This one's also from the Department of Placebo Effects - read on. An interesting paper out in Nature details a study where volunteers took small doses of testosterone or placebo, and then participated in a standard behavioral test, the "Ultimatum Game". That's the one where two people participate, with one of them given a sum of money (say, $10), that's to be divided between the two of them. The player with the money makes an offer to divide the pot, which the other player can only take or leave (no counteroffers). A number of interesting questions about altruism and competition have been examined through this game and its variants - basically, the first thing to ask is how much the "dictator" player will feel like offering at all. (If you like, here's the Freakonomics guys talking about the game, which features in a chapter of their latest, SuperFreakonomics).

What's been found in many studies is that the second players often reject offers that they feel are insultingly low, giving up a sure gain for the sake of pride and sending a message to the first player. I think of this as the "Let me tell you what you can do with your buck-fifty" option. So what does exposure to testosterone do for this behavior? As the authors of the new paper talk about, there are two (not necessarily exclusive) theories about some of the hormone's effects. Increases in aggression and competitiveness are widely thought to be one of these, but there's also a good amount of literature to suggest that status-seeking behavior is perhaps more important. But if someone is going to be aggressive about the ultimatum game, they're going to make a lowball offer and damn the consequences, whereas if they're looking for status, they may well choose a course that avoids having their offer thrown back in their face.

Using known double-blind conditions for testosterone dosing in female subjects (sublingual dosing four hours before the test), the second behavior was observed. Update: keep in mind, women have endogenous testosterone, too. The subjects who got testosterone made more generous offers (from about $3.50 to closer to $4.00). The error bars on that measurement just miss overlapping, p = 0.031. But here's the part I found even more interesting: the subjects who believed that they got testosterone made significantly less fair/generous offers than the ones who believed that they got the placebo (P = 0.006). Because, after all, testosterone makes you all tough and nasty, as everyone knows. As the authors sum it up:

"The profound impact of testosterone on bargaining behaviour supports the view that biological factors have an important role in human social interaction. This does, of course, not mean that psychological factors are not important. In fact, our finding that subjects’ beliefs about testosterone are negatively associated with the fairness of bargaining offers points towards the importance of psychological and social factors. Whereas other animals may be predominantly under the influence of biological factors such as hormones, biology seems to exert less control over human behaviour. Our findings also teach an important methodological lesson for future studies: it is crucial to control for subjects’ beliefs because the pure substance effect may be otherwise under- or overestimated. . ."