The incubation theory of fear/anxiety: experimental investigation in a human laboratory model of Pavlovian conditioning.

The aim of this work was to test Eysenck's incubation theory of fear/anxiety in human Pavlovian B conditioning of heart rate (HR) responses. The conditioned stimuli (CSs) were phobia-relevant slides (snakes and spiders) and the unconditioned stimuli (UCSs) were aversive noises. The subjects were presented with two levels of noise intensity during acquisition and three levels of nonreinforced CS presentation (CS-only) in a delay differential (CS+/CS-) conditioning paradigm (2 x 3 x 2). Consistent with the incubation theory, conditioned HR acceleratory responses were sustained (resistance to extinction) for high-noise intensity and short-presentations of CS-only subjects. During the extinction phase, HR acceleratory responses quickly extinguished in low-noise intensity groups after the first presentations of CS-only. These findings were interpreted as support for the incubation theory of phobic fear.