Lingerie sharpens the financial mind

According to recent news reports, the sight of lingerie or a sexy woman significantly impairs male decision making. Unfortunately, the details have got a little blurred in the re-telling from the original research paper – to the point where most reports flatly contradict the study’s conclusions.

The study involved a well-researched financial task known as the ultimatum game where one participant is given a sum of money (10 euros in this study) and has to decide how to split it with another. If the other participant accepts the split, both get to keep the money. If they don’t, no one gets anything.

Researchers Bram van den Bergh and Seigfried Dewitte asked heterosexual male participants to play the game in pairs.

Before they started the game, they were variously shown pictures of sexy women in bikinis, landscapes, older women, younger women, or given t-shirts or lingerie to handle.

When participants saw gratuitous pictures of bikini-clad girls (like the one on the right), lingerie and the like, they were more likely to accept unfair splits than in the other conditions.

Although the average difference in the lowest accepted offers between ‘sexy’ and ‘unsexy’ conditions was pretty small (only 0.39 euros), the researchers could be statistically confident that the difference was reliable.

One frequently repeated claim in the news stories is that men with higher levels of testosterone were particularly likely to be affected in this way.

This was never actually measured in the study, however. What was measured was the difference in length between the second and fourth finger (digit ratio) which is thought by some to indicate the amount of testosterone the person was exposed to as a developing child in the womb.

This is one subtlety that many news reports left out, as firstly, it’s controversial as to whether digit ratio does relate to testosterone exposure in the womb, and secondly, it’s not clear how this relates to current levels of testosterone at all. In fact, immediate levels of testosterone can fluctuate wildly.

Probably, the study is best thought of as an interesting but preliminary finding, as there are many questions that could be asked about the study design and experience of the participants that might have affected the results.

Petra Boynton has a good analysis of some of these, including why the story has proved so popular with the media.

The best write-up of the study’s details I’ve found is from Nature, who do the study justice and point out that the results actually contradict the idea that sexy images makes men less rational. In the study, they actually made men more rational.

If you’re being offered money in the ultimatum game, for each offer, the single most rational thing to do is accept money every time, no matter how low the offer is, because if you don’t, you get nothing. You’re given the choice between something and nothing – a no brainer.

In reality, people don’t do this, a sense of fair play stops most people accepting paltry offers. Actually, this probably makes sense in everyday life (who wouldn’t want to enforce fairness in society) but in terms of the experiment, it can be self-defeating.

The fact that men who saw sexy images were more likely to accept lower offers rather than reject them and get nothing at all, suggest that their short-term rationality was actually enhanced.

Perhaps it is no co-incidence that the bikini celebrated its 60th birthday this week. I shall be monitoring the economy carefully for any signs of change.

Link to write-up of study from Nature.
Link to analysis from Petra Boyton.
Link to abstract of original research paper.