If you're going through a tumultuous breakup and your otherwise hostile ex insists on "being friends," science is here to give you a little tough love: Run in the opposite direction.

According to a new study, some people with the so-called "dark triad" personality traits -- like narcissism and psychopathy -- keep their exes around for strategic, self serving reasons.

Previous research and expert analysis suggests that individuals with dark personality traits like psychopathy engage in behaviors and relationships that are beneficial for their personal gain. Researchers from Oakland University wanted see if this theory also applied to connections with former partners.

In the first part of their study, the researchers asked more than 300 participants to name reasons why they would want to be friends with an ex. Then, they narrowed these reasons down to seven concrete categories, such as "reliability/sentimentality," "pragmatism," and "sexual access."

The researchers assigned high scores to positive categories (like a former partner was "reliable, trustworthy and of sentimental value"), and lower scores to more negative categories (practicality and sexual access). Then, for the second experiment, they gave the list of seven categories to approximately 500 new participants, and asked each of them to rank the categories in order of personal importance to them. These new participants were also given clinical assessments that measured their prevalence of dark personality traits.

The results revealed, unsurprisingly, that highly ranking a practical reason for remaining friends with an ex predicted a clinical assessment of narcissism or psychopathy.

The findings "suggest that [a post-relationship friendship] may provide opportunity for ex-partners to exchange desirable resources (e.g., love, status, information, money, sex) after romantic relationship dissolution," the study authors wrote in their conclusion. Translation: Not everyone's post-breakup intentions are pure -- particularly if they have dark personalities. It's not a bad idea to proceed with caution when it comes to an ex. The findings offer some fascinating insight on human relationships, specifically when it comes to emotional turmoil. Experts say that maintaining a relationship after a falling out is difficult, especially because -- surprise! -- ulterior motives may be at play.

"[Exes] are less emotionally supportive, less helpful, less trusting, and less concerned about the other person’s happiness," Juliana Breines, a social experience researcher and postdoctoral fellow at Brandeis University, wrote in a Psychology Today blog. "This is especially true, not surprisingly, for former partners who were dissatisfied with the romantic relationship, and in cases when the break-up was not mutual."

That isn't to say that all exes are terrible people only using you for their pleasure. It is very possible to have a cordial relationship with a former partner. The basic takeaway here is, if it doesn't feel like a real friendship to you, or things ended badly, there could be a less-than-kosher reason your ex tries to maintain the connection.