Facing our ancestors: judgements of aggression are consistent and related to the facial width-to-height ratio in men irrespective of beards

Snap judgements of threat based on exposure to the human face were likely maintained throughout history because they facilitated survival when encountering strangers. If an evolved adaptation, then such judgements should rely on static facial cues that are not masked by facial hair, as may have been the case for our ancestors. We show that the facial width-to-height ratio (FWHR) is not obscured by facial hair and that it reliably and consistently cues observers' (n = 56) judgements of aggression, but not of masculinity, in bearded (r = .59) and in non-bearded (r = .66) versions of the same male faces. The high reliability of the FWHR irrespective of facial hair and the evidence that judgements of threat based on the FWHR have some accuracy, suggests our perceptual system may have evolved to be sensitive to the FWHR along with the perceptual bias to extract information preferentially from the upper-face.