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Testosterone Promotes Fair Play

Oxytocin seems to make us more trusting; testosterone evidently makes us less lackadaisical in our interactions.

In various experiments using inhaled oxytocin, Marcus Heinrichs and Paul Zak have shown that it makes people behave more trustingly and/or more cooperatively in economic exchanges.

A new study found that men with higher testosterone were less likely to accept low-ball deals. New Scientist reports on research by Terry Burnham of Harvard. Burnham had volunteers play the Ultimatum Game, where one person can share some or all of a cash prize with another person. The other person can accept or refuse the split; if he refuses, both get nothing. Burnham found that men with higher testosterone levels were less likely to accept a measly portion.

This is one of those cases that seem odd to economists who believe that economic decisions are rational. After all, some cash, even five bucks, is better than nothing, right? Yet, participants in this game typically do reject ungenerous offers.

Scientists have proposed various theories for the evolution of this behavior: Is there some "altruism gene" that drives us to try to enforce cooperative behavior in others? Are the refuseniks trying to punish the greedy person?

According to the article,

He speculates that testosterone produces a greater aversion to unfair deals because the hormone is linked to dominance-seeking behaviours.

In other words, Burnham believes that high-testosterone men reject measly offers because accepting such deals would put them in a subordinate social position. He adds that our ancestors who accepted a subordinate position probably faced an evolutionary disadvantage.

These findings are similar to research by Zak. Instead of looking at men with naturally high levels of testosterone, he administered it to some subjects before the Ultimatum Game. In the study, men received a dose of testosterone the night before the game.

The men on testosterone tended to be more generous when they were doling out the money, and more likely to punish the other if the split wasn't fair.

He told me, "We essentially create alpha males in the study. This is consistent with the animal literature. In primates, the hierarchy is maintained by the alpha male by sharing access to food and females."

Zak thinks this research uses a different pathway from the cooperative social behavior triggered by and/or in response to oxytocin.

For more on Zak's work, see my recent interview with him, "Oxytocin, Trust and Greed."