There are a few options available to you if you suspect your partner is being a 24 carat love rat.
You could just cut your losses and dump them. Or you could confront them. Or you could snoop through their emails and texts and keep a beady eye on their spending, but you also risk driving yourself mad that way (and getting caught).
Then again, if your partner is a man, maybe the signs were there all along - quite literally stamped over his face - and we're not talking lipstick marks or love bites.
A new study has found that, if you know what to look for, male cheaters actually automatically give away their adulterous antics.
When it comes to their extra-curricular shenanigans, men who stray cannot keep a poker face, a study published in the Royal Society Open Science journal found.
Their findings also stated that men and women could in fact predict when a man was being unfaithful to a decent degree of accuracy simply by looking at a photo.
Interestingly, women were pretty much impossible to read.
Male cheats will quite often have more typically masculine "angular" features.
These include squarer jaws and chins and prominent brows.
The research was conducted by the University of Western Australia and researchers who worked on it said humans may have developed the ability to spot a love rat because this could have given ancient humans an evolutionary advantage.
"Given the reproductive costs of being cheated on, evolutionary theories predict that it would be [beneficial] for individuals to evolve strategies to prevent sexual infidelity,' they said.
They arrived at this conclusion after asking 1500 people to look through photos of 200 men and women who'd been quizzed on their fidelity and whether they'd pursued anyone outside of their relationship.
Both men and women were able to judge faithfulness for men with a level of accuracy that was significantly better than chance alone.
20 per cent of the subjects were even able to definitely detect unreliable men.
Yet when it came to women, they proved to be impossible to read in the same way.
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