Killing for revenge?: Research has shown that humans are not the only animals that use revenge as deterrence. But people seem inclined toward long-term planning when it comes to their vengeance, and the U.S. Navy SEALs that killed Osama bin Laden might have just been the final step in that process. Image: Wikimedia Commons/U.S. Navy/Christopher Menzie
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Spontaneous patriotic chants and flag-waving crowds were sparked by word that Osama bin Laden had been killed earlier this week. Despite the man's loathed reputation as the mastermind of the September 11 terrorist attacks, the jubilation over bin Laden's death raises the question: Why the celebration? Was it relief, a sense of justice—or the simple pleasure of revenge?
As draconian as lethal retribution might seem, science has shown that the human brain can take pleasure in certain kinds of revenge. Magnetic resonance imaging (MRI) scans have revealed that thinking about revenge activates the reward center—where the feel-good neurotransmitter dopamine is lodged—in much the same way that sweet foods or even drugs can.
But the news also brought out some more jumbled sentiments, including sadness for the reminder of the past tragedy and ambivalence about the intentional killing of another person. With all of this gray area—colored in this instance by politics, history and the sheer scale of the international stage—is there a way to understand revenge in a basic, biological way?
To find out, Scientific American spoke with Michael McCullough, a psychology professor and director of the Evolution and Human Behavior Laboratory at the University of Miami, as well as the author of Beyond Revenge: The Evolution of the Forgiveness Instinct (Jossey-Bass, 2008). He explains that the impulse for revenge evolved as a simple cost-benefit equation and why it is best served cold—but not too cold.
[An edited transcript of the interview follows.]
As a psychologist and someone who has written and thought a lot about this concept, how do you think about revenge?
We want to be very precise in the kinds of behavior that qualify as revenge. We think about behaviors that are generated by psychological mechanisms that were designed for biological functions. Why do I want to make such a niggling distinction? Because there are behaviors that can look like revenge but that aren't. Anytime I impose a harm on you, it might be revenge or it could be something else—I could try to hurt you because I'm trying to get away from you so that you don't harm me in the future, which wouldn't qualify as revenge.
We think there are mechanisms up in the heads of social animals that are designed to deter them from posing harms in the first place. So revenge is the output of mechanisms that are designed for deterrence of harm—behaviors designed to deter individuals from imposing costs on you in the future after that individual has imposed costs on you in the first place.
You'll hear people say things that sound right: it's to "balance the scales," or "right a wrong," or "serve justice," but those don't really meet the level of achieving a function that biology cares about.
So is revenge not about some sort of human desire for justice?
When I don't have my psychologist hat on, and someone has done something to make me feel vengeful, I do feel like I want to teach them a lesson. I think: "I'm going to feel better once I take care of this hangnail of a moral wrong that's on my mind right now." But we want to make a clear distinction between the way revenge feels to us as human critters and what the mechanisms are designed to do.