Effects of sex and sex-related facial traits on trust and trustworthiness: An experimental study

Abstract

The ability to trust others, including strangers, is a prerequisite for human cooperation. Economically it is not rational to trust strangers, as trust can be easily exploited. Still, generally, the level of trust toward strangers is relatively high. Trust is closely related to trustworthiness: when trusting others, one expects them to reciprocate. Some individuals elicit more trust than others. Apparently, humans use subtle cues for judging the trustworthiness of their interaction partners. Here, we report on an experiment that investigates trust and trustworthiness in a population of 176 mainly Dutch students. The aims of our study were: (1) to investigate how the sex of interaction partners and their facial appearance (femininity/masculinity) affect the degree of trust and trustworthiness, compared to fully anonymous conditions; (2) to test whether individuals who elicit trust in their interaction partners are trustworthy themselves. Each subject of our experiment played five one-shot Trust Games: one with an anonymous interaction partner, and four “personalized” games after seeing a 20 s silent video of their interaction partner (twice same-sex, and twice opposite-sex). The degree of facial sexual dimorphism was investigated with geometric morphometrics based on full-face photographs. Our results revealed that, despite the already high level of trust in the anonymous setting, the personalization of interactions had a clear effect on behavior. Females elicited more trust in partners of both sexes. Interestingly, females with more feminine faces elicited less trust in both male and female partners, while males with more masculine facial shape were more trusted by females, but less trusted by males. Neither sex nor facial femininity/masculinity predicted trustworthiness. Our results demonstrate that (1) sex and sex-related facial traits of interaction partners have a clear effect on eliciting trust in strangers. However, (2) these cues are not reliable predictors of actual trustworthiness.

Facial cues to physical strength are not always associated with facial masculinity: Comparative study of Europeans and Southern Siberians

“…Comparison of our results with the results of other studies shows that the pattern of sexual dimorphism varies between populations, whereas the handgrip strength relative to facial shape patterns demonstrates cross‐population consistency. Relatively wider faces (especially in the lower face), which is specific to male faces in Europeans (Fink et al, 2005; Rostovtseva et al, 2023), were characteristic of stronger Russian men in our study. At the same time, relatively narrower faces were characteristic of weaker Russian men, which corresponded to female‐like faces in this population.…”

“…The distance between camera and participant was 170 cm. Seventy digital landmarks and semilandmarks were placed on full-face photograph, following configuration we used previously in our earlier studies (Rostovtseva et al, 2023). This configuration was also adopted for profiles.…”

“…To explore correlation between frontal and profile facial sexual dimorphism in each population, individual shape scores for sex-typicality were calculated using linear discriminant analysis (LDA) for two groups (men and women). The LDA procedure was conducted on the Procrustes coordinates of the facial landmarks and semilandmarks (Rostovtseva et al, 2023) using "MASS" package for R (Venables & Ripley, 2002). Visualization of the facial shape differences was realized with thin-plate deformation grids using tpsRegr 1.45 (Rohlf, 2015).…”

“…Configurations of landmarks (black) and semilandmarks (yellow) are presented. Full‐face landmarks configuration (A) was adopted from Rostovtseva et al (2023); profile landmarks configuration (B) was developed by the authors. In case of eyes, for aesthetic reasons, we have replaced the black circles with black crosses.…”

“…For instance, in some Asian and African (the Maasai) populations, against the background of generally larger absolute sizes of male faces, women tend to have higher relative widths of the lower jaw (bigonial width) (Butovskaya et al, 2022; Rostovtseva et al, 2021; Tanikawa et al, 2016). In contrast, in European populations, higher relative lower jaw width is a male‐specific feature (Fink et al, 2005; Rostovtseva et al, 2023).…”