Preferences for variation in masculinity in real male faces change across the menstrual cycle: women prefer more masculine faces when they are more fertile

In women cyclical shifts in preference have been documented for odour and certain physical and behavioral male traits. For example, women prefer more masculinised male faces when at peak fertility than at other times in their menstrual cycle. In previous studies, the face images used have all been manipulated using computer graphic techniques. Here, we examine variation in preferences for perceived masculinity in unmanipulated real male faces to address consistency with findings using manipulated masculinity in faces. We show that women prefer greater masculinity in male faces at times when their fertility is likely to be highest (during the follicular phase of their cycle) if they are in a current romantic relationship. These results indicate that women's preferences for perceived sexual dimorphism in real male faces follow a similar pattern as found for manipulated sexual dimorphism, suggesting that manipulated and real masculinity in male faces generate similar results in preference studies. Cyclical preferences could influence women to select a partner who possesses traits that may enhance her offspring's quality via an attraction to increased masculinity at times when conception is most likely, or serve to improve partner investment via an attraction to reduced masculinity when investment is important.