Cue exposure and overt fear responses as determinants of extinction of avoidance in rats.

Five groups of eight rats each were trained in a one-way avoidance apparatus, given differential posttraining exposure to shock' and/or nonshoek sides, and extinguished. During posttraining exposure fear responses were recorded using a time-sampling method. Results showed that prevention of the avoidance response in the presence of shock cues facilitated extinction; but exposure to nonshoek cues slowed extinction. Overt fear responses failed to predict significantly the order of extinction either within or between groups. The results are congruent with the assumptions that during acquisition fear responses develop to both shock and nonshoek sides, exposure reduces fear responses, and extinction speed is a function of the resultant relative aversiveness of the two sides.