1959, American psychologist Harold and his colleagues reported a research result: let newborn monkey babies be separated from their mothers from the first day of birth and stay with their two mothers for the next 165 days? Mother thread and mother cloth. Mother Alice has a bottle on her chest, but Mother Cloth doesn't. Although the little monkey can drink milk when he is with his mother, he would rather not drink milk than be with his mother. Harlow concluded that physical contact is even more important to the development of young monkeys than breastfeeding? Only when they need food, they will go to their mother line, and most of the time they will snuggle up to their mother cloth. Although the object of this experiment is monkeys, many psychologists think it is also applicable to human babies.