Dimitri Christakis of Seattle Children's Research Institute analyzed data on 3- to 5-year-old children of 565 parents who kept track of what their kids watched.
About half the parents had their kids watch programming that the researchers had vetted to emphasize nice behavior and not being aggressive.
Christakis said the children exposed to nicer behavior and non-aggressive behavior showed less aggression and more good social behavior six months and even one year later.
"One of the central findings of this study is that it should not just be about turning off the television," Christakis said. "It should be about changing the channel."
The findings were published in the journal Pediatrics.