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Last week, the World Health Organization issued new guidelines on how much time parents should permit young children to spend absorbed in digital screens, whether phones, tablets, or TVs. Kids younger than 1 year old, the organization advised, shouldn’t have any screen time, and kids ages 2 to 4 should have their passive screen time capped at an hour a day. “Children under five must spend less time sitting watching screens,” the WHO stated in a press release.

Sitting is a significant word here, as this advice comes in conjunction with the recommendation that parents limit their children’s “sedentary” time and instead promote “active play,” so that children grow up to be physically and mentally healthy.

Juana Willumsen, a children’s-health expert at the WHO, notes that the recommended limits on sedentary screen time don’t include videochats with relatives, programs that have children actively participating (say, dancing along to whatever’s on-screen), or e-books that a parent reads along with them.

A significant number of American youngsters appear to have screen-time habits that go against the WHO’s recommendations. According to a nationally representative 2017 survey from the children’s-media watchdog group Common Sense Media, half of 3-to-5-year-olds in the United States stare at screens for more than two hours every day, which includes the quarter overall whose daily screen time exceeds four hours.

“The gist of the WHO recommendations is that small children should be spending more time in active play and less time being sedentary—and that the sedentary time should be more focused on activities that boost cognitive development, like blocks and puzzles, and less focused on videos and electronic games,” says Vicky Rideout, an independent consultant who researches kids’ technology use and who worked on the Common Sense Media survey. “And by and large, I think those are sound recommendations.”

But Emily Oster, an economist at Brown University and the author of Cribsheet: A Data-Driven Guide to Better, More Relaxed Parenting, From Birth to Preschool, noted that the trade-off between idle screen time and enriching playtime isn’t so simple. Screen-time recommendations, she wrote to me in an email, “sometimes seem to assume that the alternative to TV is always high-quality engaged time with an adult. If that’s the case, then it may be right that screens are bad. But if the alternative is a grumpy, stressed-out adult who needs a break, the calculus may be different.”

Moreover, Oster told me that it’s hard to assess how sensible the WHO’s new guidelines are, based on the available scientific evidence. “To the extent we do have data, it focuses on TV exposure,” she said. “There, the evidence is reassuring that TV doesn’t seem to have the negative effects that are sometimes feared. But screens are ever more ubiquitous and if we are looking for evidence on the impact of iPad or phone screen exposure in small children, it is simply not available.” Because these data are relatively scant, some of the biggest questions about kids and screens are difficult to answer with certainty. Willumsen says that the WHO recommendations are “based on the best scientific evidence, integrating [children’s] different behaviors and considering the child’s whole day.”

Jessica McCrory Calarco, a sociologist at Indiana University who studies parenting, brought up a broader concern about recommendations like those from the WHO and other organizations. “If parents are letting their kids watch TV, or keeping them cooped up inside, or keeping them strapped in a car seat for an hour or more, it’s not because they think it’s good for their kids,” she wrote to me in an email. “Parents make those decisions because they don’t have any other choice. Or, at least, because the alternatives require more money or more space or more energy or more patience than those parents have on any given day.” Some such out-of-reach alternatives include paid child care, extracurriculars, and having ready access to safe outdoor spaces or a library with high-quality children’s programming.

When I asked the WHO about how screen time for kids can serve parents’ needs, Willumsen said, “For children 2 years and older, the recommendation is that they spend no more than one hour per day passively entertained by screens—parents can get a break.”

“These are simply recommendations from an expert health organization—no one is forcing parents to do anything,” Rideout says. “I think most parents appreciate having some specific advice, and having a goal to aim for.”

In this realm and others, a goal to aim for is indeed something many parents want—especially from a trusted group of health experts. But because of the issues that Oster and Calarco raise, it’s hard for anyone, no matter how expert, to come up at this stage with a definitive, catchall prescription that accounts for every dimension of parenting—even if there’s a lot of demand for one. Maybe the problem isn’t so much the nature of the answer as the nature of the question: Guidelines that cover everyone are hard to devise, no matter how much evidence is brought to bear.

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