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Hormones affect men's sense of fair play

Next time you have to negotiate a deal with a male business contact, you might want to check his hormone levels first. A new study shows that men with high levels of testosterone are more likely to turn down low offers, even if they stand to gain money by accepting them.

According to researchers, the finding demonstrates that our hardwired biology can cause us to make irrational economic decisions.

In what is known as the "low ultimatum game", an anonymous individual can offer either a large or small chunk of cash to another person, without any opportunity for negotiation.

The player who receives the offer knows how much the other player has in total, and therefore knows the fraction they have been offered. If the deal is accepted, both players keep their split of the total. But if the deal is refused, neither gets anything.

Often, the person offered the free money rejects it if it represents too small a slice of the pie. The refusal to accept this money has puzzled economists because the cash comes with no strings attached.

Morality v biology

To make sense of this decision, some experts have proposed that the person refusing the paltry payout wants to punish the other player for making an unfair offer.

But Terry Burnham at Harvard University in Cambridge, Massachusetts, US, suspected that this irrational economic decision might have more to do with basic biology than moral convictions.

He recruited 26 male graduate school students to play the low ultimatum game. Each subject started out with $40 and could anonymously offer either $5 or $25 of this sum to another player.

Burnham also took saliva samples from all the volunteers and measured their levels of testosterone. This revealed considerable variability in the levels of the hormone. While the subject with the most testosterone had 497 picomoles per litre of saliva, the one with the least only had 30% of this amount - 153 picomoles per litre.




This, says Burnham, suggests that people with more testosterone are less tolerant of what they see as inequitable deals - possibly due to the hormone's influence on the brain: "You have to be very careful about being fair with them."


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.

Burnham says that the new findings suggest that biological traits that evolved to give individuals an advantage - rather than behaviours that evolved to give a general group advantage - explain the irrational refusal of free money in the low ultimatum game.

Put another way, it is unlikely that people reject bad deals because they want to punish others for the greater good of the group.

Magnanimous and peacekeeping


This, he says, is in line with the idea from primate studies that found high testosterone males sometimes play a "magnanimous and peacekeeping" role.

Previous studies have found that other hormones can influence economic decisions. Researchers recently reported that a whiff of the hormone oxytocin can make someone more willing to invest their money in an anonymous trustee.

And, lastly, if you are seeking to determine your business contact's testosterone levels and saliva is hard to obtain, look out for a wedding ring. Married men tend to have less of the hormone.

Journal reference: Proceedings of the Royal Society B (DOI: 10.1098/rspb.2007.0546)



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