It is well-known that unpredictable occurrences of aversive events can produce various disturbances in the organism. Less is known about possible other relevant aspects of predictability. In the present experiment the hypothesis was tested that sudden (unpredictable) increases in the intensity of a painful UCS contribute to the development and maintenance of fear of the UCS. In the experimental condition, Ss received 17 painful electrical stimulations of medium intensity, alternated with three strong stimulations. In the control group, Ss received 20 strong stimulations which followed a predictable pattern because they were of constant intensity. Subjective fear ratings and autonomic responses (SCR, HRR) to a warning signal that preceded the UCS were higher in the experimental condition than in the control group, despite the fact that the control group received more stimuli of the high intensity level. Before experimental manipulation HR deceleration afterher the warning stimulus was observed in both groups. The experimental manipulation resulted in HR acceleration after the warning stimulus, while the control Ss continued to show a deceleration. These findings support the notion that unpredictability of UCS intensity is important for the acquisition of fear.
|Number of pages||11|
|Journal||Journal of Psychophysiology|
|Publication status||Published - 1992|