CLASSICAL CONDITIONING OF RABBITS NICTITATING MEMBRANE RESPONSE AT BACKWARD, SIMULTANEOUS, AND FORWARD CS-US INTERVALS

Employing interstimulus intervals (ISIs) of -50 msec., 0 msec., 50, 100, 200, 400, and 800 msec., it was found that: (1) groups receiving training at ISIs of 100 msec. or longer showed a marked increase in CR frequency over trials, whereas groups receiving 50-, 0-, or -50-msec. pairings showed no evidence of conditioning; (2) the ISI-CR frequency function revealed a concave-down shape in acquisition and extinction with a maximum at the 200-msec ISI; (3) the latency of CRs decreased over acquisition trials, and all conditioned groups differed from each other in mean CR latency in acquisition and extinction. The relevance of these findings to theoretical accounts of ISI effects was discussed. (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1969 American Psychological Association.