4 crazy signs she's cheating on you

A tired tongue may be a red flag.

You subconsciously perform oral sex more often when you fear your girl may be messing around, finds new research from Oakland University.

Researchers recruited 231 men, all in current relationships, and asked each a series of questions about his partner’s attractiveness, his relationship satisfaction, his sexual habits, and other questions proven to accurately predict the chances of female infidelity. Here’s what the researchers discovered: The more a guy’s answers indicated his woman might be cheating, the more often he performed oral sex, according to the study.

Huh? Bear with us, because this is nuts: Along with humans, animals like orangutans, lemurs, and short-nosed fruit bats also head downtown. Why? At some point in our species’ past, a guy’s tongue could detect whether another man had been, uh, picking flowers in his garden, explains the Oakland study.

And so if a guy (human or lemur) has an inkling his lady might be running around on him, instincts tell him it's time to employ his tongue detector, says study coauthor Michael Pham, who studies evolutionary psychology at Oakland.

Of course, none of this proves she is cheating on you, Pham stresses. It’s just a sign you feel there’s a greater threat of “sperm competition” from other men, he explains.

That, or you just love oral sex.

Sound crazy? Here are three more weird signs she may be cheating, according to research.

Going deep. Men who subconsciously believe their women may have other suitors are more likely to “perform deeper and more vigorous” thrusts during sex, finds a study from Florida Atlantic University. The researchers say this is an attempt to “displace” another man’s semen. Let's move on.

She gets around. Literally. Women who are ovulating and actively seeking new partners walk around more, finds a UCLA study that employed step counters. The researchers hypothesize that increased mobility ups the number of men a woman is likely to encounter. (Or she could just like walking ...)

Personality pitfalls. Openness, cleverness, and outgoingness are all female personality traits that research has tied to a greater likelihood of cheating, finds a study in Personality and Individual Differences.