Big Five Personality Traits Study Identifies 1,260 Genetic Variants

One of the most profound existential questions anyone can pose is, "What makes me, me?"

Identical twins share almost the same genetics but can grow into people with markedly different personalities – perhaps the clearest illustration nature provides that DNA is not destiny.

Even so, part of what makes you who you are is encoded in A-T-C-G. The issue is not whether DNA is connected to personality, but how strongly.

The biggest genetic study yet of the Big Five personality traits has now identified more than a thousand genetic variants linked with the ways people typically think, feel and behave.

That does not, however, mean researchers can determine your personality from a few fragments of DNA like genetic tasseographers. These findings cannot be applied meaningfully to an individual; instead, genetics can uncover personality patterns across entire populations.

"If we'd want to know someone's personality at an individual level, genetics isn't really a fruitful path; we can simply measure personality and get a very clear picture, genes wouldn't add anything there," genetic epidemiologist Michel Nivard of the University of Bristol in the UK, a senior author of the study, told ScienceAlert.

"What genes do offer us is a way to link personality, in the aggregate across groups of people, to all other outcomes we have ever previously studied with a genome-wide association study."

The study, led by psychologist Ted Schwaba at Michigan State University, was published in Nature. Psychologist Elliot Tucker-Drob of the University of Texas at Austin is a co-senior author.

Big Five personality traits and genetic data

To investigate the genetic contribution more closely, Nivard and colleagues combined genetic and personality information from 46 cohorts. The largest analysis included roughly 1.14 million people.

Their focus was the Big Five, the five broad dimensions psychologists use to characterise personality: extraversion, agreeableness, conscientiousness, neuroticism and openness to experience.

They then carried out genome-wide association studies, or GWAS, scanning the genomes of very large groups for genetic variants that repeatedly coincided with differences in these personality traits.

Importantly, the team did not anticipate finding one conclusive "extraversion gene" or "neuroticism gene". The genetics underlying personality are much more complex.

"In a way we knew that we'd find many variants, which also means that the individual variants have very, very small effects on personality," Nivard explained.

"There are definitely no genes with an effect that is perceptible at an individual level like [those that] exist for outcomes like Alzheimer's."

As expected, the analysis identified a remarkable 1,260 lead genetic variants connected with the Big Five personality traits, 824 of which had not previously been associated with them.

DNA accounts for a modest share of personality differences

Despite the large number of variants involved, the researchers found that DNA accounts for only a limited share of the personality differences between individuals.

Across the Big Five traits, the genetic variation measured in the study explained about 7.4 to 10.6 percent of these individual differences, Nivard told ScienceAlert.

Nor was a person's set of genetic variants especially effective at forecasting their personality. When the team used genetic data to make their best predictions in separate groups, it explained under 4 percent of personality variation.

This indicates that genes matter to some extent, but are far from the complete explanation.

"Our genes clearly influence our personality predispositions," Nivard said. "We can account for a portion of those genetic effects, but there are clearly also substantial environmental causes of personality, which collectively explain the majority of individual differences."

This introduces a further challenge. Humans are extremely complex and are heavily influenced by their environment, diet and culture. How can researchers establish that genetics, rather than outside influences, are affecting personality?

One approach is to study families.

The researchers examined siblings and fraternal twins, who have much of the same family environment but receive different combinations of their parents' genes. If a genetic variant associated with, for instance, extraversion also indicates which sibling is more extraverted, a shared upbringing becomes a far less probable explanation.

That was broadly what the researchers observed: genetic effects on personality within families were almost the same as those detected between unrelated individuals.

Agreeableness varies across cultures and cohorts

Not every analysis was as clear-cut and consistent. Genetic patterns linked to agreeableness differed substantially among the groups examined.

"Agreeableness, the personality trait of being kind, sympathetic, cooperative, warm, honest, straightforward, and considerate, as opposed to selfishness, insincerity, and zero-sum thinking, isn't measuring the exact same thing across cultures, cohorts, and age," Nivard said.

Nivard said the variation may simply result from questionnaires placing emphasis on different elements of agreeableness. Yet it could also point to real cultural differences in the factors that shape the trait – an issue requiring further research to disentangle.

The researchers say the work could nevertheless be valuable where personality overlaps with other aspects of life.

For instance, they identified genetic connections between extraversion and the risk of COVID-19 infection during the early years of the pandemic, potentially reflecting more extraverted people's greater need for social contact.

Previous research has linked personality itself with whether someone is likely to vote in elections. Scientists have also associated personality traits with longevity.

Ultimately, personality genetics gives researchers another means of examining how personality influences choices, behaviour and health – rather than a method for reading somebody's identity from their DNA.

"I would hate for people to come away thinking that genetics set their personality in stone, or that their individual personality is measurable via their genome," Nivard said.

"If you want to know more about your personality relative to others, take one of the many free tests online, and you'll learn so much more!"

The research has been published in Nature.

This article was fact-checked by Fiona MacDonald and edited by Fiona MacDonald. While we take pride in our process, we are only human. If you spot an error, please let us know.