What’s the first thing you do when you burn or cut one of your hands? You might think the answer is that you put it under a faucet or wrap a towel around it. But that’s actually not the first thing you do. The first thing is reflexive, unthinking — something your ancestors could have done in the wild: you grasp the hurt hand with the other one. We have known at least since the ’60s that this kind of self-touch actually reduces pain. If you try to keep your other hand away, you will hurt a lot more. It’s not just the pressure you apply. Pain is reduced far more when it’s your own hand, not anyone else’s. (No jokes, please.)
Now a new study shows that self-touch also minimizes more complex kinds of pain. The study comes amid a flood of experiments in the past few years showing that the body and mind work together to heal physical and mental discomfort. One major example is recent research showing that simply the act of deciding to seek help for a medical problem such as back pain or depression or sexual dysfunction can reduce the severity of that problem, even before you have received a single treatment. (More on Time.com: The Complicated Link Between Abortion and Mental Health)
In the new experiment, the authors — a team led by Marjolein Kammers of the Institute of Cognitive Neuroscience at University College in London — used self-touch to reduce a complicated physical sensation called central pain. Phantom-limb pain — when your brain feels pain in a limb that has been amputated — is one kind of central pain. Dystonia, a painful movement disorder, is another.
Central pain is also the major player in the carnival-like experiment called the thermal grill illusion. In the thermal grill illusion, you are made to touch a very warm object — say, a heated-but-not-scorching grill — and then, immediately afterward, a cool object such as a room-temperature grill. Quite reliably, your brain will fool you into believing the second object is excruciatingly hot, even though nothing has happened to your flesh. The first grill wasn’t hot enough to burn, and the second is actually cool. But your brain is confused: that’s central pain. Even though the thermal grill illusion was first written about in the 19th century, neurologists have never been able to understand precisely how it works and whether it could be used in treating pain. (More on Time.com: Cell Phones and Cancer: A Muckraking Scientist’s Persuasive New Book)
Kammers’ team replicated the thermal grill illusion using water. Her participants immersed their index and ring fingers in 109-degree-Fahrenheit (39-degree-Celsius) water. Their middle fingers were put in 57-degree-Fahrenheit (14-degree-Celsius) water. In this condition, the two middle fingers felt much hotter than they did when the four index and ring fingers were immersed in neutral water.
But Kammers added a new twist to the thermal grill illusion: after their fingers felt the thermal-grill sensation, she asked participants to press the fingers of their two hands together. When they did so, their middle fingers hurt a lot less than when they touched someone else’s hand.
Kammers and her team struggled to explain the findings. Something is surely happening in a brain region called the somatosensory cortex, but psychological responses are also involved. It’s all a bit murky. Still, the findings are exciting because they suggest that the body and brain have instinctive ways of healing that we could come to understand one day and then magnify. In short, you might conclude that it’s OK to touch yourself.
More on Time.com: