Opposites attract? Usually not, according to a new study

When it comes to romantic attraction, the belief that “opposites attract” has been promoted in popular culture for decades. But now, a study from the University of Colorado, Boulder, is challenging this idea. The experts have found that individuals are more often attracted to people who are similar to themselves.

Based on an extensive analysis of over 130 traits, covering millions of couples spanning more than a century, the evidence suggests that similarities, not differences, are the driving forces behind human attraction.

“Our findings demonstrate that birds of a feather are indeed more likely to flock together,” said Tanya Horwitz, a doctoral candidate in CU Boulder’s Department of Psychology and Neuroscience and the Institute for Behavioral Genetics (IBG).

Human mating isn’t random

The study was focused on traits ranging from political inclinations to substance use habits. Out of the myriad traits analyzed, between 82% to 89% showed that partners were more likely to share similarities than not. Only 3% demonstrated any significant divergence.

Matt Keller is the senior author and the IBG Director. He provided a unique insight into the implications of these findings. Keller stated, “A lot of models in genetics assume that human mating is random. This study shows this assumption is probably wrong.” 

This concept of “assortative mating” – where individuals with similar characteristics tend to partner up – can significantly affect the conclusions of genetic research.

How the research was conducted 

To ensure a comprehensive and robust analysis, the team at CU Boulder executed a meta-analysis of prior research and conducted their own original study. 

The researchers scrutinized 22 traits across 199 studies encompassing millions of couples. Their analysis spanned over a century, with the earliest research dating back to 1903. 

In addition to this, the team utilized the UK Biobank dataset, observing 133 traits across nearly 80,000 opposite-sex pairs. It’s essential to note that same-sex couples weren’t a part of this research, and the authors are currently studying these patterns separately.

Which traits drive attraction?

The traits displaying the highest correlations included political and religious beliefs, educational levels, and certain IQ measures. For example, political values had a correlation of .58 on a scale where 1 denotes absolute similarity. 

Substance use patterns also revealed substantial correlations. By contrast, traits such as height, weight, and medical conditions had positive yet lesser correlations. 

For some traits, like extroversion, not much of a correlation was found. “People have all these theories that extroverts like introverts or extroverts like other extroverts, but the fact of the matter is that it’s about like flipping a coin: Extroverts are similarly likely to end up with extroverts as with introverts,” said Horwitz.

Opposites don’t seem to attract

The study’s meta-analysis did not find any substantial evidence to support the idea that opposites attract. However, in the UK Biobank sample, they identified a few traits with a negative correlation, albeit modest, such as chronotype, tendency to worry, and hearing difficulty.

“These findings suggest that even in situations where we feel like we have a choice about our relationships, there may be mechanisms happening behind the scenes of which we aren’t fully aware,” explained Horwitz.

Study implications 

The researchers also explored the wider implications of their findings. For instance, Horwitz suggested that if short individuals predominantly partner with other short individuals and tall with tall, there might be more people at height extremes in subsequent generations. This principle could also apply to psychiatric, medical, or other traits.

There might be societal ramifications as well. Some preliminary studies have suggested that couples in the U.S. are increasingly matching based on educational backgrounds. This could inadvertently intensify the socioeconomic divide. 

Moreover, the strength of attraction based on various traits can differ across different populations and may evolve over time. 

Future research 

The researchers caution that the correlations were fairly modest and should not be overstated or misused to promote an agenda. However, they hope the study will be a catalyst for further research. 

“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,” said Horwitz.

The study is published in the journal Nature Human Behaviour.

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