The reason why we naturally clutch our hand when it gets hurt has been revealed in a new study.
University College London researchers said that self-touch offers significant relief for acute pain under experimental conditions - the relief comes from a change in the brain's representation of the rest of the body.
"We show that levels of acute pain depend not just on the signals sent to the brain, but also on how the brain integrates these signals into a coherent representation of the body as a whole," said Patrick Haggard.
Haggard and his colleague Marjolein Kammers studied the effects of self-touch in people who were made to feel pain using an experimental condition known as the thermal grill illusion (TGI).
"In our version, the index and ring fingers are placed in warm water and the middle finger in cold water. This generates a paradoxical feeling that the middle finger is painfully hot," Haggard explained.
When TGI was induced in an individual's two hands and then the three fingers of one hand were touched to the same fingers on the other hand immediately afterwards, the painful heat experienced by the middle finger dropped by 64 percent compared to a condition without self-touch.
The results suggest importance of body representation in the experience of pain and may lead to a better understanding of the brain mechanisms involved in chronic pain as well.
"Our work suggests that therapies aimed at strengthening the multisensory representation of the body may be effective in reducing pain," Haggard said.
The report is published online on September 23 in Current Biology.