Facial Metrics, Aggression, and the Use of Military Force

Presidents cite many reasons to justify their decisions to use military force. Regardless of the explanation provided, putting soldiers in harm's way entails a high degree of risk. Some presidents are more willing than others to undertake risky policies, and psychological dispositions help to account for their willingness. According to evolutionary psychology theories of conflict, facial characteristics serve as important cues of aggression, and a substantial body of empirical evidence supports the association between the facial width-to-height ratio (FWHR) and conflict behavior. All else equal, individuals with greater FWHRs are more likely to choose aggressive foreign policies. Empirical analyses of 1953–2000 show that US presidents with higher FWHRs are four times more likely than those with lower FWHRs to use military force. The results hold independent of traditional explanations such as power, ongoing war, elections, the misery index, and alternative measures of leader psychology.