance situation, with 4 intensities of CS. Each of 4 groups of 8 subjects each was trained to a different intensity. Each training group was then split, and 2 subjects from each training group were extinguished at each intensity. Performance measures (the same as in expt.) during training were significantly related to CS intensity (p=0.025 or better), but extinction measures were related neither to intensity of training lights nor to intensity of extinction lights. In general, results support the postulation of a stimulus intensity effect on response strength but suggest that the effect is on performance rather than learning.