Temporary escape from daily reality by forming mental pictures.

In daydreams—exercises of imagination—the person forms a mental image of a past experience or of a situation that he or she has never actually experienced. Some psychologists use the acronym TUIT (Task-Unrelated Images and Thoughts) to describe episodes of daydreaming. A daydream may be triggered by a situation, a memory, or a sensory input (sight, taste, smell, sound, touch).

Psychologists estimate that one-third to one-half of a person's thoughts while awake are daydreams, although a single daydream rarely lasts more than a few minutes. Daydreaming is generally not harmful, unless the daydreaming episodes interfere with activities of daily living. When the day dreamer's daily routine is disrupted—a student does not hear the teacher assigning homework; for example, he or she may be using daydreams as a defense mechanism. In extreme situations, the daydreamer begins to confuse...