Come together. Oxytocin helps forge bonds between prairie mates.

A Whiff of Trust

Simply sniffing the hormone oxytocin is enough to boost one's trust, a new study finds. The research suggests, among other applications, that oxytocin treatment could help people with severe anxiety better open up to their psychotherapists.

Oxytocin is known to play a key role in social bonding: in monogamous prairie voles, for example, it helps mates bond, and in female rats it jumpstarts mothering behavior. But little is known about its function in humans.

A team led by economist Ernst Fehr at the University of Zurich in Switzerland had male students play a trust game, which pairs up strangers: an "investor," who starts with a small sum of real money, and a "trustee." If the investor chooses to send some of his money to the trustee, this amount is tripled in the trustee's hands. The trustee then chooses to send back some--or none--of his profits to the investor. If the pair trust one another and cooperate, they both benefit greatly. But since they play anonymously via computers, and each pair plays together only once, basic economic theory suggests the trustee should pocket whatever he gets--and suspecting this, the investor shouldn't send anything in the first place. But trust and fairness seem to be hard-wired: The investors do hand over their money, and the trustees send money back, with both parties tending to benefit, numerous studies have shown (ScienceNOW, 31 March, 2005.)

In the new study, published 2 June in Nature, investors who took a sniff of oxytocin forked over about 20 percent more money than the control group, and the proportion of those that decided to hand over their entire wad doubled. Further testing suggested that the hormone works by making the investors less worried about betrayal. Oxytocin didn't induce generosity among the trustees, though: the hormone made no difference in how much money they returned.

Up to this point, there had been no direct evidence that animal studies of oxytocin's effect on social behavior applied to humans, says neurobiologist Larry Young at Emory University in Atlanta, Georgia. "We're just seeing the tip of the iceberg of what oxytocin does in people," he says.

Related sites
Fehr's home page
Neuroeconomics blog