‘It’s not Brave New World, nor a case of genetic castes, but intelligence is inherited’

13th November 2015 at 00:00
Professor Robert Plomin urges teachers to stop ‘freaking out’ about genetics – and questions growth mindset

Robert Plomin has devoted much of his career to understanding how our genes influence our intelligence and educational success. But he’s in two minds about whether he should be talking about it.

On the one hand, it’s getting serious now. Research consortia are studying hundreds of thousands of people to develop DNA tests that could identify how an individual’s genes might affect their learning: which children are likely to struggle with skills such as reading, for example, and which are more likely to take it in their stride and race ahead.

So far, these tests can explain only about 5 per cent of IQ differences. But that progress has been made in just a few short years. The education system needs to be prepared for the debates a DNA test for intelligence would unleash, Professor Plomin believes.

On the other hand, the professor, who researches behavioural genetics at King’s College London, feels he is addressing a hostile audience. Since it was revealed that he had met former education secretary Michael Gove and his advisers in 2013 to brief them on his research, he feels that teachers have shown little interest in hearing about the evidence, collected painstakingly over decades.

Twin studies

“My goals have diminished considerably,” Professor Plomin tells TES. “I’d be very happy if in the near future we could have discussions in education with teachers and put genetics and education together in the same sentence without people freaking out.”

Professor Plomin’s own career owes something to intelligence tests: born into a family where no one had attended university, his academic ability was identified through testing, opening up scholarships and opportunities. In turn, his research has focused on trying to understand how children in the same family who grow up together and share genes can still be so different.

In 1994, Professor Plomin began one of the major world studies of twins, with more than 15,000 families. Studying twins allowed him to isolate the effects of genetics, comparing the similarities and differences between identical twins, who share all their genes, and non-identical twins, who share only half of them, like any other sibling.

Examining identical twins who grew up apart, along with adopted children who were raised in different environments from their genetic relatives, helped him to further disentangle the effects of nature and nurture.

This year, the twins all completed their A-levels, allowing Professor Plomin and his team to draw conclusions about their achievement in school over time, as well as their performance in intelligence tests. The results, he says, are remarkably consistent: about 60 per cent of the variation between children in intelligence scores and school achievement can be explained by genetic differences.

Most of us assume that each person has some measure of natural intelligence that is innate and can’t be taught, but that educational achievement depends on the effort we put in to learn, Professor Plomin says. But, he adds, both those assumptions are wrong. “The most highly heritable cognitive test on most of the IQ batteries is vocabulary,” he says. “You obviously have to learn vocabulary, so how can there be heritable influences on it?

“I have one grandchild who’s totally into words, she’s constantly asking about words and nuances. She wants to know precisely what words mean. Whereas my grandson couldn’t care less. He’s like, whatever. And that’s the way genetic influence works, I think. It creates an appetite and an interest so you then snowball these propensities.”

Shaping inclinations

Genes don’t predestine an educational future for young people, but they do shape our inclinations from a very early age, Professor Plomin suggests. Those genetic effects remain clearly visible in educational results, despite the effort and interventions of teachers.

This interpretation challenges some educational ideas popular with teachers, such as the growth mindset theory put forward by Professor Carol Dweck of Stanford University. If we have natural strengths or weaknesses, and find schoolwork significantly easier or harder as a result, being told that our difficulties are all in our heads is likely to be exasperating.

“Growth mindset, I feel, is greatly overplayed,” Professor Plomin says. “If you try to tell kids who have trouble learning, ‘You can do it, you can change’, you can actually do some harm. Because some kids are going to find it really difficult; it isn’t just a matter of positive thinking. Kids aren’t stupid. I don’t believe the evidence base is all that strong.”

He says he tried to interest Professor Dweck in a research project to measure the effects of growth mindset and try to determine if it was influenced by genes, but she didn’t pursue the idea.

He did run a similar experiment on the notion of “grit”, promoted by Professor Angela Duckworth at the University of Pennsylvania. It found that psychological traits of persistence were themselves highly heritable, with about 30 to 40 per cent of the effect attributable to the influence of genes. And overall the effect of grit is small, Professor Plomin says. (Professor Duckworth’s research directly contradicts the idea that either intelligence or environment, in the form of family income, are better predictors of success than her measure of grit.)

“That’s not to say you can’t change growth mindset or you can’t give kids more grit. You can, and it’s probably not a bad idea at some level,” Professor Plomin says. “But if you think that’s really what it’s all about, God, it’s just a tiny piece of the action. With grit we found it’s about 1 per cent of the variance. And it doesn’t predict anything more than traditional personality measures do. I don’t want to knock it, but what I don’t like is that it’s a silver bullet, a quick fix. ‘Change these kids’ mindsets and they’re all going to go to Oxbridge.’ That’s nuts.”

Just as the genetic influence on education doesn’t mean a fixed outcome for any student, it doesn’t follow that children will have the same abilities as their parents. When news emerged that Mr Gove had taken an interest in genetics and intelligence, the Times columnist Libby Purves pondered the potential fallout for the education system. “If Mr Gove were to agree openly, there would be a torrent of furious anecdotal evidence of genius flowering in unexpected quarters and high achievers producing pig-thick offspring,” she wrote.

In fact, that evidence isn’t anecdotal: it’s almost exactly what the data predicts. As Professor Plomin puts it, “The first law of genetics is ‘Like begets like’. The second law of genetics is ‘Like doesn’t beget like’. That’s what sex is about: to mix up genes to create these combinations.”

Statistically what this means is that the combinations of genes that are likely to produce exceptional talent will be hidden somewhere among parents in the middle of the ability curve, because that’s where 80 per cent of the population is. Conversely, the chances are that high-achieving parents are more likely to have children whose intelligence is closer to the average – if not exactly “pig-thick”.

Tarnished theories

This is one of the reasons why Professor Plomin doesn’t think understanding intelligence as a product of genes entails a dystopian world. “Policy choices are about values, but I would say the value of ‘keep everyone in their place’ is very wrong from a genetic point of view,” he says. “It’s not Brave New World, it’s not a case of genetic castes.”

The study of genetics and intelligence has been tarnished by accusations of racism for years, not just because of the dark history of eugenics but also because of the 1994 publication of The Bell Curve by Richard J Herrnstein and Charles Murray. This notoriously argued that the disparities in educational and career achievement between black and white Americans were largely explained by lower IQ.

Professor Plomin criticised these conclusions at the time, but admits he has “ducked” the issue of race. He says the data simply doesn’t show a large racial gap compared with the variation in the population as a whole. All sorts of social factors are likely to be an issue, but he says it is hard to isolate them.

One explanation may be that poverty provides fewer opportunities for children to develop their abilities. Research by Professor Eric Turkheimer at the University of Virginia found stark differences in the extent to which students’ test scores were explained by their genes, depending on their social class. Among wealthy children, genetic factors accounted for 72 per cent of the variation in IQ. But among the poorest, environmental factors accounted for 58 per cent of the differences.

The result for schools is slightly counterintuitive: the more you perfect a fair education system that provides the same environmental benefits for everyone, the more genetic differences become apparent. Education can narrow the achievement gap and raise the average, but after that the variation will be increasingly determined by inherited ability.

“I think that if any policy comes from this it’s to foster choice and opportunities, to fit in with personalised learning and let kids develop the way their genetic propensities are pushing them,” Professor Plomin says.

He suggests that accepting these genetic factors is a decisive step in education becoming an evidence-based discipline, just as other disciplines such as clinical psychology have had to accept that a genetic basis doesn’t put them out of business. “I hope it’s that way for education, that teachers come to realise that it’s not a major threat,” he says. “And maybe we’ll come to reach that stage where people say, ‘Oh, we always knew that!’ And at some level they do: how can you teach a class of 30 kids and not recognise that they differ tremendously?”

Intelligence and genetics: what Professor Plomin wants teachers to know

Genes are generalists: kids who are higher than average at reading are likely to do well in maths, too. “When people say, ‘Oh, but I’m good at reading, I’m no good at maths’, actually, they’re pretty good at maths but maybe just not as good as they are at reading,” Professor Plomin says.

Personalised learning is key to capitalise on students’ natural inclinations. “If kids differ genetically, as a parent and teacher you want to make opportunities available for children so they can find out what they like to do.”

Genetic testing could help early intervention with reading difficulty – at a cost. “You can’t intervene with reading at 3 and 4, but you can intervene with language. The interventions that work, in medicine as well, are usually intensive and expensive.”

Genetics makes it more rather than less likely that talent can come from anywhere. “The vast majority of the brightest people in the next generation will not come from the top of the distribution, they’ll come from the middle.”

High-flying parents are likely to have children who are more average. “If you take the brightest people, their kids will regress halfway back to the population mean.”

Private schools might be bad value for money – at least on purely educational outcomes. “Parents who are mortgaging their house to spend hundreds of thousands of pounds to get their kids into the right private schools might want to pay attention to the fact that genetics accounts for a huge amount.”

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