Friday, October 4, 2013

Effect sizes and baby rearing (review of Baby Meets World)

In these first months of M's life, I've been reading a fair number of parenting advice or interest books focused on babies. My motivation is partially personal and partially professional. Regardless, it has been entertaining to sample the vast array of different theories and interpretations of what is going on in M's cute little head (and body).

I recently finished Baby Meets World: Suck, Smile, Touch, Toddle, by Nicholas Day, and it is my favorite of the scattered group I've read. Day is a clear, funny writer who also blogs entertainingly for SlateBaby Meets World is a tour of the history and science of parenting, broken down by the four activities in its subtitle.

But unlike many books about developmental science it is also a cry of rage and despair by a new parent who has completely had it with parenting advice. This feels exactly right to me. Rather than urbanely walking through the latest research on sucking along with a Gladwell-esque profile of a scientist, Day shows us the absolute weirdness of its past - from deciding whether to use goats or donkeys as wet nurses to the purported link between thumb sucking and chronic masturbation.

The implication, drawn out very clearly in a recent New York Times blog post, is that our current developmental studies may not have much more to offer parents than Freud's hypotheses about thumb sucking:
... [E]xperiments have the most meaning within [their] discipline, not outside of it: they are mostly relevant to small academic disputes, not large parenting decisions. But when we extract practical advice from these studies, we shear off all their disclaimers and complexities. These are often experiments that show real but very small effects, but in the child-rearing advice genre, a study that showed something is possible comes out showing that something is certain. Meager data, maximum conclusions. (p299)
People often ask me how relevant my own work on language development is to my relationship with M. My answer is, essentially not at all. I am a completely fascinated observer; I continually interpret her behavior in terms of my interest in development. Nevertheless, I see very few - if any - easy generalizations from my work (and that of most of my colleagues) to normative recommendations for child rearing beyond "talk to your child."

While this kind of recommendation is without a doubt critical for some families, it's not necessarily the kind of thing that you need to hear if you're already in the market for baby advice books. For example, rather than telling me that M needs to hear 30 million words, you should probably counsel me to talk to her less (let the baby sleep, already!). One size doesn't fit all. There are some interesting applied studies that have near-term upshot for baby-advice consumers (e.g. work on learning from media). But overall this is the exception rather than the rule in much of what I do, which is primarily basic research on children's social language learning.

Parents who have read parenting books often say "you must do X with your child" or "you can't do Y," whether it's serving refined sugar, giving tummy time, or using the word "no" (don't, do, and don't, respectively - according to some authorities).  But the effect size of any child-rearing advice, whether reasonable or not, is likely to be small: the people who had parents that followed it aren't immediately distinguishable from those whose parents didn't. Consider the contrast between the range of variation in parenting practices across cultures and the consistency of having reasonable outcomes - nice, well-adjusted people. People grow up lots of different ways and yet they turn out just fine. This is the message of Day's book.

Of course there are real exceptions to this rule. But these are not the small variations in child rearing for your standard-issue helicopter parents - BPA-free tupperware or not? - or even the culturally-variable practices like whether you swaddle. They are huge factors like poverty, stress, and neglect, which have systematic and devastating effects on children's brain, mind, and life outcomes. Remediating them is a major policy objective. We shouldn't confuse the myriad bewildering details of babyrearing with the necessities of providing safety, nutrition, and affection.


  1. I decided right from the beginning that my child is my child, not my research subject. And although I do note things he says or does, I've never tracked anything systematically. I wanted to be a participant in my son's childhood, not an observer. That said, having him has changed the things I'm interested in, and he is an 'exception' that has challenged my ideas about 'the rule'. I see that as a good thing. I now see much more variation in the way kids learn, which of course makes the whole enterprise more challenging to figure out. But on a less serious note, we noticed quite early on that despite the fact that both parents are evidence-based social scientists, we became quite the opposite: superstition ruled our early days. Things like, "he finally slept well when he was swaddled in the blue blanket, bounced on the bosu ball exactly 37 times, while a particular song was playing at a particular volume, while we were wearing some particular clothes, and a passing car horn honked 3 times, so we have to repeat that all exactly tonight". Maybe it's wrong to call it superstition, more like desperation born of sleep deprivation and an unwillingness to actually try to determine what, if anything, was the actual cause.

  2. Thanks for the comment! I love this kind of "causal learning" that you describe - bounce 37 times. Babies have so little in the way of behavioral outputs that you care about (please eat! please sleep! please smile!), but so many inputs, stretched out over so much time. I find it incredibly easy to make up explanatory constructs that have absolutely no reality, as though somehow I'm completely unwilling to admit that there's that much variability/noise in this little human being's behavior.