When a friend or relative introduces their new partner, it can seem like a case of deja vu. Now research has backed up what many have long suspected: people really do have a type when it comes to coupling up.

Psychologists say they have found that people tend to go for partners with personalities similar to their own, and that even when this is taken into account, people’s former and new partners tend to be alike in character. In other words, it might not be a complete surprise that your friend’s new boy- or girlfriend seems just as obnoxious as the last.

“The results revealed a significant degree of distinctive partner similarity, suggesting that there may indeed be a unique type of person each individual ends up with,” the study’s authors write.

They say the results may help predict not only who might get together with whom, but also the chances of a relationship’s success.

However, Geoff MacDonald, a co-author of the study from the University of Toronto, said that while dating the same type of partner every time might explain why some people’s relationships consistently go wrong, there was another possibility. “I bet what would contribute more to the variance is what are you doing in the relationship,” he said.

Writing in the Proceedings of the National Academy of Sciences, MacDonald and his colleague, Yoobin Park, report how they used data collected from a long-running study in Germany to come to their conclusions.

They looked at patterns of responses to 21 questions probing personality traits, including extraversion, conscientiousness and neuroticism. During the nine-year study, some participants ended their relationships and found with new partners, who then also completed the questionnaire.

Using data from 332 participants and their exes and new partners, the team found that people tended to choose partners with personality patterns similar to their own. But the team also found that current and ex-partners tended to have similar clusters of personality traits, above and beyond similarities to the participant.

The researchers say passive factors such as people attending similar social events or working in the same profession may play a role in why exes and new partners tend to have similar personalities. But they say this is unlikely to be the full story, since similarities to the participant themselves – who might also be expected to be in the shared environment – were taken into account, meaning active choice of personality appeared to be important too.

Experts said the data showed that other factors played a large role in why someone ended up with a partner of a certain type. “For example, active processes like ‘I seek out partners who are extroverted and want to date them’ and passive processes like ‘I am extroverted and so I go to parties where I meet other extroverted people’ all add up to only 8% of the personality variance in who we choose as a partner,” said Dr Paul Eastwick, of the University of California, Davis, who was not part of the research team.

Robin Dunbar, a professor of evolutionary psychology at Oxford University, said there had been much debate about whether or not opposites attract in relationships. “Our own research has shown that friends tend to resemble each other – a phenomenon known as homophily,” he said. “Now it seems we have proof that it also applies to romantic partners, especially in respect of their personalities.”

That might not be too surprising, he said. “After all, for a relationship to last, whether its a friendship or a romantic relationship, you really need to be interested in the same things and have the same attitudes to life – otherwise you just end up arguing all the time.”