ترجیحات برای تنوع در مردسالاری در چهره های واقعی مردان سرتاسر چرخه قاعدگی را تغییر می دهد:زنان چهره مردانه تر زمانی که آنها بارور تر هستند را ترجیح می دهند

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.

Research on facial attractiveness has used both real and computer graphic manipulated faces. In some areas, the results generated have differed depending on the technique used. Computer graphic studies which manipulate masculinity have tended to suggest that feminine male faces are attractive while studies of real faces using rated masculinity have usually demonstrated preferences for masculinity (see Rhodes, 2006). This has led Rhodes (2006) to suggest that real faces may reveal a truer picture of female preferences than computer manipulated images. One area that has received much attention is cyclic variation in attraction to masculine face traits. Generally such studies have used manipulated faces (Johnston et al., 2001, Penton-Voak and Perrett, 2000 and Penton-Voak et al., 1999), and so it is important to examine whether the effects seen in these studies are also found using variation in masculinity amongst real faces. If similar effects are seen using both real and manipulated faces we can conclude that results of studies using the two image types are comparable. Below we briefly review the literature and reasoning behind studying cyclic preferences for masculinity. Women differ in their preferences and one biological explanation for within-individual variation lies with hormonal changes across the menstrual cycle. Many studies have demonstrated that women’s preferences for certain male traits change across the menstrual cycle. Increased preferences for facial masculinity (Frost, 1994, Johnston et al., 2001, Penton-Voak and Perrett, 2000 and Penton-Voak et al., 1999), vocal masculinity (Feinberg et al., 2006 and Puts, 2005), dominant behavior (Gangestad, Simpson, Cousins, Garver-Apgar, & Christensen, 2004), for taller men (Pawlowski & Jasienska, 2005) and for masculine body shapes (Little, Jones, & Burriss, 2007a) that coincide with the late follicular (i.e., fertile) menstrual cycle phase have been reported. Cyclic shifts are also seen for other mate choice relevant traits whereby fertile women generally rate men as more attractive (Danel & Pawlowski, 2006) and are more attracted to facial symmetry (Little, Jones, Burt, & Perrett, 2007b). Changes in preferences for masculine men are potentially adaptive. Human males bring two factors to a parenting relationship: investment in their partners and offspring, and potential heritable benefits (e.g., genes for high quality immune systems). Masculinity in males has long been thought to be an indicator of quality via classic handicap models (Folstad & Karter, 1992); as higher testosterone levels handicap the immune system (Kanda, Tsuchida, & Tamaki, 1996) and, therefore, only high quality males can afford to be masculine (Thornhill & Gangestad, 1999). The relationship between masculinity and quality is controversial and there are several lines of reason involved in why it might be preferred (Getty, 2002 and Thornhill and Gangestad, 1999). While masculine faced men are healthier than their feminine faced counterparts (Rhodes et al., 2003 and Thornhill and Gangestad, 2006), masculinity in a partner also carries a cost. Men with masculine faces have higher circulating testosterone levels (Penton-Voak & Chen, 2004) which are linked to marital instability and lower levels of attachment in relationships (Booth and Dabbs, 1993 and Burnham et al., 2003). As might be expected then, masculine faces are seen as more dominant but not seen as possessing traits that would be desirable in a long-term partner (Boothroyd et al., 2007 and Perrett et al., 1998). Thus, variation in preferences during the menstrual cycle may enable women to maximize the benefits of their mate preferences, potentially shifting priorities between heritable benefits to offspring and investment (Penton-Voak et al., 1999). Although peaks in sexual desire and activity have been reported at different stages across the menstrual cycle (Regan, 1996), some studies have reported that women with partners may be more likely to engage in extra-pair sexual activity at peak fertility (Baker & Bellis, 1995). Further evidence for possible extra-pair sexual behavior comes from studies showing that women at peak fertility are more likely to have sexual fantasies about men other than their primary partner (Gangestad, Thornhill, & Garver, 2002), express a greater interest in attending social gatherings where they might meet men at peak fertility (Haselton & Gangestad, 2006), and report being more committed to their partners during the luteal phase of the menstrual cycle and less committed in the late follicular phase (Jones et al., 2005). These studies suggest a possible mechanism whereby women may maximize their chances of becoming pregnant with the offspring of males chosen for extra-pair affairs. Such males may be selected for possessing superior or alternative genes to the woman’s current partner. As an alternative or perhaps complementary explanation for shifting preferences alterations in progesterone level have been associated with increased commitment to a partner, and increased preferences for less masculinized male faces during the luteal phase of the cycle. This may reflect an increase in the care and support that is available during hormonal profiles similar to those that characterize pregnancy (Jones et al., 2005). In this way, rather than acquiring direct benefits for offspring from masculine men, women instead maximize investment from feminine men when raised progesterone prepares the body for pregnancy (Jones et al., 2005). Preferences for masculinity in faces have also been found to be moderated by other factors relating to potentially strategic choice. Already having a partner has also been shown to predict female face preferences. An increased preference for genetic fitness over signs of parental investment would be expected in extra-pair copulations when a woman has already acquired a long-term partner. Indeed, Little, Jones, Penton-Voak, Burt, and Perrett (2002) have shown that women who have partners prefer masculinity in faces more so than females without a current romantic partner. Another factor that influences preferences for facial masculinity is the type of relationship being looked for. Studies have shown that women tend to prefer more masculine faces when judging for a short-term than for a long-term relationship. Indeed, in a variety of studies cycle effects are often more likely seen when women judge for short-term relations (Gangestad & Thornhill, 2008). In a similar way to already having an investing partner, short-term relations minimise the need to value investment from partners. The current study again examined preferences for sexual dimorphism in male faces across the menstrual cycle, but with a key difference. Previous studies of shifting face preferences for masculinity have used computer graphic manipulations of shape and colour (Johnston et al., 2001) or manipulations of shape alone (Johnston et al., 2001, Jones et al., 2005, Penton-Voak and Perrett, 2000 and Penton-Voak et al., 1999). As noted earlier, Rhodes (2006) has suggested, however, that findings from studies using computer graphic methods to manipulate sexual dimorphism might reflect an artefact of the methods used to manufacture stimuli, and should thus be treated cautiously. Studies reporting associations between ratings of the masculinity and attractiveness of unmanipulated facial images may thus represent a more valid reflection of female mate preferences (Rhodes, 2006). The goal of this study is to address whether similar results are seen for preferences in real faces varying in perceived masculinity. Here, we examine attraction to perceptual masculinity in real unmanipulated faces by asking women to choose between faces rated as relatively more or less masculine. We predicted (following similar results for preferences for manipulated masculinity in male faces) that women would prefer more masculine real male faces when in the follicular phase of their cycle. We also predicted that menstrual cycle shifts may be greater for women with partners, again following findings from manipulated face and body preferences, and that there may be an interaction between fertility and partnership status if shifting preferences across the menstrual cycle serve to focus individuals on the quality of potential extra-pair partners.