Assessing the roles of shape prototypicality and sexual dimorphism in ratings of the trustworthiness of faces

Perceptions of the trustworthiness of faces predict important social outcomes, including economic exchange and criminal sentencing decisions. However, the specific facial characteristics that drive trustworthiness perceptions remain poorly understood. Here we investigated this issue by exploring possible relationships between ratings of the trustworthiness of face images and objective assessments of two aspects of face shape that researchers have previously suggested are important for perceptions of trustworthiness: distinctiveness and sexual dimorphism. We found that faces with more distinctive shapes were rated as less trustworthy. By contrast, sexual dimorphism of face shape was not significantly correlated with trustworthiness ratings. These results suggest that distinctiveness of face shape plays a more important role in trustworthiness perceptions than does sexual dimorphism and suggest that perceptions of trustworthiness may stem, at least in part, from the ‘anomalous-is-bad’ stereotype.