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