Other eye-grabbing highlights from the survey:
- 42 percent of young children now have their very own tablet device — up from 7 percent four years ago and less than 1 percent in 2011.
- Screen media use among infants under 2 appears to be trending downward, from 58 minutes a day in 2013 to 42 minutes in 2017. This decline correlates with a drop in sales of DVDs, and particularly those marketed at babies, such as Baby Einstein. Updated pediatricians' recommendations released last year call for limited, but not banned, screen use among the youngest set.
- Nearly half, 49 percent, of children 8 or under "often or sometimes" use screens in the hour before bedtime, which experts say is bad for sleep habits.
- 42 percent of parents say the TV is on "always" or "most of the time" in their home, whether anyone is watching or not. Research has shown this so-called "background TV" reduces parent-child interaction, which in turn can hurt language development.
The growth of mobile is a dramatic change. But other aspects of kids' media use have been more stable over time, this periodic census reveals.
When you take every source of screen media together, children 8 and under spend an average of about two-and-a-quarter hours (2:19) a day, a figure that's flat from 2011 (2:16). That implies mobile is apparently cannibalizing, not adding on to, the boob tube and other types of media.
And, whether young kids are looking at small screens or big ones, most often they are passively watching videos, not using interactive apps. Video watching has dominated children's media use for decades.
Finally, young children are still being read to by their parents about 30 minutes a day.
More questions than answers
What does all this mean?
Researchers don't really know, and that concerns observers like Pamela Hurst-Della Pietra, the founder of Children and Screens: The Institute of Digital Media and Child Development.
"How different is the brain of a child who's never known anything but sustained digital media exposure to the brain of her parents, or even older siblings? she asks. "And what are the implications for parents, educators or policymakers?"
Hurst-Della Pietra says these are questions "we're only beginning to ask, let alone answer." Children and Screens is getting ready to release its own series of reports that sets an agenda for future research.
Steyer, of Common Sense Media, agrees. "I would argue there are big implications for brain and social-emotional development, many of which we don't know the answer to," he says.
The public conversation about kids and screens is somewhat schizophrenic. American schools, even preschools, are buying millions of electronic devices, and there are tens of thousands of apps meant to enhance learning for even the smallest babies.
On the other hand, doctors warn, and parents worry, about negative effects from too much screen time, ranging from obesity to anxiety.
One part of the Common Sense report that really plays up this contradiction is the section on the so-called digital divide. The phrase reflects the idea that learning how to use computers and the Internet at home helps kids get ahead in school and in life.
Unlike in previous years, this census shows both rich and poor families now appear to have nearly equal access to smartphones. At the same time, kids from lower-income families are spending twice as much time with screens daily as those from the most advantaged families. Is this a boon or a danger?
Lynn Schofield Clark at the University of Denver studies media use with a focus on disadvantaged youth and youth of color. She says the missing ingredient in understanding the real impact of the digital divide is time.
That is, parenting time: showing a kid how to use a laptop, how to do Internet research, picking out highly rated educational apps or steering a child toward programs with positive messages.