The effects of shock intensity on fear incubation (enhancement): A preliminary investigation of Eysenck's theory

Rats were presented with three levels of shock intensity during acquisition followed by three levels of nonreinforced CS exposure during extinction (3 × 3) in the context of a one-way avoidance situation. Extinction effects were directly dependent upon the differential shock-intensity levels which were delivered during acquisition. Avoidance behavior was sustained and, in fact, increased (incubation) for high-shock groups despite increased duration of nonreinforced CS exposure. These results were interpreted as support for Eysenck's (1968) theory of fear incubation.