Ms. He, a reader in Beijing, asked: My baby is over 2 years old and likes to hide and seek. But every time he just hides his little head, exposes his body, or just covers his eyes. He thinks he can't see you and you can't see him. What is the reason for this lovely performance of children?

Wu Jun, director of pediatrics department of Peking University Shougang Hospital, replied: To understand this problem, we have to understand a concept-object permanence. Piaget, a famous Swiss educator, put forward the viewpoint of "the eternity of an object", arguing that an object exists as an independent entity, even if the individual can't perceive it, it still exists. Simply put, it's there whether you look at it or not. However, the psychological development level of infants is limited. They feel that only what they see exists, and what they can't see disappears or is gone. This is why babies who have been playing hide-and-seek for months cry when they see their parents covering their faces, because they think their parents are gone. At this point, if mom and dad suddenly take their hands away, it will make the baby giggle.

Usually, children can get the permanence of objects at the age of 3, and understand that objects still exist even if they are invisible, but because of the great limitations of thinking, they still can't see things from the perspective of others. Therefore, parents should patiently cooperate with their children to continue to experience the hide-and-seek game of "hiding their heads but not their feet" and wait for his cognitive development.