杏吧原创

IT IS an age-old question: are we shaped more by nature or nurture? Robert Plomin, a geneticist at King鈥檚 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鈥檛 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.

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鈥檚 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鈥檛 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鈥檛 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鈥檛 as many studies on personality, but we know that identical twins reared apart are as similar in personality as identical twins reared together. I鈥檝e 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鈥檛. 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鈥檛 matter, then what does? What are these environmental influences, if they aren鈥檛 how we are raised?

People in the field have tried very hard to find systematic sources of environmental influences, but we haven鈥檛 been successful. We have studied friends or peers outside the family, but they don鈥檛 seem to be a systematic source of influence. So we鈥檙e 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鈥檚 a correlation between parenting and kids鈥� outcomes. That鈥檚 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鈥檛 causal.

鈥淒on鈥檛 send your kids to private school because you think it will make them achieve more. They won鈥檛鈥�

In other words, reading to a child doesn鈥檛 seem to influence the child鈥檚 reading behaviour. That contradicts every piece of advice I鈥檝e heard.

I鈥檓 not saying don鈥檛 bother if they like it. I have one grandchild who loves to read. I have another who just wants to roughhouse. I鈥檓 actually responding to the differences I get from the children more than I am creating those differences.

So there鈥檚 no point trying to encourage good behaviour?

I鈥檓 not saying you can鈥檛 change kids鈥� behaviour. If your son is hitting your daughter, you can say: 鈥淭hat鈥檚 not allowed.鈥� And you can stop him. But you鈥檙e not changing the kid鈥檚 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鈥檝e said. Our studies have only dealt with a certain range of differences, maybe 98 per cent of the population. We aren鈥檛 studying the environmental outliers, like severe abuse and neglect, because those families probably wouldn鈥檛 participate in studies. As in all of science, we can鈥檛 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鈥檚 exam results?

That鈥檚 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 鈥渢iger mums鈥� who devote their lives to getting their kids to play the violin. But you can鈥檛 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鈥檚 an open question as to whether those kids would achieve as well without that sort of pressure 鈥� 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 鈥� and family life 鈥� nice for kids. And if you鈥檙e failing at school, that isn鈥檛 very nice. If kids don鈥檛 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鈥檛 necessarily changing their learning ability or their sociability or shyness. That鈥檚 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鈥檛 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鈥檚 because they selected the kids who did well in their earlier exams. It鈥檚 a self-fulfilling prophecy of selection. They would have done just as well, whatever school they went to.

Are you really arguing that there鈥檚 no advantage to sending your child to a private or grammar school?

If you want your kid to go to private school because it鈥檚 just a nicer place and has lots of sports fields, fine. Some parents admit it鈥檚 also because they want them to meet the 鈥渞ight sort of people鈥�. But I think it鈥檚 good to be clear about what it is you鈥檙e doing. Don鈥檛 do it because you think you鈥檙e going to make them achieve more because they won鈥檛.

Shouldn鈥檛 we try to reduce inequalities between private and state schools?

I actually would prefer if we didn鈥檛 have any selective schools and we just had good community schools. But if you鈥檙e 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鈥檛 tutor your child to get them a better polygenic score for intelligence.

Some people might find that prospect scary.

I don鈥檛 think it is so scary. Right now, it鈥檚 very coarse, but what鈥檚 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.

鈥淭hink of parents as resource managers, whose job it is to find out what their kids like to do鈥�

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鈥檛 work: to be successful, interventions have to be intensive and expensive. That鈥檚 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鈥檓 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鈥檛 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鈥檚 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: 鈥淎ren鈥檛 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鈥檙e not?鈥� Even in the West, ascribing everything to upbringing has done a lot of harm.

Can you empathise with those who don鈥檛 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鈥檛 in control. If you think your kids are clay that you can mould, forget it. I think it鈥檚 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鈥檚 a relationship 鈥� enjoy it as best as you can, and watch who your children become.