<prompt> All are feature of Autistic disorder EXCEPT: March 2013 b75 mentally retardedUsually appears by 2-3 years of ageAbsent social smileThird person hallucination  <response>: Ans. D i.e. Third person hallucination Autism Difficulty in concentration and communication, Lesion in frontal and temporal lobe and cerebellum, Delayed speech and language development, Problems in forming social relationships in early childhood, Stereotyped movements, Poor speech, Lack of social interaction, 