STEVE INSKEEP, host:
A supportive touch doesn't just work for doctors seeking to win the trust of patients. A friendly touch on the arm or the shoulder of a student or an athlete can improve performance. And when a waitress does it, it helps to get a bigger tip. But why does this have such a universal effect? Michelle Trudeau explains what's happening in our brains and our bodies.
MICHELLE TRUDEAU: Let's start on the outside, with the skin, our largest organ, covering about 20 square feet. Spread out, your skin would be the size of a twin mattress.
If somebody touches you, say, holds your hand or gives you a hug, there's pressure pushing on your skin at the point of contact. Now, just under the skin are pressure receptors.
Dr. TIFFANY FIELD (Director, Touch Research Institute, University of Miami, Florida): They're actually called Pacinian corpuscles, and they receive pressure stimulation.
TRUDEAU: That's Tiffany Field, a pioneer of the science of touch. She runs the Touch Research Institute at the University of Miami.
Dr. FIELD: So the pressure receptors send a signal to the brain.
TRUDEAU: Directly to a very important nerve bundle deep in the brain called the vagus nerve - sometimes called the wanderer, because the vagus has branches that wander throughout the body. They reach all the way to internal organs.
Dr. FIELD: And the vagus also goes to other parts of the body, like the heart, and slows the heart down.
TRUDEAU: Field describes some studies in which subjects were asked to do something stressful, like public speaking or taking a timed math test. The subjects' partners were part of the experiment, giving hugs or holding hands with the subjects when the researchers told them to.
Dr. FIELD: And they found that, in fact, people who were given this stressful task, if they'd been holding hands or being hugged, they would have a lower blood pressure and lower heart rate, suggesting they were less stressed.
TRUDEAU: When we hug or hold hands, it decreases our stress hormone cortisol. That's the hormone that's pumped out by our adrenal glands when we're facing a stressful situation, like filing a report on deadline.
Matt Hertenstein, a psychologist at DePauw University in Indiana says that being able to tamp down our cortisol levels is healthy for us.
Professor MATT HERTENSTEIN (Psychologist at DePauw University, Indiana): Having this friendly touch, just somebody simply touching our arm and holding it, buffers the physiological consequences of this stressful response.
TRUDEAU: In addition to calming us down, a friendly touch also increases release of a hormone that affects trust behaviors, oxytocin. It's called the cuddle hormone.
Prof. HERTENSTEIN: Oxytocin is a neuropeptide, which basically promotes feelings of devotion, trust and bonding.
TRUDEAU: And oxytocin levels go up with holding hands or hugging or a massage. This hormone makes us feel close to one another.
Prof. HERTENSTEIN: So it really lays the biological foundation for connecting to other people.
TRUDEAU: Touching makes us feel close. But being touched also just feels good. We usually want more. So what's going on in the brain that accounts for these feelings?
Hertenstein says recent studies from England have pinpointed an area of the brain that becomes highly activated in response to friendly touch, a region called the orbital frontal cortex, just above your eyes, which happens to be the same area that responds to sweet tastes, pleasing smells and other rewarding things.
Prof. HERTENSTEIN: A soft touch on the arm makes the orbital frontal cortex light up, just like those other rewarding stimuli. So, touch is a very powerful, rewarding stimulus - just like your chocolate that you find in your cupboard at home.
TRUDEAU: So the surging of oxytocin makes you feel more trusting and connected. And the cascade of electrical impulses slows your heart and lowers your blood pressure, making you feel less stressed, more soothed - all initiated by a simple, supportive touch. So the next time a friend is stressed or worried, give them a hug or a shoulder rub. It'll make them feel better. Their biology practically guarantees it.
For NPR News, I'm Michelle Trudeau.
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