Scientists Discover: Opposites Do Not Attract, Debunking Widely Believed Myth

A revolutionary study challenges the commonly held belief that "opposites attract", indicating that individuals are often drawn to partners who bear resemblance to them in numerous traits. The far-reaching research reveals significant implications for genetics and societal trends, emphasizing the impact of assortative mating—people with similar traits pairing up—on subsequent generations and socio-economic frameworks.

The cliche that opposites attract has been largely dismissed by a comprehensive analysis carried out by CU Boulder, which examines over 130 traits and includes data from millions of couples spanning more than a hundred years.

According to the main author, Tanya Horwitz, a Ph.D. candidate in the Department of Psychology and Neuroscience and the Institute for Behavioral Genetics (IBG), the study confirms the tendency of like-minded people, or "birds of a feather", to congregate and partner up.

The findings of the research, which appeared in Nature Human Behaviour on August 31st, align with what has been suggested by independent studies for many years, thereby contradicting the notion that opposites attract. In analyzing traits that touched on aspects such as political preferences, age at first sexual intercourse and drug habits, they found profuse evidence that partners tended to be alike for 82%-89% of these traits.

A mere 3% of traits examined suggested that individuals showed a tendency towards choosing partners who were dissimilar to them. Apart from illuminating hidden factors that shape human relationships, the study has profound repercussions for genetic research.

According to Matt Keller, the senior author and director of the IBG, contemporary models in genetics postulate that human mating is indiscriminate. However, the current study exposes that this theory is probably flawed, as assortative mating could impact the results of genetic research.

The authors executed both a review (meta-analysis) of former research and their own original data analysis for this paper. Using the meta-analysis, they surveyed 22 traits across 199 studies which included millions of paired males and females, whether co-parents, engaged partners, married partners, or cohabitating partners. They utilized data from the UK Biobank, which covered almost 80,000 opposite-sex couples in the UK and included 133 traits, many of which have been under-studied.

Same-sex couples were excluded from the study as differing patterns may be present in such relationships, and is currently being investigated separately by the authors.

The findings show high correlations in traits such as religious and political viewpoints, educational attainment, and certain indices of intelligence quotient. Substance use also showed significant correlations with partners who were heavy smokers, heavy drinkers, and teetotalers being more likely to pair up with people who had congruent habits.

Other traits like physical appearance, health conditions, and personality traits showed weaker yet positive correlations. In some cases, minimal correlation was found. For example, it is equally likely for extraverts to pair up either with other extraverts or introverts.

In the meta-analysis, the researchers found no convincing proof supporting the idea that opposites attract. However, they discovered minor negative correlations for a few traits in the UK Biobank sample.

The researchers identified that the tendency to worry, whether someone is an early bird or a night owl, hearing problems and birth year were traits that partners were likely to share. Also, even traits that are not generally examined, such as whether a person was breastfed as a baby or the number of sexual partners a person had, exhibited some correlation.

Horwitz pointed out that these results indicate that, even in scenarios where we believe we decide our relationships, there might be unconscious processes taking place.

The authors explained that there can be numerous reasons why couples share traits. Some might have grown up in the same environment, some could be attracted to those who are like themselves, while others could become more similar the longer they stay together. The cause of this similarity could shape the subsequent effects.

For example, Horwitz explains, if short people are more likely to produce offspring with short people and tall people with tall people, there could be more people at the height extremes in the next generation. The same goes for psychiatric, medical, or other traits. There could also be social implications.

For instance, some small previous studies have suggested that people in the U.S. are growing more likely to couple up with people with similar educational backgrounds—a trend that, some theorize, could widen the socioeconomic divide.

Notably, the new study also showed that the strength of correlations for traits differed across populations. They likely also change over time, the authors suspect.

The researchers caution that the correlations they found were fairly modest and should not be overstated or misused to promote an agenda (Horwitz points out that assortative mating research was, tragically, co-opted by the eugenics movement). They do hope the study will spark more research across disciplines, from economics to sociology to anthropology and psychology.

“We’re hoping people can use this data to do their own analyses and learn more about how and why people end up in the relationships they do,” she said.