Psychologists have no way of knowing exactly what someone is thinking at any one time. The only way to figure out what could be going on in a person's head is through metacognition. This is defined as thinking about or an awareness of one's own thoughts. Psychologists try to use this awareness to learn all that they can about thought. But several things must be kept in mind when studying thought. The first is that people are falliable, and a psychologist must trust that whatever a person tells them is, in fact, what is going through that person's brain. Psychologists attempt to correct for this lack of accuracy through calibration, but this can still cause problems because of the illusion of knowing.