Postconditioning delay and intensity of shock as factors in the measurement of acquired fear.

Abstract

Two experiments were run on the classical conditioning of fear in rats and the measurement of its effect through the learning of another response (hurdle jumping). In Exp. I the effect of intensity of shock (30, 40, 50, 60, or 100 v.) used during conditioning was investigated. At each shock level one group was given forward conditioning (light-shock) and one backward conditioning (shock-light). For all groups, hurdle-jumping trials were given immediately after conditioning in which S could escape the light by jumping a hurdle and were continued on the next day. Evidence of learning following both forward and backward conditioning, was obtained but only on the second hurdle-jumping day. Performance generally improved following conditioning with the higher shock levels. The results of Exp. II indicated that learning does occur on the first day of hurdle jumping when a postconditioning delay of 1 day is used.