Facing the truth: are there hemifacial differences in the communication of trustworthiness?

As the right hemisphere is dominant for emotion processing, the left cheek expresses emotion more intensely than the right cheek. This prompts a leftward bias: people offer the left cheek to communicate emotion and viewers perceive left cheek poses as more emotive. Perceptions of trustworthiness are positively influenced by emotional expressivity, with smiling faces deemed more trustworthy than neutral faces. Thus as the left hemiface is more emotionally expressive than the right, the present study sought to determine whether people offer the left cheek to communicate trustworthiness, and the right to express untrustworthiness. One hundred and twenty-six participants (57 males, 69 females) completed a posing task asking them to read one of two scenarios (randomly assigned: trusted babysitter; untrustworthy car salesman), consider it for 30 seconds, and then pose for a photograph communicating their trustworthiness or untrustworthiness. Contrary to expectation, binary logistic regression results indicated no posing bias for communicating trustworthiness, however people were more likely to offer the left than right cheek when posing to communicate untrustworthiness. The novel finding of a left cheek bias for untrustworthiness is previously unreported, and highlights the need for future investigations of trustworthiness to examine both sides of the trustworthy coin.