For many kids today, watching TV is a major part of life.

"The typical child under the age of 2 now watches about 2-3 hours of TV a day.  And when you keep in mind that they're only awake for about 10-12 hours a day, you realize they're spending 20-30 percent of their waking hours in front of a screen," said Dr. Dimitri Christakis of Seattle Children's Hospital.

The statistics may seem shocking, but one reason for this is that these days, parents are often led to believe that TV is "educational," even for babies.

"There isn't any evidence at all that infant TV viewing is helpful or beneficial to them in any way.  In fact, the best available evidence suggest, in fact, that it's harmful," said Christakis.

According to studies conducted by Dr. Christakis, TV viewing impacts both infants and preschoolers in different, yet significant, ways.

For babies between the ages of 0-2, Christakis found fast-paced TV over-stimulates their developing brains and appears to have a direct effect on attention disorders later in life.

"TV programming for infants uses rapid sequencing and cuts and edits. It's the way infants are kept interested in the screen," he said.

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According to studies conducted by Dr. Christakis, TV viewing impacts both infants and preschoolers in different, yet significant, ways. 

"A baby who watched 2 hours of TV, on average, per day, before the age of 2 would be 20 percent more likely to have attention problems at age 7, compared to a child who didn't watch any at all."

With preschoolers, age 2-5, TV has more of a behavioral impact. Distinctions between fantasy and reality are very much blurred when it comes to violent programming, including cartoons.

That's why Dr. Christakis urges parents to be extremely selective in what their child watches.

"It's as simple as monkey see monkey do quite honestly for kids that young.  They do imitate what they see," he said.

And, parents shouldn't rely solely on the ratings guide in determining appropriate programming for their child.

"The parental ratings are a huge disservice to parents with respect to that.  Every single G-rated movie that's been available on DVD or videos since 1970 has contained at least one act of significant violence, and the average length is about 10 minutes for a feature-length movie," said Dr. Christakis.

When it comes to allowing children to watch TV, Dr. Christakis isn't saying "don't do it." Instead, he recommends no more than an hour a day and suggests using TV as a way to engage your child.

"Get your child excited about lions because they watched lions on TV, but then go to the zoo and see lions," he said.

But the truth of the matter is that more than how much children watch, it's important for parents to pay attention to what they watch and how they watch.