It may be educational, but what is that TV show really teaching your preschooler?

"Children who spent more time watching educational programs increased their relational aggression toward other children over initial levels," Gentile said. "This study shows that children can learn more than one lesson out of a given program. They can learn the educational lesson that was intended, but they're also learning other things along the way."

This unintended impact has to do with the portrayal of conflict in media and how preschool-age children comprehend that conflict. Gentile said TV and movie producers often incorporate an element of bad behavior in order to teach children a lesson at the end of the program. This type of conflict is also found in children's literature.

However, since children between the ages of 2 and 5 do not typically understand the plot of shows, Gentile said they do not know how the beginning of a story relates to the end.

"Even though educational shows like Arthur have pro-education and pro-social goals, conflict between characters is often depicted with characters being unkind to each other or using relational aggressive tactics with each other," Gentile said. "Preschool children really don't get the moral of the story because that requires that they understand how all the parts of the show fit together. You need pretty complicated cognitive skills and memory skills to be able to do that, which are still developing in young children."

For the study, researchers observed how the children interacted with others in the classroom and on the playground at day care centers. They also relied on behavior reports from teachers and parents. They found that children exposed to educational programs were more aggressive in their interactions.

Researchers observed each child for approximately 2.5 hours throughout the study. They note that the aggression they witnessed was generally not physical. Jamie Ostrov, a professor of psychology at the University of Buffalo in New York and another member of the research team, said the behaviors often mirrored those incorporated in children's programming.

"The most common relationally aggressive behaviors were children saying, 'I won't be your friend anymore unless you do what I say,' or 'You can't come to my birthday party' as well as socially excluding a peer from play," Ostrov said. "From our viewing, this type of relational aggression is much more common in young children's programming than physically aggressive behavior."

Lessons for parents

Researchers caution parents against completely pulling the plug on TV and movies for their children. Gentile said there is a benefit to educational programming, but it could also teach undesirable behaviors. Parents may already limit the content and the amount of media their children consume, but he said parents can be more involved when their children are in front of the TV.

"Parents can watch with their kids and help them to understand the plot. Parents can comment along the way and then explain the message at the end. They explain how the insulting behavior or the ignoring behavior was not appropriate. This will help children interpret and get the message and help them learn to watch it for those messages," Gentile said.

Researchers asked parents about the specific media their children were exposed to during the study. Ostrov said most programs were educational or informational in nature with an emphasis on social and emotional issues. Programs such as "Arthur," as well as "Curious George" and "Reading Rainbow," were among those most often mentioned by parents. Gentile said to more fully understand the issues presented in these programs there needs to be more analysis of the content.