Real Face Analysis of Masculinity-Femininity, Facial Ratios, and Attractiveness.

Background: Previous studies have evaluated the influence of facial features in determining male and female sex using prototypical renderings or artificially altered faces in relatively small sample sizes. Using a large set of human photographs and raters, this study hypothesized that certain anatomic facial ratios are associated with perceptions of masculinity/femininity, can interact to predict sex, and are associated with ratings of attractiveness differently in males and females.

Methods: Ratings of masculinity-femininity and binary self-identification (male or female) were compared with facial anatomic ratios from 827 frontal facial photographs. Ratios were used to characterize facial feature relativity, where higher ratio scores indicated relatively more facial feature representation.

Results: Femininity was associated with prominent middle third ratio, nose length, lip vermillion height, eye height, and eye width ratios; masculinity was associated with prominence of the upper and lower facial thirds, nose width, chin height, and philtrum height ratios (all P < 0.01). Subgroup analysis demonstrated many of these relationships persisted when evaluating masculinity in females and femininity in males. Misgendering in males was associated with greater middle third ratio and upper lip ratio, whereas misgendering in females was associated with increased nose width ratio.

Conclusions: This study demonstrates associations of femininity with increased horizontal middle third representation, and masculinity was associated with increased upper and lower horizontal representation. These facial ratios interact to predict male and female sex, which could have implications for optimizing facial feminization/masculinization outcomes and building algorithms for artificial intelligence analysis of faces.