This is a pretty good study, and clearly violent video games have a negative effect on teens. But it is ridiculous to cite the violence in cities like Detroit, Baltimore, and others without mentioning race. Check out the book "The Color of Crime". Or even better, just turn on TV shows like "The First 48" and "Live PD" which show you the complete lack of empathy that urban "youths" have... I doubt that they are all playing HALO or other games Grossman mentions.