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Why Do Killers Kill?

Cultural differences in attributions of causality

Nobody really knows the answer to that question because every killer and every killing is unique. Nevertheless, most people have their pet theories about why people do bad things. Anders Behring Breivik, who killed 77 people in Norway last year, must be mentally ill, right? And Bernie Madoff must have been grotesquely greedy in order to bilk investors of millions of dollars. Most interesting to me, though, is the fact that our pet theories depend, in part, on where we were born.

Several years ago, two graduate students—Michael Morris and Kaiping Peng—noticed that an American newspaper (The New York Times) and a Chinese newspaper (World Journal) used very different language when reporting on two high-profile murder cases that were very similar. An American postal worker in Michigan lost his job. He shot his supervisor, the person who handled his appeal, several bystanders, and then himself. A Chinese graduate student in Iowa lost an award competition. He shot his adviser, the person who handled his appeal, several bystanders, and then himself.

When American reporters wrote about the shootings, they focused on the flawed characters of the killers, saying they were mentally unstable, darkly disturbed, or had a bad temper. Chinese reporters, however, pointed to the strained relationships in the killers’ lives, noting that they were socially isolated and didn’t get along with their victims.

These observations led Morris and Peng to conduct a series of experiments that demonstrate convincingly that European Americans and Asians often think differently about causality. European Americans as a group tend to explain behavior in terms of presumed personality traits and other dispositions that are internal to the actor. Why did Sam help? “Because Sam is a considerate person.” Asians as a group tend to explain behavior in terms of situational factors that are external to the actor. “Sam helped because it was dark and there was no one else to help.”

Subsequent studies by Peng and his colleagues revealed an even more surprising finding; that the differences between independent European Americans and interdependent Asians go even deeper—to the perception of physical causality. In one study, American and Chinese students were asked to observe a ball in a container of liquid and then explain the movements of the ball. The Americans were more likely to say that the ball’s movements were caused by something about the ball itself, like its density or shape. The Chinese were more likely to explain the ball’s movements as the result of something external to the ball, like the viscosity or movement of the liquid. These findings dovetail nicely with the earlier findings about how people explain the behavior of murderers and other people.

Developmental psychologist Joan Miller has showed that people learn over time to explain behavior in the way that is common to their culture. She asked Hindu East Indians and Americans to explain why people sometimes do bad things and sometimes do good things. The children in her study gave very similar explanations, regardless of their cultural upbringing. Adolescents, however, showed the divergent pattern usually observed in adults: Indians explained behavior contextually and Americans explained behavior dispositionally.

Why do killers kill and helpers help? Sometimes the explanation lies in the eye of the beholder—and we often see what culture has taught us to see.


Miller, J. G. (1984). Culture and the development of everyday social explanation. Journal of Personality and Social Psychology, 46, 961-978.

Morris, M., & Peng, K. (1994). Culture and cause: American and Chinese attributions for social and physical events. Journal of Personality and Social Psychology, 67, 949-971.

Peng, K., & Knowles, E. (2003). Culture, ethnicity, and the attribution of physical causality. Personality and Social Psychology Bulletin, 29(10), 1272-1284.