What shapes your personality? Your genes and environment play a big role.

Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. By signing up, you confirm you are 16+, will receive newsletters and promotional content and agree to our Terms of Use and acknowledge the data practices in our Privacy Policy. You may unsubscribe at any time. I consider myself to have a somewhat challenging personality. The popular Myers-Briggs test labels me an ‘INTJ,’ commonly referred to as an “Architect.” We’re supposedly independent, determined, curious, and original, but we’re also considered combative, overly critical, dismissive of emotions, and more concerned with “rationality and success over politeness.” My family would generally agree with that description of me. Perhaps thankfully, we are a rare bunch: only two to four percent of people, and about one percent of women, are INTJs. I’m expecting my first child, a daughter, in January. The prospect of meeting a mini “Architect” has me wondering: Are we born with our personalities? The answer is complicated—and still evolving. “All of it comes from genes, and all of it comes from [the] environment in a sense,” says Matthew Keller, a behavioral geneticist at the University of Colorado Boulder. Dozens of twin studies have found that personality is partly heritable, but exactly how genes shape who we become is far from straightforward, and it’s even less clear how environmental factors play a role. The very definition of personality is complex and somewhat “squishy,” Ted Schwaba, a personality psychologist at Michigan State University, concedes. Most people think of personality as traits. The adjectives we use to describe a person: creative, hard-working, honest, kind. But personality also encompasses identity, life story, reputation, and how other people see you, says Schwaba. Brent Roberts, a personality psychologist at the University of Illinois Urbana-Champaign, adds that skill, ability, interests, and motivations also play a role. Someone can have remarkable talent in, say, soccer or music, but without the interest or motivation to pursue those areas, one’s ability may never become central to what they do. “Personality is really any kind of stable characteristic of a person that makes them who they are,” says Schwaba. Myers-Briggs Explained in Less than 5 Minutes – 16 Personalities The Myers-Briggs test is a popular self-report questionnaire that categorizes people into 16 different personality types. Video: Myers-Briggs Explained in Less than 5 Minutes – 16 Personalities, Frank James While personality itself remains somewhat difficult to define, most psychologists use the standardized “Big Five” model to measure it. The framework scores people along five broad traits: openness, conscientiousness, extraversion, agreeableness, and neuroticism, the tendency to experience negative emotions. Though imperfect, the model lets researchers compare personality across people and over time. The Big Five and other measures of personality have proven consistent predictors of school and work performance, relationships, health, and even longevity. How much of personality is genetic? Throughout much of the 20th century, researchers studied twins to understand how genes and environment shaped personality. One 1996 study compared 123 pairs of identical twins, who share nearly all their DNA, with 127 pairs of fraternal twins, who share about half, and found that genetic differences accounted for roughly 40 to 60 percent of variation across the Big Five traits. That estimate has endured. A 2015 meta-analysis of more than 100,000 people found that personality is about 40 percent heritable. Heritability tells us how much of the variation in personality, or other traits, can be linked to genetics. If something is 100 percent heritable, all the differences we see among people would be linked to genetics, Keller explains. If it is 0 percent heritable, then genetics would explain none of those differences. So, when researchers say personality is about 40 percent heritable, they don’t mean 40 percent of a person’s personality comes from their genes. An outgoing mother may pass along genetic variants that make her child more likely to be outgoing too, but her daughter is not destined to share the trait. And just because a trait is heritable doesn’t mean it is immutable or set at birth. Environmental factors still matter. Height, for example, is roughly 80 to 90 percent heritable, yet genes don’t determine exactly how tall someone will become. A child with tall parents may have the genetic potential to be tall, but without proper nutrition may never reach that potential. The Big 5 OCEAN Traits Explained – Personality Quizzes Most psychologists use the standardized “Big Five” model to measure personality. Video: The Big 5 OCEAN Traits Explained – Personality Quizzes, Practical Psychology Both height and personality are genetically complex. A 2022 study of 5.4 million people identified more than 12,000 genetic variants associated with height, while a 2024 study of the Big Five identified 254 genes associated with at least one trait. There is no single gene for height nor is there a single gene for being extroverted, agreeable, or conscientious. Instead, these traits appear to arise from the combined effects of many genes, each with a very small influence. Schwaba likens individual genetic variants to grains of sand on a beach. One grain tells you nothing about what the beach will look like, but collectively thousands of them help shape the landscape. What else shapes our personality? If genes explain only part of personality differences, what explains the rest? Scientists are still trying to figure that out. Over the past few decades, researchers have investigated everything from parenting and birth order to socioeconomic status and major life events. Except for extreme experiences such as abuse, trauma, or severe deprivation, most non-genetic aspects have turned out to have surprisingly small effects. Roberts calls it “death by a thousand cuts.” No single experience appears to explain much, but thousands of small environmental influences may accumulate over a lifetime to shape personality. Studying environmental factors is much harder than studying DNA. Scientists can sequence a genome, but understanding environmental impacts requires psychologists to follow thousands of people for decades. Researchers do know that personality isn’t fixed; it can change over the course of one’s life. People can even deliberately alter some traits. Therapy can change personality, Schwaba says, and adults can even become more outgoing, for example, if they put intensive effort into socializing and pushing themselves outside their comfort zone. Scientists aren’t certain when personality first emerges. Schwaba says individuality is obvious by preschool, but recently he and a colleague found themselves wondering whether future extroverts might kick more in the womb. “We don’t actually know of a study on that,” he says. Will my daughter be a mini-Architect? Maybe in some ways. The genes she inherits may nudge her personality in certain directions, but they won’t lock her into them. Who she becomes will depend on a lifetime of experiences that scientists are still trying to untangle. In Ask Us Anything, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you’ve always wondered to the bizarre things you never thought to ask. Have something you’ve always wanted to know? Ask us. 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