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The Parenting Issue | Magazine

How much can parents really control how their kids turn out? 

There are as many parenting approaches as diet plans. But in the great nature-nurture debate, there’s really no debate at all.

Photo illustration by C.J. Burton for The Boston Globe

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SO IT’S HAPPENED. My daughter Olivia, who is in the fifth grade, has started lobbying for a phone. You’ve probably been there yourself, and maybe you can relate. But let’s just say that this request has been particularly disturbing to me.

In 2009, while awaiting Olivia’s arrival, my wife, Andrea, and I constructed a parenting plan that included the following set of screen-time rules: zero screen time. It wasn’t especially nuanced, but it pretty well summed up our concerns about how watching television and using computers and apps can negatively affect the developing brain. And anyway, zero screen time was what the American Academy of Pediatrics — the gold standard as far as we’re concerned — was recommending for kids younger than 2. We tacked on an extra six months, just to be safe. So until Olivia was 2½, televisions and other screens could not be used in our house while she was awake.

When her younger sister, Violet, came along a few years later, we imposed the same rule. If she was awake, the screens were dark. Even today, the girls are allowed to watch television only on weekends. The Internet is used exclusively for schoolwork, and only while supervised. And phones? The only time our daughters are allowed to pick one up is for calls or FaceTime with relatives. (We’re not totally crazy, by the way: We recently bought a video game system that the girls can use during their allotted screen-time sessions — albeit to play dance and soccer games that get them off the couch.)

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Screen use is just one part of our parenting plan. Like many parents, we have invested a lot of time and energy researching strategies for just about everything in our kids’ lives — from their sleep schedules and diets to their ratio of planned activities to free time. It’s early, and things can change, but for now they’re both doing well in school, have developed good friendships, and, generally speaking, are happy and well adjusted. So far, so good.

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This start was, of course, precisely what we’d hoped for. But something happened around the time of Violet’s birth that started me down a path that has led me to some rather unexpected questions.

From the moment Violet began to display a personality, it was evident that she shared many traits with her big sister, and with her parents. But there were elements that clearly belonged to her alone. From the earliest age, she enjoyed attracting attention. She lit up when she could get people to coo or laugh. Such was her delight in knocking over block towers or trashing teddy bear tea parties that she earned the family nickname “Destructo.” All of these delightfully extroverted qualities made her unique in our family, and I marveled at how that could be possible. She was being raised with the same plan as her sister. Where had these traits come from?

And just like that, I was tumbling down a rabbit hole. I began to question just how much our parenting had to do with the people our daughters were becoming. The more I thought about it, the more the answer seemed inevitable: not much at all. I started bringing the subject up with family and friends. “I think only 25 percent of who Olivia and Violet are has anything to do with how we’re raising them,” I’d say. “The rest is just random chance. It’s luck.” This notion, as it happened, did not go over well. Some parents rejected it outright, others got legitimately angry. No one (my wife included) entirely agreed with me.

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But I kept poking around, looking for what science had to offer. It turns out that researchers have been circling around this very question for a very long time, and, I was startled to discover, their conclusions are rather unambiguous. If anything, according to the research, my 25 percent estimate had been vastly overestimating the influence of our parenting.

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Photo illustration by C.J. Burton for The Boston Globe

THERE ARE AS MANY PARENTING APPROACHES out there as diet plans. Perhaps you’ve encountered one or two yourself: attachment parenting, slow parenting, tiger parenting, free-range parenting, helicopter parenting, snowplow parenting . . . OK, those last two are actually snarky diagnoses of parenting behaviors, but you get the idea. An entire industry has sprouted to promote methods for raising super fantastic kids, with more announced seemingly every day. Is it possible that all of it, all the books and blogs and podcasts, all of the expert advice, is simply bunk? How much does parenting actually matter when it comes to long-term outcomes for our children — to the personalities they develop, to their success, sense of fulfillment, and overall happiness? I wanted to find out.

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Which gets us back to Olivia and her requests for a phone. The first time, I laughed it off. So around Christmastime she started asking instead for an iPod touch, which is basically a phone in sheep’s clothing. When I laughed again, she started demanding to know when, exactly, she’d be able to get a phone. “How about in eighth grade?” she asked, mentioning the organization Wait Until 8th, which encourages parents to “take the pledge” to hold off on phones until their kids reach that grade. The idea of an eighth-grader with a phone struck me as absurd.

Over the next few days, though, I found myself returning to that exchange. Why couldn’t Olivia have a phone in eighth grade? When would we feel comfortable with her having one? What were we afraid would happen? In turning these questions over in my mind, I kept coming back to what research suggests about parenting: That most of who our children become is determined not by parenting, but by their genes, with their peer groups playing an important supporting role. (I find this argument persuasive, as I’ll explain later, but it’s important to note that there are tragic exceptions, including children who experience trauma, abuse, and neglect in their many forms.)

But if I truly believe this, if our kids truly were born not as blank slates to be filled by Andrea and me with our parenting — if they came into this world already programmed to be the people they are for the most part going to become — then what could having a phone possibly do to change the arc of Olivia’s life in some awful way? Not much, it would seem. But a phone?

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Struggling to reconcile my fears with what the research is telling me, a single, unavoidable question begins to form in my mind: Does parenting actually matter at all?

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IF YOU’RE LOOKING FOR INSIGHT into just how much — or how little — parenting affects childhood development, a good place to start is with the Harvard cognitive psychologist Steven Pinker. In the 1990s, Pinker helped bring to prominence the work of the psychology researcher Judith Rich Harris. In 1995, Harris caused a stir when she published an article in Psychological Review that began with this stark claim: “Do parents have any important long-term effects on the development of their child’s personality? This article examines the evidence and concludes that the answer is no.”

Pinker was moved enough by the piece’s challenge to his own assumptions that he wrote the forward to the groundbreaking work Harris published three years later, The Nurture Assumption: Why Children Turn Out the Way They Do. The book — which has been called an “utterly persuasive assault on virtually every tenet of child development” — argues that genes and peers have a far greater influence than parents on the adult that a child will become. When Pinker released The Blank Slate: The Modern Denial of Human Nature, in 2002, he included a chapter in the bestseller that touched on some of the themes found in Harris’s work.

By the time Harris passed away, in 2018, she and Pinker had become friends. So on a blustery afternoon in January, I take the elevator up to the ninth floor of Harvard’s William James Hall, where Pinker has his offices. Pinker specializes in psycholinguistics and visual cognition, studying, among other things, how language is acquired, but he’s also a kind of public intellectual whose informative, often entertaining, and sometimes controversial opinions are regularly featured in the media. On the day I visit, we sit down in the office of one his research assistants because a documentary film crew is busily setting up in his office for an interview about rationality and emotion in the history of science.

In The Blank Slate, Pinker writes that “about half of the variation in intelligence, personality, and life outcomes” is influenced by genes. I ask him if parenting is what accounts for the other half.

“There are environmental effects,” he says. “But this is an important point that Harris makes: Environmental effects must not be equated with parenting effects. There is also the culture, and when we talk about kids, culture equals peer group, pretty much.” A social circle, in other words, helps shape a kid’s personality and developmental outcomes, but a parent for the most part does not. There is evidence that parenting can have some early effect, he says, but it gets “diluted over time, and whatever effects of the families there are tend to peter out as the children get older.” Difficult to believe? Pinker can point to exhaustive studies that confirm as much.

“What’s sometimes called the first law of behavioral genetics is that all behavioral traits are partly heritable,” he says. “The second law is that the effects of families are far weaker than the effects of genes.” This explains why, for instance, identical twins brought up in different homes have been consistently shown to wind up quite similar to each other. And why, statistically speaking, adopted kids who aren’t biological siblings but are brought up in the same home turn out to be not very similar at all.

There’s still another contributor to child outcomes — a “unique environment” that’s covered by the third law of behavioral genetics — but that one is less clear. One of the few things researchers can say for sure about the third law is that it’s not related to parenting. “It just refers to what we can’t explain,” Pinker says. There are, however, some theories about these mystery influences. “One of them,” Pinker says, “is that there are mutations in the genome after conception that will differ, even between twins, and make us all different from one another in a way that’s not predictable either from our parents or from our upbringing.”

From Pinker’s perspective, there just isn’t much evidence that the strategies parents employ while raising their kids wind up mattering very much. Harris understood this. “Her argument,” Pinker says, “is that if you were to switch the kids around within a [specific] neighborhood — that is, transplant them to other families — you’d see very little, if any, long-term difference.”

This is a staggering contention that can be difficult to accept — which may explain some of the criticism that The Blank Slate received upon publication. (It received plenty of acclaim, too, including being named a finalist for the Pulitzer Prize.) Nearly two decades later, Pinker seems to still find the criticism annoying. “A lot of the critiques were certainly ignorant, including coming from many so-called experts in child psychology,” he says. “They just could not wrap their minds around the idea that genes mattered. They would say, ‘Well, what about all the brilliant parents who have such brilliant children?’ Like, not getting the point: Yes, but they shared the [parents’] genes.”

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MUCH OF THE RESEARCH Pinker cites has come from the study of twins. Researchers have been conducting these kinds of studies for generations with the goal, generally speaking, of figuring out just how much of a particular trait is influenced by our genes and how much has to do with something else.

These questions seem to be of intense interest to researchers because there have been a lot of twin studies. In 2015, a team co-led by the Dutch behavioral geneticist Tinca Polderman made international headlines with the release of a meta-analysis of essentially every such study published between 1958 and 2012. That meant analyzing the results of 2,748 research projects — 50 or so per year — involving more than 14 million pairs of twins (some pairs may have participated in multiple studies). The team compiled the findings and created a database that allows anyone to easily look up what five decades of research shows about the genetic component of 28 different “functional trait domains.”

A researcher I talked to called the analysis “one of the most important papers published in the last 50 years in science.” So I decide to call up Polderman, an assistant professor at Vrije Universiteit Amsterdam, and find out what the research actually tells us.

I start by asking Polderman to explain how twin tests work. “We have two types of twins,” she says, “monozygotic twins and dizygotic twins.” Monozygotic twins are genetically identical, while dizygotic twins — what we know as fraternal — are, on average, 50 percent identical, just like any other siblings. Since both types grow up in the same family, the shared environment is controlled. Twin researchers choose a trait — say depression, IQ, or blood pressure— measure it in twin pairs of each type, and then average the results. For traits in which identical twins score very similarly and fraternal ones do not, she explains, researchers can conclude that genes play an outsize role. When the difference between the two types of twins is less pronounced, the trait may be more influenced by environmental factors.

I ask Polderman what the studies reveal about the influence of parenting. “For shared environmental influences” — the technical term that encompasses parenting — “we find very, very limited evidence,” she replies.

There is evidence that the shared environment can contribute to things like criminal behavior and educational attainment, Polderman continues, “but I’m not sure whether it’s parenting, or whether, for instance, it’s the shared neighborhood, or poverty, or anything else you could speculate about.” It’s likewise possible that parenting contributes to early performance on school and IQ tests. But again, that may well be telling us more about socioeconomics than anything else. “It can be a matter of money, what parents can pay,” she says. “It can also be a matter of providing books in the house at that point in time, or providing educational television programs, maybe. Or, nowadays, educational games.”

Polderman tells me that despite all her work studying twins, she wasn’t prepared for just how little her own parenting would shape her two sons, who are now adults. “I thought, actually, that the influence of parenting would be quite substantial on their behavior,” she says. Instead, her experience tracked exactly with what she was seeing in her twin studies, especially when it came to their different attitudes toward their schoolwork. “So I think, in the end, that the influence of parents is, on this kind of thing, quite limited.”

Of course, there’s another way to look at this. Every parent understands the feelings of overwhelming guilt that often accompany the raising of kids. Each failure, public tantrum, and refusal to eat vegetables can feel like a referendum on your fitness to bring up children, and even your worth as a human being. But Polderman no longer makes judgments when, for instance, she sees a friend struggling with a screaming child on the supermarket floor. “I think they are excellent parents,” she says. “It’s just, it’s in the children. And it’s not the parents’ fault, or the parents’ . . . reward when it turns out well.”

“So what the hell is the point of being a parent?” I ask, exasperated. “What’s our job here? Is it just to keep our kids alive?”

“I think your task as a parent is to create an environment for your child that is as safe and as stable and as predictable as possible,” she says. “Within that environment, a child can develop most optimally. Because I think at extreme conditions, like neglect or abuse — or traumatic life events — will surely also have quite a big impact on child development.”

And there it was — the fear, underlying everything, of a life-altering traumatic event. It was absurd to think that giving Olivia a phone would qualify as one, yet isn’t that what I’ve been imagining? “Am I actually going to cause long-term harm to her in some way if she has a phone?” I’m asking myself as much as Polderman, and I answer my own question: No. I’m not. “So, why am I still so resistant? Why are we still so resistant as parents — the evidence here is overwhelming, isn’t it? That it’s luck? That it’s not really what we’re doing as parents?”

“Well, in a way, yes, I can only agree on that,” Polderman replies, thankfully taking my outburst in stride. “Well, still, of course, I think it might matter.” She says sitting around with a phone or laptop all day was the kind of thing that could lead to obesity, for instance.

At last! Some evidence that keeping a phone away from Olivia is a good idea — and that at least something I’ll do as a parent can overcome genes.

That would have been a good time to hang up the phone, but something’s nagging at me and I can’t. I finally ask, “Was obesity one of the traits that you looked at in the twin study?”

“I think so, yes,” Polderman replies. “I’m just quickly looking at our website.” I hear the clicking of computer keys as she searches her database. “OK, here I have it,” she says. “Weight maintenance functions. Yeah, so, about 75 percent of the difference is explained by genetic differences. I see that the shared environment is measured quite low, again, around 10 percent. So it’s mainly genetic.”

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SO WHERE DO I COME DOWN these days on the great nature-nurture debate? I’m fairly certain that there’s really no debate at all. When it comes to the development of Olivia and Violet, the die was largely cast before they were even born. But that, I have decided, is not the same as saying that parenting doesn’t matter. I am confident that it does, but not in the ways that we sometimes assume.

No, I do not believe that we have much ability to shape the adults that our daughters will become. But, as Steven Pinker told me, citing Judith Rich Harris, “It’s a mistake to think that if parents can’t shape their children’s personalities, [that] they have no effect on their children. No one thinks that they can shape the personality of their spouse, but no one would say it doesn’t matter how I treat my husband or wife. Of course it matters how you treat them. It matters to the quality of your relationship.”

There’s something else, too, and this one is coming not from any research I’ve found. In my experience, the most powerful thing in life, more powerful than fear, than love, than even genes, is choice. Andrea and I can’t really make it any more or less likely that our daughters will surround themselves with supportive people, or pursue fulfilling careers, or use money wisely, or eat right. But it’s my belief — OK, it’s my hope — that a childhood overflowing with love, support, respect, concern, communication, and structure can inform our daughters’ future decisions. We may not be able to lead them to our hoped-for outcomes, but we can demonstrate that the options exist. And once you know a thing is possible, it becomes a choice you can make.

I’m saying that DNA is not destiny, and also that I now understand that a phone will neither warp Olivia’s brain nor damage her prospects. But she’s still not getting one anytime soon.

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John Wolfson is editor of Boston College Magazine. Send comments to magazine@globe.com.