High-testosterone men tend to lose their drive for a good deal after perusing sexy pictures.© Getty

It seems that the more macho a man is — at least according to his hormones — the more the sight of an attractive woman will affect his judgement.

Researchers at the University of Leuven in Belgium asked men to play an ultimatum game, in which they split a certain amount of money between them. High-testosterone men drove the hardest bargain — unless they had previously viewed pictures of bikini-clad models, in which case they were more likely to accept a poorer deal.

The sight of flesh had less effect on the bargaining tactics of low-testosterone men.

The testosterone dose that interested the researchers was that encountered by their participants when developing in the womb. This can be measured by comparing the lengths of the index and ring fingers — a relatively long ring finger is a sign of a high-testosterone man.

For these men, even handling a bra was enough to sap their resolve, report economists Bram Van den Bergh and Siegfried Dewitte, who publish their findings in the journal Proceedings of the Royal Society B¹. Pictures of landscapes or elderly women, or handling a t-shirt, had no effect on the men's steely bartering power.

Alluring ads

The discovery might help to explain advertisers' reliance on sexy women to hawk their products, the researchers speculate. "Commercials and advertisements are populated with beautiful and sexy women, but the consequences on cognitive processes of males had not been fully investigated," Van den Bergh says.

This is not the first study to show the effect of a well-turned ankle on male behaviour. For example, the sight of a beautiful woman makes men more likely to accept a small cash sum up front rather than a larger one later, perhaps so as to appear wealthy straight away (see 'Women addle men's maths').

But that doesn't explain why sultry sirens can sell anything from computers to carving knives. Perhaps men faced with an attractive woman just don't strive so hard for a good deal, Van den Bergh suggests.

Fight for fairness

In the game, one player, the proposer, was given 10 euros and had to offer a cut to the other, the responder, who had already secretly declared the minimum he would accept. If the offer is less than this minimum, both players get nothing.

As something is always better than nothing, one would expect the responder to set his sights low, leaving the proposer safe to make a paltry offer. But the responder's pride and an aggressive sense of fairness often leave both players out of pocket.

High-testosterone men fight hardest for a large cut, the researchers found. But the most testosterone-driven men were also the most likely to slacken their cash demands after viewing sexy women. Perhaps they relaxed and began to care less about money. Or perhaps, the researchers suggest, with a 'mate' to impress the men were driven to have some wealth, however modest.

The sight of a potential mate might therefore actually make men more sensible, Van den Bergh says. "Since a few coins is better than no coins at all, men thus become more economically rational after exposure to lingerie or sexy women," he says.

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• References

  1. Van den Bergh B.& Dewitte S. Proc. R. Soc. Lond. B, doi:10.1098/rspb.2006.3550 (2006).