Do Intensity Ratings and Skin Conductance Responses Reliably Discriminate Between Different Stimulus Intensities in Experimentally Induced Pain?

The present study addresses the question whether pain-intensity ratings and skin conductance responses (SCRs) are able to detect different intensities of phasic painful stimuli and to determine the reliability of this discrimination. For this purpose, 42 healthy participants of both genders were assigned to either electrical, mechanical, or laser heat-pain stimulation (each n = 14). A whole range of single brief painful stimuli were delivered on the right volar forearm of the dominant hand in a randomized order. Pain-intensity ratings and SCRs were analyzed. Using generalizability theory, individual and gender differences were the main contributors to the variability of both intensity ratings and SCRs. Most importantly, we showed that pain-intensity ratings are a reliable measure for the discrimination of different pain stimulus intensities in the applied modalities. The reliability of SCR was adequate when mechanical and heat stimuli were tested but failed for the discrimination of electrical stimuli. Further studies are needed to reveal the reason for this lack of accuracy for SCRs when applying electrical pain stimuli. Perspective: Our study could help researchers to better understand the relationship between pain and activation of the sympathetic nervous system. Pain researchers are furthermore encouraged to consider individual and gender differences when measuring pain intensity and the concomitant SCRs in experimental settings. (C) 2011 by the American Pain Society