Children adapt to the environment mainly through communication. After the child is born, his emotions become more and more social. Until childhood, emotion is still a tool to adapt to the environment, that is, a tool for communication.
Adults' understanding of a newborn is almost entirely determined by his facial expressions and movements. Before children master a language, they mainly use expression as a communication tool. In early childhood, expression is still an important communication tool, and its role is no less than language. Children often use expressions instead of language to answer adults' questions, or use expressions to assist their own language expression.
Emotional expression reappears earlier than language expression, and infants mainly express their emotions through facial expressions and physical activities, that is, the movements and activities of the body and limbs. After speech occurs, emotions are expressed through speech activities and facial expressions.
Emotion, as a tool of information exchange, has infectious characteristics. In infancy, emotional infection is particularly prominent.
For babies, emotional contagion is often more important than language. Emotion can become a communication tool because it has a signal function and can provide information exchange to others. Emotions are often not one-way expressions, but mostly have communication objects.