In Long-Term Relationships, Do We Turn Into Our Partners? 

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Soon after my friends Jessica and Jeremy got married, they bought one other the same gifts during the holiday season: ski jackets. This may not seem remarkable, but they didn’t just buy one another ski jackets. Without discussing it at all, they independently bought each other the same yellow jackets. Last year, they also bought one another the same tan wool socks.

One may wonder whether Jessica and Jeremy were interested in purchasing the same sorts of gifts before they started dating, or whether their interests became more similar after they got married. Research suggests that both processes operate when couples resemble one another (Kassin et al., 2011): Not only do we choose to date those who are similar to us in many ways, but we also become more similar to our partners over time.

We Start Out Similar

Psychological research shows that even before we start dating, we tend to be similar to our future romantic partners in a variety of ways. For example, even friends tend to resemble one another in racial background, age, education, and height (Kassin et al., 2011). Romantic partners also share similar attitudes (Byrne and Blaylock, 1963; Luo and Klohnen, 2005), similar traits such as imagination and intelligence (Keller and Young, 1996), and similar personalities (Luo and Klohnen, 2005). Couples that are less similar to one another may never even agree to date, but if they do become involved, their relationships may be at greater risk for dissolution (Clarkwest, 2007; Fugère et al., 2015). Interestingly, we also tend to resemble our partners in levels of physical attractiveness (Feingold, 1988: Montoya, 2008), such that members of a couple are usually both highly attractive, both moderately attractive, or both less attractive. We are even more attracted to others who look more like us (Fraley and Marks, 2010; read more about this topic here). Couples that are more similar to one another are not only more likely to date one another but are also more likely to stay together over the long term.

We Become More Similar

Although we may already be similar to our partners when we begin dating, the relationship between similarity and liking is bidirectional—similarity leads to liking but liking also leads to similarity (Kassin et al., 2011). Over time, romantic couples become more likely to resemble each other in a variety of ways.

Voice Pitch

Although women find men’s voices more masculine and more attractive when they are lower pitched (Saxton et al., 2006; Simmons et al., 2011) and men rate women with higher-pitched voices as more attractive (Collins and Missing 2003), when men and women enter relationships with one another, they match their voice pitches to one another. Men actually speak to their romantic partners in a higher-pitched voice and women speak to their romantic partners in a lower-pitched voice (Farley et al., 2013). The researchers speculate that matching the voice pitch of our partners may be an indication of affection.

Similar Attitudes

Although our attitudes may already match our partner’s, including political attitudes and attitudes toward relationships (Byrne and Blaylock, 1963; Clarkwest, 2007; Luo and Klohnen, 2005), attitude similarity is so important to us that when we become aware of a specific disagreement, we either change our attitudes to match our partner’s or we try to change theirs to match ours. Davis and Rusbult (2001) found that when dating couples became aware of differences in attitudes they would compromise and match their partners on topics that were less important to them, and to try to change their partner’s attitudes to match theirs on issues that were more important to them.

Similar Looks

As mentioned above, we often match our partners in levels of physical attractiveness (Feingold, 1988; Montoya, 2008). Interestingly, we also prefer partners who resemble our own physical characteristics, such as hair color and eye color (Fraley and Marks, 2010; Little et al., 2003). However, we also begin to physically resemble our partners more so over time. Zajonc et al. (1987) showed participants facial photographs of male and female members of couples around the time of their weddings and their 25th anniversaries. Although participants could not reliably match couples at the time of their weddings, they could match couples at the time of their 25th anniversaries. Zajonc and colleagues speculated that couples mimic one another’s facial expressions throughout the years, and thus their facial structures look more similar to one another over time.

If you have ever wondered whether you’re "turning into" your partner, your question is justified. We do start out similar to our partners and we become more similar over time. When I asked my friend Jessica if I could share her story about purchasing the same gifts, she agreed, with the stipulation that I mention that “Jessica, the much younger and more vibrant of the pair, is slowly turning into her husband Jeremy, as evidenced by the unknowing purchase of matching jackets and wool socks.”