Trustworthy? The brain knows.

Abstract

Deciding whether to trust another individual is one of the most important decisions a person has to make, especially in social contexts. The ability to make accurate judgements of trustworthiness is predicted to be evolutionarily advantageous. There is evidence for a consistent consensus when rating faces on trustworthiness, and faces rated as both untrustworthy and trustworthy have been shown to activate the amygdala. We investigated the extent to which amygdala activation corresponds to measured trustworthiness associated with facial stimuli. Using functional magnetic resonance imaging (fMRI) we scanned 6 participants while they viewed faces of people that varied on The Dark Triad personality characteristics. There was significant activation in the amygdala in response to faces associated with high psychopathy, high Machiavellianism and high trusting behaviour. The findings support recent work demonstrating the relationship between facial morphometric geometry and personality traits. The psychopathy findings in particular supports recent work suggesting threat to be a large component of implicit trustworthiness decisions and also suggests the neural substrates associated with cheater detection are attuned to facial geometry that might represent psychopathy.