Do those with more testosterone coursing through their bodies make riskier, more aggressive decisions? Popular culture and even rodent studies seem to have borne out this trite truism about the sex hormone, but researchers in Switzerland and the U.K. tested whether this perception really held true for humans in a controlled environment—and arrived at counter-intuitive findings.

"We wanted to verify how the hormone affects social behavior," Christoph Eisenegger, a neuroscientist at the University of Zurich and lead author of a new paper on the subject, said in a prepared statement. "If one were to believe the common opinion, we would expect subjects who received testosterone to adopt aggressive, egocentric and risky strategies."

To test the idea, the research team gave 121 women either 0.5 milligrams of testosterone or a placebo and had them play an ultimatum bargaining game. With real money on the line, one player was in charge of proposing how the two would split the funds via a computer interface. The other player could reject an offer if she thought it unfair—and if the game ended in a stalemate, no money was distributed. Given the common wisdom about testosterone, the players who had gotten the testosterone boost should be more likely to take a riskier, antisocial approach and lowball the initial offer in an effort to keep more money for themselves.

The behavior of the test subjects, however, did not ultimately confirm the stereotypes, according to the results, published online Tuesday in Nature (Scientific American is part of Nature Publishing Group).

Those who had received testosterone actually made "significantly higher offers" than those who had gotten the placebo (offering an average of 39 percent of the money and 34 percent, respectively)—even after controlling for baseline testosterone levels and perceived testosterone consumption, the paper authors noted. These testosterone-fueled offers worked, "thereby reducing bargaining conflicts and increasing the efficiency of social interactions," the researchers wrote. They attributed this shift to a desire of the testosterone group to maintain their images—by avoiding rejection—aligning with the so-called social status hypothesis.

But might the different bargaining approach be based on an increase in altruism? The authors refute this explanation, noting that if this were the case they would have seen more offers accepted under the influence of testosterone (which they didn't, finding, in fact no significant change in the ways the receivers responded to the offers when compared with a similar test of 180 women who had received no testosterone).

This study isn't the first to cut away at some of the myths about testosterone. Previous research has found that although the hormone is often prevalent in violent individuals—both male and female—it alone doesn't lead to violence.

Does this mean testosterone has no role in complicating such social negotiations? It is likely more complex than that, Michael Naef, an economist at Royal Holloway,  University of London and co-author of the study, noted in a prepared statement. Indeed, the cultural concept of testosterone itself might be to blame for some antisocial and aggressive behavior. The researchers found that of those who strongly believed they had gotten the testosterone pill—whether or not they had it or the placebo—actually "behaved much more unfairly," the authors wrote. And: "In a society where qualities and manners of behavior are increasingly traced to biological causes and thereby partly legitimated, this should make us sit up and take notice," Naef said.

Image courtesy of iStockphoto/mrsmuckers