Being friends with an ex is hard, which is why so few of us succeed at it.
But now there's a very scientific reason why some people manage to be besties with an ex: their personality type.
According to a recent study conducted by psychologists at Oakland University, the reason why some couples are able to remain friends after a relationship is over is because they're more likely to have "dark triad" personality traits: narcissism, psychopathy and Machiavellianism.
For former couples who do stay friends, the friendship is maintained mostly as a way to access sex, money or information, not for any sentimental reasons or attachments to the former partner.
"Narcissists hate to fail or lose, so will do what they can to maintain some connection if they didn't make the choice to end it."
The study analyzed the answers of over 860 people and found that women were slightly less likely to stay friends with an ex because it was more practical or could lead to sex. However, men were slightly more likely to value practicality and sex more than women.
"Men rated sexual access higher on importance than women did, which is consistent with other research showing that men are more likely than women to form [cross sex friendships] due to sexual attraction," study authors Justin Mogilski and Dr. Lisa Welling wrote.
Narcissism expert Dr. Tony Ferretti told Broadly these findings — that people with "dark" personality traits (especially narcissistic ones) would want to hang on to past relationships — make sense because these types of people value relationships in terms of self-interest.
"Narcissists hate to fail or lose, so will do what they can to maintain some connection if they didn't make the choice to end it," Dr. Ferretti said. "They can experience narcissistic injury when rejected by a partner and have difficulties letting it go or healing from it."
People with these personality traits, he explained, "may stay connected to [exes in order to] have access to valuable resources. They also have inside information about their exes vulnerabilities and weaknesses that they can exploit and manipulate which gives them a sense of power and control."
So, next time you're deciding whether you should stay friends with an ex, take a good hard look at yourself!