Evidence for expectancy as a mediator of avoidance and anxiety in a laboratory model of human avoidance learning.

A laboratory model was developed to study human avoidance learning. Participants could avoid an electric shock signalled by a 5-s conditioned stimulus (CS) by pressing one of a set of response buttons. Self-reported shock expectancy and skin conductance were recorded during a subsequent 10-s interval before shock. Shock expectancy declined when the correct avoidance response was learned and returned when the response was unavailable. Learning transferred to another shock CS. Parallel effects were observed on skin conductance once performance anxiety was controlled by requiring responding on all trials. Learning was faster when the Pavlovian contingencies were trained before introduction of the instrumental response. The results support a cognitive model of anxiety in which performance of an avoidance response reduces expectancy of an aversive outcome and thereby reduces anxiety.