The Adorable Reason Long-Term Couples Resemble One Another

a black and white photo of an elderly couple
Image by Tony Alter / CC BY

As some of you may be aware, last weekend I posted the final installment of a long-running feature in Poly Land, the PQ series, in which I answered every single chapter end question in the book More than Two with its very own essay.

While it feels great to have accomplished the task I set out to tackle two years ago, I was immediately presented with a new decision: What should I write about on the weekends now?

After much consideration and a lot of soul-searching, I bring you the very first installment of a new series, in which I geek out with brief takes about some of my favorite psychological studies and concepts.

I call it Psyched for the Weekend.

The Adorable Reason Long-Term Couples Resemble One Another

Looking at pictures of my late paternal grandparents, their physical resemblance to one another is uncanny. It’s particularly pronounced in the photos of them together late in life. They look like a couple of salt and pepper shakers. A matching pair.

But they haven’t always been that way. In the photos of them taken when they’re much younger newlyweds, I can still see evidence of love, of mutual adoration, affection. But they look very different from one another. In the later pictures, they match. In the earlier ones, they don’t.

When I was younger, I was very puzzled by this pattern, one I noticed with other elderly couples. Why did they look so much like one another? Could living with one another make you look alike?

I would find out later when I went to school for psychology that I’m not the only person who ever wondered this. In fact, a 1987 study conducted by Zajonc, Adelmann, Murphy, and Niedenthal set out on a similar course of inquiry.

In the study, Zajonc et al. had participants act as impartial judges, having them pair up men in one set of photographs with the women from another that most closely resembled them.

Half of the photos were of the couples when they were newly married; the other half were of them taken 25 years later.

Participants weren’t very good at matching the young couples up. They were right sometimes but only as often as one would expect by chance.

However, they were significantly better at matching the 25-year photos together, suggesting that the couples truly had begun to resemble one another over the years.

And interestingly, there was another strong link: The higher the level of marital satisfaction that a couple reported, the more likely they were to look like one another (anecdotally, this pattern follows with my paternal grandparents who looked so much alike; they absolutely adored one another).

While other possible contributing factors were bandied about as possibilities (including shared diet, environmental exposures from cohabitation, etc.), here’s what the study authors thought was most likely behind it:

Among the explanations of this phenomenon that were examined, one based on a theory of emotional efference emerged as promising. This theory proposes that emotional processes produce vascular changes that are, in part, regulated by facial musculature.The facial muscles are said to act as ligatures on veins and arteries, and they thereby are able to divert blood from, or direct blood to, the brain. An implication of the vascular theory of emotional efference is that habitual use of facial musculature may permanently affect the physical features of the face. The implication holds further that two people who live with each other for a longer period of time, by virtue of repeated empathic mimicry, would grow physically similar in their facial features. Kin resemblance, therefore, may not be simply a matter of common genes but also a matter of prolonged social contact.

Or in other words, after years of mirroring each other’s expressions, couples form facial wrinkles in the same places, giving them a similar appearance.

Gosh, it’s lovely when science is this adorable.

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This post is part of an ongoing Poly Land feature called Psyched for the Weekend, in which I geek out with brief takes about some of my favorite psychological studies and concepts. For the entire series, please see this link.

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Books by Page Turner:

A Geek’s Guide to Unicorn Ranching

Poly Land: My Brutally Honest Adventures in Polyamory 

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