When I was in graduate school, a classmate confided in me that she was attracted to a mutual friend’s husband. She didn’t plan to pursue the man, but she told me that she found him attractive because he had all the qualities she was looking for in a boyfriend: He was handsome, he was stable, he had a good job and a nice home, and she fantasized about what a relationship with him might be like.
Why are women like this attracted to men who are already in relationships?
We call this phenomenon “mate-choice copying,” and it occurs in other animals, including fish and birds. In other species, females prefer males who have been seen with other females or who have mated with other females (Uller and Johansson, 2002). In humans, women tend to show a propensity to copy others’ mate choices, more than men do (Yorzinski and Platt, 2010). The idea is that females strive to choose a good partner, and the interest of other women signals that a man has the right qualities—in a sense, he is “pre-screened.” But women don't prefer all mated men. There are some conditions under which women find men who are in relationships more attractive (or not):
The Female Partner Should Be Attractive
The attractiveness of the female partner matters more than the man's looks. Regardless of the actual physical attractiveness of the men, women tend to rate men as more appealing when they are dating an attractive female partner (Waynforth, 2007; Yorzinski and Platt, 2010). However, this same research finds that the reverse is also true: Men are perceived as less appealing when they date an unattractive female partner.
The Men Must Be Perceived as Potentially Available
Although a good-looking partner may enhance men's attractiveness, a man must also be perceived as available in order to truly interest women. Bressan and Stranieri (2008) found that the preference for mated men was strongest when the men were described as having a girlfriend, a bit weaker when the men were described as being in love, and the weakest when they were described as being married. Similarly, Uller and Johansson (2002) report that women found men who were not wearing a wedding ring to be more attractive. Attempts to lure men away from partners are perceived as less effective when men are in committed relationships (Schmitt and Buss, 2001).
Although Mated Men are Attractive, Women May Choose Not to Pursue Them
Just as my friend admired her married friend from afar, women may choose to admire married men but not pursue them as relationship partners. Women who rate as agreeable and conscientious on personality measures are less likely to pursue mated men (Schmitt and Buss, 2001). However, women may choose to try to attract mated men when they are particularly dissatisfied with their current relationships (Schmitt & Buss, 2001).
.... And Some Women Are Not Attracted to Mated Men
Mate choice copying is less common among women who have had more sex partners (Waynforth, 2007). Waynforth suggests that women with more sexual experience don’t feel like they need to copy others’ choices—and are confident in their own. Bressan and Stranieri (2008) found that women who already had partners of their own preferred mated men, but only when they were not fertile. When the same women were in the fertile portion of their menstrual cycles, they preferred single men.