The hormone is oxytocin, which in nonhuman mammals is associated with social attachment, as well as a number of physiological functions related to reproduction. As such, it is believed to help animals overcome their natural tendency to avoid proximity and allow others to approach them. Hypothesizing that oxytocin might have a comparable role in human prosocial approach behaviors, such as trust, Michael Kosfeld of the University of Zurich and his colleagues devised a double-blind study to compare trusting tendencies in subjects given an oxytocin nasal spray and those given a placebo. After receiving either a single dose of the hormone or the placebo, participants played a trust game in which an investor chooses how much money to fork over to a trustee, who then decides how much to return after the amount is quadrupled. Subjects played the game using monetary units, which were exchanged for real money at the end of the experiment.
According to the researchers, oxytocin increased investor trust markedly, with 45 percent of the oxytocin group exhibiting the highest trust level, compared to just 21 percent of the placebo group. The team rejected the possibility that oxytocin might be promoting risk-taking in general, rather than social risk-taking specifically, because when investors were paired with a computer trustee instead of a human one they did not take such risks.
Describing the work today in the journal Nature, Kosfeld and his collaborators acknowledge that their findings could be misused. They add, however, that the work could ultimately help patients with mental disorders associated with social dysfunction, such as those afflicted with autism or social phobia.