There are many reasons why a one-and-a-half year old child cannot speak, and it is necessary to consult a doctor to clarify the cause of the disease. There may be hearing impairment, dysarthria, mental retardation, social disorder and other reasons. 1. Hearing impairment: If a one-and-a-half year old child has hearing impairment, he or she cannot accurately perceive the sounds and cannot imitate them, and thus cannot speak. 2. Dysarthria: If the child has a short tongue tie, cleft palate, etc., it will easily lead to dysarthria and thus unable to speak. 3. Intellectual disability: If the child has cerebral palsy, Down’s syndrome, hypothyroidism, etc., resulting in a lower level of intelligence than that of children of the same age, the child may still be unable to speak at the age of 1.5 years. 4. Social disorder: If there is little communication with the child, or the baby has autism, etc., resulting in social disorder, which leads to the inability to speak. If your child still can’t speak at 1.5 years old, it is recommended that you seek medical attention to identify the cause of the problem and make timely and targeted treatment to avoid missing the opportunity for treatment.