Why We Reflexively Self-Grab When Wounded - Scientific American

January 1, 2011

2 min read

Add Us On GoogleAdd SciAm

Why We Reflexively Self-Grab When Wounded

Why the instinct to clutch a wounded part of the body helps to relieve discomfort

By Ferris Jabr

Join Our Community of Science Lovers!

Sign Up for Our Free Daily NewsletterEnter your emailI agree my information will be processed in accordance with the Scientific American and Springer Nature Limited Privacy Policy. We leverage third party services to both verify and deliver email. By providing your email address, you also consent to having the email address shared with third parties for those purposes.Sign Up

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

If you’ve ever accidentally brushed your hand against a hot stove, you’ll probably remember immediately clutching the burn with your other hand—an instinct that seems to help relieve the pain. In contrast, we often pull back in fear if someone else tries to touch a wound. Although psychologists have long recognized this distinction, no one properly understood the cognitive mechanisms that allow reflexive self-touch—rather than a stranger’s touch—to soothe pain. A new study published online September in Current Biology suggests that touching an injured area on one’s own body reduces pain by enhancing the brain’s map of the body in a way that touch from another cannot mimic.

In the study cognitive neuro­scientist Marjolein Kammers of University College London and her colleagues asked blindfolded par­ticipants to place their index and ring fingers in tubs of warm water while their middle fingers rested in cool water, a common experimental trick that creates the illusion that the middle fingers are burning hot. When the participants withdrew from the water and touched only their middle fingers of both hands together or joined only their outer fingers, they found little relief. Touching all three fingers to an experimenter’s hand also failed to reduce pain. Only when the participants entwined their three affected fingers on both hands did they soothe themselves, diminishing perceived pain by 64 percent.

Uniting two parts of the same body, Kammers explains, sends diverse signals to the brain about temperature, spatial position and identity that can come only from self-contact. In this case, bringing all three fingers together probably provided the brain with enough comparative information to readjust its interpretation of skin temperature on each finger. “When you get input from many different signals, the brain increases the coherence of its body map, which reduces acute pain,” Kammers says. The new findings parallel previous work demonstrating that adding more sensory input can relieve chronic phantom limb pain experienced by some amputees: when a mirror tricks the brain into thinking the body is whole again, the pain subsides.

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American

Subscribe

Subscribe to Scientific American to learn and share the most exciting discoveries, innovations and ideas shaping our world today.

Subscription PlansGive a Gift Subscription