Despite all of their training, mistakes do happen. And when they happen, they often end up as front-page news. The news coverage gets particularly heated when white police officers shoot an unarmed African-American suspect or an innocent bystander.

Research suggests that there is a for white people to shoot unarmed black suspects more often than unarmed white suspects. These findings in laboratory studies have been obtained both with trained police officers as well as with college students role-playing as police officers. This is called the shooter bias.

An interesting set of studies by Saul Miller, Kate Zielaskowski and Ashby Plant in the October, 2012 issue of and Social Psychology Bulletin explored why this happens.

One possibility is that there is a pervasive stereotype in the United States that black men are more dangerous than white men. One possibility is that this stereotype causes people to be more likely to make the snap decision to shoot a black man than to shoot a white man. A second possibility is that people are prone to shoot anyone who belongs to a different social group than they do, and that specific stereotypes about whites and blacks are not the primary cause of the shooter bias.

To explore this issue, college students participated in a simulated shooting task in which they saw faces of men. The faces were either paired with a gun or with a neutral object. They had to press a button within 630 milliseconds of the appearance of the face to decide whether to shoot. The task was to shoot when there was a gun and not to shoot when there was no gun.

In these studies, all participants filled out a questionnaire assessing their belief about whether the world is a dangerous place. This questionnaire has items like “There are many dangerous people in our society who will attack someone out of pure meanness, for no reason at all”- the more that someone believes that the world is a dangerous place, the more likely they may be to have a shooter bias.

In the first study, all of the faces were White males. Participants were given a personality quiz at the start of the experiment and on the basis of that quiz were told that they had either a “red” or a “green” personality. In actuality, the color was randomly assigned to them. They were given a sticker of their color to wear. The faces they saw during the study appeared either on a red or a green background, and participants were told that this color reflected the personality of the individual shown.

In this study, participants who were moderate or low in their belief that the world is dangerous showed no shooter bias. But, people who were high in their belief that the world is dangerous were more likely to shoot an unarmed person if that individual’s personality color was different from their own than if it was the same.

This result suggests that the shooter bias can happen, even in the absence of a cultural stereotype that a person is dangerous.

In a second study, white college students saw white, black, and Asian faces. For this group of students, the cultural stereotype that black men are dangerous was strong, but there was no cultural stereotype that Asian males are dangerous. In this study, there was a broad tendency for all participants (regardless of their belief that the world is dangerous) to mistakenly shoot unarmed black men more often than to shoot either Asian or white men. For participants whose belief that the world is dangerous, though, they were also more likely to mistakenly shoot Asian men than to shoot white men.

What does all of this mean?

There seem to be two sources of shooter bias. First, there are cultural stereotypes (like the stereotype that black men are dangerous) that influence people’s snap judgments. On top of that, for people who are already concerned that the world is dangerous, there is a bias against anyone who is in a different group.

This work suggests that the belief that the world is dangerous is an important factor. People with a low level of belief that the world is dangerous are much less likely to mistakenly shoot an unarmed person.

One reason that this finding is important is that many advocates of concealed weapon laws justify the importance of these laws on the premise that the world is a dangerous place. The idea is that if more people were carrying weapons, then that would make the world safer. Unfortunately, promoting the belief that the world is dangerous may also promote a mindset that increases the likelihood that innocent people will get shot. More research should explore this issue. In addition, future studies should explore whether teaching people that the world is not as dangerous as they think it is can reduce the shooter bias.