Jennifer Linder of Linfield College and Douglas Gentile of Iowa State University conducted the study of 95 fifth-grade girls from three Oregon elementary schools.
The researchers found higher levels of physical aggression in designated children's programs -- rated TV-Y and TV-Y7 -- than among programs for general audiences rated TV-G, TV-PG, etc.
"Parents assume that higher ratings indicate more aggression, but the TV ratings don't measure what parents expect that they measure," Gentile said in a statement.
The researchers had the girls nominate their favorite television programs and frequency of viewing. Each of the 76 nominated programs was then analyzed for content showing indirect, physical and verbal aggression.
"Indirect aggression is identified as harmful behaviors that are non-physical such as rumor-spreading, social exclusion and ignoring," Linder said.
The content analysis of the programs was then compared with their respective industry ratings.
The study, published in the Journal of Applied Developmental Psychology, found TV-Y7 programs -- those designed for children age 7 or older, including cartoons such as "Digimon," "Pokmon" and "Scooby Doo" were found to contain the highest level of physical violence -- nearly three times as much as the next highest category of TV-14.
Linder and Gentile said that the ratings' "fantasy violence" label for animated violence is misleading and may serve to increase children's access to harmful violent content by reducing parental concern.