A new study has discovered that exchanging a few flirtatious words with a co-worker or someone online can be more damaging to a relationship than physically cheating.

The study was inspired by the notion that men are more upset than women by sexual infidelity and women are more upset than men by emotional infidelity. The proposed explanation is that men, in contrast to women, face the risk of unwittingly investing in genetically unrelated offspring. Previous studies have relied on small college or community samples of heterosexual participants but this study, unpretendingly, examined upset over sexual versus emotional jealousy among 63,894 gay, lesbian, bisexual, and heterosexual participants. Participants imagined which would upset them more: their partners having sex with someone else (but not falling in love with them) or their partners falling in love with someone else (but not having sex with them). As expected, it was only straight men who were more perturbed by their partner's sexual infidelity (54 percent vs. 35 percent). Women, massively, were far more upset about emotional infidelity (63 percent vs. 46 percent). This was consistent across all age groups, incomes, relationships types, and relationship lengths. When gay and bisexual participants were surveyed, they agreed that emotional infidelity was more damaging. In total, 70 percent of bisexual men, 73 percent of bisexual women, 68 percent of gay men, and 6 percent of lesbian women said that a partner developing feeling for someone else was far more heartbreaking than cheating.