Hormone Spray Elicits Trust in Humans

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It sounds like the stuff of science fiction, but scientists have discovered that a whiff of a certain hormone makes people more willing to trust others with their money.

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.


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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.

Kate Wong is an award-winning science writer and senior editor for features at Scientific American, where she has focused on evolution, ecology, anthropology, archaeology, paleontology and animal behavior. She is fascinated by human origins, which she has covered for nearly 30 years. Recently she has become obsessed with birds. Her reporting has taken her to caves in France and Croatia that Neandertals once called home to the shores of Kenya’s Lake Turkana in search of the oldest stone tools in the world, as well as to Madagascar on an expedition to unearth ancient mammals and dinosaurs, the icy waters of Antarctica, where humpback whales feast on krill, and a “Big Day” race around the state of Connecticut to find as many bird species as possible in 24 hours. Wong is co-author, with Donald Johanson, of Lucy’s Legacy: The Quest for Human Origins. She holds a bachelor of science degree in biological anthropology and zoology from the University of Michigan. Follow her on Bluesky @katewong.bsky.social

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