Wanting to remain friends with an ex might seem like a benign enough act but it could suggest rather more sinister personality traits. 

Psychologists at Oakland University, while investigating the reasoning behind post-relation communication, discovered the dark side behind such actions.

During two surveys, a total of 861 participants were prompted to give reasons why someone might remain friends with an ex-partner. Then they rated the importance of staying friends for each reason given, and completed two personality tests.

“We found that men rated pragmatic reasons and potential for future sexual access as more important behind remaining friends than women did,” study co-author Lisa Welling said. “Also, dark traits predicted the importance of these motivations in both sexes. Overall, we suggest personality characteristics predict why people keep a door opened for former partners, with some individuals having less than honorable intentions.”

RELATED: How often couples should have sex, according to science

Scientists found that most people wanted to stay friends with their exes for reasons of reliability, sentimentality and trustworthiness. It turned out that those people, who scored higher on measures of dark personality are more likely to remain friends with exes to try and attain desired resources — or sex. 

Specifically, they might be psychopaths or at least have "dark triad" traits, including narcissism, psychopathy and Machiavellianism.

“However, reasons that indicate an ex-partner is reliable, trustworthy, and of sentimental value were rated as the most important for remaining friends overall,” Welling added. 

Experts believe their research provides more information on how sex and personality can influence our decisions in the “mating market.” It could provide a tool to use in future investigations on the motivations behind staying friends with an ex-partner and may help us better understand this aspect of human relationships.

-Dmitry Belyaev