If I asked you to tell me what makes two people compatible, what would your answer be? If you are like the students in my course on the psychology of close relationships, your answer is likely to be “similarity.” People tend to think that having a partner who is similar is important for relationship success. But, of course, some people also argue that “opposites attract.” So which is it?
Imagine taking 200 couples and then mixing up the couples so that you randomly assign partners from different couples to each other. According to research, if you look at the similarity between members of couples and compare it to two people randomly put together, partners in actual relationships tend to be more similar to each other that the randomly paired partners.
But knowing that partners tend to be similar doesn’t necessarily mean that similarity matters. Just because partners tend to be similar does not mean that more similar couples are in more satisfying relationships or that their relationships last longer. Perhaps dissimilar partners are less common but just as satisfied and successful.
What we know about similarity and relationship success is that similarity can matter, but it looks like it's about values and background more than personality. Researchers have shown that similarity in couples tends to be more about shared values and background, such as their social class and religion. And these are the factors that appear to predict relationship success—couples with more similar attitudes, values, and backgrounds tend to experience more lasting satisfaction, companionship, intimacy, and love and are less likely to break up.
Similarity of personality, on the other hand, does not appear to matter as much. While some research found that people report being most attracted to others with similar personalities, similar personalities did not strongly predict relationship outcomes.
How similar partners are might be a function of how they met. One cross-sectional study of 137 married or cohabiting heterosexual couples found that couples who “fell in love at first sight” were less similar than couples who were “friends first,” particularly on levels of extraversion, emotional stability, and autonomy. However, contrary to the researchers’ hypothesis, partners who “fell in love at first sight” did not report lower relationship quality, suggesting that their dissimilar personalities were not necessarily a burden on the relationship.
While similarity in personality might not matter as much as we instinctively think, certain personality traits do seem to matter. In particular, neuroticism (the tendency to experience negative emotions) has been shown to predict lower relationship quality. Though this may not be true across the lifespan: Most of this research is done with younger couples, and in a sample of older, long-term marriages there was no link between neuroticism and relationship satisfaction. Some research has found that being open to experiences, agreeable, and conscientious all bode well for relationship quality, but the findings generally are not as strong as those with neuroticism. When asking people what traits they value most in partners, the answer is loyalty and honesty.
So which factors actually do matter for who we end up with and whether our relationships are successful? Stay tuned for my next post.
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Kenny, D. A., & Acitelli, L. K. (1994). Measuring similarity in couples. Journal of family psychology, 8(4), 417.
Markey, P. M., & Markey, C. N. (2007). Romantic ideals, romantic obtainment, and relationship experiences: The complementarity of interpersonal traits among romantic partners. Journal of social and Personal Relationships, 24(4), 517-533.
O’Rourke, N., Claxton, A., Chou, P. H. B., Smith, J. Z., & Hadjistavropoulos, T. (2011). Personality trait levels within older couples and between-spouse trait differences as predictors of marital satisfaction. Aging & mental health, 15(3), 344-353.
Weidmann, R., Ledermann, T., & Grob, A. (2017). The interdependence of personality and satisfaction in couples. European Psychologist.