title: Voluntary facial displays of pain increase suffering in response to nociceptive stimulation.
abstract: Facial expressions of pain are an important part of the pain response, signaling distress to others and eliciting social support. To evaluate how voluntary modulation of this response contributes to the pain experience, 29 subjects were exposed to thermal stimulation while making standardized pain, control, or relaxed faces. Dependent measures were self-reported negative effect (valence and arousal) as well as the intensity of nociceptive stimulation required to reach a given subjective level of pain. No direct social feedback was given by the experimenter. Although the amount of nociceptive stimulation did not differ across face conditions, subjects reported more negative effects in response to painful stimulation while holding the pain face. Subsequent analyses suggested the effects were not due to preexisting differences in the difficulty or unpleasantness of making the pain face. These results suggest that voluntary pain expressions have no positively reinforcing (pain attenuating) qualities, at least in the absence of external contingencies such as social reinforcement, and that such expressions may indeed be associated with higher levels of negative affect in response to similar nociceptive input.
  
  
  CONCLUSIONS
  This study demonstrates that making a standardized pain face increases negative affect in response to nociceptive stimulation, even in the absence of social feedback. This suggests that exaggerated facial displays of pain, although often socially reinforced, may also have unintended aversive consequences.
authors.affiliation: Waisman Laboratory for Brain Imaging and Behavior, Waisman Center, Madison, Wisconsin 53705, USA. tvsalomons@wisc.edu
authors.forename: Tim V
authors.initials: TV
authors.lastname: Salomons
authors.forename: James A
authors.initials: JA
authors.lastname: Coan
authors.forename: S Matthew
authors.initials: SM
authors.lastname: Hunt
authors.forename: Misha-Miroslav
authors.initials: MM
authors.lastname: Backonja
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Davidson
mesh_terms: D000328:Adult; D000339:Affect / Q000502:physiology; D001143:Arousal / Q000502:physiology; D001519:Behavior; D015928:Cognitive Behavioral Therapy / Q000379:methods; D004644:Emotions / Q000502:physiology*; D005145:Face / Q000502:physiology*; D005149:Facial Expression; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D009619:Nociceptors / Q000502:physiology; D010146:Pain / Q000523:psychology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000523:psychology*; D014836:Volition / Q000502:physiology