Watching too much television can shorten the attention span of your child. Dr. Dimitri Christakis, a pediatrician at the University of Washington, studied over 1,300 American children and "found that watching television before the age of 3 increases the chances that children will develop attentional problems at age 7."

Researchers asked parents how much TV their kids watched at ages one and three. Then the parents were asked to rate how well their children could focus at age seven. The more hours of television their child watched before age four, the greater the risk of having attention problems at age seven. How can TV harm a developing brain? "Our hypothesis is that it's the rapidity of image-change that's potentially damaging to children's brains," Christakis said. "They are experiencing events unfolding in a surreal fashion - this is not how life unfolds." This means that even "good" children's programming may not be good for young children because it exploits rapid image-change to keep children constantly watching the screen.

Dr. Christakis tells the parents he works with that "they should not let their child watch television during the first two years of life, and subsequently they should exert extreme caution both with respect to the amount and content."