Kids and Developmental Milestones: What’s the Connection?
Ask Science talks with Nicholas Day, author of Baby Meets World, about the surprising truth behind developmental milestones in babies. (Hint: They don’t matter as much as you think!)
A few years ago, my wife and I were talking with some other parents and one of them asked if our youngest son had started to walk yet. Some of the parents were amazed and a little concerned that a boy of his age hadn’t started walking yet. After all, babies are supposed to start walking exactly 14.5 months after they’ve left the womb, right? So if you have a 15-month-old who hasn’t started walking yet, that means your child must be abnormal, doesn’t it? Shouldn’t you schedule some appointments with your pediatrician, psychologist, and possibly an attorney?
As parents, we often have concerns when our children’s development doesn’t follow the “typical” pattern, as dictated by countless books, magazine articles, and web sites. When writer https://www.slate.com/authors.nicholas_day.html became a first-time parent, he fell into the same trap of reading and believing “expert” opinions on what his son should and should not be doing at a given age. Then he started doing his on research on developmental milestones. He discovered that there was a lot more to developmental milestones than he had been led to believe.
That’s why he decided to write a book called to set the record straight and put a lot of worried parents at ease. Let’s check out what he has to say on the subject.
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“Is This Child ‘Normal’ or Shall I Take Him to the Clinic?”
This quote is from the foreword to a book by the president of the British Psychological Society, published in 1956, and it neatly summed up the concerns the book was meant to address. The book’s splendid title: The Normal Child and Some of His Abnormalities.
A half century later, the language for talking about these things hasn’t gotten much more precise.
After our family moved across the country when our son Isaiah was a toddler, we had to complete a one-page questionnaire for his new daycare. The form was constructed like a Mad Libs game, with blanks for us to finish the sentences, and about halfway through it, we hit these:
Developmentally, my child is ___________________.
My child walked at ___________________________.
Isaiah at this point was in his mid-twos. He’d already run the terrifying gauntlet of early milestones. I had thought we were through with this.
We weren’t.
At an interview a few months later for a preschool—long story, honest—the admissions director asked us, very earnestly, “And do you remember when he started to walk?” We tried to remember. “And is he meeting all his developmental milestones—running, climbing?” Climbing? Climbing what? We nodded numbly.
The Trouble with Milestones
A wave of new motor development research has overturned the paradigm on which developmental milestones were founded—the omnipotent power of neural maturation: the idea that the development of our bodies obediently follows the development of our brains. But the most compelling work in motor development today looks at the subject from the perspective of the infant—someone who has no idea what she’s going to be doing next. (It could be standing; it could be flying.) And once you’re down there on the floor with the infant, you can see that, before walking emerges, there’s something of a free-for-all going on. Infants aren’t obeying. They’re discovering. Motor development, far from being generic and prescribed, is a creative act.
Most developmental milestones are the legacy of an earlier era of motor development research—when psychologists thought that all this was much more predictable than it actually is. But although the milestones are outmoded, they still stand. They don’t even wobble much. Developmental psychologists have pretty much discarded the concept of developmental milestones, but developmental milestones remain the only thing that most people know about developmental psychology.
No parent would have much reason to suspect that milestones are suspect. They are still prominently featured in child development textbooks and pediatricians’ offices. They’re around mostly because they never went away. No one advocates for milestones; they aren’t endorsed by the relevant medical journals or committees. Nonetheless, they continue to be the most common tool pediatricians use to track developmental progress.
The vast majority of milestone lists—from standard pediatric references to sidebars in baby manuals—use the median age. A few lists provide a range of ages or some broad parameters. But the median percentile is what gets the major billing: unequivocal, memorable, it catches the eye of the doctor and the parent. It sticks with you.
Of course, half of all children will always be beneath the median—otherwise it wouldn’t represent the fiftieth percentile. “In other words,” as the pediatrician Laura Sices https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2707752/, “After reviewing 50th percentile milestone information, as many as half of parents could conclude that their child is possibly ‘delayed.’” Instead of medians, it would make far more sense, in almost all circumstances, to talk about the tenth to ninetieth percentiles—the vast age range of normal variation.
Even these broad parameters risk being too narrow, though. https://www.ncbi.nlm.nih.gov/pubmed/9783818, 45 infants were assessed monthly on their motor skills until they were 18 months old. During this time, their percentile rankings for motor skills rose and fell wildly, for no apparent reason. Sometimes the babies had small flurries of accomplishment; sometimes they fell into a rut. Nearly a third of them ranked below the tenth percentile at least once—the red line for “at risk” development. But every one of them ultimately turned out just fine. None actually warranted the “at risk” label.
Time and again, studies have failed to predict future problems from motor development measures, and once you grasp just how many infants appear at risk, you realize why such studies keep failing: at any random point in time, a perfectly healthy baby is indistinguishable from an infant with developmental problems. By design, developmental screening is guaranteed to return scores of false positives.
Should We Stop Tracking Developmental Milestones?
Given how crucial early intervention can be, doctors and therapists will never stop screening for developmental problems, nor should they. But since it is so tricky to identify delays, they might never get much better at it, either. Medically, we may always have to trade a preschool’s worth of false positives (needless anxiety about developmental problems) for a few accurate diagnoses (actual developmental problems). That’s probably a trade worth making: for children with serious problems, early therapy can be extraordinarily beneficial. But the rhetoric of milestones doesn’t imply that doctors and therapists have to make this sort of trade. It implies a precision that’s the very opposite of the reality.
Even if screening can’t be improved, the language for talking about screening certainly can be. At the very least, the word “normal” should be scratched from the developmental vocabulary: what’s typical in infancy is variation. Rather than a long list of milestones, parents would sleep better with fewer but more relevant guidelines. We’d all do better to acknowledge just how unstructured infancy actually is. Later is just fine and earlier isn’t any better.
If your pediatrician, mother, brother, uncle, second cousin, dog walker, or cashier at the local grocery store gives you advice about your child’s milestones, here’s what you should keep in mind:
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Think twice before worrying. Most advice about milestones—when so-and-so should really be doing something—is not worth taking. Remember that deviation from the norm is actually normal. It’s not by itself the sign of a serious problem.
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When a milestone occurs doesn’t matter. There are no detailed, sophisticated, long-term studies that link early motor milestones with future achievement. There’s simply no scientific reason to think that earlier is better.
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Healthy babies screw around. By moving lots of different ways, infants adapt to the many different environments they will encounter. If your baby spends his time moving in the craziest, least efficient way imaginable, that’s actually adaptive. It’s a good thing.
Nicholas Day has been a wine salesman, a wedding cake baker, a fairground maintenance man, and a stay-at-home father. He writes about the care of children for https://www.slate.com/authors.nicholas_day.html and the feeding of them for https://food52.com/. His writing has also appeared in Salon, Washington Post, Chicago Tribune, Chicago Reader, and Time Out Chicago, among other publications. Check out his wonderful new book, Baby Meets World, and connect with him on Twitter @NicksDay.
Conclusion
Thanks to Nicholas Day for his insightful, panic-free advice. If you liked today’s episode, you can become a fan of https://www.facebook.com/qdteinstein or https://twitter.com/qdteinstein where I’m https://twitter.com/qdteinstein. If you have a question that you’d like to see on a future episode, send me an email at mailto:everydayeinstein@quickanddirtytips.comcreate new email.
Toddler and Mother with Child images from Shutterstock
About the Author
Dr. Lee Falin earned a B.S. in Computer Science from the University of Illinois, then went on to obtain a Ph.D. in Genetics, Bioinformatics, and Computational Biology from Virginia Tech.
