Testosterone Makes People Suspicious of One Another

Image: flickr/an untrained eye

A dose of testosterone might be enough to save gullible types from being ripped off, a new study reveals.
Testosterone is linked to aggression, competition and social status. Now scientists have found that the hormone also reduces naive individuals’ confidence in others.

“Testosterone reduces trust just enough to make people vigilant and careful,” said psychologist Jack van Honk of Utrecht University in the Netherlands, who led the study published May 24 in Proceedings of the National Academy of Sciences.

In the study, a few dozen females received half a milligram of testosterone under the tongue — enough to increase hormone levels tenfold. The women viewed pictures of faces and judged how trustworthy they looked. The drug decreased ratings by about half, and the effect was only strong for females who are normally easily fooled.

Van Honk speculates that the effect does not occur in cautious individuals, because the hormone would make them so paranoid that they would become socially disabled.

“I think that people are going to see that testosterone has beneficial effects on social behaviors and carries properties that might be important for applications in certain psychiatric diseases, one of them being social anxiety disorder,” he said

“It’s interesting work that fits nicely with recent work suggesting that testosterone influences social motivation and perception,” said Pranjal Mehta, a psychologist at Columbia University who was not involved in the study. Future studies should test whether testosterone decreases trust in all individuals in more competitive situations, he said. “It’s absolutely critical to test the effect of the hormone in real-world social contexts,” he said.

Previous studies have found that oxytocin, a hormone involved in bonding, increases faith in others. The two hormones together may keep trust at an optimal level, van Honk said. In future studies, he would like to determine which brain circuits regulate trust through these hormones.

 By Janelle Weaver

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