Most babies will laugh when teased at 2-3 months of age. If the baby is still unable to be teased or makes few sounds after 5-6 months of age, it is important to look for mental retardation, as well as language delay or autism spectrum disorders. When autism spectrum disorder is present, the baby cannot be made to laugh, and cannot recognize relatives, makes very little eye contact, and has no sense of dependence on others, most of the babies should be watched out for autism. And when the baby can not properly find the sound source, no response to sound to pay attention to the hearing impairment and mental retardation may exist, so after birth must be regularly to the child health department for medical examination, in order to achieve early detection, early intervention, early treatment.