Psychological projection is a form of defense mechanism in which someone attributes thoughts, feelings, and ideas which are perceived as undesirable to someone else. For example, someone who harbors racist ideas while believing that racism is socially undesirable might come to believe that a friend is racist, projecting his or her racism onto the other person. Projection may manifest in all kinds of ways, and while it may be a defense mechanism, it can also be very destructive.

The concept of psychological projection was developed by Dr. Sigmund Freud, a noted figure in the field of psychology. Dr. Freud believed that people used psychological projection to reduce their own stress or feelings of guilt, thus protecting themselves psychologically. This psychological phenomenon is sometimes referred to as “Freudian projection” in reference to Dr. Freud's work in the field.

In a general sense, psychological projection can mean that people assume that other people share their thoughts or beliefs, good or bad. For example, someone who likes dogs might assume that all people like dogs, or an unfaithful spouse might conclude that everyone is unfaithful, since this would reflect his or her own experiences. As a defense mechanism, this allows people to feel more comfortable about themselves because they think they see traits in common with others.

People can also fall victim to the projection bias, in which they assume that their current mental state will remain consistent in the future. The projection bias has been studied by a number of researchers to see how psychological projection influences things like decision making and purchasing habits. For example, someone in the heat of summer often has trouble shopping for winter clothing, because he or she has a hard time imagining the need for heavy coats in the midst of bikini season.

Being aware of psychological projection in interpersonal relationships can be very important. Before attributing thoughts or ideas to someone else, you may want to reflect on whether those beliefs can also be seen in yourself. If they can, there's a chance that you might be projecting, and you may want to seek out a more reliable source on what someone else is thinking.

Projection can take a range of forms. For instance, if you find that you dislike someone, you may decide that he or she doesn't like you, responding to social norms which dictate that people should all like each other and get along. By deciding that this person doesn't like you, you can justify your decision not to like him or her, thereby setting yourself up for a self-fulfilling prophecy, because most people end up disliking the people who dislike them, even if they didn't start out that way. Projection may also cause you to assume that other people are as competent as you are at a specific task, or to think that other people share your political and social beliefs.