What DNA Can—and Can't—Tell Us About Intelligence

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By Florence Oxley

Intelligence is central to the human experience. Your ability to think, reason, and learn governs your professional and private life.

Perhaps the commonest way of conceptualising intelligence is in terms of IQ. Around 70 percent of people have an IQ between 85 and 115, with an average of 100. Around 2 percent pass the 130 mark—the threshold for joining MENSA, the world’s largest intelligence society, with 140,000 members worldwide. Undisputed genius Albert Einstein never took an IQ test, but some believe he had an IQ of 160.

But How Much Does IQ Really Say About You?

Some argue that IQ tests are limited and reductionist: They measure abstract reasoning but not the many other traits that make you successful (or not) like creativity, motivation, emotional regulation, and sociability. What’s more, you can get quite inconsistent results by taking different IQ tests or even taking the same test at different times, depending on your energy levels, concentration, comfort, and even your caffeine levels.

Nonetheless, IQ has been found to be closely associated with life outcomes. For example, it has been found to predict your line of work more strongly than your age, education, family background, or personality traits (like confidence or being hardworking). One study found that physical scientists have an average IQ of 114, production line factory workers, 87, and nurses, clerical workers, technicians, and management staff, 100.

It’s important to note, though, that IQ can predict outcomes, but it doesn’t cause them. Having a higher IQ may perhaps increase your likelihood of working as a physical scientist but it determines neither your job options nor your job choices.

What’s DNA Got to Do With It?

People’s differences in intelligence are influenced in part by genetics. That is, we can predict people’s IQ relative to others by looking at their inherited DNA differences. We can capture and compare people’s unique genetic tendencies for intelligence using polygenic scores, which add together the DNA variants linked to intelligence. As with IQ scores, it’s important to emphasise that polygenic scores are predictors, not determinants, of intelligence.

In a new meta-analysis that pooled data across almost half a million participants, polygenic scores for intelligence correlated at .25 with people’s differences in IQ scores. This translates to a difference of approximately 4 IQ points.

This may seem like a small effect, but IQ has been found to be the single best predictor of school grades, and its influence grows with each stage of education, with long-term implications for income and employment prospects. Four IQ points could, in theory, mean the difference between completing a Master’s or PGCE after your undergraduate studies versus not. Holding a postgraduate degree is associated with earning up to 18 percent more in salary compared to an undergraduate degree.

How Much Can DNA Really Tell Us?

Polygenic score predictions are still very variable. For example, polygenic scores predict certain abilities (e.g., verbal and non-verbal ability, problem-solving) better than others (e.g., working memory, factual recall). At this moment, we cannot explain most of the variability in polygenic score predictions, which is a problem: Until we know why polygenic scores give sometimes stronger and sometimes weaker predictions, they cannot be considered reliable tools.

Another thing to note is that populations of non-European ancestry are severely underrepresented in behavioural genetic research and that polygenic scores don’t predict outcomes equally well across genetic ancestry groups. For example, polygenic scores for education can predict the difference between a B+ and an A- in school exams in children of European ancestry, but they account for only half this grade difference in African-American children. Efforts are underway to address these issues—but it’s still early days.

Feeling Queasy?

Talking about intelligence, DNA, and people’s prospects can leave an odd taste in your mouth. There’s widespread concern that genetic information could be used—and abused—to justify discrimination, inequality, and exclusion. Some fear a low polygenic score for IQ could see you or your children denied job opportunities or university places. Worse still, this knowledge could be misapplied to promote genetic engineering, to eradicate "undesirable" traits from society.

Such fears are exacerbated by genetic determinism—the misperception that genetics seals people’s fates from birth—and genetic essentialism—the belief that ethnic and cultural groups share some immutable genetic essence, which separates them from others. These fallacies leave discoveries about DNA and IQ vulnerable to misinterpretation and misuse.

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But we argue that understanding how DNA influences intelligence could in fact benefit society. Polygenic scores could provide an early warning system for primary school students who might need extra support. Genetics could help teachers and parents to identify children’s learning needs and to support kids accordingly. Providing the right support early on makes a real difference in children’s learning and social-emotional development, with lifelong benefits for well-being.

Learning about the genetic differences and similarities between individuals could also help people rethink racial prejudices. Promoting genetic literacy could help break down the dangerous, essentialist thinking that was historically invoked to support genetic discrimination.

The more we discover about how DNA and our experiences work hand-in-hand in shaping us, the sooner we’ll leave behind the idea that our genes determine where we’ll go in life. Behavioural genetic research could highlight ways to boost children’s life chances by changing the environment. Genes are not our destiny but rather the coordinates of where our journeys start.

DNA and IQ: Where Do We Stand?

So, are polygenic scores fit for purpose? The short answer is: It depends on your purpose!

For now, they’re too blunt a tool to help identify our mental strengths and weaknesses, but they’re valuable tools for researching how genetics and experience shape us. Future research may hone polygenic scores to a point where they can make a real-world difference in policy and practice. The first step for us today is to dispel the myths surrounding the genetics of intelligence and to safeguard against the risks of genetic determinism and discrimination.