Trust and valence processing in the amygdala*

In this issue of SCAN, Todorov and Engell report a new study showing not only that human amygdala activation to faces is most strongly modulated by the perceived (un)trustworthiness of faces among a series of 14 personality trait dimensions (such as attractiveness, aggressiveness, intelligence, caring, and so forth), but also that such effects appear to reflect a more general response to negative valence and may arise in an ‘implicit’ manner while observers are engaged in a memory task (without any requirement to make explicit affective or social judgments on faces). The important conclusion drawn by these authors is that the amygdala has a key role for an automatic appraisal of the valence of unknown faces, rather than for processing other specific attributes. These findings are novel and intriguing, but also raise a number of questions about the exact meaning of valence, trust and automaticity in such appraisals.