A psychologist tells children a story in which a puppet named Maxi puts a ball in one cupboard and then leaves the room. While she is gone, another puppet moves the ball to another cupboard. Then Maxi comes back. At this point, the psychologist asks the children in which cupboard Maxi will look for the ball. Most 3-year-olds probably will say the cupboard, and most 5-year-olds will say the cupboard.