Stereotyped behavior as a type of repetitive behavior was studied by observing four major groups of exceptional children by a natural observation method. The total 400 subjects are made up as follows: 46 with visual disturbance, 85 with auditory disturbance, 29 with infantile autism and 240 with mental retardation. 2. From analyses of our observational data, it was inductively proved that each group has its own characteristic sterotypy. There were marked differences in stereotypy between the auditory disturbance group and the visual disturbance group. Autistic children showed a perfect form of stereotypy and outstandingly bizarre characteristics. It was also found that blindism and autism have much in common. Stereotyped behavior shown by mentally retarded children differed with different intelligence levels. 3. There was no significant difference in the stereotypy appearance rate among the blind as well as the deaf-mute. Comparison between the blind with mental retardation and the blind with normal intelligence showed that there was significant difference of 0.5% or less. When taking the intelligence factor into account, significant differences aroused. As against the autism group, each group showed a significant difference of over 0.5%. In conclusion, it can be said that mental retardation factor has close bearing on the stereotypy appearance rate. 4. With respect to the cause of stereotyped behavior, the author based its argument on its own theory that blindism accrues from congenital visual disturbance. Weighing the fact that stereotypy differs between the blind and the deaf-mute, the author discussed with reference to the theory developed by Kaufman and Berkson that the inability of the child to monitor normal stimulation due to sensory disturbance produces frustration in him and this frustrated bodily need manifests itself in stereotyped movements. As for stereotypy of the mentally retarded children, the author pointed out that the arousal level theory is applicable only to the cases of severe-grade mental regardation, and that it fails to explain the parallelism between the differences of intelligence level and stereotypy. As regards stereotyped movements of the autistic children, due consideration was given to subtleties in action and bizarre nature of their behavior. Based on Orniz's theory that autistic children lack the constancy of central perceptual reception, the author maintained that the occurrence of stereotypy in autistic children suggests the underlying mechansims of perception are functioning pathologically as well as neurophysiologically. 5. As our observation as been conducted for a short period of time, the results might have been rather cross sectional. But the author thinks this shortcoming would have been made up for by Rutter's five-year follow-up study and the records available at the institutions which proved autism-stereotypy has continued to appear for a long period.
