Two pedals drive the bi-cycle of violence: reactive and appetitive aggression.

The Good: when you fight to counter threat, your aggression is a reactive defense, and often morally justifiable. The Bad: when you loot and rob, hurt and kill, to obtain social status or material goods, that is an extrinsic reward. This is instrumental aggression. And The Ugly: The intrinsic enjoyment of violence. This 'appetitive aggression' describes a lust for violence, underlying first-person shooter gamers, hunting, and extreme acts of violence, such as murder and massacres. Although violence often results from a combination of these forms of aggression, the differentiation is necessary to understand their interplay, as they drive two interconnected cycles of violence: the reactive cycle, fueled by the motivation to overcome negative feelings, and the hedonically driven appetitive cycle.