Plomin, DNA makes us Who We Are
.. and has to be an indispensable tool for all Social Science ..
MH: I read this book while in search of evidence to support my hypothesis—previously discussed here and here—that in the smallest/simplest Type 1 human society of ‘individual differentiation’ in the Palaeolithic period the differentiations affecting the mode of governing society were biological — i.e. differentiations of age, sex, physique, intelligence and personality. I was confident this was the case for age (e.g. elders as repositories of knowledge), sex (male-female dynamics/roles), and physique (stature, strength, etc.) but not so sure about intelligence and personality. In the case of ‘personality’ I especially had in mind ‘charisma’, which has an important place in political sociology (psychologists today use the word ‘extraversion’ but other personality traits contribute to charisma). In this acclaimed book by Robert Plomin of Kings College London (CBE given for his services to scientific research) I found the clearest evidence that intelligence and personality traits are predicted by the genes in the DNA of every individual. Presumably this was already the case when the first true archaic (and highly differentiated) humans emerged to form group societies 500,000 years ago. I selected some extracts that may interest readers of Social Science Files.
The Source:
Robert Plomin, Blueprint: How DNA Makes Us Who We Are, MIT Press & Penguin 2018
Prologue
… Blueprint focuses on psychology for two reasons. First, psychology is the essence of who we are, our individuality. Most of the same conclusions apply to other sciences such as biology and medicine, but the implications of the DNA revolution are more personal for psychology.
A second reason is that I am a psychologist who has for forty-five years been at the centre of genetic research on mental health and illness, personality and mental abilities and disabilities. One of the best things in life is to find something that you love to do, and I fell in love with genetics when I was a graduate student in psychology at the University of Texas at Austin in the early 1970s. It was thrilling to be part of the beginning of the modern era of genetic research in psychology. Everywhere we looked we found evidence for the importance of genetics, which was amazing, given that genetics had been ignored in psychology until then. I feel lucky to have been in the right place at the right time to help bring the insights of genetics to the study of psychology.
I have been waiting thirty years to write Blueprint. My excuse for not doing it sooner is that more research was needed to document the importance of genetics, and I was busy doing that research. However, in hindsight, I have to admit to another reason: cowardice. It might seem unbelievable today, but thirty years ago it was dangerous professionally to study the genetic origins of differences in people’s behaviour and to write about it in scientific journals. It could also be dangerous personally to stick your head up above the parapets of academia to talk about these issues in public. Now, the shift in the zeitgeist has made it much easier to write this book. A huge bonus for waiting is that the story is much more exciting and urgent now because the DNA revolution has advanced in ways no one anticipated thirty years ago. Now, for the first time, DNA by itself can be used to make powerful predictions of who we are and who we will become. ….
Chapter 8 The DNA blueprint
… Parents matter, but they don’t make a difference
Parents obviously matter tremendously in their children’s lives. They provide the essential physical and psychological ingredients for children’s development. But if genetics provides most of the systematic variance and environmental effects are unsystematic and unstable, this implies that parents don’t make much of a difference in their children’s outcomes beyond the genes they provide at conception.
We saw in the previous chapter that shared environmental influence hardly affects personality, mental health or cognitive abilities after adolescence. This even includes personality traits that seem especially susceptible to parental influence such as altruism, kindness and conscientiousness. The only exception from hundreds of traits that shows some evidence of shared environmental influence is religious and political beliefs. As a parent, you can make a difference to your child’s beliefs, but even here shared environmental influence accounts for only 20 per cent of the variance.
Furthermore, when differences in parenting correlate with differences in children’s outcomes, the correlation is mostly caused by genetics. These correlations are caused by the nature of nurture rather than nurture. That is, parenting correlates with children’s outcomes for three reasons considered earlier. One reason is that parents and their children are 50 per cent similar genetically. Put crudely, nice parents have nice children because they are all nice genetically. Another reason is that parenting is often a response to, rather than a cause of, children’s genetic propensities. It is awkward to be an affectionate parent to a child who is not a cuddler. Finally, children make their own environments, regardless of their parents. That is, they select, modify and create environments correlated with their genetic propensities. Children who want to do something like play sports or a musical instrument will badger their parents to make it happen.
In essence, the most important thing that parents give to their child is their genes. Many parents will find this hard to accept. As a parent, you feel deep down that you can make a difference in how your children develop. You can help children with their reading and arithmetic. You can help a shy child overcome shyness. Also it seems as if you must be able to make a difference because you are bombarded with child-rearing books and the media telling you how to do it right and making you anxious about doing it wrong. (These books are, however, useful in providing parenting tips, for example, about how to get children to go to sleep, how to feed fussy children and how to handle issues of discipline.)
But when these best-selling parenting books promise to deliver developmental outcomes, they are peddling snake oil. Where is the evidence beyond anecdotes that children’s success depends on parents being strict and demanding ‘tigers’ or giving their children grit? There is no evidence that these parenting practices make a difference in children’s development, after controlling for genetics.
This conclusion is also difficult for many of us to accept in relation to our own parents. As you think about your childhood, your parents no doubt loom large, seeming to be the most significant influence in your life. For this reason, it is easy to attribute how we turned out, in good ways and bad, to our parents. If we are happy and confident, we might credit this to our parents’ love and support. Or if we are psychologically damaged, we might blame this on inadequate parenting. However, the implications of genetic research are just as applicable here. These differences in parenting are not correlated with differences in children’s outcomes once you control for genetics. Your parents’ systematic influence on who you are lies with the genes they gave you.
If you are still finding it difficult to accept that parenting is less influential than you thought, it might be useful to review two general caveats about genetics that we considered earlier. The first caveat is that genetic research describes what is, not what could be. Parents can make a difference to their child but, on average in the population, parenting differences don’t make a difference in children’s outcomes beyond the genes they share. Parents differ in how much they guide their children in all aspects of development. They differ in how much they push their children’s cognitive development, for example in language and reading. Parents also differ in how much they help or hinder their children’s self-esteem, self-confidence and determination, as well as more traditional aspects of personality such as emotionality and sociability. But in the population, these parenting differences don’t make much of a difference in their children’s outcomes once genetics is taken into account. Over half of children’s psychological differences are caused by inherited DNA differences between them. The rest of the differences are largely due to chance experiences. These environmental factors are beyond our control as parents. As we saw in the previous chapter, we don’t even know what these factors are.
The second caveat is that genetic research describes the normal range of variation, genetically and environmentally. Its results do not apply outside this normal range. Severe genetic problems such as single-gene or chromosomal problems or severe environmental problems such as neglect or abuse can have devastating effects on children’s cognitive and emotional development. But these devastating genetic and environmental events are, fortunately, rare and do not account for much variance in the population.
Again, parents and parenting matter tremendously, even though differences in parenting do not make a difference in children’s psychological development. Parents are the most important relationship in children’s lives. Still, it is important that parents get the message that children are not blobs of clay that can be moulded however they wish. Parents are not carpenters building a child by following a blueprint. They are not even much of a gardener, if that means nurturing and pruning a plant to achieve a certain result. The shocking and profound revelation for parenting from these genetic findings is that parents have little systematic effect on their children’s outcomes, beyond the blueprint that their genes provide.
It is also important for parents to know that, beyond genetics, most of what happens to children involves random experiences over which parents have no control. The good news is that these don’t make much of a difference in the long run. The impact of these experiences is not stable across time, as discussed in the previous chapter. Some children bounce back sooner, some later, after difficult experiences such as parental divorce, moving house and losing friends. They bounce back to their genetic trajectory.
In the tumult of daily life parents mostly respond to genetically driven differences in their children. This is the source of most correlations between parenting and children’s outcomes. We read to children who like us to read to them. If they want to learn to play a musical instrument or play a particular sport, we foster their appetites and aptitudes. We can try to force our dreams on them, for example, that they become a world-class musician or a star athlete. But we are unlikely to be successful unless we go with the genetic grain. If we go against the grain, we run the risk of damaging our relationship with our children.
Genetics provides an opportunity for thinking about parenting in a different way. Instead of trying to mould children in our image, we can help them find out what they like to do and what they do well. In other words, we can help them become who they are.
Remember that your children are 50 per cent similar to you. In general, genetic similarity makes the parent–child relationship go smoothly. If your child is highly active, chances are that you are too, which makes the child’s hyperactivity more acceptable. Even if you both have short fuses, you can at least understand it better if you recognize your genetic propensities and work harder to defuse situations that can trigger anger. It is also useful to keep in mind that our children are 50 per cent different from us and that siblings are 50 per cent different from each other. Each child is their own person genetically. We need to recognize and respect their genetic differences.
Most importantly, parents are neither carpenters nor gardeners. Parenting is not a means to an end. It is a relationship, one of the longest lasting in our lives. Just as with our partner and friends, our relationship with our children should be based on being with them, not trying to change them.
I hope this is a liberating message, one that should relieve parents of the anxiety and guilt piled on them by parent-blaming theories of socialization and how-to parenting books. These theories and books can scare us into thinking that one wrong move can ruin a child for ever. I hope it frees parents from the illusion that a child’s future success depends on how hard they push them.
Instead, parents should relax and enjoy their relationship with their children without feeling a need to mould them. Part of this enjoyment is in watching your children become who they are. …
Chapter 14 Our future is DNA
Blueprint began with a sales pitch about a new fortune-telling device that promises to transform our understanding of ourselves and our life trajectories. It predicts important traits like schizophrenia and school achievement better than anything else, including family background, parenting and brain scans. It is 100 per cent reliable and 100 per cent stable, unchanging from day to day, year to year, birth to death, which means that it predicts adult traits from conception or birth just as well as it does in adulthood. The device is also unbiased, and not subject to coaching, faking or anxiety. And the one-time total cost for this new device is about £100.
I hope this no longer sounds like just another pop-psychology claim without evidence to back it up. The device is, of course, polygenic scores, backed up by the best science of our times.
Polygenic scores are the ultimate psychological test because, for the first time, they can tell our genetic fortunes. Although polygenic scores only tell us about genetic propensities, not about environmental effects, we have seen that inherited DNA differences are the major systematic cause of who we are. DNA differences account for half of the variance of psychological traits. The rest of the variance is environmental, but that portion of the variance is mostly random, which means we can’t predict it or do much about it.
Even though polygenic scores have just burst on to the stage in the last few years, they are already beginning to transform clinical psychology and psychology research. As we enter the era of personal genomics, they will eventually affect all of us.
The transformative power of polygenic scores comes from three unique qualities. The first is that predictions from polygenic scores to psychological traits are causal, meaning that DNA differences cause differences in psychological traits. Predictions from polygenic scores are an exception to the rule that correlations do not imply causation. Earlier, we considered examples in which ‘environmental’ measures are assumed to be the cause of correlations with psychological traits – for example, correlations between parents reading to children and children’s reading ability, between bad peers and bad adolescent outcomes, and between stress and depression. Always in psychology it is possible that X and Y are correlated because X causes Y or Y causes X or a third factor causes the correlation between X and Y. The gist of the nature-of-nurture phenomenon is that genetics is a third factor that causes correlations between ‘environmental’ measures and psychological traits.
In contrast, correlations between a polygenic score and a trait can only be interpreted causally in one direction – from the polygenic score to the trait. For example, we have shown that the educational attainment polygenic score correlates with children’s reading ability. This correlation means that the inherited DNA differences captured by the polygenic score cause differences between children in their school achievement, in the sense that nothing in our brains, behaviour or environment can change inherited differences in DNA sequence.
In this way, polygenic score correlations eliminate the usual uncertainty about what is cause and what is effect when two variables are correlated. However, the correlation between a polygenic score and a psychological trait does not tell us about the brain, behavioural or environmental pathways by which the polygenic score affects the trait. A long slog up these pathways will be required to understand the intervening processes, especially because tens of thousands of DNA differences are involved, each with very small and highly pleiotropic effects. It is remarkable that polygenic scores can predict psychological traits without knowing anything about these intervening processes.
The second unique benefit of polygenic scores is that they can predict just as well from birth as they can later in life. Because inherited DNA differences do not change from cradle to grave, a person’s polygenic score does not alter throughout the course of their life. In other words, if we had DNA from ourselves as infants and again as adults, the SNP genotypes would be identical and so too would the infant and adult polygenic scores. For this reason, polygenic scores can predict adult traits from infancy just as well as from adulthood.
In contrast, there is nothing else that can tell us if an infant is going to get a PhD or a psychosis. Infants’ psychological characteristics, such as their temperament and cognitive development, tell us little about what infants will be like as adults. Even for intelligence, the most predictive psychological trait, no traits in the newborn predict later intelligence. When infants are two years old, intelligence tests predict less than 5 per cent of the variance of scores when the individuals are eighteen years old. In contrast, polygenic scores can predict just as much variance in adult intelligence as they can, not just at two years of age, but even at birth.
The third unique feature of polygenic scores is that they can predict differences between family members. Before the DNA revolution, genetic predictions were limited to estimates of family resemblance. For example, your risk of schizophrenia is 9 per cent if you have a first-degree relative who has been diagnosed as schizophrenic, a nine-fold increased risk, as compared to the population risk of 1 per cent. This prediction is the same for all children in a family. But genetic risk is not the same for all children in a family because siblings are 50 per cent different genetically (unless they are identical twins).
Polygenic score predictions are specific to an individual, not general to a family. This means that a polygenic score for schizophrenia can show that one sibling has a greater vulnerability than another sibling. Or that one sibling has a higher polygenic score for educational attainment, which could help parents understand why that sibling finds school much easier. Polygenic scores will expose the wide range of genetic differences between siblings. Polygenic score differences are just as great between parents and their offspring as they are for siblings. Children are only 50 per cent chips off the old block.
These unique features of polygenic scores will transform clinical psychology by changing the way we identify, treat and think about psychological problems. Specifically, polygenic scores will make a difference in five ways.
For the first time in psychology, polygenic scores will make it possible to identify problems on the basis of causes rather than symptoms. In psychology, problems are identified solely on the basis of symptoms, after the problem begins to make itself known. For example, depression is diagnosed by asking people about symptoms of depression, such as sadness, hopelessness and lack of enjoyment. Learning disabilities are diagnosed by poor performance on cognitive tests.
Not a single psychological problem is identified on the basis of causes rather than symptoms. People can of course be depressed for many reasons, but polygenic scores can predict the extent to which individuals are depressed for genetic reasons.
A second way in which polygenic scores will transform clinical psychology is by moving away from diagnoses and towards dimensions. One of the big findings in this book is that the abnormal is normal, meaning that, from a genetic perspective, there are no qualitative disorders, only quantitative dimensions. This finding comes from research showing that genetic risk for psychological problems is continuous from low to high risk. There is no point at which genetic risk tips over into pathology. It’s all quantitative – a matter of more or less.
Polygenic scores provide unambiguous proof that genetic influence is continuous. Because polygenic scores aggregate thousands of DNA differences, they are perfectly normally distributed as a bell-shaped curve. Even when GWA studies are based on differences between diagnosed cases versus controls, polygenic scores derived from these case-control GWA studies are also normally distributed. This means that they not only predict whether someone is at risk for the disorder or not, they also predict variation throughout the distribution – from people who are frequently or severely depressed to people who are seldom depressed. Individuals whose polygenic scores are at the 20th percentile will be less depressed on average than those at the 40th percentile, who, in turn, will be less depressed on average than those at the 60th percentile.
The abnormal is normal, in the sense that we all have many of the thousands of DNA differences that contribute to the heritability of any psychological problem. Our risk depends on how many of these DNA differences we have. Polygenic scores will contribute to the demise of diagnoses because polygenic scores make it clear that genetic risk is continuous, not dichotomous. It is worth repeating once again: There are no disorders to diagnose and there are no disorders to cure. Polygenic scores will be used to index problems quantitatively rather than deciding whether someone ‘has’ a disorder.
A third transformative impact of polygenic scores is to move clinical psychology from one-size-fits-all treatments to individually tailored treatments. Polygenic scores will really take off in clinical psychology as soon as we discover treatments that interact with genotypes, in the sense that the success of treatments depends on polygenic scores. Treatments can then be tailored to individuals on the basis of their polygenic scores. For example, profiles of polygenic scores might be used to predict whether a depressed person will respond better to talking therapies or drugs, or to a certain type of talking therapy or drug.
Individually tailored treatments have received the most attention in medical research using an individual’s genotype to select appropriate drugs, known as pharmacogenomics. More generally, ‘precision medicine’ or ‘personalized medicine’ is a model for customizing healthcare on the basis of genetic or other biological information. The goal is to identify the most effective treatments for an individual, sparing the expense, side effects and wasted time for those who will not benefit from the treatment.
The fourth way in which polygenic scores will change clinical psychology is by shifting the focus from treatment towards prevention. As Benjamin Franklin said, an ounce of prevention is worth a pound of cure. In psychology as well as medicine, we have had to wait for problems to occur and then try to fix them. Many psychological problems, such as alcohol dependence and eating disorders, are difficult to cure once they become full-blown problems, in part because they cause collateral damage that is difficult to repair. Preventing problems before they occur is much more cost effective economically, as well as psychologically and socially.
Prediction is the sine qua non for prevention and polygenic scores are the perfect early-warning system. They can predict from birth just as well as later in life. In addition, polygenic scores are not just biomarkers – their prediction is causal.
Although we know surprisingly little about specific interventions to prevent the emergence of psychological problems, polygenic scores will facilitate research on prevention because, for the first time, polygenic scores make it possible to identify individuals who are at risk. For example, for depression, some treatments seem likely to be useful as preventive interventions. Cognitive behavioural therapy and well-being training seem obvious candidates to prevent depression as well as alleviate its symptoms. However, the effects of large-scale preventive programmes administered in schools, in the community or on the internet are small and temporary. We cannot afford intensive and expensive preventive interventions for everyone, but if we can target individuals at high genetic risk it would be cost effective to intervene at a personal level, for example, providing extended one-on-one cognitive behavioural therapy. Polygenic scores make the possibility of targeted prevention a reality.
Another example is attention deficit hyperactivity disorder. There have been attempts to prevent hyperactivity by giving parents instruction and creating education programmes and preschool programmes based on playing games, but success so far has been modest. Again, it seems likely that you get what you pay for. More intensive, and thus more expensive, interventions have a better chance of success, but this would only be feasible if we can identify children at high risk. And now we can do this, using polygenic scores.
The fifth transformative feature of polygenic scores is that they will promote positive genomics. As we have seen, polygenic scores are always perfectly normally distributed, which means that both ends of the distribution are the same size. Clinical psychology focuses on the negative end of the distribution – the problems, disabilities and vulnerabilities. Polygenic scores, on the other hand, will inspire a switch of focus to the other, positive, end of the distribution – strengths instead of problems, abilities instead of disabilities, and resiliencies instead of vulnerabilities.
The positive end of the polygenic score distribution should not be defined as merely low risk. It is possible that this ‘other end’ of the distribution of polygenic scores for psychopathology has its own problems. The word ‘risk’ should be avoided in relation to polygenic scores because it misses this deeper meaning of polygenic scores implied by their normal distribution. For example, my low polygenic score for bipolar disorder might mean something other than being at low risk for the disorder. It might mean that I am flat in affect, failing to experience the highs and lows of life. Using hyperactivity as another example, a high polygenic score will predict impulsiveness and inattentiveness, although no polygenic score is currently available. Does a low score just imply a low risk for being impulsive and inattentive? Or does it predict the opposite problems of being compulsive and obsessive? Similarly, the low end of the polygenic score for BMI might not just predict low risk for obesity. It might signal fussiness about food that leads to eating disorders like anorexia.
As these examples suggest, it is possible that, when it comes to polygenic scores for disorders, intermediate scores are better than extremely low scores. Everything in moderation, as my mother used to remind me, without effect. (Mothers matter, but they don’t make a difference.) I always preferred Oscar Wilde’s take: ‘Everything in moderation, including moderation.’
Because polygenic scores are so new, next to nothing is known about the ‘other end’ of the normal distributions of polygenic scores for disorders. In addition to stimulating research on positive genomics, polygenic scores will foster the promotion of health, in addition to the prevention of illness. For cognitive traits, polygenic scores will shift research from disabilities to abilities, including promotion of high ability.
Clinical psychology will be changed beyond recognition by polygenic scores, which focus on causes instead of symptoms, dimensions instead of diagnoses, individually tailored rather than one-size-fits-all treatments, prevention instead of treatment, and a positive emphasis on health rather than illness.
Polygenic scores will also revolutionize psychological research. For forty years I have been trying to understand what causes people to differ so much in their psychology, beginning with the fundamental question of the relative importance of nature and nurture. Research has consistently shown that inherited genetic differences account for the bulk of psychological differences, especially systematic differences, between individuals. …
… Although it might seem far-fetched and perhaps dystopian, dating websites might extend their data to include polygenic scores. As research on polygenic scores progresses, it could become possible to include polygenic scores for psychological traits typically included on dating websites such as mental health, intelligence, earning potential, ambitiousness, physical fitness, personality traits and relationship qualities – and even good sense of humour. Unlike the hype of dating websites, polygenic-score information could be verifiable through password-protected links to a direct-to-consumer company that provides specified polygenic scores. Whether greater control over selection of a mate increases the long-term prospects of a couple remains to be seen, however. …
[MH: A sense of humour was undoubtedly one of the personality traits that facilitated the emergence of language and male-female pair-bonding in the Palaeolithic.]
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