Estimating aggression from emotionally neutral faces: Which facial cues are diagnostic?

The facial width-to-height ratio, a size-independent sexually dimorphic property of the human face, is correlated with aggressive behaviour in men Furthermore. observers' estimates of aggression from emotionally neutral faces are accurate and are highly correlated with the facial width-to-height ratio We investigated whether observers use the facial width-to-height ratio to estimate propensity for aggression In experiments 1a - 1c, estimates or aggression remained accurate when laces were blurred or cropped. manipulations that reduce featural cues but maintain the facial width-to-height ratio Accuracy decreased when faces were scrambled, a manipulation that retains featural in but disrupts the facial width-to-height ratio In experiment 2, computer-modeling software identified milt facial metrics that correlated with estimates of aggression, regression analyses revealed that the facial width-to-height ratio was the only metric that uniquely predicted these estimates In experiment 3, we used a computer-generated set of faces varying in perceived threat (Oosterhof and Todorov, 2008 Proceedings of the National Academy of Sciences of the USA 105 11087-11092) and found that as emotionally neutral faces became more 'threatening', the facial width-to-height ratio increased Together. these experiments suggest that the facial width-to-height ratio is an honest signal of propensity for aggressive behaviour