Four hours is a good chunk of a standard school day, nearly twice as long as the world's best marathon time and about the amount of time it'd take you to road trip from Los Angeles to Fresno.
It's also, according to new research, the daily average for how much "background television" exposure children get every day.
Background TV is just what it sounds like: Think about when you're lying in bed, and you can hear the TV in the next room. You're not engaged in the act of TV-watching, but the sounds coming from the set are still stimulating your mind, maybe distracting you.
The study, which appeared Monday in Pediatrics, looked at 1,500 families in 2009 to arrive at its estimate. It also found that younger, low-income and black children were all prone to even more hours of background TV than the four-hour average.
There's nothing wrong with watching TV, says Deborah Linebarger, an associate professor of education at the University of Iowa and one of the study's authors. But it's not good to have the TV on all day, especially if no one's watching. She says that's because the constant stimuli of the TV impairs a person's "executive function" – a person's ability to pay attention, concentrate, inhibit impulse and not interrupt.
TV noise is a barrier to the brain's development of these skills.
"The other issue that makes TV kind of unique is, unlike traffic noise or airplane noise that you can habituate and adapt to, the TV is completely different, because the sounds are constantly changing," explained Linebarger.
Also unlike traffic and airplane noise, the sounds coming from the TV are things you can understand, like words and music. Because of that, folks have a tendency to strain to listen and try to figure out what the sound is, even though they weren't watching whatever's playing in the first place.
That means it'll take that much extra effort to regaining your concentration on whatever it was you were doing before, said Linebarger. And with three minutes of background TV-watching for every minute of intentional TV-viewing, the level of distraction is high.
As for why background TV exposure is higher among black and low-income families, Linebarger said those groups report watching it more – and many just leave the set on throughout the day, whether they're watching it or not.
"Exact reasons aren't clear other than they have a greater preference for watching television than middle-income families and European families," she said. "They enjoy it more and report more value in it."
Low-income folks, she added, may gravitate toward TV more because they have less money to spend on other activities. She also cited another study on similar subject matter in which many participating families said they'd given their child a TV for their bedroom because it wasn't safe to go outside.
The professor emphasized this doesn't mean the best kind of TV is no TV.
"If you sit down to watch something, that's great," Linebarger said. "Sit down with a purpose, but when it's over, turn it off."
She also recommended turning it off when a child is sleeping (when possible) or if you find yourself and other viewers not really paying attention to it.
Photo by Detlef Reichardt via Flickr Creative Commons.