3-year-old baby’s mental development delayed performance about the following points: 1, abnormal crying or quiet, the first is often cry, mainly after being stimulated to cry for a long time or very hard, and some performance is not crying quiet some abnormal, these two situations appear need to pay attention to; 2, poor chewing ability, 3-year-old children can chew things normally, but if the mental development delayed, chewing ability will decline to learn very late, and sometimes there will be swallowing disorders or vomiting; 3, slow response to external stimuli or hypersensitivity; 4, dull expression, some babies with congenital mental retardation have abnormal facial posture, such as the tongue often dragged outside the mouth, drooling, dull expression, etc.; 5, motor development is backward, some babies even 3 years old and unstable walking situation, indicating that the baby The 3-year-old baby’s mental retardation is also manifested in the weak language expression ability, even can not complete the speech, diction is very unclear, some children even to the outside reaction is relatively slow, or no interest in the surrounding people and things, do not like to communicate with people.