Dallas ? Scientists who monitor television and other entertainment research say one message is clearly being broadcast: Media violence can foster aggression in youngsters.

Decades of studies on television and movies, along with a growing body of data on video games, have yielded undeniable evidence of a media-aggression link, an expert panel argues in a newly released treatise. Violence in such media more often contributes to milder forms of aggression, but its effects on more severe forms “are also substantial,” the eight-member panel writes.

The panel makes its case in the most recent issue of the journal Psychological Science in the Public Interest.

“The research is clear, it’s solid, it’s consistent, that there are these harmful effects,” said panelist and media violence researcher Craig Anderson. “These harmful effects occur in both the short term and the long term. And the harmful effects are large enough that we as a society should be concerned.”

The data are clearest for TV and movies, but the emerging body of video-game studies points in the same direction, the panel said.

With television, scientists have decades-long studies where early exposure to violent media, along with later aggression, was measured, said researcher Jeanne Funk, who studies video games and violence. But video games haven’t been around long enough for that to happen. While she praises the panel’s work, she said, “I think we need a lot more than we have now on video games.”

The new panel report outlines explanations of media violence’s effects:

• Children learn social behaviors by observation, even though they are often unaware that learning has occurred. And they imitate what they’ve seen.
• Frequent exposure to violence may make aggressive thoughts or social “scripts” more readily available in a child’s mind making it easier to summon aggression-related emotions or behaviors in a given circumstance.
• Media violence causes physiological arousal, which may amplify an existing aggressive mood or tendency, among other things.
• Repeated exposure to media violence may “desensitize” a viewer, diminishing the unpleasant physical effects of seeing violence.

“Many youths who consume media violence will not be obviously influenced by it,” the panelists point out, “but the psychological processes that can produce the effect operate in everyone, thereby putting all at some risk.”