The facial width-to-height ratio shares stronger links with judgments of aggression than with judgments of trustworthiness.

Variation in the facial width-to-height ratio (face ratio) is associated with judgments of aggression and of trustworthiness made by observers when viewing men's faces. Although judgments of aggression and of trustworthiness are correlated, they represent distinct constructs. We thus investigated the hypothesis that judgments of aggression share stronger associations with the face ratio than judgments of trustworthiness, and that judgments of aggression mediate the link between the face ratio and trustworthiness. Across 4 separate studies, involving 129 observers rating subsets of 141 photographs (original photographs of individuals who provided consent for their use) of clean-shaven (65 faces), unshaved (22 faces), or digitized male faces (54 faces; digitized faces were creating using facial modeling software), this hypothesis was supported. The correlations between the face ratio and judgments of aggression were moderate to strong in all 4 studies (rs = .45 to .70). Reaction time was measured in Study 4: Participants judged aggression faster than trustworthiness; thus, temporal precedence also supports the hypothesis that aggression mediates the link between the face ratio and trustworthiness. Sensitivity to the face ratio may therefore be part of a perceptual mechanism specialized to assess aggressiveness rather than trustworthiness in others, likely because of the greater necessity for rapid judgments of aggressive potential than trustworthiness.