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Oxytocin Increases Trust — Under Certain Conditions

Researchers report effects of the “trust hormone” get negated when a partner is perceived as dishonest.
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Oxytocin, the subject of this month’s Miller-McCune magazine cover story, has been called “the love hormone” or “liquid trust.” As our Michael Haederle reports, raising levels of the neuropeptide has been shown to make people more altruistic and generous.

Before we start putting this stuff into the water, however, it’s worth asking the question: Does it also make us more gullible? Trust is great, but not everyone is trustworthy.

A research team led by psychologist Moira Mikolajczak of the Universite catholique de Louvain in Belgium addressed that question in a study, which was recently published in the journal Psychological Science. The researchers conducted an experiment featuring 60 young men, half of whom inhaled a dose of oxytocin 45 minutes ahead of time. The others were given a placebo; no one knew which group they were in.

The participants then played a variation on a standard Trust Game. Each played the role of an investor, who had the option of handing over some or all of his money to a trustee. This procedure gave each investor a chance to triple his money — but only if the trustee was reliable and fair. If the trustee was dishonest, he could lose it all.

Before each round of the experiment, participants were given a brief description of their trustee. “We combined trustworthy academic fields (philosophy) and activities (practicing first aid) to make some partners seem reliable, and untrustworthy academic fields (marketing) and activities (playing violent sports) to make other partners seem unreliable,” the researchers report.

After some practice rounds in which a computer played the role of trustee (returning random amounts of money), each participant played 10 rounds with 10 different partners — five trustworthy and five untrustworthy.

Not surprisingly, participants invested less money with the untrustworthy trustees, regardless of their oxytocin levels. But the hormone did have a distinct effect.

Playing with either the computer or with a reliable human partner, those who had inhaled oxytocin invested more of their money. The hormone apparently made them more trusting of the outcome and more likely to take a risk.

However, with the untrustworthy partner, those with his oxytocin levels invested slightly less than the other test subjects. The hormone “completely lost its trust-enhancing effect” when the participants were skeptical of their partner’s honesty.

The researchers call this a crucial distinction. After all, they note, gullibility potentially “exposes one to financial exploitation and even sexual abuse.”

Their conclusion: “Oxytocin is not the magical ‘trust elixir’ described in the news, on the Internet or even by some influential researchers.” Rather, its effects are context-dependent — which is a good thing.