Valid facial cues to cooperation and trust: male facial width and trustworthiness.

Decisions about whom to trust are biased by stable facial traits such as attractiveness, similarity to kin, and perceived trustworthiness. Research addressing the validity of facial trustworthiness or its basis in facial features is scarce, and the results have been inconsistent. We measured male trustworthiness operationally in trust games in which participants had options to collaborate for mutual financial gain or to exploit for greater personal gain. We also measured facial (bizygomatic) width (scaled for face height) because this is a sexually dimorphic, testosterone-linked trait predictive of male aggression. We found that men with greater facial width were more likely to exploit the trust of others and that other players were less likely to trust male counterparts with wide rather than narrow faces (independent of their attractiveness). Moreover, manipulating this facial-width ratio with computer graphics controlled attributions of trustworthiness, particularly for subordinate female evaluators.