Contrary to the old saying “opposite attract,” you have probably noticed that romantic couples have a tendency to look more alike than they do different. But why is this the case? Is it because people have a tendency to select partners who look like them, or is it because couple members actually grow physically similar to one another over time? Surprisingly, psychologists have found support for both of these explanations.

Similarity in physical appearance is an important factor in initial attraction, and it is part of the reason couple members often look like each other right from the start. What appears to be driving this is a predisposition to select partners whose genes resemble our own. As some evidence of this, research has found that the spouses of identical twins are more similar to one another both physically and psychologically than are the spouses of fraternal twins [1]. Thus, the more genes that two people share in common, the more likely they are to look for similar characteristics in their partners. As additional evidence of this phenomenon, consider a study in which heterosexual participants rated the attractiveness of a set of faces [2]. Embedded in this series of images was an image of their own face that had been digitally morphed into the other sex. Despite not recognizing the morphed face as their own, participants rated it the most attractive of all. These and numerous other studies tell us that “like attracts like.”

However, what is even more fascinating than this is that romantic partners’ similarity to each other only grows over time! For instance, in a classic study by Bob Zajonc and colleagues, college undergraduates were asked to evaluate photographs of either newlywed couples or photos of the same couples after 25 years of marriage [3]. Specifically, participants saw images of two faces at a time and were asked to evaluate how similar each pair was and how likely they were to be married. Sometimes the pair that was presented was an actual married couple, and sometimes it was just two random people of similar age put together.

Results indicated that perceived facial similarity did indeed increase over time. Participants rated the faces of older married couples as being more similar than those of newlyweds and random pairs. Also, for young couples, participants could not distinguish between newlyweds and random pairs in terms of whether they were actually married; however, among older couples, participants were better at detecting which couples were married and which ones were not (presumably on the basis of those differences in facial resemblance). One other fascinating result is that the faces that were judged to be most similar belonged to the couples who reported being the happiest.

How do we explain this pattern of results? We cannot say for sure, but the authors argue that it is a function of empathy. The idea is that romantic partners frequently empathize with each other and “share” their emotional states. And sharing emotions means that we also share the same facial expressions, which may be the real key to increased physical similarity. That is, by moving their facial muscles the same way over time, romantic partners may come to have the same pattern of wrinkles around their mouths and eyes, among other things. Of course, other explanations are possible. For instance, increased resemblance could have something to do with residing in the same environment or having a similar diet.

Regardless of the explanation, while we do indeed seem to be initially drawn to similar-looking partners, it appears that we also start to look more similar to our partners as we age.

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[1] Rushton, J., & Bons, T. (2005). Mate choice and friendship in twins: Evidence for genetic similarity. Psychological Science, 16, 555-559. doi:10.1111/j.0956-7976.2005.01574.x

[2] Penton-Voak, I. S., Perrett, D. I., & Peirce, J. W. (1999). Computer graphic studies of the role of facial similarity in judgements of attractiveness. Current Psychology: A Journal for Diverse Perspectives on Diverse Psychological Issues, 18, 104-117. doi:10.1007/s12144-999-1020-4

[3] Zajonc, R. B., Adelmann, P. K., Murphy, S. T., & Niedenthal, P. M. (1987). Convergence in the physical appearance of spouses. Motivation and Emotion, 11, 335-346. doi:10.1007/BF00992848

Image Source: 123rf.com

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