IT IS an age-old question: are we shaped more by nature or nurture? Robert Plomin, a geneticist at King’s College London, has spent his career teasing apart the contributions of DNA and environmental factors to countless human traits, from body weight to personality and academic success. Environment is undoubtedly a key influence on almost every aspect of our lives. But Plomin argues that genetics plays a more important and measurable role, even to the extent that our parenting and schooling don’t matter that much. We caught up with him to discuss his sometimes controversial views.
Give us an example showing how little influence parenting has on the way children turn out.
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Take our propensity to be overweight. If zero means parents have no influence and one means total influence, when two siblings grow up together, their body mass index has a correlation of about 0.4. It’s easy to see how people attribute that mainly to nurture, because parents provide both siblings with the same food. But it turns out that isn’t true, and obesity runs in families for reasons of genetics. A killer piece of data is that the correlation for weight is 0 between adoptive siblings who grow up in the same family but don’t share genes. Even more striking is that if you were adopted at birth away from your sibling, .
Is this true for intelligence and personality too?
Definitely for cognitive abilities. There aren’t as many studies on personality, but we know that identical twins reared apart are as similar in personality as identical twins reared together. I’ve studied identical twins who have grown up apart, and I find it amazing how they are so similar in things like the way they laugh or talk.
What do these findings mean for who we are, and who we become?
Twin and adoption studies have shown us that , and half isn’t. But whatever the environment is, it makes two kids in the same family as different as those in two different families. The effects of the environment are random. The implications of these findings are enormous because it means inherited differences are the major systematic [non-random] force in making us who we are.
If how our parents raise us doesn’t matter, then what does? What are these environmental influences, if they aren’t how we are raised?
People in the field have tried very hard to find systematic sources of environmental influences, but we haven’t been successful. We have studied friends or peers outside the family, but they don’t seem to be a systematic source of influence. So we’re stuck with saying this is an important aspect of our integral differences but nobody has much of a clue as to what it is. They must be random, chance events. It could be an illness at a particular time, such as a virus, that affects the wiring of the brain. It could be a budding romantic relationship that goes wrong, an encounter with a special person or a mentor. It could be anything.
It is almost unbelievable that how children are raised is so unimportant in how they turn out.
I know. What confuses people is that there’s a correlation between parenting and kids’ outcomes. That’s always been assumed to be due to the nurturing environment: parents reading a lot to their kids makes them more likely to read. But parents reading a lot could reflect their own genetic propensity for reading. When you do adoption studies, you find that parental reading isn’t causal.
“Don’t send your kids to private school because you think it will make them achieve more. They won’t”
In other words, reading to a child doesn’t seem to influence the child’s reading behaviour. That contradicts every piece of advice I’ve heard.
I’m not saying don’t bother if they like it. I have one grandchild who loves to read. I have another who just wants to roughhouse. I’m actually responding to the differences I get from the children more than I am creating those differences.
So there’s no point trying to encourage good behaviour?
I’m not saying you can’t change kids’ behaviour. If your son is hitting your daughter, you can say: “That’s not allowed.” And you can stop him. But you’re not changing the kid’s personality.
What about the fact that people who are abused as children can be permanently affected by it?
There is an important caveat to what I’ve said. Our studies have only dealt with a certain range of differences, maybe 98 per cent of the population. We aren’t studying the environmental outliers, like severe abuse and neglect, because those families probably wouldn’t participate in studies. As in all of science, we can’t generalise beyond the sample we study. We are talking about averages in a population, but it could be different for any one individual.
What about outliers in the other direction, like those parents who go to great lengths to boost their children’s exam results?
That’s the other caveat: we are studying what we actually see now in a particular population with these existing environmental differences. Some novel influence could have a bigger effect. That could be “tiger mums” who devote their lives to getting their kids to play the violin. But you can’t assume that tiger mums do make a difference, because the mums who are so concerned about achievement probably have kids who are genetically more likely to be achieving anyway. It’s an open question as to whether those kids would achieve as well without that sort of pressure – or even better.
Are you saying that there is no point trying to make your child do well at school?
Not at all. As parents, we should try to make school life – and family life – nice for kids. And if you’re failing at school, that isn’t very nice. If kids don’t do their homework, they get in trouble at school. If your child is having trouble with other kids, you want to help them. But you aren’t necessarily changing their learning ability or their sociability or shyness. That’s an important distinction.
How about the influence of the school environment? We know that going to a private school helps you get into a good university.
We actually don’t know that. Our paper from last year showed that most of the reason those at private schools and grammar schools do better is because of their . Those schools select the very best kids and then they get better exam results, but it’s because they selected the kids who did well in their earlier exams. It’s a self-fulfilling prophecy of selection. They would have done just as well, whatever school they went to.
Are you really arguing that there’s no advantage to sending your child to a private or grammar school?
If you want your kid to go to private school because it’s just a nicer place and has lots of sports fields, fine. Some parents admit it’s also because they want them to meet the “right sort of people”. But I think it’s good to be clear about what it is you’re doing. Don’t do it because you think you’re going to make them achieve more because they won’t.
Shouldn’t we try to reduce inequalities between private and state schools?
I actually would prefer if we didn’t have any selective schools and we just had good community schools. But if you’re going to select, you should take genetics into account, and I think eventually we will. The best predictor for exam results is the , which adds up the results from hundreds of genetic tests. We can today predict 15 per cent of the variance of GCSE scores with DNA alone. DNA is an objective, unbiased predictor. You can’t tutor your child to get them a better polygenic score for intelligence.
Some people might find that prospect scary.
I don’t think it is so scary. Right now, it’s very coarse, but what’s coming along are much more specific genetic studies that will let us predict which kids are likely to develop a reading problem. Then we could intervene before kids get to school, rather than waiting until the problems become full-blown, as we do now.
“Think of parents as resource managers, whose job it is to find out what their kids like to do”
So we would do genetic tests at around age 3 or 4 and then give extra reading coaching to children with a low score?
Actually it would be language interventions at that age. Kids with reading problems had language problems when they were younger. And there are good intervention programmes for language. But the cheap and easy ones don’t work: to be successful, interventions have to be intensive and expensive. That’s why you need to target them. I also think we will have specific STEM polygenic scores, for abilities in science, technology, engineering and math. I’m working with educational foundations to think about how we could use DNA to help personalise education rather than having a universal, one-size-fits-all curriculum.
Isn’t treating people differently based on genetic tests heading towards eugenics?
The only people who ask me questions about eugenics and the Nazis are journalists such as yourself, not the general public. It’s not an unimportant question, but the belief that environment dictates everything has done worse damage than genetic determinism. No one has ever asked those who hold that belief: “Aren’t you concerned about the abuses of the past, where environmentalism has led to totalitarian regimes that assume everybody is the same and puts people into gulags if they’re not?” Even in the West, ascribing everything to upbringing has done a lot of harm.
Can you empathise with those who don’t like your ideas about parenting?
I think my latest book actually has a good message for parents: that they should lighten up and enjoy their children. Because, despite what they think, parents aren’t in control. If you think your kids are clay that you can mould, forget it. I think it’s better if we think of parents as resource managers, whose job it is to find out what their kids like to do and give them opportunities to do it. Why not accept that it’s a relationship – enjoy it as best as you can, and watch who your children become.
