A cognitive bias is a flaw in judgment which is caused by memory, social attribution, and statistical errors. Cognitive biases are common to all humans, and many of them follow predictable and obvious patterns. Humans develop cognitive biases for a range of reasons; they help the brain to process information quickly, for example, even when that processing is sometimes erroneous. Many social psychologists have dedicated a great deal of time to understand cognitive bias, since it is an important part of the human mind.

Understanding and recognizing cognitive bias in yourself and in others is a very useful skill. If you account for bias when evaluating a situation or someone's retelling of an event, you can make more accurate decisions which are based on fact, rather than on tricks of your mind. Cognitive bias is a powerful force in decision making, especially in groups, and it also skews our perspective of people and the world.

Should you find yourself on a jury at some point in your life, your knowledge of cognitive bias could be extremely important. Cognitive bias can make a witness extremely unreliable, and it is something that you should consider when listening to testimony. Cognitive bias also plays a role in your interpretation of the speeches from the prosecution and defense, and in how you look at witnesses in a courtroom.

Hundreds of cognitive biases have been identified by social scientists. The selection below is very small, and the descriptions of these biases and the ways in which they work are truncated. If you want to learn more about specific cognitive biases, you can explore wiseGEEK for individual social psychology articles, or you might want to take a course in social psychology at your local college.

One cognitive bias which you are probably well acquainted with is the bandwagon effect, in which people tend to go along with what other members of a group are doing. This effect is part of a larger group of interesting social behaviors sometimes called “groupthink.” Speaking of groups, you might also be familiar with the effects of the ingroup bias, in which people tend to view “their” group as better and more diverse, while outsiders are collectively viewed as inferior.

You may also have been guilty at some point of projection bias, in which you make an assumption that other people think like you do. Projection bias can lead to the false consensus effect, in which people mistakenly believe that a group of people agrees on a subject when this is not, in fact, the case. In a courtroom, you should be especially wary of anchoring, the tendency of your brain to weight the first information you receive more heavily.

You should also beware of confirmation bias, a very common form of cognitive bias. The phenomenon of confirmation bias explains why people tend to ignore information which does not fit with their beliefs while they weight agreeable information more heavily. Another common cognitive bias is the fundamental attribution error, in which people ascribe behaviors to people's personalities, rather than social and environmental factors.