CS-US interval and US intensity in classical conditioning of the rabbit's nictitating membrane response

Abstract

Interstimulus intervals (ISIs) of 125, 250, 500, and 1000 msec. and UCS intensities of 1, 2, and 4 ma. made up a 4 * 3 factorial design with 12 male and female albino rats per cell. The 250-msec ISI produced the highest percentage of CRs and CR amplitude during acquisition. The percentage of CRs and CR amplitude was an increasing function of intensity of UCS during acquisition. Analyses of latency, temporal peak, and topography of CRs revealed that responses on CS-alone trials centered around the point at which the UCS was usually presented. Generally, CR strength (percentage of CRs and CR amplitude) was determined by both ISI and UCS intensity, whereas timing of CR (latency, peak, and topography) was determined mainly by ISI. (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1968 American Psychological Association.