DNA Tests for IQ Are Coming, But It Might Not Be Smart to Take One

Antonio Regalado, MIT Technology Review, April 2, 2018

Ready for a world in which a $50 DNA test can predict your odds of earning a PhD or forecast which toddler gets into a selective preschool?

Robert Plomin, a behavioral geneticist, says that’s exactly what’s coming.

For decades genetic researchers have sought the hereditary factors behind intelligence, with little luck. But now gene studies have finally gotten big enough—and hence powerful enough—to zero in on genetic differences linked to IQ.

A year ago, no gene had ever been tied to performance on an IQ test. Since then, more than 500 have, thanks to gene studies involving more than 200,000 test takers. Results from an experiment correlating one million people’s DNA with their academic success are due at any time.

The discoveries mean we can now read the DNA of a young child and get a notion of how intelligent he or she will be, says Plomin, an American based at King’s College London, where he leads a long-term study of 13,000 pairs of British twins.


As of now, the predictions are not highly accurate. The DNA variations that have been linked to test scores explain less than 10 percent of the intelligence differences between the people of European ancestry who’ve been studied.

Even so, MIT Technology Review found that aspects of Plomin’s testing scenario are already happening. At least three online services, including GenePlaza and DNA Land, have started offering to quantify anyone’s genetic IQ from a spit sample.


Several educators contacted by MIT Technology Review reacted with alarm to the new developments, saying DNA tests should not be used to evaluate children’s academic prospects.

“The idea is we’ll have this information everywhere you go, like an RFID tag. Everyone will know who you are, what you are about. To me that is really scary,” says Catherine Bliss, a sociologist at the University of California, San Francisco, and author of a book questioning the use of genetics in social science.”


Finding the genes

To psychologists, IQ tests measure something called “g”—the general factor of intelligence. People who are better at math, spatial reasoning, verbal ability, and other skills that tests can measure have higher g.

And that’s not all. The g factor is strongly correlated with income, happiness, health, and life span. More g seems to be a good thing all around. To Plomin it’s the “omnipotent variable” in life.

It’s also highly heritable. Comparisons of twins, both identical and fraternal, separated at birth or raised together, had shown that genetics must account for more than half of intelligence—a huge effect for genes. The rest is due to your schools, your diet, and other environmental factors.


Each genetic variable found so far has only a tiny effect, either weakly increasing IQ on average or weakly decreasing it. The trick to turning the discoveries into a personal DNA IQ test? Simply add up all the pluses and minuses you find in a specific person’s genome.

These types of assessments are called “polygenic scores.” And they’re quickly becoming a very big deal (see “10 breakthrough technologies 2018: Genetic fortune telling”). That’s because they work for any trait, including heart disease, diabetes, and schizophrenia—in all, more than 2,000 traits so far.

Plomin was quick to sign up. Last year, he spit in a tube and had his DNA scores calculated by his research center. Now, during talks, he presents his genetic rankings. He’s on the high end of the risk for arthritis (he has some), lower than average for depression, and in the 94th percentile for being overweight.


Of course, he knows his percentile rank for predicted academic achievement, too. “It’s 99-point-something—it’s embarrassing,” he says.

Are you Einstein or Bozo?


Plomin, however, points out that IQ tests with colored blocks barely work for little kids, failing to accurately capture how they will do on tests later in life. Your DNA, on the other hand, is there from the day you are born and doesn’t change. Early in life, Plomin says, DNA may already provide a better intelligence prediction than any test does.

Still, the issue is accuracy—or lack of it. Right now, the polygenic scores capture only a fraction of the genetic determinants of intelligence and none of the environmental ones. That means the predictions remain fuzzy.


So far, the major consumer DNA testing companies have steered clear of intelligence reports. “There are obviously some concerns about how it gets used and gets talked about,” says James Lu, cofounder of California-based Helix, a leading app store for DNA tests.

Given the history of eugenics, big companies have to fear being called out as Nazis and racists. What’s more, customers might not be pleased to receive a prediction of less than average intelligence.


But 23andMe doesn’t offer any reports about intellectual faculties. And that’s not because it doesn’t have the data. It does. Because it surveys customers on how long they stayed in school, a proxy for intelligence, the Google-backed company has been playing a supporting role in the search for intelligence genes by contributing its customers’ DNA data to the largest of the gene hunts.

So why not tell customers? In response to MIT Technology Review’s question, 23andMe gave us a statement. “Educational attainment is something we have looked at previously but are not currently pursuing for our product for several reasons,” said Shirley Wu, director of product science for 23andMe. “One being the pitfalls of potential misinterpretation of such a report.”


Although it’s still taboo to talk about, some medical scientists are trying to figure out how to use the polygenic intelligence scores to pick the smartest embryo from an IVF dish, choose the best sperm donor, or discover fetuses at high risk for an expanded menu of cognitive disorders, including autism.

Dalton Conley, a sociologist at Princeton University, says as soon as the IQ predictions reach the double digits—something that could occur very soon—we will need to have a “serious policy debate” about such “personal eugenics.” One concern is that IVF is expensive. That could lead to a situation in which the wealthy end up using IQ-test technology to pick kids with select genes while the poor don’t, leading to an unequal society that Conley calls a “genotocracy.”

Others suggest that genetic models of intelligence will be used to compare races, ethnic groups, or people from different parts of the world. In an editorial about the genetics of race published in the New York Times on March 23, Harvard University biologist David Reich cited the new genetic IQ predictors and cautioned that “all traits influenced by genetics are expected to differ across populations.”

The warning was implicit: differences in IQ could be due to genes, not circumstance, and polygenic scores might prove it.


Plomin says he’s writing a book, titled Blueprint, that he thinks is “going to piss a lot of people off” by arguing that DNA is the “major systematic force in making people who they are.”

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