The main symptoms of mental retardation in 2-year-old children: first, abnormal crying, some babies will cry for a longer period of time after being stimulated, but sometimes it takes repeated stimulation or continuous stimulation to cause crying. There are also children who cry sharply or cry in a small and weak voice. Other babies do not like to cry and seem to be unusually well-behaved. In this case, we need to highly suspect that the child has mental retardation. Secondly, the ability to suck is poor, some babies will appear to chew food later, especially when eating solid food, swallowing disorders or vomiting will occur easily. The earliest symptoms shown by mentally retarded babies are difficulty in breastfeeding, not being able to suck, and especially easy to spit up, which indicate that the child’s nervous system has been damaged, and his or her intelligence will be affected to a certain extent in the future. By the time the child reaches two weeks old, the child may still be slow to eat, chewing or feeding with certain difficulties. Thirdly, the child’s motor development is lagging behind. Generally speaking, a 3-month-old child can hold his head up, a 6-month-old can sit, and a 1-week-old can walk. For children with mental retardation, gross motor development is behind, at least 4-6 months behind. Fourthly, the duration of sleep is abnormally increased. If the child’s sleep time increases abnormally, if the child basically sleeps all day long during the newborn period, and the sleep time is still around 16-18 hours when the child reaches 1 week old, the child needs to be highly suspected of having mental retardation. Fifth, dull expression. Generally, children have rich expressions, especially after the first month of life, and they talk and laugh. If the child still has a dull expression after 6 months of age, it is highly suspicious of mental retardation.