Why do many couples look alike? Does the doppelganger couple phenomenon apply to international couples too? I asked inter-ethnic/racial couples about whether they have ever heard that they look alike. Among 110 survey participants, a whopping 85% said yes. Because their romantic partners are from another country, they are unlikely to be genetically related. Take me and my husband for example. I am an Asian from Korean parents and my husband is a Caucasian from American parents. Our wedding guests were surprised by how similar our moms looked. They looked like the Asian and western version of each other. My husband and I have also often heard that we look similar, despite our racial differences.

Some may be baffled by how unrelated and biracial couples can look similar. Although races are often used to classify people, human facial features are not so distinctively different race-to-race. Even skin color is in a continuum of shades. Think about cats or dogs. Different breeds have different looks but all share commonalities within their species. Inter-ethnic/racial similarities are not unusual. Facial features overlap across races. Still, how do we end up with a partner who looks like us, even when we choose someone from another country? Are we drawn to people who resemble us? Or, do we grow to look alike?

Attraction to Familiarity

Through the evolution, our brain has developed a liking for the familiar because the familiar often meant safety. To ensure our safety, the brain makes snap judgments of strangers: “Can I trust this person?” In the initial judgment, familiarity plays a key role. The most familiar face is obviously our own. Subconsciously, we tend to trust and favor faces that have a resemblance to ourselves. In 2013, psychologists in Norway asked participants to choose the most attractive face image of their romantic partners. Unknowingly, the participants preferred the images that blended their own facial features with their partners. Familiarity helps let our guard down when we meet someone new. We see people who are like us as more trustworthy or at least more predictable and thus safer. So, we are instinctively drawn to people who are similar to us.

Assimilation through Mimicry  

Without realizing it, we mimic others’ facial expressions and verbal and body language. We do this because it helps us understand their feelings and thoughts. Dr. Tanya Chartrand, a neuroscientist at Duke University, found that Botox treatment impairs our ability to understand others by restricting facial mimicry. Dr. Chartrand and Dr. John Bargh also found that the more we mimic each other, the more we like them, and vice versa. Frequent mimicry indicates constant effort to understand each other, an indication of a good relationship.

Over time, this unconscious mimicry creates similar wrinkles and lines, leading to generally similar facial images. This phenomenon was scientifically examined back in 1987 by psychologist Dr. Robert Zajonc. He asked participants to match the photos of men and women who most closely resemble each other. Participants matched couples much more successfully when given their photos taken around 25 years after their marriage than when given those taken at the time of their marriage. The study showed that couples developed facial similarity through empathic mimicry. Happier couples developed greater similarity. In addition, couples adopt similar phrases and gestures. Eventually, couples, especially loving couples, look, speak, and act similarly to each other. In my survey, 32% said they feel like they developed similarity in facial expressions, 25% in personality or ways of thinking, 18% in language expressions, 15% in interests or preferences, and 10% had none.

Influence on Each Other

Experiences change our brain throughout our lives. Dr. Louis Cozolino at Pepperdine University calls it “experience-dependent plasticity.” In his book, the Neuroscience of Human relationships, he explains that close relationships (re)shape the brain. To keep a happy relationship, we constantly adapt to meet the wants and needs of our loved ones. International couples in particular confront a bigger pressure to leave their comfort zone, their home country, and adapt to a new environment and even start a new career.

Living as an international couple brings both challenges and opportunities. Because the wariness of unfamiliarity is so ingrained in all of our brains, it takes time for people in your new home – likely to be your partner’s country – to see you as a person. They don’t trust you or respect you in the same way they do with their fellow citizens. You face invisible boundaries everywhere. You need to find or make openings by exploring different possibilities. Our 15 years together has been a journey of constant self-transformation. We tried many things and some worked out, making us who we are now. Nothing came easy but we supported each other the entire way. Couples grow together, shaping each other’s brains, identities, and lives. In a way, we are each other’s creation that reflects our preference and expectations. As a result, we become similar outside and inside.