Psychology, Department of


Document Type


Date of this Version

March 1997


Published in Journal of Experimental Psychology: Animal Behavior Processes, Vol. 23 (1997), No. 3, pp. 312–324. Copyright © 1997 by the American Psychological Association. Inc. “This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.” Used by permission.


In a sample of 208 Holtzman-descended albino rats, we found evidence with 4 measures of conditioning (freezing, defecation, side crossing, and nose crossing) that a single 2-s, 1.0-mA immediate shock could condition fear to a context (Experiments 1, 2, and 4). When we reduced the shock intensity to 0.5 mA, we obtained a complete immediate-shock conditioning deficit according to all measures in Experiment 3 and to all but the defecation measure in Experiment 4. Results suggest two conclusions: (a) Differences in shock potency between laboratories may help explain discrepant findings about whether immediate shock supports contextual conditioning; (b) theories of contextual conditioning need a mechanism that permits that conditioning to result from immediate shock.