The Moral Molecule

Neuroscience and economic behavior

Handshake or Hug? Why We Touch

Why I spent $6,000 on massages for strangers

In the last several months, I've moved several colleagues from the handshake greeting to the hug. For my colleague Mark, it happened after the series of long intensive days working on a new project several weeks ago. Somehow that all that time together made shaking hands seem too trivial. Still, it can be a bit uncomfortable to initiate a hug. Or maybe it's just a guy thing to worry about hugging another guy.

Come to think of it, why do we even have this ritual where with nearly everyone we meet we must touch our palms together? True, in some Latin cultures, the handshake is replaced with a kiss or two. But isn't that really intimate for people who are just friends? Why all this touching?

I thought I would investigate this a couple years ago. My real interest was to find out if touching would somehow make people "nicer," especially towards strangers. But I couldn't crack the lawsuit problem: if I asked participants in an experiment to touch each other, surely someone would be touched inappropriately and I would get sued. And for most of us, being forced to touch someone is weird and uncomfortable. Touch needs to be freely given and accepted to have a positive effect.

So, what to do? Many of the experiments I run involve blood draws, and I noticed that when one has a white lab coat on it is easy and acceptable to comfort a nervous person with a touch on the shoulder. Then it hit me: clinicians can touch us in a caring way and it doesn't bother us.

This is the reason I spent $6,000 on massages for strangers (and I never even got a massage myself!). Participants in this experiment came in, got a blood draw, and then were randomized to get massaged for 15 minutes by a licensed massage therapist or to rest quietly for 15 minutes. Most people then made a single decision involving money and another person, and then received a second blood draw (a control group just did blood draw-massage-blood draw to isolate the effect of massage alone). Not surprisingly, we had no trouble recruiting 150 participants for this experiment!

I wanted to test a "pay it forward" idea: would massage by a therapist make you more likely to sacrifice money to help another person? And if so, why? If you have been reading The Moral Molecule, you'll have guessed that the target brain mechanism that would connect touch to sacrifice was oxytocin. Our idea was not without precedence: stroking the belly of rats had been shown to release oxytocin. But no one knew if touch would do the same thing in humans.

In September, 2008 my colleagues and I reported our results in the journal Evolution and Human Behavior (see www.neuroeconomicstudies.org for the details). Here's what we found. Massage alone did not raise oxytocin, but primed the brain to release this neurochemical after one received a signal of trust. This neuroeconomics experiment (I will describe neuroeconomics in a future article), used computer-mediated monetary transfers between strangers to measure trust. The gist of this method is that one can take money out of one's account and entrust it to a stranger because this will cause the amount entrusted to grow threefold. The stranger can then return some money to the person who trusted him or her, or keep it all. And everyone knows that they only do this once so there is no chance to build up a reputation for reciprocity and make money by doing this task repeatedly. A full description of this approach can be found my June, 2008 article in Scientific American (www.sciam.com) called "The Neurobiology of Trust."

We knew from research that we published in 2004 and 2005 that monetary transfers denoting trust caused the brain to release oxytocin. And we showed that there was a positive relationship between the amount of oxytocin released and the amount people choose to return to the person who trusted them-even though they were under no obligation to do so. Adding massage was like putting the human oxytocin system on steroids. Those who were massaged and trusted sacrificed 243% more money to the person who trusted them compared to those who were trusted but not massaged. And the change in blood levels of oxytocin strongly predicted this behavior.

Interestingly, women were more susceptible to the effect of touch: they had larger changes in oxytocin and sacrificed more money to those who trusted them. This may be why at lease anecdotally, women touch others more than men. Oxytocin not only is a potent anti-anxiety agent, it activates reward pathways in the brain. Yes, our brains are designed to make it feel good to be good-even to strangers.

So, hugs or handshakes? Either one, along with a display of trust, is likely to cause oxytocin release and increase the chances that this person will treat you like family even if you've just met him or her. We touch to initiate and sustain cooperation. That's a pretty neat trick for a little nine amino acid molecule!

Paul J. Zak is a neuroeconomist at Claremont Graduate University in Claremont, CA.  His book The Moral Molecule will be published in 2012.

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