There is a pretty good body of literature linking expose to violent music, video games, movies, and TV shows to increase in aggression related thoughts, affect, and arousal. A new study covered by Reuters used brain imaging technology to study these effects from a new angle. Results showed that regions of the brain related to aggression and “fight or flight” instincts were activated after playing.
Those who played the violent video game showed more activation in the amygdala, which is involved in emotional arousal, and less activation in the prefrontal portions of the brain associated with control, focus and concentration than the teens who played the nonviolent game.
“Our study suggests that playing a certain type of violent video game may have different short-term effects on brain function than playing a nonviolent, but exciting, game,” said Dr. Vincent Mathews, a professor of radiology at Indiana University School of Medicine in Indianapolis and the study’s author.
Due to the politics around censorship and violent media, many people don’t take studies like these seriously. I cannot speak for the current research since I haven’t read the actual source, but most other studies that I have read on this topic have been extremely sound methodologically, and generally use an experimental design, which can demonstrate a real cause-effect relationship. Based on all of this work it is pretty clear that at the least, some violent media content has an impact on behavior.