title: Laterality of pain: modulation by placebo and participants' paranormal belief.
abstract: OBJECTIVE
  To investigate the effects of placebo and paranormal belief on the laterality of pain perception.
  
  
  BACKGROUND
  The right hemisphere is dominantly involved in both the mediation of pain sensation and the belief in paranormal phenomena. We set out to assess a possible influence of long-term belief systems on placebo analgesia in response to unilateral nociceptive stimuli.
  
  
  METHODS
  Forty healthy participants (20 high and 20 low believers as indexed by the Magical Ideation Scale) underwent a placebo analgesia study measuring stimulus detection, pain threshold, and pain tolerance by electrostimulation on the right and left hand. Placebo treatment consisted of the application of a sham cream on the hands.
  
  
  RESULTS
  Placebo had a positive influence on pain perception in the 3 variables. Enhanced pain sensitivity for the left side was only found for the disbelievers. Placebo treatment resulted in a double dissociation: in believers, it increased tolerance exclusively on the left side, in disbelievers on the right side.
  
  
  CONCLUSIONS
  Our results confirm laterality effects in pain perception. However, only disbelievers conformed to the expected higher left-sided sensitivity. Placebo effects were dissociated between believers and disbelievers suggesting that short-term reactions to a placebo are modulated by a person's long-term belief system.
authors.affiliation: Department of Neurology, Neuropsychology Unit, University of Zürich, CH-8091 Zürich, Switzerland. cklemenz@gmx.ch
authors.forename: Caroline
authors.initials: C
authors.lastname: Klemenz
authors.forename: Marianne
authors.initials: M
authors.lastname: Regard
authors.forename: Peter
authors.initials: P
authors.lastname: Brugger
authors.forename: Oliver
authors.initials: O
authors.lastname: Emch
mesh_terms: D000328:Adult; D003469:Culture; D004558:Electric Stimulation; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000523:psychology*; D010147:Pain Measurement / Q000523:psychology; D017288:Pain Threshold / Q000523:psychology*; D015990:Placebo Effect; D011795:Surveys and Questionnaires