A gender split between sexual and emotional drivers can also be seen in attitudes toward wandering partners. Women say they would be more upset if their partner fell in love with someone else than if their partner had sex with that person (65 percent, compared to 47 percent of men), but men say they’d be more distressed by their partner having a sexual affair than falling in love (53 percent, compared to 35 percent of women).
"Men are more threatened sexually by the sense of competition and comparison; women are more threatened by the loss of the emotional intimacy," says Leiblum.
"Whenever there is an affair there’s a sense of competitiveness with the third party. Men see it as a comment on their sexual competency and masculinity, whereas for women it’s not the sex, it’s the meaning of having the emotional bond with someone else."
It's not all about mushiness for ladies—one in five who cheated said they were looking for more satisfying sex than they were getting from their primary partner.
"I was miserable in my marriage of nine years," writes a 28-year-old woman who ended up divorcing her husband to be with her affair partner. "My husband and I never had sex and the sex we did have was boring!"
Women are also twice as likely to use an affair to get out of a bad relationship.
Actions aside, 71 percent of people say it's never OK to be unfaithful. Yet, one in four men and one in 10 women think cheating is justified if a partner has no interest in sex.