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Does Testosterone Have a Bad Rap?

8 December 2009 (All day)
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Testosterone has a reputation for causing violent and antisocial behavior. But that's a bad rap, according to a new study. Women given the hormone acted more fairly in an economic game than did those given a placebo. Interestingly, however, women in the placebo group were more antisocial if they thought they had received testosterone, indicating that our negative attitudes toward the hormone have a powerful sway on behavior.

Scientists led by Ernst Fehr, a professor of neuroeconomics at the University of Zurich in Switzerland, suspected that testosterone is really about gaining and maintaining social status. And although status concerns lead to aggression, they theorized that testosterone does not necessarily make a person more self-seeking.

The team tested this idea by recruiting 121 women in their 20s to play a game that tests fairness. Two players, A and B, have to agree on the division of 10 money units, in this case Swiss francs. A proposes a division; B can only accept or reject. If B rejects the offer, neither gets any money. All the women were given a dose of either testosterone or a placebo under the tongue. Then 60 women designated as A played the game three times with three different partners, communicating through a computer.

A "fair" offer would be a 50-50 split. So, according to common wisdom, A would make more unfair offers if she were high on testosterone. The status hypothesis predicts the opposite: An unfair offer is more likely to evoke a rejection, which is an affront to A's status. So A is more likely to make an offer that B will accept.

The status hypothesis won. The women given the testosterone made significantly higher offers on average, the group reports online today in Nature: 3.9 francs versus 3.4 francs for the placebo group. "Our interpretation of this finding is that testosterone renders concerns for social status more prominent," says Fehr.

But the results changed depending on what the women believed they had received. Based on questionnaires, the researchers divided the volunteers into women who thought they had received testosterone and those who thought they had received placebo. Those who got the hormone but thought they got a placebo were the most fair; in more than 60% of their offers, they proposed a 50-50 split of the francs. Women who got the placebo but thought they got testosterone were the most unfair; in only 10% of the offers did they propose an even split of the money. That indicates, says Fehr, that the subjects' negative assumptions about testosterone--not the hormone itself--led to antisocial behavior.

Fehr says the group used women because the pharmacokinetics of testosterone doses in women are well-understood. He hopes to do the same experiment with men.

The research should help "demystify the wrong ideas about ... the 'antisocial' hormone testosterone," says Jack van Honk, a neuroscientist at Utrecht University in the Netherlands. But economist Niklas Zethraeus of the Stockholm School of Economics isn't convinced that testosterone influences fairness one way or the other. His group published a study this year using a larger sample that found no connection between sex hormone levels and economic behavior.

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