Can oxytocin promote trust and generosity?

Given its reputation as a facilitator of social bonding, oxytocin has recently taken center stage in the budding area of "neuroeconomics," which aims to investigate the brain mechanisms that underlie economic behavior and decision-making.

Researchers in the area have been looking to see how exogenously administering the hormone might influence behaviors such as trust and generosity, with the hopes of eventually applying such findings to larger socioeconomic issues such as how the reported levels of interpersonal trust in a given society might influence its rate of economic growth, according to the Web site of Claremont Graduate University economist Paul J. Zak, PhD, one of the field's leaders.

In one study, reported in the June 2, 2005, issue of Nature (Vol. 435, No. 7042, pages 673-676), behavioral economist Michael Kosfeld, PhD, of the University of Zurich, Zak and colleagues had 29 pairs of male college students play an investment game with tokens in which one member of the team acted as an investor and the other as a trustee. Half of the participants inhaled an oxytocin spray and the other half a placebo.

Of the investors who whiffed oxytocin, about half gave all of their tokens to the trustees, and most of the rest handed over the majority of their tokens. By contrast, only a fifth of investors on placebo parted with their tokens, while another third proffered most of theirs.

In another study, published in the Nov. 7, 2007, issue of the online Public Library of Science journal PLoS ONE (Vol. 2, No. 11), Zak and colleagues found an even stronger relationship between oxytocin and generosity than the team had found earlier with trust. Here, participants who inhaled either oxytocin or a placebo were asked to decide how to split a sum of money with a stranger. Those who received the hormone offered the stranger 80 percent more money than those receiving the placebo, the team found.

While intriguing, it's important to put findings like these into context, given that one-time administrations of oxytocin may not reflect natural physiological processes, and because the media tend to seize on such findings and confer overblown labels such as "the love hormone" and "the trust hormone" onto oxytocin, says social psychologist and oxytocin researcher Shelley E. Taylor, PhD, director of the University of California, Los Angeles Social Neuroscience Lab.

"Oxytocin is developing a reputation of being the sort of thing you'd want to dump in someone's coffee in the morning to make them soft and nice and fuzzy and good to you," she says. "That's just not the case. Oxytocin is much more complex than that."

--T. DeAngelis