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Testosterone makes naive people less trusting

Testosterone makes you distrustful, at least if you tend to be trusting of others by nature. Psychologists from the University of Utrecht in the Netherlands discovered this when they gave women a single tiny dose of 0.5 mg testosterone.

Testosterone makes naive people less trusting
Their study, which was published in the prestigious PNAS journal, is one of a series of studies that we have already written about. In other studies, in which women were given low doses of testosterone, the researchers observed reduced levels of empathy, reduced awareness of social rejection and an increased sensitivity to faces with an angry expression. The study described here was set up in much the same way as the other studies: women were given 5 ml water containing 0.5 mg testosterone, 5 mg cyclodextrin and 5 mg ethanol.

Fifteen minutes after receiving the drops the women's testosterone level had risen by a factor of ten, and ninety minutes afterwards it had returned to normal.

In the intervening period the women were shown 150 photos of faces. They had to say how much they would trust the person in each of the photos. The researchers then repeated the procedure, but gave the women a placebo.

When they were given testosterone the women became less trusting, as the figure below shows.

Testosterone makes naive people less trusting

Some women were fairly distrustful by nature [low trusting]. When the researchers looked at the results for this group separately, they noticed that the testosterone had had almost no effect on these subjects. Testosterone only had an effect on the women who were generally trusting of others [high trusting].

Testosterone makes naive people less trusting

Based on previous studies, the researchers suspect that testosterone shifts decision-making processes from the advanced, rational parts of the brain to more primitive areas. These are more tuned to defending the interests of the individual and his or her group.

The researchers think that their results also apply to men. "The relation between testosterone and social behavior apparently has much communality in human males and females", they write.

Proc Natl Acad Sci U S A. 2010 Jun 1; 107(22): 9991-5.

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