Assortative mating and couple similarity: Patterns, mechanisms, and consequences

Assortative mating and couple similarity: Patterns, mechanisms, and consequences. S. Luo. Social and Personality Psychology Compass, http://onlinelibrary.wiley.com/doi/10.1111/spc3.12337/full

Abstract: Assortative mating refers to the tendency of two partners' characteristics to be matched in a systematic manner, usually in the form of similarity. Mating with a similar partner has profound implications at the species, societal, and individual levels. This article provides a comprehensive review of research on couple similarity since 1980s. The review begins with the general patterns and trends observed in couple similarity on a range of domains including demographic variables, physical/physiological characteristics, abilities, mental well-being, habitual behaviors, attitudes, values, and personality. Next the bulk of the review focuses on analyses of 4 mechanisms leading to similarity: initial active choice, mating market operation, social homogamy, and convergence. Specific future research avenues are outlined to improve understanding of these mechanisms. Finally, the review discusses genetic, social, and psychological consequences of couple similarity.

My comment: Pearson reported in 1903 positive correlations in spouses' height, span of arms, and forearm length in 1,000 couples. [...] Previous research has examined couple similarity on a variety of attitudes and values: political orientation, religiosity, authoritarianism, family role attitudes, risk attitudes, personal values, etc. Strong similarity correlations with a typical range of .40s to .70s are reported for attitudes and a weaker range of .10s to .40s for values [...] Moderate partner similarity for abilities and intelligence has been documented, with correlations typically ranging from .20s to .40s [...], although there appears to be a gradual tendency to decline [...]. Additionally, partner correlations on verbal ability are higher than those on perceptual speed or spatial ability [...] patients' partners tend to have related disorders. For example, partners of schizophrenic patients are more likely to have non‐affective functional psychosis such as schizotypal, schizoid, paranoid, borderline, and narcissistic disorders, but not neurotic disorders [...] Moderate similarity in couples has been observed on a variety of habitual behaviors, hobbies, and lifestyle including alcohol, coffee, and tea consumption; smoking; circadian rhythm; and physical exercise with a typical range of .20s to .50s [...]. Diet similarity is lower than alcohol consumption [...]. Moreover, these correlations are not due to age assortment [...] traits such as Big Five factors, attachment avoidance and anxiety, positive and negative affectivity, self-esteem, and sensation seeking [show] correlations [...] with weak magnitude rarely above .30. [...] Ahmad, Gilbert, and Naqui's (1985) study of the height of 1,500 Pakistan couples in arranged marriages, which yielded a similarity correlation (r = .36) comparable to free‐choice marriages (BUT WE ARE TALKING JUST ABOUT HEIGHT, WHICH IS MEASURABLE BY THE COMMUNITY).

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Social consequences
At the societal level, AM has profound implications for social and economical inequality (e.g., Schwartz, 2013). The discussion here primarily focuses on variables related to SES such as income and education. Homogamy on these variables produces an increasing number of couples of equal status, which leads to a larger gap between classes and reinforces their social status (Blossfeld, 2009). Harpending and Cochran (2015) used simulations to illustrate the powerful effect AM has on class stratification: When a population free of castes starts to practice 100% homogamy on a given variable (e.g., income), two castes begin to emerge after just one generation; after three generations, the two castes have grown to be 1.75 standard deviations apart.