Together

Do opposites attract? What studies actually found

It's a familiar idea about love, and one researchers have tested many times. The short version: partners tend to be more alike than different, feeling alike seems to matter more than being alike, and neither predicts happiness as well as you might hope.

Couples tend to be alike, not opposite

A 2023 review, which its authors describe as the first formal meta-analysis of partner similarity across many kinds of traits, combined 480 partner correlations from 199 studies across 22 traits, and added an analysis of up to 79,074 couples in the UK Biobank. The resemblances were overwhelmingly in the same direction: partners were similar, not opposite. In the UK Biobank data, of the 118 traits where partners were reliably related, only three showed partners being opposite rather than alike.1

How alike depends a lot on the trait. Partners were most similar on political and religious attitudes, education, and some substance-use habits. Personality and body measurements showed weaker, though still positive, resemblance. Among the traits in the combined studies, extraversion showed the least partner similarity and political values the most. One of the few genuine "opposites" was being a morning or an evening person.1

The authors point out that couples can end up alike for different reasons: choosing someone similar, meeting within the same social circles, or growing more alike over time.1 A study of 291 newlywed couples found the same broad picture: substantial similarity on attitude-related measures, but little on personality.2

Being alike versus feeling alike

A 2008 meta-analysis of 313 studies pulled apart two things: actual similarity (what questionnaires show) and perceived similarity (how alike people think they are). Both were linked to attraction. But actual similarity mattered mostly when people hadn't met or had only interacted briefly, and its link to attraction wasn't significant in existing relationships. Perceived similarity was linked to attraction at every stage.3

Speed dating shows this in real time. In one study, people went on about a dozen four-minute dates. Feeling similar to someone predicted romantic liking; actually being similar, based on questionnaires, did not.4

It's hard to tell from studies like these which way the arrow points. Feeling similar might lead to liking, or liking someone might make us notice what we share. Either way, "we just click" and "we match on paper" are not the same thing.

What about opposites completing each other?

The idea that people seek partners who fill in what they lack is called complementarity. One set of three experiments tested it head-to-head against similarity and attachment security. Being similar and being secure predicted attraction; complementarity wasn't among the findings that held up.5

There is one narrower version with some support. A study of 106 couples who had been together at least a year found that those with the best relationship quality were more alike in warmth but less alike in dominance, roughly, in who tends to take the lead.6 That's a single, fairly small study, and it's a long way from "opposites attract" in general.

Does being alike make couples happier? Barely.

The most striking answer comes from three large, nationally representative samples of married couples in Australia, the UK and Germany. A person's own personality accounted for about 6% of the differences in how satisfied they were with their relationship. Their partner's personality added 1 to 3%, mostly through agreeableness, conscientiousness and emotional stability. How similar the two were accounted for less than half a percent once those were taken into account.7

Not every study agrees exactly. The newlywed study above did find that couples more alike on personality-related measures reported better marriages.2 Results like these shift from sample to sample, which is part of why it's wise to hold them loosely.

Prediction before meeting is even harder. In a speed-dating study, people answered more than 100 questions about themselves and what they wanted before their dates. A computer model could partly predict how much someone tended to like others in general, and how much others tended to like them, but it couldn't predict the unique spark between two particular people from anything they'd reported beforehand.8

Why this area is easy to oversell

Many attraction findings come from short lab studies, small samples or brief first meetings, and many rely on people describing themselves. In the research above, the largest samples found the smallest role for personality matching. That doesn't mean similarity is meaningless. It means a match on paper is a weak guide to how a real relationship will feel.

What to take from it

Shared values and a sense of being on the same page are common in couples, and feeling understood seems to matter more than matching on a checklist. In the largest studies, your own personality, and your partner's (especially how agreeable, conscientious and emotionally steady they are), mattered more than how alike the two of you were. That's one reason BrainMatch doesn't hand out compatibility scores: the research simply doesn't support them.

This article is general information, not advice. BrainMatch isn't built on or validated by these studies. We simply want to share what's known, including how much isn't.

Sources

  1. Horwitz, T. B., Balbona, J. V., Paulich, K. N., & Keller, M. C. (2023). Evidence of correlations between human partners based on systematic reviews and meta-analyses of 22 traits and UK Biobank analysis of 133 traits. Nature Human Behaviour, 7(9), 1568–1583. https://pmc.ncbi.nlm.nih.gov/articles/PMC10967253/
  2. Luo, S., & Klohnen, E. C. (2005). Assortative mating and marital quality in newlyweds: A couple-centered approach. Journal of Personality and Social Psychology, 88(2), 304–326. https://doi.org/10.1037/0022-3514.88.2.304
  3. Montoya, R. M., Horton, R. S., & Kirchner, J. (2008). Is actual similarity necessary for attraction? A meta-analysis of actual and perceived similarity. Journal of Social and Personal Relationships, 25(6), 889–922. https://doi.org/10.1177/0265407508096700
  4. Tidwell, N. D., Eastwick, P. W., & Finkel, E. J. (2013). Perceived, not actual, similarity predicts initial attraction in a live romantic context: Evidence from the speed-dating paradigm. Personal Relationships, 20(2), 199–215. https://doi.org/10.1111/j.1475-6811.2012.01405.x
  5. Klohnen, E. C., & Luo, S. (2003). Interpersonal attraction and personality: What is attractive – self similarity, ideal similarity, complementarity, or attachment security? Journal of Personality and Social Psychology, 85(4), 709–722. https://doi.org/10.1037/0022-3514.85.4.709
  6. Markey, P. M., & Markey, C. N. (2007). Romantic ideals, romantic obtainment, and relationship experiences: The complementarity of interpersonal traits among romantic partners. Journal of Social and Personal Relationships, 24(4), 517–533. https://doi.org/10.1177/0265407507079241
  7. Dyrenforth, P. S., Kashy, D. A., Donnellan, M. B., & Lucas, R. E. (2010). Predicting relationship and life satisfaction from personality in nationally representative samples from three countries: The relative importance of actor, partner, and similarity effects. Journal of Personality and Social Psychology, 99(4), 690–702. https://doi.org/10.1037/a0020385
  8. Joel, S., Eastwick, P. W., & Finkel, E. J. (2017). Is romantic desire predictable? Machine learning applied to initial romantic attraction. Psychological Science, 28(10), 1478–1489. https://doi.org/10.1177/0956797617714580