From Harry Potter to My Best Friend’s Wedding (pictured), many blockbuster films feature friendships between men and women

There’s got to be a good reason, right? University of Texas researchers have found that women are more jealous than men of their spouse’s opposite-sex friends. In the study, women reported higher levels of jealousy overall than men when imagining the spouse’s friend was female. This suggests that women’s feelings of jealousy are more associated with attractiveness. Previous studies have found men are more jealous of sexual infidelity, but these new results did not show any differences in jealousy about sexual concerns. However, men were found to be more emotionally upset when their spouse’s friend was attractive—regardless of their sex. Researchers write, “Perhaps emotional jealousy functions as an adaptive solution to any situation that threatens diversion of a mate’s resources and investment, not just diversion to a potential mate.”