A neurolinguistic study of autistic children employing dichotic listening

A neurolinguistic study of 20 high functioning right-handed autistic children (19 males and 1 female) was carried out using a dichotic listening test of two-syllabic meaningful words with which to detect the level of binaural separation ability and the condition of hemispheric lateralization of language by examining the degree of ear advantage. The autistic children ranged from 5 to 15 years in age. Their IQ ranged from mildly retarded to normal. (The mean IQ was 67.6 and the mean mental age was 5 yr. 9 mo.). We compared them with non-autistic mentally retarded and normal children as controls, being matched by mental age and right handedness. The autistic children were found to be significantly lower on the level of binaural separation ability than the controls and to have a clearly higher incidence of a left ear advantage than the controls. The autistic and mentally retarded children showed lower advantage than normal children. These results indicate that the autistic children have a dysfunction or immaturity of the central auditory nervous system and an abnormality in the process of hemispheric lateralization of language.