The study, published last month in Proceedings of the National Academy of Sciences, relied on data from the German Family Panel Study, a nine-year exploration of couple and family dynamics involving thousands of teenagers, young adults, and middle-aged participants. For this study, psychology researchers Yoobin Park and Geoff MacDonald used data from 332 participants with at least two partners during the previous nine years who had completed a Big Five personality assessment. That's a standard, research-backed personality test that measures people on five factors: agreeableness, conscientiousness, extraversion, neuroticism, and openness to experience.

The fact that the scientists examined the romantic partners' first-person testimonials rather than rely on a participant's characterization of their current partner or ex is important. Asking someone to compare their beloved to an ex-partner could understandably introduce bias into the study, so the scientists sought out people whose partners had filled out their own self-reports to filter out the rosy glow of a newly developing relationship and the bitterness from a relationship gone bad.

Even so, when the study authors compared the partners' personalities, they found significant consistency between the participant's current partner's and their past partners. In other words, a participant's current significant other described him or herself in the same ways as the participant's previous beaus.

"It's common that when a relationship ends, people attribute the breakup to their ex-partner's personality and decide they need to date a different type of person," lead author Yoobin Park said in a press release about the study. "Our research suggests there's a strong tendency to nevertheless continue to date a similar personality."

Previous research established that individuals often date people who are similar to themselves, though it has been a bit unclear whether people consciously pair themselves with romantic partners who are similar to them or whether these pairings result from shared environments like work or church.

Park and MacDonald's findings went further, showing that individuals tend to pick partners with similar personalities to each other, regardless of how similar the partners were to the individual.

"The effect is more than just a tendency to date someone similar to yourself," Park said.

In fact, some people are more likely to date people similar to themselves than others. The researchers found that a more neurotic person, for example, was more likely to date someone different from him or herself, while people who were high in agreeableness, extroversion, and openness to experience were more likely to date someone similar to themselves.

At the same time, however, the romantic partners of those high in extroversion and openness to experience were less similar to each other, meaning that people with these personality traits were less likely to "have a type." The scientists suggest that this could be because someone who's more sociable and open to new experiences has a larger, more varied network of friends and potential romantic partners.

If you find that you're having the same problems in a series of romantic relationships, there can be some wisdom in your friends' advice to date someone who's "not your type." But what you learn from past relationships can be helpful when dating a similar partner in the future.

"In every relationship, people learn strategies for working with their partner's personality," says Park. "If your new partner's personality resembles your ex-partner's personality, transferring the skills you learned might be an effective way to start a new relationship on a good footing."

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It sounds like it's just about marriage, but "The All-or-Nothing Marriage: How the Best Marriages Work" by psychology professor Eli J. Finkel is a fantastic exploration of the science on love, dating, and every kind of relationship. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.