If someone has cheated on you once, don't always expect that person to turn over a new leaf if you give them another chance. In fact, a scientific study proves that that person will probably just cheat on you again. 

A new paper published in the journal Nature titled "The brain adapts to dishonesty" explores the age-old adage that a person is "once a cheater, always a cheater." The study focused on the part of the brain called the amygdala, which supplies a negative response to the individual when they lie. It's the region that is associated with emotion, and plays "a key role in signaling, processing and assessing arousal." 

It was discovered that with each time a human being is caught messing around with someone else, the response to their wrongdoing is reduced. "We speculate that the blunted response to repeated acts of dishonesty may reflect a reduction in the emotional response to these decisions or to their affective assessment and saliency," the paper reads. 

It appears that the brain also tends to rationalize the individual's cheating ways, leading to the lack of a negative response when that person is caught. "When participants were dishonest for the benefit of someone else, dishonesty at a constant rate was observed," the study says. "This is consistent with the suggestion that the motivation for acting dishonestly contributes to its affective assessment, such that when a person engages in dishonesty purely for the benefit of another it may be perceived as morally acceptable."

Next time your significant other cheats on you, it will be your best friend and science telling you, "I told you so."