Rats that were shocked while moving down a runway escaped by moving forward on the first trial, but thereafter retreated from the shock or remained in the starting place. Other experiments tested the effect of shock on the extinction of a running response previously used to escape (or avoid) shock. After avoidance training shock during extinction did not affect the speed of extinction; after escape training it led to faster and more abrupt extinction. The results are thought to depend upon the high intensity of shock used and to support the usefulness of the fear construct. From Psyc Abstracts 36:01:1EK28S. (PsycINFO Database Record (c) 2006 APA, all rights reserved)