Twenty years ago, developmental psychologist Douglas Gentile conducted a national survey to assess the patterns of media use in American households with children. The results revealed that parents who moderate their own screen time also monitor their kids’ screen time more carefully. Subsequently, those same children end up watching less television and participating in more alternative activities like reading, peer socialization, and family outings.

But one finding in particular stuck with Gentile. Children with a TV in their bedroom watched more hours per week than those without and also performed worse in school.

“Even back then, you could see in the data that kids who had a TV in their bedroom seemed to have a wide range of negative outcomes associated with it — but it wasn’t the main point of that study,” said Gentile, who currently is a professor of developmental psychology at Iowa State University and director of the Media Research Lab. “The finding just got buried in the other things that were also reported.”

He circled back to look at this phenomenon more closely in a longitudinal study published by Developmental Psychology in September 2017. The results demonstrate that the presence of TV or video games in a child’s bedroom not only can affect school performance, but also impacts the risk of obesity, video game addiction, and physical aggression.

In 2001, American Academy of Pediatrics released a recommendation for parents to remove television sets from children’s bedrooms. However, a 2015 report titled “The Common Sense Census: Media Use By Tweens and Teens” indicated that 47% of 8- to 12-year-olds and 57% of 13- to 18-year-olds in the U.S. have a TV set in their bedroom.

“The average kid from 8 to 18 years old is in front of a screen over 50 hours a week. That’s a full-time job and hours of overtime, on top of school and everything else,” Gentile said.

“The average kid from 8 to 18 years old is in front of a screen over 50 hours a week.”

Gentile and his colleagues analyzed data from three groups of subjects: a 6-month longitudinal sample of American children aged 7 to 11, a 13-month longitudinal sample of American children aged 6 to 12, and a 24-month longitudinal sample of Singaporean children aged 8 to 17. Participants were asked if they have a TV or video games in their bedroom, how much time they spend watching TV and playing video games, and their favorite TV shows/video games.

In all three samples, children who had a TV in their room at the beginning of the year performed more poorly in school both concurrently and in the future as compared to children who had a TV elsewhere in the house. Previous studies have cited something called the displacement hypothesis as the reason for this link — as in, kids are spending more time in front of the TV and less time on educational activities as a result of increased media accessibility.

Because children with bedroom TV have a higher total screen time than those who have a TV elsewhere in the house, this displacement effect is expected to be greater in the former group. Similarly, bedroom media increase the risk for video game addiction and obesity by increasing total screen time, leaving less opportunity for outdoor play or exercise.

“Having a TV in the bedroom causes kids to spend more time with it, which, down the road, leads to less reading for pleasure, and then poor school performance.”

“What this study does for the first time, to my knowledge, is show that the displacement hypothesis is at least partially accurate,” Gentile said. “Having a TV in the bedroom causes kids to spend more time with it, which, down the road, leads to less reading for pleasure, and then poor school performance. It is displacing other things, and that’s part of the reason why we have these negative outcomes.”

As a solution to this issue, Gentile recommends that parents set limits on media consumption at the beginning of the school year and continue to enforce those limits. As the next step, Gentile and his colleagues plan to investigate whether the negative effects seen in this study are even stronger for more private media like smartphones and tablets.

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