Unless you’re a swinger, having sex with someone else counts as cheating. Oral, too. But then there’s the fuzzy area between friendship and infidelity—and chances are, your girlfriend sees those shades of grey as more black and white than you do.

“Men aren’t as attuned to identifying ambiguous behaviours as cheating as women are,” says Daniel Kruger, Ph.D., a University of Michigan psychologist, who’s studied gender differences in definitions of infidelity.

In other words, what you consider totally innocent could be her dealbreaker. Here are signs you might be in an affair without even knowing it.

TELLING ANOTHER WOMAN ABOUT YOUR RELATIONSHIP TROUBLES

Whether you’re complaining about your girlfriend’s habit of leaving wet towels on the floor—or talking about her distaste for doggystyle—you’re revealing weaknesses in your relationship to another woman. And that can, in fact, be an act of intimacy.

Kruger calls this “informational infidelity,” which your partner will likely interpret as a sign of emotional bonding—often a bigger threat to women than sexual connection.

“If he’s fooling around on the side, she still has the relationship—the investment,” says Kruger. “But if a guy is falling for another woman, he might abandon her.”

CHECKING OUT YOUR EX’S FACEBOOK PAGE

You may genuinely just be interested in seeing what your she’s up to—the same way you’d check out an old college buddy’s page. Even so, the assumption will probably be that you’re flipping through her Spring Break pics or fantasizing about your past.

“Socially, we’re primed to think that men don’t care about emotions and feelings—that all they care about is sex,” says Justin Sitron, Ph.D., a professor of human sexuality at Widener University.

Even though she can innocently look at her last guy’s Facebook page, she doesn’t think you can.

BUYING A DRINK FOR ANOTHER WOMAN

We’re not talking about sidling up to a hot stranger at the bar and ordering her a dirty martini. Even buying your female co-worker a cold one could be veering into dangerous territory.

“It could be seen as being generous and nice,” says Kruger. “But it could also be construed as hitting on someone, especially if you’re buying a drink just for the woman—not, say, a round of beers for everyone.”

Translation: Buy drinks for the whole crew, or not at all.

TAKING A FEMALE FRIEND TO YOUR ‘SPOT.’

That Italian restaurant you and your girlfriend always go to? The ice cream joint where you had your first date? Consider those places off-limits—even if you’re just catching up with your childhood best friend, who happens to be a woman.

For starters, your partner is already primed to be a little leery, since our culture isn’t too accepting of opposite-sex friends, says Sitron. And taking a female pal to your special spot? Bad idea any way you slice it.