Do Opposites Really Attract? What the Evidence Shows

"Opposites attract" is one of the most repeated ideas about romance, and it is almost the opposite of what more than half a century of relationship research actually finds. People overwhelmingly end up with partners who are similar to them - in age, education, values, even in how attractive other people rate them. The more interesting question is not whether this is true, but which kind of similarity actually matters.

What hundreds of studies actually found

In 2008, the psychologists R. Matthew Montoya, Robert Horton and Jeffrey Kirchner pooled the results of a large number of previous studies on similarity and attraction. They separated two things that get confused in everyday talk about "having a lot in common": actual similarity - real, measurable overlap in traits, attitudes or interests, checked against each other objectively - and perceived similarity, meaning how similar the two people believe themselves to be, whether or not that belief is accurate. Both were linked to greater attraction overall. But the two behaved differently depending on the setting. Actual similarity mattered most in first encounters, the classic laboratory situation of meeting a stranger and rating how much you like them. In established relationships, that link grew markedly weaker. Perceived similarity, on the other hand, kept predicting attraction and liking across every kind of relationship the researchers looked at, including long-standing ones.

Feeling alike matters more than being alike

That distinction is the heart of the "opposites attract" myth. If you ask long-term couples why their relationship works, many will say it is because they are so alike - and they are usually reporting something real about how they feel, even when it does not fully match how alike two independent tests would find them to be. The perception of common ground does much of the work that people attribute to similarity itself, which is a variant of a pattern that shows up across social psychology: what you believe about a relationship shapes how you feel in it, sometimes more than the objective facts do. A follow-up meta-analysis by Montoya and Horton in 2013 looked at why perceived similarity works this way, and pointed to a fairly mundane mechanism: believing someone is like you makes you expect that they like you back, and that expectation of being liked is itself one of the strongest predictors of liking someone, independent of any real overlap in traits.

What happens once people actually marry

A 2005 study of newlywed couples by Shanhong Luo and Eva Klohnen looked directly at married spouses rather than volunteers rating a stranger's profile in a lab. Using a couple-centered method that compares each partner's whole personality profile rather than single traits in isolation, they found that couples showed real, above-chance similarity on attitudes and values - things like political and religious outlook - but not much on core personality traits. In other words, people do not typically marry someone with an identical temperament, even though they do tend to marry someone who sees the world roughly the way they do.

What predicted how satisfied these couples were, though, ran the other way. Similarity in personality-related traits predicted marital quality better than similarity in attitudes did, and one specific kind of match stood out above the rest: how similar partners were in attachment style predicted marital happiness more strongly than any other single trait. The whole-profile approach also outperformed simply comparing single trait scores, even after accounting for how each partner rated their own personality - meaning the fit between two full personalities carried information that neither partner's individual traits could supply on their own.

The honest limits

None of this proves that similarity causes happiness, in either direction. These are correlational studies: happy couples might genuinely search for and find overlap, but people who are already happy together may also come to see themselves as more alike than they are, simply because feeling close makes differences easier to overlook. Most of the couples and volunteers in this research were also from the United States and similar Western, educated populations, and relationship norms elsewhere can differ enough that the same pattern may not hold everywhere. And a meta-analysis and a single newlywed study, however well designed, describe averages - not any particular couple. It also does not tell us much about the early, more precarious stage of dating, before a couple has had the years together needed for a study like Luo and Klohnen's to include them - the dynamics of who initially catches your attention may run closer to the meta-analysis's lab findings than to the newlywed data.

What this means for you

The tidy version of "opposites attract" does not survive contact with the data, but neither does its opposite, the idea that you need to be a carbon copy of your partner to be happy. What the evidence points to instead is that shared values give a relationship a starting foothold, that feeling understood matters at least as much as being objectively alike, and that emotional security - each partner trusting the relationship will hold - looks like a better predictor of lasting satisfaction than any tally of shared hobbies. If you are curious how your own patterns line up with this, our tests on relationship satisfaction and love styles look at some of the ingredients this research points to, and the your type test is a lighter way to start thinking about what you tend to look for in a partner. None of them can tell you whether a specific relationship will work - for that, and especially through a difficult patch, a couples therapist is a far better guide than any test.