BehindTheMedspeak: Men with wide faces are more violent

Just published in the Proceedings of the Royal Society is a most interesting study by Justin Carré and Cheryl McCormick of Brock University in Ontario, Canada.

Long story short: The wider a man's face, the more violent he's likely to be.

Let's start with an article appearing in the current (August 21, 2008) issue of The Economist deconstructing the science and putting it in perspective, for those of us who prefer to just put a toe in at first.

Facing the truth

The shape of your face betrays how aggressive you are — if you are a man

Physiognomy, the art or science of predicting inward character from outward form, has had its ups and downs over the years. A century ago, the idea that a person’s character could be seen in his face was more or less taken as given. It then fell out of favour, along with the idea that behaviour is genetically determined, as Marxist ideas of the pliability and perfectibility of mankind became fashionable. Now, it is undergoing something of a revival. It has been found, for example, that women can predict a man’s interest in infant children from his face. Trustworthiness also shows up, as does social dominance. The latest example comes from a paper just published in the Proceedings of the Royal Society by Justin Carré and Cheryl McCormick, of Brock University in Ontario, Canada. This suggests that in men, at least, it is also possible to look at someone’s face and read his predisposition to aggression.

The thesis developed by Mr Carré and Dr McCormick is that aggressiveness is predictable from the ratio between the width of a person’s face and its height. Their reason for suspecting this is that this ratio differs systematically between men and women (men have wider faces) and that the difference arises during puberty, when sex hormones are reshaping people’s bodies. The cause seems to be exposure to testosterone, which is also known to make people aggressive. It seems reasonable, therefore, to predict a correlation between aggression and face shape.

To test their thesis, Mr Carré and Dr McCormick looked at the fine, old Canadian sport of ice hockey. This is, famously, not a gentle game. It is also a game in which the rules provide a plausible proxy for aggressiveness, namely the amount of time a player spends off the ice in the penalty box for such infringements as knocking his opponent’s teeth out with a well-aimed stick.

The two researchers obtained photographs of several university and professional ice-hockey teams, and measured the facial ratios of the players. They also obtained those players’ penalty records. Just as they expected, the wider a player’s face, the more time he spent in the cooler.

Ice hockey, though, is mostly a man’s game (women might argue that they are too sensible to get involved, although the Canadian ladies did win a gold medal at the last winter Olympics). To find out whether the theory was true for females as well, Mr Carré and Dr McCormick turned to that stock experimental subject, the university undergraduate. They recruited several dozen of both sexes and got them to play a game against what they thought was a person in another room but was actually a computer. Various measures of aggression taken during this game suggest that men are the same everywhere, be they students or sportsmen. Aggression was not, however, predictable in women students — or, at least, not from the shapes of their faces.

It seems, therefore, that facial ratio in men is a biologically honest signal of aggressiveness. Honest signals are those, such as luxuriantly feathered tails, that cannot be mimicked by individuals who would like the benefits without the costs. In the case of aggressiveness, the benefit to the aggressive individual is, paradoxically, that he will not have to get into fights in order to prove the point. The fear induced by his face should be enough by itself. At least, that is the hypothesis. The experiment to prove it has yet to be done.

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Here's the abstract of the article.

In your face: facial metrics predict aggressive behaviour in the laboratory and in varsity and professional hockey players

Facial characteristics are an important basis for judgements about gender, emotion, personality, motivational states and behavioural dispositions. Based on a recent finding of a sexual dimorphism in facial metrics that is independent of body size, we conducted three studies to examine the extent to which individual differences in the facial width-to-height ratio were associated with trait dominance (using a questionnaire) and aggression during a behavioural task and in a naturalistic setting (varsity and professional ice hockey). In study 1, men had a larger facial width-to-height ratio, higher scores of trait dominance, and were more reactively aggressive compared with women. Individual differences in the facial width-to-height ratio predicted reactive aggression in men, but not in women (predicted 15% of variance). In studies 2 (male varsity hockey players) and 3 (male professional hockey players), individual differences in the facial width-to-height ratio were positively related to aggressive behaviour as measured by the number of penalty minutes per game obtained over a season (predicted 29 and 9% of the variance, respectively). Together, these findings suggest that the sexually dimorphic facial width-to-height ratio may be an ‘honest signal’ of propensity for aggressive behaviour.

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As always, there are a few out there who aren't satisfied with anything less than the full Monty.

For you, here's the scientific paper in its entirety, complete with figures, tables and references.