In the United States, there are now more televisions per home than human beings. And:

  • Children between 8 and 18 watch an average of three hours of television per day
  • Close to one in three children lives in a home where the TV is on either all or most of the time
  • On average, 61 percent of kids under the age of 2 regularly use some kind of screen technology (television, iPad, etc.).

The upshot? Most kids are watching a lot of TV.

Scientists have measured the effects of television on the human brain for decades, and one of the most well-established facts is that watching television reduces a person's theory of mind.

Theory of mind (ToM) refers to your ability to correctly grasp and understand mental states (knowledge, beliefs, intents, desires) both for yourself as well as others. Especially in children, ToM also involves your ability to understand that other people have desires, beliefs, and intentions different from your own. ToM is, then, a measure of empathy.

And according to science, watching television diminishes it.

In 2013, a paper came out in the Journal of Communication titled "The Relation Between Television Exposure and Theory of Mind Among Preschoolers."

Its findings suggested that preschoolers with a TV in their bedrooms (i.e., those frequently exposed to TV in the background) had a weaker grasp of the beliefs and desires of others. They also found that the TV-exposed children experienced reduced cognitive development--it limited brain development.

Even more concerning:

  • For every two hours of television watched in one's youth, the odds of developing type 2 diabetes go up by 20 percent
  • For each added hour of TV watched in childhood, the odds of developing symptoms of depression go up by 8 percent
  • With each added hour of TV, the odds of being convicted of a crime go up by 27 percent.

That last one is particularly alarming. It seems that increased television watching early in life significantly increases the odds of engaging in criminal behavior later.

This is not to say that a child who spends two hours a day watching Blue's Clues will grow up to be an expert in grand theft auto (actual grand theft auto, not the video game). In fact, recent research suggests that a full 50 percent of the risk of developing antisocial behavior comes from one's genes, not the environment. Still, that means 50 percent is affected by environmental factors, of which television is a major one.

The fact is, television is the least interactive of any new media. Heavy watchers are often isolated while consuming it. This is bad for growing brains, when interaction is a critical part of socialization and learning.

It's particularly bad for kids who might already tend towards combative behavior.

As criminologist and neuroscientific researcher Joseph Schwartz says, "Watching more TV may trigger various neurobiological changes that ultimately exacerbate any underlying inclinations toward aggressive behavior."

Thus, if you have, say, a young son who is already exhibiting aggressive behavior at school, it's particularly important not to allow too much exposure to the tube.

There's no doubt that parenting in the age of constant and ubiquitous screens is challenging. But all this science put together makes it clear that it's critical to be mindful of what's going on around the house.

While it can be easy to plunk a kid down in front of the TV, it could set him or her up for issues like aggression and depression later in life. It's worth investing the time and energy it takes to get them to do something else, since letting TV take over does compromise a child's mental health.

Building strong brains requires discipline, but it's worth it in the end.

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"I find television very educating. Every time somebody turns on the set, I go into the other room and read a book." --Groucho Marx