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

Abstract

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 argued are important for perceptions of trustworthiness: distinctiveness and sexual dimorphism. Here we report that faces with more distinctive shapes are rated as less trustworthy, but that sexual dimorphism of face shape is 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.

Assessing the roles of symmetry, prototypicality, and sexual dimorphism of face shape in health perceptions

“…Sexual dimorphism of face shape was objectively measured for each of the 50 male and 50 female face images using the facefuns package (Holzleitner & DeBruine, 2021) in R (R Core Team, 2021), which implements shape analysis of images that have been delineated with standard landmarks. This method has been used in many previous studies to assess sexual dimorphism of face shape (e.g., Cai et al, 2019;Dong et al, 2023;Holzleitner et al, 2019;Leger et al, 2023;Komori et al, 2011). Shape components were first derived from Principal Component Analysis (PCA) of 132 Procrustes-aligned landmark points (see Holzleitner et al, 2019 for a diagram showing these facial landmarks) on each of the 50 male and 50 female face images.…”

“…Previous work has shown that measures of face shape derived from manually placed and automatically generated image landmarks are highly correlated (Jones et al, 2021b). Scores representing sexual dimorphism of face shape were then calculated from each photograph using a vector analysis method (e.g., Cai et al, 2019;Dong et al, 2023;Holzleitner et al, 2019;Leger et al, 2023;Komori et al, 2011). This method uses the shape principal components to locate each face on a female-male continuum.…”

“…Third, many studies have tested for possible links between health perceptions of faces and symmetry, prototypicality, or sexual dimorphism using face stimuli in which these physical characteristics were experimentally manipulated using computer graphics methods (e.g., Alharbi et al, 2020;Jones et al, 2001;Penton-Voak et al, 2001). However, several recent studies have reported that findings for social judgments of faces that were obtained using this method are often not observed (or, if observed, have considerably smaller effect sizes) in studies using natural face images and objective assessments of physical characteristics of faces (Dong et al, 2023;Jones & Jaeger, 2019;Jones et al, 2023;Lee et al, 2021;Leger et al, 2023;Scott et al, 2010). Given such results, many researchers have expressed concerns about the appropriateness of experimentally manipulated face images for studying social judgments of faces (Dong et al, 2023;Jones & Jaeger, 2019;Jones et al, 2023;Leger et al, 2023;Scott et al, 2010).…”

“…However, several recent studies have reported that findings for social judgments of faces that were obtained using this method are often not observed (or, if observed, have considerably smaller effect sizes) in studies using natural face images and objective assessments of physical characteristics of faces (Dong et al, 2023;Jones & Jaeger, 2019;Jones et al, 2023;Lee et al, 2021;Leger et al, 2023;Scott et al, 2010). Given such results, many researchers have expressed concerns about the appropriateness of experimentally manipulated face images for studying social judgments of faces (Dong et al, 2023;Jones & Jaeger, 2019;Jones et al, 2023;Leger et al, 2023;Scott et al, 2010). Nonetheless, Boothroyd et al (2007) reported that experimentally manipulated masculinity did not influence the perceived health of male faces and also reported that masculinity and health ratings of natural male faces were not significantly correlated.…”

Cross-Cultural Differences in Perception of Facial Trustworthiness Based on Geometric Morphometric Morphs

“…These facial features partly correspond to female-like facial shape in these populations (Ekrami et al, 2021; Kleisner et al, 2021; Mezentseva et al, 2023). Indeed, a number of studies demonstrate that perceived facial trustworthiness is related to morphological facial femininity/masculinity in Europeans, with male-specific appearance generally eliciting less trust than female-specific (Rostovtseva et al, 2023; Stirrat & Perrett, 2010; although see Leger et al, 2023 for alternative results). Another important source of facial shape variation related to trustworthy look is the resemblance of facial features to specific emotional expressions.…”