Arntz, A., Van Eck, M., & de Jong, P. J. (1992). Unpredictable sudden increases in intensity of pain and acquired fear. Journal of Psychophysiology, 6(1), 54-64.
13 Ss (aged 18–28 yrs) received 17 painful electrical stimulations of medium intensity, alternated with 3 strong stimulations. 13 matched controls received 20 strong stimulations, which followed a predictable pattern because they were of constant intensity. Subjective fear ratings and autonomic responses of skin conductance response, heart rate (HR), and respiration to a warning signal that preceded the unconditioned stimulus/stimuli (UCS) were higher in the ...