Dreams are a product of the sleeper's mind. They include events and feelings that he has experienced. Most dreams are related to events of the day before the dream and the strong wishes of the dreamer. Many minor incidents of the hours before sleep appear in dreams. Few events more than two days old turn up. Deep wishes or fears, especially those held since childhood, often appear in dreams, and many dreams fulfill such wishes. Events in the sleeper's surroundings, a loud noise, for example, may become part of a dream, but they do not cause dreams. Some dreams involve deep feelings that a person may not realize he has. Psychiatrists often use material from a patient's dreams to help the person understand himself better. Dreaming may help maintain good learning ability, memory, and emotional adjustment.