There was Gardner's Theory<span> of Multiple Intelligences
here's a link with further info: </span><span>www.springhurst.org/articles/MItheory.htm</span>
Depending on the research you find, it could vary. Explain to them that while watching TV is not an "evil" thing, it can have some affects in the youth. Tell them how it can affect the behavior with friends, family and other people whom are around them. In addition you could even as far as mentioning academic success and failure.