Millions of women use hormonal contraception and it has been suggested that such use may alter mate preferences. To examine the impact of oral contraceptive (pill) use on preferences, we tested for within-subject changes in preferences for masculine faces in women initiating pill use. Between two sessions, initiation of pill use significantly decreased women's preferences for male facial masculinity but did not influence preferences for same-sex faces. To test whether altered preference during pill use influences actual partner choice, we examined facial characteristics in 170 age-matched male partners of women who reported having either been using or not using the pill when the partnership was formed. Both facial measurements and perceptual judgements demonstrated that partners of women who used the pill during mate choice have less masculine faces than partners of women who did not use hormonal contraception at this time. Our data (A) provide the first experimental evidence that initiation of pill use in women causes changes in facial preferences and (B) documents downstream effects of these changes on real-life partner selection. Given that hormonal contraceptive use is widespread, effects of pill use on the processes of partner formation have important implications for relationship stability and may have other biologically relevant consequences.
Biological approaches to human attractiveness have documented several traits linked to mate preferences (Roberts and Little, 2008). These include preferences for visible facial and body traits, such as symmetry and sexually dimorphic cues (Thornhill and Gangestad, 1999 and Little et al., 2011), vocal cues, such as pitch (Feinberg et al., 2006 and Feinberg et al., 2008), and odour cues, such as those associated with genetic profiles (Wedekind et al., 1995 and Roberts et al., 2008). Sexually dimorphic traits, relative masculinity/femininity, in faces have received much attention from those interested in evolutionary approaches to human preferences and perception (see e.g., Thornhill and Gangestad, 1999). This is because masculinity in male faces has been proposed to relate to both inter-sexual selection (Thornhill and Gangestad, 1999 and Little et al., 2011), influencing attraction to the opposite-sex, and intra-sexual selection (Swaddle and Reierson, 2003), relating to competition between members of the same sex. In terms of attractiveness to the opposite-sex, there are benefits that could be associated with sexual dimorphism: (1) indirect benefits, genetic benefits that are passed to offspring such as genes associated with strong immune systems, and (2) direct benefits, benefits that are directly passed to mates or offspring, such as resources or avoidance of disease. In line with links to both types of benefit, masculine-faced men are perceived as dominant (Perrett et al., 1998), report better health (Thornhill and Gangestad, 2006) and are physically stronger (Fink et al., 2007). However, masculine faced men also receive negative attributions, such as being seen as poor parents (Perrett et al., 1998), and have more short-term partners (Boothroyd et al., 2008) which suggests low investment in relationships. Facial masculinity in men then appears to be associated with a trade-off between investment and quality (Perrett et al., 1998). For example, masculinity may be negatively linked to levels of investment (direct benefit) but also positively to quality in terms of genes for health/dominance (indirect benefits) as well as current health/resources (direct benefits). Such a trade-off is consistent with variation in masculinity preferences, such as increased preferences for masculinity in short-term contexts (Little et al., 2002).
