Times 2 - features

September 04, 2002


What really shapes a child's life

In the second of two extracts from his new book, Steven Pinker argues against one of the most entrenched myths of our culture - that 'good' parents can succeed in shaping the lives of their children. What shapes us is often beyond a parent's control.

The nature-nurture debate is, of course, far from over when it comes to identifying the endowment shared by all human beings and understanding how it allows us to learn. But when it comes to what makes people within the mainstream of a society different from one another whether they are smarter or duller, nicer or nastier, bolder or shyer the nature-nurture debate, as it has been played out for millennia, really is over, or ought to be.

Everyone knows that the behaviour of parents and the behaviour of their children are correlated. Loving parents have confident children, authoritative parents (neither too permissive nor too punitive) have well-behaved children, parents who talk to their children have children with better language skills, and so on.

Everyone concludes that to grow the best children, parents must be loving, authoritative and talkative, and if children do not turn out well, it must be the parents' fault. But the conclusions depend on the belief that children are blank slates. Parents, remember, provide their children with genes, not just a home environment. The correlations between parents and children may be telling us only that the same genes that make adults loving, authoritative and talkative make their children self-confident, well-behaved and articulate.

Behavioural genetics provides ways of disentangling these correlations, and other similarities and differences among people. Let's begin with the contribution of the genes.

Heritability the proportion of the variation among individuals that can be attributed to differences in their genes can be measured in several ways. The simplest is to take the correlation between identical twins who were separated at birth and reared apart. They share all their genes and none of their environment, so any correlation between them must be an effect of their genes.

Another technique is to compare biological siblings, who share half their genes and most of their environment, with adoptive siblings, who share none of their genes (among those that vary) and most of their environment. The results come out roughly the same no matter what is measured or how it is measured: about half of the variation (sometimes more, sometimes less) in a sample of people from a given culture comes from genetic differences.

General intelligence is substantially heritable and so are the five major ways in which personality can vary (summarised by the acronym OCEAN): openness to experience, conscientiousness, extroversion-introversion, antagonism-agreeableness and neuroticism. And traits that are surprisingly specific turn out to be heritable, too, such as dependence on nicotine or alcohol, number of hours of television watched and likelihood of divorcing.

When people hear about these findings, they have an odd response: "So you're saying it's all in the genes!" When it comes to genes, people suddenly lose their ability to distinguish 50 per cent from 100 per cent, "some" from "all", "affects" from "determines". The numbers say that our genes play a role in making us different from our neighbours, but our environments play an equally important role. At this point everyone draws another, equally erroneous, conclusion. We are shaped both by our genes and by our family upbringing: how our parents treated us and what kind of home we grew up in.

Not so fast. Behavioural genetics allows us to distinguish two very different ways in which our environments might affect us. The shared environment is what impinges on us and our siblings alike: our parents, our home life and our neighbourhood (as compared with other parents and neighbourhoods in the sample). The non-shared or unique environment is everything else: anything that impinges on one sibling but not another, including parental favouritism (Mum always liked you best), the presence of the other siblings, unique experiences such as falling off a bicycle or being infected by a virus, and, for that matter, anything that happens to us over the course of our lives that does not necessarily happen to our siblings.

Here is the second stunning discovery from behavioural genetics. In measuring the relative effects of a shared and a unique environment we find that the effects of shared environment are small, often not statistically significant, and frequently zero. What this means concretely is that twins who grew up together are no more similar than twins who were separated at birth and reared apart, and that adopted siblings are not similar at all. Whatever experiences siblings share by growing up in the same home within a given culture makes little or no difference to the kind of people they turn out to be.

These two discoveries the partial heritability of psychological traits, and the negligible effects of shared environment lead to a third one. A substantial portion of the variation in complex human behavioural traits is not accounted for by the effects of genes or families. Identical twins reared together (who share both their genes and a family environment) are far from identical in their intellects and personalities. There must be causes that are neither genetic nor common to the family that make identical twins different and, more generally, make people what they are. As with Bob Dylan's Mr Jones, something is happening here but we don't know what it is.

The new consensus about nature and nurture from behavioural genetics half the variation from the genes, little or none from the family, the rest from something else began to congeal in the 1980s, but it wasn't until the late 1990s that its implications for child-rearing were first explored. A parade of experts has long furnished parents with advice, ever changing in content, never changing in certitude, on how to nurture a happy and successful child. The current recipe runs something like this: Parents should stimulate their babies with colourful toys and varied experiences. They should read and talk to their babies as much as possible to foster their language development. They should interact and communicate with their children at all ages and no amount of time is too much. Parents should set firm but reasonable limits, neither bossing their children around nor giving them complete licence. Physical punishment of any kind is out, because that perpetuates a cycle of violence. Nor should parents belittle their children or say that they are bad, because that will damage their self-esteem. On the contrary, they should shower them with hugs and unconditional affirmations of love and approval. And parents should communicate intensively with their adolescent children and take an interest in every aspect of their lives.

But what do we really know about the long-term effects of parenting? Natural variation among parents, the raw material of behavioural genetics, offers one way of finding out. Some mothers stay at home, others are workaholics. Some parents lose their tempers, others are infinitely patient. Some are unreserved in their affection, others are more guarded. Some homes are filled with books, others with blaring TV sets. According to the conventional wisdom, these differences should make a difference.

At a bare minimum, two children growing up in one of these homes with the same mother, father, books, TVs and everything else should turn out more similar, on average, than two children growing up in different homes. Seeing whether they do is a remarkably direct and powerful test.

But they don't. Remember the second discovery of behavioural genetics that effects of the shared environment are negligible. All those differences among parents and homes have no predictable long-term effects on the personalities of their children. Not to put too fine a point on it, much of the advice from the parenting experts is flapdoodle.

If this conclusion came only from behavioural genetics, one might wonder whether they were an artefact of some peculiarity in its methodology, but decades of research on the different circumstances in which children grow up are quite consistent with the conclusion.

All things being equal, children turn out the same way whether their mothers work or stay at home, whether they are placed in daycare or not, whether they have siblings or are only children, whether their parents have a conventional or an open marriage, whether their conceptions were planned, were accidental or took place in a test tube, and whether they have two parents of the same sex or one of each. Even growing up without a father in the house, which does correlate with troubles such as dropping out of school, remaining idle and having babies while a teenager, does not seem to cause the troubles directly. Rather they seem to be a correlate of the true causes, which may include poverty, neighbourhoods with lots of unattached men, frequent moves (which force children to start from the bottom of the pecking order in new peer groups) and genes that make both fathers and children more impulsive and quarrelsome.

And this leaves us with a maddening puzzle. No, it's not all in the genes; around half the variation in personality, intelligence and behaviour comes from something in the environment. But whatever that something is, it cannot be shared by two children growing up in the same home with the same parents. And that rules out all the obvious somethings. What is the elusive Mr Jones factor? If you grew up in a different part of the world from where your parents grew up, consider this question: do you sound like your parents or like the people you grew up with? What about the way you dress, or the music you listen to, or the way you spend your free time? Consider the same question about your children if they grew up in a different part of the world from where you grew up or for that matter, even if they didn't. In almost every case people model themselves after their peers, not their parents.

Socialisation acquiring the norms and skills necessary to function in society takes place in the peer group. Children have cultures, too, which absorb parts of the adult culture and also develop values and norms of their own. Children do not spend their waking hours trying to become better and better approximations of adults. They strive to be better and better children, ones that function well in their own society. Is this the crucible in which our personalities are formed?

I am convinced that children are socialised that they acquire the values and skills of the culture in their peer groups, not their families. But I am not convinced, at least not yet, that peer groups explain how children develop their personalities: why they turn out shy or bold, anxious or confident, open-minded or old-school. Socialisation and the development of personality are not the same thing, and peers may explain the first without necessarily explaining the second. One possibility is that children differentiate themselves within a peer group, not by their choice of a peer group. Within each group, some become leaders, others foot soldiers, still others jesters, loose cannons, punching bags or peacemakers, depending on what niche is available, how suited a child is to filling it, and chance. Once a child acquires a role, it is hard to shake it off, both because other children force the child to stay in the niche and because the child specialises in the skills necessary to prosper in it.

Fitting into a niche in a peer group is largely a matter of chance. But once we allow Lady Luck into the picture, she can act at other stages in life. When reminiscing on how we got to where we are, we all can think of forks in the road where we could have gone on very different life paths. If I hadn't gone to that party, I wouldn't have met my spouse. If I hadn't picked up that brochure, I wouldn't have known about the field that would become my life's calling. If I hadn't answered the phone, if I hadn't missed that flight, if only I had caught that ball. Life is a pinball game in which we bounce and graze through a gauntlet of chutes and bumpers. Perhaps our history of collisions and near misses including random events during the wiring of our brains in utero and in early childhood helps to explain what made us what we are.

Not everyone is so accepting of fortune, or of the other forces beyond a parent's control, such as genes and peers. As with other discoveries about human nature, people hope it isn't true. But the truth doesn't care about our hopes, and sometimes it can force us to revisit those hopes in a liberating way.

Yes, it is disappointing that there is no algorithm for growing a happy and successful child. But would we really want to specify the traits of our children in advance and never be delighted by the unpredictable gifts and quirks that every child brings into the world? People are appalled by human cloning and its dubious promise that parents can design their children by genetic engineering. But how different is that from the fantasy that parents can design their children by how they bring them up? Realistic parents would be less anxious parents. They could enjoy their time with their children rather than constantly trying to stimulate them, socialise them and improve their characters. They could read stories to their children for the pleasure of it, not because it's good for their neurons.

"So you're saying it doesn't matter how I treat my child?" What a question! Of course it matters. Parents wield enormous power over their children and their actions can make a big difference to their happiness. Child-rearing is, above all, an ethical responsibility. It is not OK for parents to beat, humiliate, deprive or neglect their children, because those are awful things for a big, strong person to do to a small, helpless one.

Also, children and parents have a human relationship a simple truth it is easy to forget under the conventional wisdom that children are raw material for parents to shape. As with other relationships, one person's behaviour towards another has consequences for the quality of the relationship. Over the course of a lifetime the balance of power shifts, and children, complete with memories of how they were treated, have a growing say in their dealings with their parents. These are well-functioning adults who still shake with rage when recounting the cruelties their parents inflicted on them as children. There are others who moisten up in private moments when recalling a kindness or sacrifice made for their happiness, perhaps one that the mother or father has long forgotten. If for no other reason, parents should treat their children well to allow them to grow up with such memories. 

Extracted from
The Blank Slate: The Modern Denial of Human Nature, by Steven Pinker, to be published by Allen Lane on September 5, £25. Available from The Times Booskhop for £20, plus £1.95 p&p, 0870 160 8080.

© Steven Pinker 2002