NEW ORLEANS, LOUISIANA--As any advice columnist or well-meaning parent will tell you, trust is the basis of all good human relationships. But what is the basis of trust? New research suggests it may take the form of a hormone called oxytocin, which surges in student volunteers when an anonymous partner in a psychology experiment entrusts them with a small sum of cash.
Oxytocin is social superglue. In a variety of animals, the hormone helps cement bonds between mothers and infants and between mating pairs. But much less is known about its role in humans.
In the new study, Paul Zak and colleagues at Claremont Graduate University in California paired college students in a simple two-player game. Both volunteers got $10 just for showing up. Student A was given the option of sending some or all of the $10 fee to student B. The researchers tripled the amount A sent before handing it over to B, who then decided how much money to return to A. Both players knew the rules, but all transactions were done anonymously to prevent students from using any prior knowledge they might have had about one another's trustworthiness. The researchers drew blood from each student B shortly after the person had received A's money, which Zak says is a signal of trust: The more A trusts B to give cash back, the more money A sends.
And the more money A sends, the higher B's oxytocin levels, Zak and colleagues reported here 9 November at the annual meeting of the Society for Neuroscience. Although oxytocin may signal that people realize they're being trusted, however, it apparently doesn't guarantee that they'll be trustworthy in return. One student B, Zak says, got the maximum payoff from A, had a very high oxytocin level, and still decided to keep the whole pot of money. "He said he knew what he should do, but he just repressed it."
It's an interesting study, says Cort Pedersen of the University of North Carolina, Chapel Hill. But he's not sure trust is really what's signaled by oxytocin. "The rise in oxytocin seems to happen when someone is the recipient of generosity, but it's a bit of a leap to say that's trust." Pedersen thinks oxytocin may be a general signal of positive social interactions in humans, as it is in other animals. "That may ultimately be part of the basis of trust," he says.