Nearly all animals show aggression, especially males, and it is likely an important evolutionary product of the effort to survive.
"In just about any species you look at, aggression is part of their behavioral repertoire," Kennedy said. "It occurs for things like getting access to territory, to food, to mates, and protecting offspring."
Aggression has survived the long path of evolution, because it proved very useful along the way. And it still does for nearly all species, but among humans, it has become a bit of a problem. Too much aggression is a bad thing, and one of the ways we hide the fact that we enjoy a little combat, is to take part in sports — either as a participant or a spectator — that sends a little dopamine flashing through our brains.
"We sanction violence by watching violent sports, boxing, football and the like," Kennedy said. "That's an ideal way for us to enjoy watching aggression in a much more socially appropriate arrangement."
Kennedy plans to move his research into the human arena, but with a less-invasive technique. Instead of inserting a tube into the brains of his human subjects, he will use sophisticated new scanners to see what's going on inside the brains of his subjects.
All he has to do is get a few guys to sit inside a scanner, and watch a little boxing or football, engaging in a little vicarious aggression. He expects to have plenty of volunteers.
Lee Dye is a former science writer for the Los Angeles Times. He now lives in Juneau, Alaska.