Crossing Arms Reduces Pain Intensity

A laser was used to generate a four-millisecond pinprick on their hands, which gave them a sensation of pure pain--pain with no touch. The participants experienced this stimulus with their arms at their sides, and then once again with their arms crossed. They were then asked to rate their perception of pain intensity. An electroencephalography (EEG) reading was also used to measure their electrical brain responses.

The results showed that the intensity of both laser-evoked painful sensations and electrically evoked nonpainful sensations were decreased when the arms were crossed over the midline. This was confirmed by both the participants' self-reporting and the EEG readings. The researchers found that these effects were associated with changes in the multimodal cortical processing of somatosensory information, without changes in the somatosensory-specific cortical processing of this information. The researchers believe that conflicting information between the brain's two maps, one for the person's body and the other for external space, results in a reduction of pain sensation. The study was published in the June 2011 issue of the journal Pain.

"In everyday life you mostly use your left hand to touch things on the left side of the world, and your right hand for the right side of the world - for example when picking up a glass of water on your right side you generally use your right hand,” explained lead author Giandomenico Iannetti, MD, PhD, of the UCL department of psychology. "This means that the areas of the brain that contain the map of the right body and the map of right external space are usually activated together, leading to highly effective processing of sensory stimuli. When you cross your arms these maps are not activated together anymore, leading to less effective brain processing of sensory stimuli, including pain, being perceived as weaker.”

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University College London
University of Milano-Bicocca