1. They've cheated in the past.
This one should be obvious enough, but anyone who's cheated in the past (even if it was a prior relationship) could cheat on you again, according to a study conducted by the University of South Alabama. That's not to say you shouldn't give someone a second chance. You just probably shouldn't be giving them an eighth chance.
2. They're introverted.
Introverted people might not be putting themselves out there and hitting on everyone they come across, but that same US of A study found that they're more likely to go along with it if someone does hit on them.
3. They look like the kind of person that would cheat.
Surprisingly, you can trust your gut when it comes to cheaters. If you've got a feeling your significant other is the cheating type, chances are you're probably right. A study by Brigham Young University found people were pretty good at "guessing" whether or not someone was a cheater, even without any background information.
4. They have a long ring finger.
A study by the University of Oxford found that people who have longer ring fingers than pointer fingers are more inclined to cheat (it's a sign of more testosterone exposure in the womb). But good luck trying to measure your SO's fingers without looking crazy.
5. They're a man.
All right, this one might not be so fair, but the same Oxford study found that men are more likely to cheat. Not every guy is going to cheat. But 57 percent of men are likely to be unfaithful compared to 47 percent of women.
6. Their father cheated.
Genes can be responsible for a partner's predisposition to cheat, according to a study conducted by Czech anthropologists. One study found that sons of cheating fathers were more likely to cheat as well. It doesn't guarantee that cheating gets passed between generations, but a family history could be a warning sign.
7. They're hanging out with someone less attractive than you a lot.
Believe it or not, you should be less worried about the hot blonde coworker and more worried about their average-looking friends. According to affair-hookup site Victoria Milan, people tend to cheat with someone less attractive than their partner. That doesn't mean you need to be suspicious of everyone; it just means your partner isn't going after every hot person they see.
8. They have anxiety and get jealous easily.
Unfortunately, if you're partner is jittery and anxious, they're more likely to cheat, at least according to a study recently published in the Journal of Applied Psychology.
9. Their friends cheat.
Seventy-seven percent of cheating men also have cheating friends, according to M. Gary Newman, author of The Truth About Cheating. That doesn't mean 77 percent of men with cheating friends cheat, but it should be a red flag if his friend's infidelity doesn't bother him.
Don't freak out though. The overall likelihood your partner will physically cheat on you is only around 6 percent.
This article originally appeared on Cosmopolitan.com. Minor edits have been made by the Cosmo.ph editors.