• Kenneth M Prkachin.
• Department of Psychology, University of Northern British Columbia, 3333 University Way, Prince George, BC, Canada V2N 4Z9. kmprk@unbc.ca
• Pain. 2005 Apr 1; 114 (3): 328-38.

AbstractThe 'facial feedback hypothesis' suggests that inhibiting or exaggerating pain displays produces parallel effects on subjective experience. Research on the regulation of emotional expressions suggests that the act of self-regulation may be detectable in the properties of facial behavior. Both issues were examined in this study. Healthy young volunteers were videotaped while they were exposed to electric shocks varying in intensity. Participants in the Augment group were instructed to exaggerate their facial reactions to the shocks. Participants in the Attenuate group were instructed to inhibit their reactions. Controls simply responded to the shocks. All groups rated the pain of each shock on numeric, sensory and affective scales. In subsequent phases, judges rated the intensity of pain displays for all participants, and facial reactions were measured with the Facial Action Coding System. Results provided no support for the facial feedback hypothesis. Judges' ratings of participants' pain indicated that the augment instructions produced distinct alterations in pain expression. The control and inhibit groups showed linear increases in pain expression with increasing pain intensity, which did not differ significantly. Fine-grained analysis of participants' facial behavior provided evidence that pain augmentation was accompanied by topographic changes in pain expression. Parallels with existing studies, methodological issues and practical implications of the findings are discussed.

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