麻豆传媒

Long blamed for aggression, promiscuity and even greed, some of testosterone鈥檚 alleged effects may be all in the mind.

Women who receive a boost of the potent sex hormone act more generously than women on a placebo, a new study finds. But the hormone鈥檚 reputation seemed to precede itself. Those who suspected they had received bona fide testosterone acted more selfishly than those who believed they got the bogus treatment, no matter what they actually received.

鈥淎lmost everybody believes that testosterone has these aggression-enhancing effects,鈥� says , a neuroeconomist at the University of Zurich, Switzerland, who led the study.

This platitude may be true in some situations, but not all. The hormone鈥檚 real role is to push men and women to seek higher status, says Fehr. His team tested this hypothesis in women because previous research had established for women how long an external dose of the hormone remains in the body.

They asked 121 women given testosterone or a placebo to play a simple game in which cooperation is paramount. Called the ultimatum game, one participant is given $10 but must offer some of it to another woman. If the second woman rejects the offer, the first loses her money.

Generous women

If testosterone plays a role in status-seeking, participants given the hormone should fear rejection more than others and so should make more generous offers, Fehr says.

That鈥檚 precisely what the team found 鈥� but only after accounting for people鈥檚 hunches about whether they had received testosterone or a placebo. Women on the placebo tended to offer $3.40, while those given the hormone tendered an average of $3.90.

Those who falsely believed they were on testosterone, however, offered about $1 less than women who believed they had taken the placebo.

When probed on their beliefs about testosterone, participants tended to buy into conventional wisdom, saying, 鈥淥h, testosterone would make me more egotistic, more risk-taking and more aggressive,鈥� Fehr says.

Greedy men

Such bias could explain the discrepancy between Fehr鈥檚 study and another study presented at an October meeting. A team led by and Karen Redwine of Claremont Graduate University in California found that testosterone makes college-age men 鈥� those in their early 20s 鈥� act more greedily when they played a similar ultimatum game. But these researchers did not probe their participants鈥� beliefs about testosterone.

鈥淚 wouldn鈥檛 expect the effects to be different for males and females,鈥� says , a psychologist at the University of Utrecht, the Netherlands, not involved in either study.

Moreover, van Honk thinks the study shows that testosterone鈥檚 reputation as an antisocial agent is wrong and that hormones can have different effects on behaviour depending on the context. 鈥淚t shows, in my opinion, that you cannot talk about good and bad hormones,鈥� he says.

Journal reference: , DOI: 10.1038/nature08711