Across two studies, sexually unrestricted men and women showed heightened sensitivity to female facial symmetry (a signal of genetic fitness) and female sexual receptivity (happy facial expressions). In Study 1, individuals assessed the attractiveness of male and female targets of varying facial symmetry. Sexually unrestricted men and women, compared to their sexually restricted counterparts, showed a stronger symmetry advantage in attractiveness ratings for female targets, an indication of greater sensitivity to facial symmetry. Study 2 asked participants to discriminate between genuine (Duchenne) and deceptive smiles on both male and female faces. Results indicated that sexually unrestricted men and women, compared to sexually restricted individuals, were better able to discriminate between these actual and deceptive signals of receptivity for female targets. Neither study found any relationship between sociosexual orientation and the perception of male targets. These results suggest that sexually unrestricted individuals are attuned to reproductively-relevant cues in female faces.
Source: “Sociosexuality and face perception: Unrestricted sexual orientation facilitates sensitivity to female facial cues” from Personality and Individual Differences, Volume 47, Issue 7, November 2009, Pages 777-782