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Laterality of Pain: Modulation by Placebo and Participants' Paranormal Belief

Klemenz, Caroline MSc; Regard, Marianne PhD; Brugger, Peter PhD; Emch, Oliver MSc

Cognitive and Behavioral Neurology: September 2009 - Volume 22 - Issue 3 - p 186-189
doi: 10.1097/WNN.0b013e3181b27aeb
Original Studies

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.

Method: 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.

Department of Neurology, Neuropsychology Unit, University of Zürich, Zürich, Switzerland

Reprints: Caroline Klemenz, MSc, Department of Neurology, Neuropsychology Unit, University Hospital Zürich, Frauenklinikstr, 26, CH-8091 Zürich, Switzerland (e-mail:

Received for publication May 7, 2008; accepted April 19, 2009

© 2009 Lippincott Williams & Wilkins, Inc.