What’s your break-up style? Do you delete your ex from all forms of communication, destroy all relics of the relationship and pretend they died in a tragic accident? Or do you mend your broken heart and try to keep at least some kind of friendship alive?

You might think that anyone in the former camp is a little harsh. And yet, according to a recent scientific study, it’s actually those who remain friends with their exes that are the ones we need to be wary of.

Researchers at Oakland University found that people who reveal ‘darker personality traits’ and ‘manipulative tendencies’ usually opted to remain friends with their exes.

The scientists discovered their results by asking 861 volunteers to list five reasons why they’d stay friends with someone following a break-up, and tested them for psychology’s ‘dark triad’ of personality traits (including narcissism, psychopathy and Machiavellianism).

The study, published in the Personality and Individual Differences journal, revealed that although many people chose to remain friends with an ex for sentimental reasons, those who scored high in the 'dark triad' were more likely to remain friends with ex partners.

People with these personality traits chose to stay friends with old lovers for ‘strategic advancement’ - and to increase their likelihood of getting sex in the future. The volunteers also reported feeling that staying friends with an ex partner was simply more 'practical' than cutting ties. 

Researchers behind the study, Justin Mogilski and Dr Lisa Welling, say that the reasons vary depending on gender and that:

“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.”

Speaking to Broadly, narcissism expert Dr. Tony Ferretti says that the study results align with his previous findings, saying that narcissists:

“May stay connected to [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.”

Ferretti also says that break-ups can injure a narcissists ego:

“They can experience narcissistic injury when rejected by a partner and have difficulties letting it go or healing from it.”

So, watch out for that ex in sheep’s clothing.