Pediatricians have long said that parents should limit the amount of TV their children watch.

New research suggests moms and dads may also want to limit the kind of shows kids see. Researchers found that some cartoons may be bad for kids' brains.

The study involved 5 dozen 4 year-olds and tested their ability to focus and problem solve after either playing with crayons, watching a slow-paced, educational cartoon, or watching a fast-paced cartoon.

They found that children who watched the fast-paced cartoon performed significantly worse.

Dr. Dimitri Christakis says, “These children's brains were actually tired from all that stimulation."

Dr. Michael Rich explains, "If you are given more time to absorb a scene, to understand what goes on, you are able to interact with it with your own questions and your own ideas."

Experts say kids' developing brains don't have enough time to process fast-paced media but there's no evidence yet to suggest any long-term health effects.

The typical pre-schooler watches 2 to 4 hours of television a day.