A large-scale study analyzing more than a million people has found that the family environment plays a smaller role than previously thought in shaping traits such as curiosity and agreeableness
Is character something we’re born with, or something we build over a lifetime? Biology versus upbringing has been argued over for generations, by scientists and non-scientists alike. Traits like curiosity, ambition, conscientiousness and agreeableness feel like the product of lived experience. But researchers have long known personality carries a genetic signature, established through a classic method: comparing identical twins with fraternal twins. Identical twins turn out to resemble one another in personality more closely than fraternal twins do, which points to DNA as part of the explanation.
What had been missing was the “where”: which parts of the genome were actually involved. A large international study published this week in Nature has now filled in that gap, pinpointing 1,260 distinct genetic variants scattered across the genome, 824 of them never previously connected to personality at all.
The researchers drew on data from 1.14 million people across 46 separate cohorts to work out which DNA variants line up with the five personality dimensions most widely used in psychology, the so-called Big Five: extraversion, agreeableness, conscientiousness, neuroticism and openness to experience.
None of this means personality can be read off someone’s DNA. What the variants show is a set of possible influences on behavior, not a blueprint. And the data confirm something else too: upbringing and social experience still outweigh genetics in shaping who someone becomes.
The consortium describes the 1,260 variants as statistically robust links to personality, a haul three to forty-three times larger than earlier studies had found, depending on the trait. Even so, all of the variants combined explain only 4.8% to 9.3% of the variation between individuals on any given trait, far short of the 40% to 60% that classic twin studies had suggested was heritable. The gap is filled by environment.
More surprising, family itself turns out to matter less than expected. Traits like educational attainment, income or intelligence tend to run in families partly because genes and home environment reinforce each other. Personality doesn’t work that way: comparing siblings, or children against their parents, produced genetic effects barely different from those seen across the general population.
“It’s one of the things that surprised me most,” says Michel Nivard, professor of genetic epidemiology at the University of Bristol and one of the study’s senior authors. He points to education as the contrast case: children of more educated parents both inherit relevant genetic variants and benefit from better schools and more resources, since the two reinforce each other. With personality, he says, that reinforcing loop is essentially absent.
The study also puts to rest the idea of a single “personality gene.” Diseases like Alzheimer’s can hinge on variants that sharply raise risk on their own; nothing like that exists here. Each of the 1,260 variants nudges the odds only slightly. Even the single variant with the largest effect, tied to extraversion, shifts someone from roughly the 50th percentile of the population to about the 50.35th, a barely perceptible difference.
Even stacking hundreds of thousands of these small effects together isn’t enough to predict any one person’s personality, the authors caution. The genetic scores only mean something averaged across large groups. As Nivard puts it, anyone curious about their own personality is better off with a twenty-minute questionnaire: it’s highly reliable and gives nearly the same result if repeated a year later. He doesn’t expect a genetic test that could forecast personality to ever really be feasible.
Conscientiousness tied to lower smoking rates
The study doesn’t stop at genetics; it links the variants to real-world behavior patterns as well, and some of the connections are notable. People carrying more variants tied to openness are more likely to move to cosmopolitan, urban neighborhoods by midlife, while those scoring higher on conscientiousness tend to gravitate toward affluent residential areas instead. Openness correlates with more nighttime activity, conscientiousness with more daytime activity. Conscientiousness also tracks with lower smoking rates and lower body mass index.
Agreeableness was the hardest of the five traits to pin down. The genetic correlations across countries were weaker, and the trait appeared less heritable overall. Nivard suspects part of the problem may be cultural: what counts as “agreeable” isn’t fixed. As a Dutch person, he notes, he comes from a culture that values directness, something that might read as disagreeable elsewhere. He says this is the first time genetics has offered an objective way to check whether different cultures are even measuring the same underlying concept when they use the same word.
One finding cuts against prior research: genetic profiles linked to openness to experience also correlated with a higher overall risk of psychiatric conditions, a connection earlier clinical work hadn’t picked up clearly. Nivard doesn’t have a firm explanation yet, calling it fascinating but still unclear. One possibility he raises is that people who are more open to new experiences might simply be more willing to enroll in studies like this one, even if they have a mental health condition, which could skew the sample slightly. He’s careful to frame this as an untested hypothesis.
In some ways, the researchers argue, the real story isn’t what came out this week but everything still to come. With a dataset this size, a million people spread across 46 cohorts and endless possibilities for cross-analysis, the findings are likely to ripple through genetics, sociology, psychology and psychiatry for years. And even that is only a fraction of what’s possible: the human genome holds somewhere between four and five million genetic variants in total, leaving plenty more ground to cover.
Geneticist Miguel Pita, who wasn’t involved in the study, argues the real achievement isn’t the finding itself. That genetics shapes personality is close to obvious, he says; what’s impressive is proving it with data on this scale. He calls it a milestone in experimental and technical design, adding that the obvious can sometimes be the hardest thing to demonstrate rigorously.
The study’s authors argue that framing this as nature versus nurture no longer makes sense as an either-or question. Nivard draws a comparison to lung cancer genetics, where the variant most strongly linked to the disease sits in a nicotine-receptor gene, even though nobody disputes that smoking, an environmental factor, is the actual cause.
Pita agrees: with anything related to personality, he says, both genes and environment always play a role, and treating it as one or the other is a debate that has run its course. Nivard shares that view, calling the gene-versus-environment framing old-fashioned, if understandably intuitive, since it’s the version most people were taught in school.
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