Here's some bad news for testosterone already somewhat damaged reputation: the hormone apparently makes people less cooperative in groups. But there's a catch — the effect has only been observed in women.
According to ScienceDaily, researchers gave 17 pairs of women either testosterone or a placebo. Then they had them work together on a simple visual recognition task. When the pairs got the placebo, they worked a lot better together than they would have alone. But when they got the hormone, each lady was more likely to think her answers were best and to ignore her partner's answers, meaning the team did worse. Says study author Nick Wright,
Our behaviour seems to be moderated by our hormones — we already know that oxytocin can make us more cooperative, but if this were the only hormone acting on our decision-making in groups, this would make our decisions very skewed. We have shown that, in fact, testosterone also affects our decisions, by making us more egotistical. Most of the time, this allows us to seek the best solution to a problem, but sometimes, too much testosterone can help blind us to other people's views. This can be very significant when we are talking about a dominant individual trying to assert his or her opinion in, say, a jury.
It's a little hard to know how these results apply to the real world. The researchers used women because giving men testosterone can have unpredictable effects, like causing their own bodies to produce less to compensate. So the study can't shed much light on how testosterone affects guys' behavior. Nor does it show how the lower levels of testosterone that naturally course through ladies' veins affect them — these effects may be different from what happens when you artificially dose women with the hormone. However, the study authors do point out that in female prisoners, higher testosterone levels are associated with antisocial behavior and aggression. They speculate "that such findings reflect a more general role for testosterone in increasing the motivation to dominate others and increase egocentricity."
In the real world, a bunch of forces — both biological and social — are at play every time we try to cooperate with other people. For instance, we learned last week that women sometimes perform worse in groups than they would alone, possibly because they lose confidence. The testosterone study suggests that just dosing women with a male hormone might not fix this problem. It looks like making people too confident in their own abilities creates problems too.