Screens
— on computers, smartphones, tablets and more — surround us more than ever. But
it might be best to look away. Nearly two out of three U.S. kids spend more
than two hours a day looking at screens, a new study finds. The kids who spend
more time staring at screens perform worse on memory, language and thinking
tests than do those who spend less time in front of a device. That’s the result
of a study of more than 4,500 kids 8- to 11-years old.
Time on devices has its pros and cons. Screen time
before bed can make it harder to sleep. But some time with devices also can
improve a student’s moods. For this study, researchers wanted to find out how
much time kids were spending on screens — whether a smartphone, a television,
an iPad or a computer. They also wanted to look at how much sleep and exercise
these kids were getting. Finally, the scientists wanted to gauge kids’ cognitive abilities.
These are mental activities — such as solving puzzles, remembering things or
learning something new.
The researchers used data gathered as part of a
large, long-term study. Called the Adolescent Brain Cognitive Development
(ABCD) Study, it surveyed more than 4,500 kids and their parents. The study
asked about screen time. It also asked about exercise and sleep, and tested
memory and learning.
So how much screen time is too much? The researchers
went with guidelines from experts. These recommend no more than two
hours of recreational screen time a day. They also advise kids to get at
least an hour of exercise each day and between nine and 11 hours of sleep at
night.
If that prescription seems strict, it was. Only five
in every 100 of the surveyed children met all three guidelines. In fact, 29 in
every 100 didn’t meet any of the guidelines. So they were “getting less than
nine hours of sleep, they’re on their screens for longer than two hours and
they’re not being physically active,” notes Jeremy Walsh. He’s an exercise
physiologist — someone who studies how bodies work during exercise. He works at
the University of British Columbia in Okanagan.
Lots of screens, not so much sleep
On average, children in this study spent 3.6 hours a
day using screens for video games, videos and other fun. They also exercised an
hour or more fewer than four days a week. At least they slept an average of 9.1
hours a night.
Less screen time was linked with better cognitive
scores. Children who spent fewer than two hours on screens scored about four
percent higher on thinking-related tests than did kids who spent more time on
their screens. Kids who met the recommendations for both screen time and sleep also
got better scores on their thinking tests. When analyzed on their own, sleep
and physical activity didn’t seem to influence test results. It was screen time
that really made a difference.
“This raises a flag,” Walsh says. The new
data add to concerns that heavy use of smartphones, tablets or televisions
can hurt growing minds. Walsh and his colleagues published their findings
online September 26 in Lancet Child & Adolescent Health.
Because the study only asked people about their
habits once, it only captures a single snapshot in time. That means that Walsh
and his colleagues can’t tell if the amount of screen time kids get
actually changes brain development. But, Walsh adds, “Without [knowing] what
kids are actually doing with their screens, we’re seeing that the two-hour mark
actually seems to be a good recommendation for benefiting cognition.”
The study can’t say whether screen time actually
hurt thinking skills. Kids who spend lots of time with devices might miss out
on other activities that improve their memory or problem-solving skills. “You
don’t know which is the chicken and which is the egg here,” cautions Michael
Rich. He is a pediatrician. That’s a doctor who focuses on
children. Rich works at Boston Children’s Hospital in Massachusetts. It could
be that smarter kids are less likely to spend lots of time on screens, he says.
If true, they would get better test scores — but it wouldn’t be because they
used devices less.
Simple cause-and-effect relationships often don’t
exist in human behavior, Rich says. Instead of broad rules for all kids, “we
need to tailor what we learn from science to individual children.”
But by looking at screen, sleep and exercise
behaviors in combination, the results offer a fuller look at children’s health.
That’s a peek that’s sorely needed, says Eduardo Esteban Bustamante. He’s a
kinesiologist — someone who studies how bodies move. He works at the University
of Illinois in Chicago. “We don’t know a lot yet about how these behaviors
interact with one another to influence kids’ cognitive development,” he says.
The
ABCD Study will keep collecting data from these families for another 10 years.
This means scientists may be able to learn more about how screen time affects
kids through their teen years and beyond. “I’m really excited to see where this
line of research goes,” Bustamante says.
cr: https://www.sciencenewsforstudents.org/article/less-screentime-linked-better-memory-learning-kids
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