From Science Daily:
Research on jealousy: Impact of sexual vs. emotional infidelity
In the largest study to date on infidelity, Chapman University has learned men and women are different when it comes to feeling jealous. In a poll of nearly 64,000 Americans this study provides the first large-scale examination of gender and sexual orientation differences in response to potential sexual versus emotional infidelity in U.S. adults.
According to the findings, heterosexual men were more likely than heterosexual women to be most upset by sexual infidelity (54 percent of men vs. 35 percent of women) and less likely than heterosexual women to be most upset by emotional infidelity (46 percent of men vs. 65 percent of women).
Participants imagined what 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). Consistent with the evolutionary perspective, heterosexual men were more likely than heterosexual women to be upset by sexual infidelity and less likely than heterosexual women to be upset by emotional infidelity. Bisexual men and women did not differ significantly. Gay men and lesbian women also did not differ.
"Heterosexual men really stand out from all other groups: they were the only ones who were much more likely to be most upset by sexual infidelity rather than emotional infidelity," said David Frederick, Ph.D., and lead author on the study. He went on to note: "The attitudes of gay, lesbian, and bisexual men and women have been historically understudied and under theorized in psychology, particularly in regards to tests of evolutionary perspectives."