The early signs of mental retardation are: 1. smiles do not appear at the age of months, do not pay attention to others’ speech, accompanied by motor development lag. 2. Poorly developed visual function, not gazing around beyond 3 months of age, often misdiagnosed as blindness. 3. Lack of response to sound beyond 2 months of age is often misdiagnosed as deafness. 4. Poor swallowing and chewing ability makes feeding difficult, and when solid food is given, swallowing is impaired and can cause vomiting. 5.After 6 months of age, the gaze at the hand persists. 6.After 1 year of age, the legs show a scissor-like gait when walking (also often a sign of cerebral palsy). 7. Mouth movements persist, and sometimes toys such as blocks are often put into the mouth after 1.5 years of age. 8. After 1.5 years of age, the child often throws things and is not interested in playing with toys. 9.After 1.5 years old, they still drool. 10.When awake, you can see teeth grinding action, which is not normal children. 11. Needs repeated or continuous stimulation to cause crying, sometimes the cry is weak. The cry is often guttural, shrill or screechy, and has no normal pitch change. 12. Lack of interest and lack of concentration are two very important characteristics. Lack of interest is manifested in the lack of interest in the surrounding things, and the interest in toys is also very short-lived and slow to respond. 13. In infancy, they often show excessive sleepiness and purposeless hyperactivity.