But if the brain is so efficient at categorization, why doesn't experience correct inaccurate stereotypes?

Before answering that question, it is important to note that we may not be exposed to very much experience in our daily life that would contradict our stereotypes. For example, residential segregation keeps the home lives of different racial groups separate to some degree. But also, our stereotypes of other groups ("out groups") often lead to feelings of anxiety when we encounter the members of an out group. One of the oldest insights of psychology is that a main way we deal with anxiety is through avoidance: We simply avoid contact with individuals by crossing the street, turning our heads, talking to someone else, hiring someone else for a job, striking up friendships with someone else we feel more comfortable with, sitting down at the lunch table with those who seem to be more like us.

Returning to the question of why stereotypes persist in the face of contradictory experience, we find two main answers. The first is that because stereotypes may help us feel better about ourselves, we avoid challenging these stereotypes. In other words, we become defensive and protective of our worldviews and only reluctantly question our deepest assumptions. And these worldviews help protect not only our self-esteem, but also real-world privileges and benefits that accrue to us as members of an in group. For example, racist discrimination by banks that hurts African American communities by limiting mortgages to these areas also benefits White neighborhoods by making more money available to them. Discrimination which in the past has limited slots available to Jews or African Americans or Asian Americans at universities has benefitted the majority population by making more slots available to its members. So, maintaining our prejudiced views of others allows us to feel better about our own group and to avoid challenging unfair social practices that benefit us.

Psychologists have found that we put energy into various mechanisms that help us maintain our view of the world. For example, we can seek out and pay attention to information that supports our views. Evidence suggests that the more strongly we hold a stereotype, the more we tend to remember confirming information about the group. There is a kind of circular process here: For example, the more we believe stereotypes about gay men being effeminate, the more likely we will remember incidents which seem to support these views.

We also discount or rationalize information that is contradictory to our beliefs. The Black person who is intelligent and articulate, the gay man who is not effeminate, or the Jewish person who is not pushy become exceptions to the rule, but the rule remains. And we may look more closely for grammatical mistakes in the Black person's speech than in a White person's; or we may think that the gay man has developed a public persona designed to fool us; or that the Jewish person is especially clever in working his or her exploitive influence behind our back.