Menstrual cycle alters face preference

Women prefer slightly feminized male facial shapes1. Such faces (Fig. 1a) are given positive personality attributions1 that might correlate with actual behaviour2. In contrast, masculine features seem to signal immunological competence3. Heritable benefits can be realized only if conception follows copulation, so women might be more attentive to phenotypic markers indicating immunological competence during the follicular phase of the menstrual cycle when conception is most likely4,5. Consistent with this hypothesis is the observation that women's preference for the odour of men with low fluctuating asymmetry (a correlate of testosterone-facilitated trait size and developmental stability) increases with the probability of conception across the menstrual cycle5.Symmetrical men report more extra-pair copulation partners6, and extra-pair copulation rates peak in midcycle7. Here we show that female preference for secondary sexual traits in male face shapes varies with the probability of conception across the menstrual cycle. Figure 1 Cyclic shifts in the degree of femininity preferred in male faces. a, Face shapes that are 50% feminized (left) and 50% masculinized (right). Top: constructed1 from 26 males, mean age 19.7 years; 37 females, 18.7 years. Centre: 21 males, 21.0 years; 40 females, 21.0 years. Bottom: 18 males, 19.8 years; 38 females, 20.8 years. b, Mean feminization preferred in Japanese and Caucasian composites by Japanese subjects (n =39) in high- and low-conception-risk phases. c, Mean femininity preferred across faces for short- and long-term conditions (experiment 2) in high-risk and low-risk phases.