Even a cursory look at human history shows that violence is endemic, but a recent study indicates it’s actually pleasurable—at least to mice. Scientists studying the brains of mice found that violence and aggression involve the same pleasure response as food. Mice even intentionally act aggressively, presumably just for that dopamine hit. According to these researchers, the reward pathways are similar in mice and humans, which could explain why I like the movie X so much.
The other side of the coin: We’re not mice. If anything, our society seems to be growing less tolerant of violence—people used to think nothing of packing a picnic lunch to watch a hanging, for instance. I think we’ve learned how to (somewhat) channel our love of violence into safer, more ritualized expressions of it, like video games and MMA. All the dopamine, none of the danger.