Preoperational StageThe preoperational stage has a large change in representative thought in the mind. In this stage children can use symbols to represent their knowledge. Children also learn language in the preoperational stage. Piaget did not think language was that important for cognitive development. He thought that children use words to explain the pictures of experience in their mind. In the preoperational stage, children have egocentricism. Egocentricism is when children cannot tell the difference between their view point and someone else’s. Piaget used the three mountains problem to show egocentricism. In the problem a doll is placed on one side of a group of mountains. A child is placed on a different side. The child is asked to tell what the doll sees. A child who has egocentricism tells what he or she sees and not what the doll sees. 