Early symptoms of mental retardation are usually characterized by quiet behavior, indifferent expression and abnormal appearance. 1. Quiet behavior: Patients with mental retardation usually have quiet behavior and seldom cry in daily life. They are not interested in the surrounding environment, their eyes cannot follow people walking around, and their motor development is backward. 2. Indifferent expression: Patients with mental retardation are usually uninterested in the outside world, and when being teased by their family members, their expression is usually indifferent. In addition, they may not be able to recognize their family members, and they may not be able to respond with babbling. 3. Abnormal appearance: Patients with mental retardation may also have abnormal appearance, such as wide eye spacing, collapsed nose, crooked mouth and eyes, etc. A few patients may also have oversized head circumference and drooling. If the early symptoms of mental retardation appear, the patient should go to the hospital in time to avoid affecting the growth and development of the patient.