Long gone are the days of believing that increased testosterone levels only lead to hostility, competitiveness and aggressiveness. Scientists and economists in the Netherlands published a study this month that revealed that testosterone can actually increase generosity in the absence of competition.

Testosterone fosters a desire for social status, which often demands positive and peaceful social interactions. In the study, “Testosterone Promotes Reciprocity in the Absence of Competition,” printed this September in Psychological Science, researchers created an investing game in which behavior was affected by testosterone levels.

Lead researcher Maarten Boksem from the Rotterdam School of Management, said that testosterone does not necessarily cause aggressive behavior, but rather promotes behavior that has the greatest chance of placing one in the most desirable social standing, which includes a good reputation.

“We hypothesized that testosterone could perhaps lead to pro-social behavior if such behavior would be beneficial for maintaining or obtaining social status,” said Boksem. “Testosterone may mediate competitive and potentially antisocial behavior when social challenges or threats need to be confronted or handled.”

The study included 54 women, each given €20 — the equivalent of $27 — to either keep or invest in another participant, the trustee. The quantity invested would automatically triple, for a maximum of €60 if the investor gave all her money, and the trustee could choose how much to keep and how much to return to the investor. The hope of the investor was that the trustee would split the tripled sum equally.

Some volunteers received a testosterone injection, while others were given a placebo shot. The women took turns being the investor and the trustee.

Co-author Stefan Trautmann, who developed techniques used in the study, said that the investing game was inspired by studies in recent years that tap into people’s social preferences. The results elucidated the differing planes of trust and self-interest tied to testosterone levels.

“The first person can transfer money to a second person, which leads to a significant increase in the whole pie. The problem is that the first person becomes vulnerable to cheating by the second person, who may just rip her off, keeping the whole pie for herself,” said Trautmann. “Think of buying an expensive photo camera on eBay without having the security of PayPal payments.” Investor women given extra testosterone, as expected, gave less money to their recipients, supporting the notion that added testosterone leads to antisocial behavior.

Trustee women injected with testosterone, however, returned more money to their investors than those who did not receive a testosterone shot, revealing the nuanced effects of testosterone. The game illustrated the contrasting effects of testosterone: as both a catalyst for aggression and competitiveness, and as a vehicle for benevolence.

Boksem said that aggressive behavior was expected in the investors, and though the pro-social behavior in the trustees was surprising, it supported the team’s hypothesis that testosterone is more complex than originally thought.

“We doubted that this drive would automatically result in aggressive and anti-social behaviors,” said Boksem in an Association for Psychological Science press release from September 30.

Trautmann acknowledged that, although Boksem’s study contributes to a broader understanding of how testosterone functions in the body, the experiment included only females.

“Now, one set of important questions is what influences the ability to cooperate in this way, [such as] situational factors [and] individual factors,” Trautmann said. “Are women more cooperative than men? Obviously often both are relevant. Studying testosterone and cooperation, we learn something about the role of testosterone- interesting to biologists — and something about cooperation — interesting to economists and psychologists.”


A version of this article appeared on page 5 of Tuesday October 8, 2013′s print edition of The Daily Nexus.