Why Do Couples Look Alike? 3 Reasons Partners Begin To Resemble Each Other, Explained

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LOIC VENANCE/AFP/Getty Images It is a truth universally acknowledged that couples who sidestep their individuality and become One Combined Being are the most irritating people at every cocktail party. They talk in plurals and “we”s, have matching shirts, and — oddly — even seem to look like each other. The first two can be stopped; but science has declared that, in the last case, the longer you’re together with a partner (and we’re talking seriously longterm here, in decades, not months), you really do start resembling each other more. It’s called convergence of appearance, if you want to get technical. But they’re still undecided as to why couples start to dress and look alike, and there are a few competing theories about why your Aunt Wilma and Uncle Wilbur could pass for each other easily in a badly lit room.
We’ve heard that we’re likely to settle down with people who look quite similar to us — even if we casually date people who look different. Opposites may attract (Kendrick Lamar’s never wrong, right?), but that appears to be confined to personality: while we seem to like a bit of difference in a partner’s character, when it comes to faces, it’s usually all us, all the time.
So what on earth is going on here —why would people start to morph slowly into their partners, and why are scientists telling us it’s actually a good sign?

1. You Look Like Each Other To Begin With

One of the greatest secrets of the dating pool is that people seem to actively attempt to date people similar to them in some way — in education level, height, age, face shape, whatever. It’s called assortative mating, and it’s used to explain why educated people tend to marry other educated people and double their opportunities. It’s not hard to understand why — you like somebody who knows what you’re talking about when you moan about your 9-to-5 and college loans — but similarity is also determined, on a certain level, by genetics. And that includes faces.

We seem to like genetic similarity; opposites don’t actually attract all that conclusively, if you trust the science. A study from 2014 shows that white people in particular pick lifetime mates who have similar DNA. Forget the obsession with band T-shirts and the inability to play Monopoly without screaming: you may not have worked out with your ex because they just weren’t that genetically compatible. 

We want to pass on our own genes, apparently, and somebody who looks just like us will bolster our chances of a similar-looking kid, as opposed to one that’s inherited their weird facial hair and knock knees. (Unfortunately, there’s been little-to-no research on how this trend plays out in mixed race couples.)

2. You’re Sharing The Same Experiences

The “facial likeness” study of the now-late psychologist Robert Zajonc of the University of Michigan in 1987 is still the benchmark for people who worry they’re developing their partner’s scowl. Zajonc and his team asked volunteers to match photographs of men and women based on their facial similarity, and found that couples who’d been married for 25 years were overwhelmingly paired together.

There are two main hypotheses for why this happened. Zajonc thought it was because a long life together meant shared experiences that left similar lines on faces — and that couples would therefore begin to look more similar. 

Others are more practical, believing that it’s simply a matter of genetic similarity becoming more evident as the rigors of age remove distinguishing features. Either way, the logic of Zajonc’s ideas is pretty easy to understand: a couple who have lived lives of hardship and difficulty will probably wear similar frown lines.  

3. The Happier You Are, The More Alike You Look 

Zajonc’s theory of emotional face-mirroring was based on a basic principle: we mimic the people we’re around the most. This phenomenon, called “unconscious mimicry,” has been known for ages, and it’s why we unconsciously take on the intonation of our friends’ voices, or copy our boyfriend’s stance at the bar. It’s meant to bond us and make us feel part of the group, but Zajonc also thought it meant mimicking a spouse over a long period of time, which would gradually reshape the face.
Genetic similarity, scientific studies show, already seems to coincide with a happy marriage — but whether that’s cause or effect is up in the air. Are you happy because you understand each other, or because you share the same gene variant (5-HTTLPR), thought to be the key to being emotionally attuned to a relationship? Does the happiness make the facial similarity, or vice versa? 
One thing’s for certain, though: just because you look similar doesn’t mean you’ll start to think the same. A 2010 study showed that people who’d been married for 40 years were just as definitively different personality-wise as they had been at the start of their marriages, even if they now shared habits, homes, and mortgages. Marriage, it seems, is only skin-deep.