michael, a man left to die after being stabbed on the street. when i heard this story, it seemed too hard to believe. >> i still can't watch that video without thinking it was staged. it's so unreal. and when we look at it, we see a couple of things. like you said, there's the bystander effect and something called the fusional responsibility. we've known about those for a while. i don't think that's what we're looking at that in this. i think we're seeing the this new phenomenon, this desensation to violence, where we're actually changing brain structures in a way, when people don't get it when they look at it now. >> are you saying as a result of what? because of movies, video games? i've heard that before. is that -- is it as simple as that? >> it is as simple and as complex. we pound, particularly our children, we pound them 24/7 with what i call promps. they're violent scenarios, lyrics in a song, scenes in a movie. all sorts of suggestions about violence to the point where the brain is now changing in these kids in the way it responds to