Why do people believe things that science has proved untrue?

Cognitive Dissonance

The world was going to end on Dec. 21, 1954, in a flood. But the cult members had no fear. They had faith, so they would be saved -- rescued by a spaceship and whisked away from God's wrath.

On Dec. 22, 1954, some of those cult members felt pretty foolish. But, to the shock of psychologist Leon Festinger, who had been studying the cult, others went the opposite way: They believed even more strongly than they had before the prophecy failed. In fact, to these true believers, the prophecy had not failed at all. They, the cult members, had managed to stop the flood with the power of their faith [source: Mooney]. That there was no flood was proof that they were right to believe.

In 1957, Festinger coined the term cognitive dissonance to describe what he had seen. It refers to the mental discomfort of facing inconsistency in one's thoughts, beliefs, perceptions and/or behaviors [source: McLeod]. He theorized that in this state of stress, the mind will tend seek a way to remove the conflict and restore cognitive harmony.

Most of us indulge this tendency to some degree. We all want to feel comfortable with our thoughts and actions, and it's a whole lot harder to change than it is to stay the same. We can see cognitive-dissonance theory at work in everyday life. A parent who believes her child to be brilliant believes the test he failed was poorly written, even though the rest of the class did fine on it. A man who catches his disheveled wife leaving a hotel with another man believes nothing happened, they just talked.

When an otherwise rational person holds an irrational belief in the face of significant evidence against it, cognitive dissonance is usually involved. How the mind facilitates this is a study in self-preservation, and it typically involves a mental tendency known as confirmation bias.