What motivates someone to be violent? This is a question many people are asking in the wake of the recent mass shootings in California. Most explanations tend to revolve around the core assumption that violence is wrong. If someone is violent, something must be broken in their moral psychology—they are intrinsically evil, they lack self-control, they are selfish, or they fail to understand the pain they cause. However, it turns out that this fundamental assumption is mistaken. It is not the breakdown of their morality at all, but rather the working of their moral psychology. Most violence in the world is motivated by moral sentiments.

I began studying this issue by asking why people disagree when and if violence is appropriate. Intergenerationally, I looked at why spanking children was more acceptable 50 years ago than today, and why it is still more acceptable in certain parts of the country. Cross-culturally, I looked at why it is incomprehensible to Westerners to kill women for sexual infidelity, yet other parts of the world encourage this practice.

To find answers, I looked at violence across cultures and history with my colleague Alan Fiske of the University of California, Los Angeles. We analyzed records of all kinds of violence, ranging from war to torture to genocide to homicide. While this was rather depressing work, it also led to some very interesting findings. We identified a pattern in that violence that was both predictive and explanatory.

The commonality was that the primary motivations were moral. This means that the perpetrators of violence felt like what they are doing was morally right. In fact, when they were committing the act, they perceived that not acting would be morally wrong. It wasn’t about a breakdown in moral sensibilities, but more that their sense of morality was different. They viewed violence as the fundamentally right thing to do even if no one else could see any possible justification for it.