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.
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Add CommentVery interesting but it would not have helped John Bobbitt.
Reply | Report Abuse | Link to thisWhat about a mother's kiss to make better,a placebo effect maybe?
Reply | Report Abuse | Link to thisAnother element to consider would be the "gate theory"---also the basis of accupuncture---whereby sending many signals to the brain can somehow block out the pain signal, or at least reduce its intensity. This is also the basis of chemicals like BenGay that is classified as a counter-irritant that causes a sensation to compete with the pain sensation. Most people apply the counter-irrritant to the injured muscle, tendon or bone but it would be just as effective if placed on a non-injured area.
Reply | Report Abuse | Link to thisWe have joint pain so we don't exercise. A study is done & concludes we get joint pain because we don't exercise. The study has a "chicken/egg" problem (not to say the study isn't useful, or even right, of course). In the "reflexive self-grab” report, perhaps there is a "horse/carriage" problem, or maybe an “apples/oranges” problem or both, & then some. This report is about a study into the “cognitive mechanisms that allow reflexive self-touch—rather than a stranger’s touch—to soothe pain.” They used “a common experimental trick that creates the illusion that the middle fingers are burning hot”. And there is reference to the “phantom limb pain…mirror trick” work, and so on. Both these illusion are after all illusions, & not common. They are both examples of mental errors, unlikely to be encountered in a normal life time. Thus, neural hard wiring fails – it’s not design to answer every remote circumstance. And, of course, meaningful additional sensory input changes our complex cognitive conclusion – our perception of pain. Regarding a “stranger’s touch”, it gives no information to the person that can correct the mental error of pain. But, the person putting two painful fingers together, or the fingers not hurting together DID reduce the pain illusion (“they found little relief”= some). And, as reported, when both hands are “entwined” we get the large drop in the pain illusion. Kammers explains, “When you get input from many different signals, the brain increases the coherence of its body map, which reduces acute pain.” In this case, the pain was an illusion, in that the sensory input was falsely interpreted as damaging, and with addition input the brain did a (“64%”) correction. In the referenced phantom limb pain, the pain is more reality base, & the illusion, the false information, reduces it (for some limited interval, at any rate).
Reply | Report Abuse | Link to this“Increases the coherence” of a “body map” seems to be just correctly sorting out incoming information. And this, of course, could result in an intensifying pain, as anecdotal experience tells. How many of us have been hurt while distracted and then when the distraction subsides realize the damage & the pain.
By the way, we are wired to grab a hurt, both to assess & reduce further damage to said injury (bleeding, bone fracture, bug biting etc). Other reasons include important nonverbal communication to our group etc – all very obvious (the discomfort relief is the weird motivator).
R. Carlson