Heterosexual romantic couples mate assortatively for facial symmetry, but not masculinity.

Preferences for partners with symmetric and sex-typical faces are well documented and considered evidence for the good-genes theory of mate choice. However, it is unclear whether preferences for these traits drive the real-world selection of mates. In two samples of young heterosexual couples from the United Kingdom (Study 1) and the United States (Study 2), the authors found assortment for facial symmetry but not for sex typicality or independently rated attractiveness. Within-couple similarity in these traits did not predict relationship duration or quality, although female attractiveness and relationship duration were negatively correlated among couples in which the woman was the more attractive partner. The authors conclude that humans may mate assortatively on facial symmetry, but this remains just one of the many physical and nonphysical traits to which people likely attend when forming romantic partnerships. This is also the first evidence that preferences for symmetry transfer from the laboratory to a real-world setting.