Implicit trustworthiness decisions: automatic coding of face properties in the human amygdala.

Deciding whether an unfamiliar person is trustworthy is one of the most important decisions in social environments. We used functional magnetic resonance imaging to show that the amygdala is involved in implicit evaluations of trustworthiness of faces, consistent with prior findings. The amygdala response increased as perceived trustworthiness decreased in a task that did not demand person evaluation. More importantly, we tested whether this response is due to an individual's idiosyncratic perception or to face properties that are perceived as untrustworthy across individuals. The amygdala response was better predicted by consensus ratings of trustworthiness than by an individual's own judgments. Individual judgments accounted for little residual variance in the amygdala after controlling for the shared variance with consensus ratings. These findings suggest that the amygdala automatically categorizes faces according to face properties commonly perceived to signal untrustworthiness.