Perceptual Preparedness in Man: Brief Forewarning Reduces Electrodermal and Psychophysical Response to Noxious Stimulation

The finding that the skin conductance response (SCR) to a noxious stimulus is reduced by a warning has been attributed to the information the warning conveys or, alternatively, to interference with the SCR to the stimulus by the preceding SCR to the warning. The purpose of this study was to test whether a low‐intensity warning stimulus can reduce the SCR to a noxious stimulus independently of SCR interference and produce similar reductions in subjective judgments of stimulus intensity. Eighty subjects were exposed to 30 pairings of a warning with a 98‐dB (SPL) noise. The interval between warning and noise was varied (0.5, 1, 3, 11 sec) from one pairing to another. Contrary to the SCR‐interference hypothesis, there was a significant linear decrease in the SCR to noise from 0‐ to 11‐sec warning trials. Warnings of 1 sec also significantly reduced magnitude estimations of noise intensity. A control procedure with an innocuous 68‐dB tone substituted for the noise indicated that the SCR to innocuous stimuli may also be reduced by warnings, but that the corresponding magnitude estimations are not similarly affected.