Do Couples Become More Alike? Science Says No

It's one of those romantic notions we love to believe: couples who've been together for decades finish each other's sentences, share the same habits, and even start to look alike. The idea that partners become more similar over time feels intuitively true—after all, shouldn't years of shared experiences mold two people into mirror images of each other?

Science says no. And the reality is even more interesting than the myth.

The Research: No Convergence Found

Multiple large-scale studies have consistently shown that couples' personalities do not converge over time. A comprehensive 2010 study examined thousands of couples and found that personality traits like openness, conscientiousness, extraversion, agreeableness, and neuroticism showed no significant convergence as relationships progressed. In fact, researchers analyzing data from 51,664 couples in the UK Biobank found evidence of partner similarity in 64 traits—but that similarity existed from the beginning, not as a result of years together.

The one notable exception? Aggression. If one partner becomes violent, the other may respond in kind and become more aggressive over time. But for personality traits, intelligence, attitudes, values, and general well-being, the convergence theory falls flat.

So Why Are Couples So Similar?

Here's the twist: you didn't become like your partner—you chose someone like you in the first place. This phenomenon is called assortative mating, and it's one of the most robust findings in relationship psychology.

From the moment couples meet, they're already remarkably similar. Research shows significant initial concordance in:

• Core personality traits (Big Five dimensions)
• Intelligence and cognitive abilities
• Political attitudes and values
• Religious beliefs
• Educational background

We're naturally drawn to people who mirror our own characteristics. It's not that decades of marriage molded you into the same person—you were attracted to your reflection all along.

What About Newlyweds?

Some studies have found evidence of slight personality convergence in very early relationships—the honeymoon phase when couples are still actively shaping their identities around each other. But this effect disappears in middle-aged and older couples. By the time you've been married for years or decades, any initial convergence has plateaued.

The bottom line: That couple who seems to think alike after 50 years of marriage? They probably thought alike on their first date, too. The similarity you observe isn't the result of gradual convergence—it's evidence that birds of a feather really do flock together.