A man’s fighting ability is written in his face

Men with faces that are wide relative to their length are more formidable fighters, on average. That's according to a new paper that also finds that observers use the width of a man's face to ascertain with accuracy his likely fighting ability. Samuele Zilioli and his collaborators believe their findings support the idea that humans have evolved specific "neurocognitive adaptations" for assessing the fighting prowess of potential opponents.

The researchers first analysed the facial structure of 241 competitors in the Ultimate Fighting Championship (UFC). Why choose this competition? "T]he 'no‐holds‐ barred' nature of the fights and the process of 'cutting' serially defeated combatants from the championship makes for a somewhat Darwinian environment, well‐suited to the investigation of fighting ability," they explained.

Having a wider face was correlated with success in the UFC, in terms of surviving in the competition for longer and clocking up more wins. This association remained even after controlling for body size. There were also links between facial width and fighting success when analysis was restricted to Caucasian or non-Caucasian competitors.

Zilioli and his colleagues next demonstrated that people use the width of men's faces to infer their fighting prowess. Dozens of male and female students with no UFC knowledge looked at composites of experienced or inexperienced UFC fighters (composites were formed by averaging the faces of 12 fighters from each category). The students consistently rated the experienced faces as more deadly. It was a similar story when more students rated composites of wide or thin-faced fighters – the wider faces were rated as more formidable.

In another stage of the research, further students rated the fighting ability of individual fighters based on their unaltered photographs – in this case there was a correlation between the students' ratings and the fighters' real-life UFC success. Finally, the researchers adopted an experimental approach. They manipulated images of the fighters, to make them artificially wider or thinner faced. Making a fighter's face wider attracted ratings of greater formidability from student participants.

These results build on past evidence showing that men with wider faces tend to be more aggressive. Zilioli's group said this raised aggression is likely related to the fact such men have greater fighting ability. Why should the width of the face be linked to fighting ability? The researchers speculated that one causal mechanism may be higher testosterone levels – certainly past research has shown men with higher basal testosterone have wider faces, as well as greater strength and aggression. From a survival perspective, there is also research published this month suggesting that a greater face width-length ratio may be part of a facial structure evolved for resistance to punches.

"Regardless of its origin, the existence of this relationship between facial structure and fighting ability would have given natural selection an opportunity to design a more accurate formidability assessment mechanism," the researchers said.

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Zilioli S, Sell AN, Stirrat M, Jagore J, Vickerman W, & Watson NV (2014). Face of a fighter: Bizygomatic width as a cue of formidability. Aggressive behavior PMID: 24910133