of good inheritance to women of child-bearing age seeking to create healthy offspring. Studies suggest women are less attracted to men with asymmetrical faces, and symmetrical faces correlate with long term mental performance and are an indication that a man has experienced "fewer genetic and environmental disturbances such as diseases, toxins, malnutrition or genetic mutations" while growing. Since achieving symmetry is a difficult task during human growth, requiring billions of cell reproductions while maintaining a parallel structure, achieving symmetry is a visible signal of genetic health. Studies have also suggested that women at peak fertility were more likely to fantasize about men with greater facial symmetry, and other studies have found that male symmetry was the only factor that could significantly predict the likelihood of a woman experiencing orgasm during sex. Women with partners possessing greater symmetry reported significantly more copulatory female orgasms than were reported by women with partners possessing low symmetry, even with many potential confounding variables controlled. This finding has been found to hold across different cultures. It has been argued that masculine facial dimorphism (in men) and symmetry in faces are signals advertising genetic quality in potential mates. Low facial and body fluctuating asymmetry may indicate good health and intelligence, which are desirable features. Studies have found that women who perceive themselves as being more physically attractive are more likely to favor men with a higher degree of facial symmetry, than are women who perceive themselves as being less physically attractive. It has been found that symmetrical females and males have a tendency to begin to have sexual intercourse at an earlier age, to have more sexual partners, and to have more one-night stands. They are also more likely to engage in infidelity. A study of quarterbacks in the American National Football League found a positive correlation between facial symmetry and salaries. Body scent Double-blind studies found that women prefer the scent of men who are rated as facially attractive. For example, both males and females were more attracted to the natural scent of individuals who had been rated by consensus as facially attractive. Additionally, it has also been shown that women have a preference for the scent of men with more symmetrical faces, and that women's preference for the scent of more symmetrical men is strongest during the most fertile period of their menstrual cycle. Within the set of normally cycling women, individual women's preference