1. What is a mentally retarded child? Mentally retarded children refer to children whose IQ is lower than that of the normal population, usually scoring less than 70 points on IQ tests. These children have learning, social and life difficulties and require special education and support. 2. What are the symptoms of mentally retarded children? The performance of mentally retarded children is mainly reflected in learning, such as delayed language development, poor memory, and inattention. At the same time, it is also difficult for them to have normal interactions with their peers.