The low intelligence level of infants can be judged from the following aspects: 1. from the situation of gross motor development. The infant’s mental retardation can cause delays in head lifting, rolling over, sitting and walking, for example, the infant cannot lift his head at 3 months and cannot sit unaided at 6 months. 2. The infant’s lag in language development. At 3-4 months of age, infants cannot communicate with their parents through babbling sounds, and at 1 year of age, infants cannot simply call their father and mother. 3. Infants are less adaptable after low intelligence and are not able to effectively understand the actions of parents or other caregivers. When parents tease infants with brightly colored toys, infants do not smile or make eye contact.