Romance: Infraction Reactions

We judge betrayals differently depending on who's been spurned and how the cheater strayed. A study from the University of Bielefeld offers a snapshot of some of the forces that feed your affair despair. —Andrea Bartz

How You would Feel If...

YOU were cheated on

You are male: You'll be more upset if you imagine your girlfriend in bed with another guy vs. falling in love with him.

You are female: You'll be madder envisioning your beau falling in love with someone vs. sleeping with her.

This is the classic finding: Raising the offspring of another man would be bad news for a male's genes, because it'd mean investing in another guy's bloodline. Since a woman knows her baby has half her genes, it's not the end of the world (biologically speaking) if her partner isn't monogamous. But a deadbeat dad won't help her raise a kid; her priority is securing a stable mate who's also a providing father.

YOUR SIBLING was cheated on

Your brother: You'll be equally upset whether the infidelity is emotional or physical.

Your sister: You'll be equally upset whether the infidelity is emotional or physical.

Here's where it gets interesting. Since siblings share half our genes, researchers figured we'd think of them like we think of ourselves: We'd be most worried about a brother raising a stranger's kid, or a sister being abandoned by her baby daddy. Surprise: People were about equally ticked off regardless of which sibling was hurt, or what kind of cheating occurred. "We didn't predict that at all," says study author Gerd Bohner.

YOUR FRIEND was cheated on

Your male buddy: You'll be more upset if a girl cheats on your chum sexually rather than emotionally.

Your female pal: You'll be most up-in-arms if your friend's boyfriend strays emotionally.

We see our bros like brothers. "We didn't think genetic considerations would come into play with friends," Bohner says. But that's what happened: "The patterns we predicted for siblings and pals were switched." It may be that because we don't know our friends as well as our siblings, we "fall back on double standards"—i.e., that female sexual infidelity is unacceptable and falling for another woman is the cruelest thing a beau can do.

Sweet Street

A reference to romance may help you get aid, a study in the Swiss Journal of Psychology shows. Women in a French town asked male passersby for directions to Valentine Street or Martin Street. (Neither destination actually exists.) A few minutes later, each man encountered a different woman struggling to retrieve her cellphone from a group of threatening guys. Those who'd been asked earlier about Valentine Street were more likely to step in and help the woman than those who'd been quizzed about Martin Street. The word "Valentine" may trigger thoughts of gender norms and chivalry. So if you're a damsel in distress, just ask the way to Lovers' Lane. —Michele Lent Hirsch