Effects of UCS intensity and duration of exposure of nonreinforced CS on conditioned electrodermal responses: an experimental analysis of the incubation theory of anxiety.

Eysenck's incubation theory of fear or anxiety was examined in a human Pavlovian conditioning experiment with skin-conductance responses as the dependent variable. The conditioned stimuli (CSs) were fear-relevant slides (snakes and spiders) and the unconditioned stimuli (UCSs) were aversive tones. Different groups of subjects were presented two tone intensities during the acquisition phase and three durations of nonreinforced CS (extinction phase) in a delay differential conditioning paradigm. Resistance to extinction of conditioned skin-conductance responses (conditioned fear responses) exhibited was largest for high intensity of tone and short presentations of the nonreinforced CS (CS+presented alone). The result tends to support Eysenck's incubation theory of anxiety.