Opposites Do What?

Welcome back. Opposites attract with magnetic poles; not so much with people. Any such attraction is usually short-lived. 

Opposite magnetic poles attract (www.stanfordmagnets.com/what-are-magnetic-poles.html).

That opposites attract was postulated by Robert Francis Winch in the 1950s. Studying spouses, he concluded that it was complementarity not similarities that made relationships work. A good couple’s personality traits complement one another. An extrovert, for example, would be better with an introvert.

Interesting, but numerous studies have since chipped away at opposites attracting. They instead find that people tend to be attracted to one another because of shared interests and attributes, with lasting relationships built on similar values.

You probably realized that long ago. In case you didn’t, a recent study by researchers with the University of Colorado Boulder really knocked it out of the park.

Examining Couples’ Traits
The researchers dug into more than a century of data to analyze 133 traits of millions of couples. They conducted systematic reviews and meta-analyses of previous research as well as their own data analysis.

Their meta-analyses examined 22 traits across 199 studies, including millions of male-female co-parents and engaged, married and cohabitating pairs. The oldest study was from 1903.

In addition, they calculated 133 trait correlations across nearly 80,000 opposite-sex pairs in the United Kingdom drawing from the UK Biobank dataset. (The researchers are exploring same-sex couples separately.)

What They Found
The researchers found that partners were likely to be similar for 82% to 89% of traits analyzed. As for opposites, individuals tended to partner with those different from themselves for only 3% of traits in only one part of the analyses.

Across analyses, political and religious attitudes, educational attainment and some substance use traits (smoking, drinking) showed the highest correlations, while psychological and anthropometric (physical measurements) traits generally yielded lower but positive correlations.

Point estimates of mean meta-analyzed and UKB partner correlations for comparable traits (Fig 1 from www.nature.com/articles/s41562-023-01672-z#Sec14 truncated to higher correlations).

A handful of traits in the UK Biobank data had small, negative correlations (e.g., whether someone is a “morning lark” or “night owl,” tendency to worry and hearing difficulty).

As you might expect, the trait for which couples were most likely to be similar was birth year.

Correlations for comparable UKB demographic/family traits (Fig 2 from www.nature.com/articles/s41562-023-01672-z#Sec14 truncated to higher correlations).

Wrap Up
If you’re prone to speculating, shared traits could have downstream consequences. The offspring of short and tall couples would tend toward more height extremes in the next generation. You might extend that to psychiatric, medical or other traits.

Some studies have suggested that people with similar educational backgrounds are more likely to couple, a trend that could widen the socioeconomic divide.

But don’t fear. The study also showed that the strength of correlations were fairly modest and differed across populations. They’re also likely to change over time.

Thanks for stopping by.

P.S.
Articles on complementary needs in American Sociological Review:
- www.jstor.org/stable/2087753
- www.jstor.org/stable/2088200
Blog post on do opposites attract: www.talkspace.com/blog/do-opposites-attract/
University of Colorado Boulder study in Nature Human Behaviour: www.nature.com/articles/s41562-023-01672-z#Sec14
Article on study on EurekAlert! website: www.eurekalert.org/news-releases/1000409