The Nurture Assumption review

On this Mother's Day, I'd like to direct everyone's attention to The Nurture Assumption, a book by science writer Judith Rich Harris about the mistaken notion that parents have much influence on their children's outcomes in life, at least in the field of personality development.

I got the idea to review this book on this day by going to church with my mother.  Predictably, the homily/sermon focused on "what your spiritual legacy will be," with special emphasis and examples from the legacy of mothers.  Mothers were doing this and ruining their children but then improved themselves and everything was okay.  Or mothers did that and saved their children from a future of emotional and financial destitution.

It's tempting to believe these anecdotes.  Everyone seems to be able to see evidence of them with their own eyes.  As Harris states in the very title of the book, our culture's default assumption is that nurture is somehow responsible for children's outcomes.  But as Harris takes pains to point out, a lot of science is about examining our assumptions and observations in the light of testing and evidence.  And her message is that, when the evidence is examined critically, there isn't much support for the notion that mothers, or fathers, have much influence on their children's personality development.

Readers of this blog who are Paleo dieters will no doubt be familiar with Dr. Kurt Harris (no relation to the author) and his emphasis on ranking different sciences' validity in constructing dietary advice.  Epidemiology is a relatively weak way to find things out about the human body compared with studies in physiology and biochemistry.  When you, essentially, take surveys instead of doing interventional studies, you open yourself to all sorts of confounding problems creeping into your results.  Science journalist Gary Taubes points out much the same thing in Good Calories, Bad Calories.

The point of The Nurture Assumption is much the same.  Harris was an author of textbooks in developmental psychology, but after years of writing textbooks, she had started noticing problems with the research she was citing in her books.  The upshot is that, if you throw out all but the gold-standard studies in developmental psychology, it appears that most of the influence on children's development is genetic.  And the rest is not attributable to parenting styles.  She suggests, then, the non-genetic remainder is attributable to another influence--peer groups.

Her theory rests on several contentions about the brain and the course of development.  For example, she says that, contrary to the assumption that children's brains are trying to figure out how to be successful adults, they are in fact trying to figure out how to be successful children.  She also contends that it is an important part of development for the brain to be able to identify the group to which it belongs and its status within that group.  Both these characteristics make it much more likely that children identify with and look to their peer groups for their ultimate personality development rather than to their parents, who are adults and not part of their group.

Harris examines what's wrong with studies that suggest nurturing is important, reviews the evidence from more robust studies (like those of twins raised apart) but also shows how her ideas are consistent with what we know of our paleo ancestors and other hunter-gatherer groups today.

The biggest obstacle to people assessing her theories fairly is the very strong and persistent tendency people have to confuse, mix-up, or ignore correlation and causation.  The recent hullabaloo over the Mother's Day TIME magazine cover article provides a perfect example:

I was riding in the car the other day when there was a talk radio show on about attachment parenting.  The interviewer asked who attachment parenting appealed to, and the interviewee answered that many of those doing attachment parenting were people who were very concerned that their children grow up into empathetic adults.

So, let's say that these empathy-valuing parents choose attachment parenting and raise some empathetic children.  What does that prove about attachment parenting?  Absolutely nothing.  It is just as likely--actually, I suspect more likely--that empathy-valuing parents pass on empathy-valuing genes to their children.  Mixing up the effects of genetics and parenting styles would be textbook human observational error, and so in the context of the research and analysis Harris presents, I am strongly inclined to favor her theory of genes + peer influence.

good read for HCPs

I wouldn't say this book blew my mind, but I did have one of those "everything makes a lot more sense now" moments.  This is definitely a book that health care professionals should read.  In addition to specific errors the health care system has made in the past, like blaming mothers for autism, the health care system has a general stance of advice-giving to the population at large that is probably largely irrelevant when it comes to the field of pediatrics.  I'm not talking about physical disease here, but child-rearing advice.  Even if you, as an HCP, are unconvinced by The Nurture Assumption's case, it worth knowing about Harris' theory and talking a more skeptical attitude to whatever child-rearing theories you do hold.