Heber, R. (1961)^<5)> proposed five levels for measured intelligence of the retarded according to the standard deviation units; i. e., profound, severe, moderate, mild, and borderline. IQ scores for these categories were calculated as follows: profound, below 25; severe, 25-39; moderate, 40-54; mild, 55-69, and borderline, 70-84. Japanese Ministry of Education (1962) has once set categories classifying the retarded by IQ as follows: severe, below 20 or 25; moderate, 20 or 25-50; and mild, 50-75. In the early work of the Special Committee on Nomenclature of the A. A. M. D., Sloan and Birch (1955)^<22)> recognized the futility of an unidimensional system; human differences of the kinds which form the bases for assessing degrees of retardation are both quantitative and qualitative, and such differences are not entirely intellective. We have been facing a great difficulty in applying standardized intelligence tests to profoundly and severely retarded persons. Even when we use standardized developmental tests for them, we, to be sure from our experiences, still find it very difficult to measure DQ scores of them. The purposes of this study were as follows; (1) to classify observed behaviors of the profoundly retarded along with the developmental steps of behavior, (2) to find out some types of conversions in their behaviors, the conversion of behavior is the hypothetical concept which the author takes for the phenomena of changing behavior pattern in its directions, contents or qualities during the observation period, (3) to apply the developmental steps of behavior to the observed behaviors appeared in ten-years record of a subject, so that developmental diagnosis from the behavioral point of view becomes possible for the severely and profoundly retarded, (4) to apply the developmental steps of behavior and types of conversions of behaviors to the behaviors observed by time-sampling, check-list method. The methods and subjects are; (1) during a day, to observe each of 5 subjects (profoundly retarded, CA 13-27, DA about 8 M.-about 11M., four males and a female) in an informal manner, and to record their observed behaviors in a diary-like fashion, (2) to observe the stereotypical behavior of the subject A. (CA 27, DA about 8M.) (3) to pursue daily records for ten years on the subject A., (4) by time-samling observation, to record the developmental steps and types of conversions of behavior on 6 subjects (3 of profound, CA 19-27, DA about 8M.-about 11 M.; 3 of severe, CA 17-21, IQ 20-36) on the check-list prepared for this study. Results and conclusions of this study were as follows: 1. We could classify behaviors of profoundly and severely retarded persons into the five developmental steps. The five steps are; (I) simple "movement", (II) impulsive "action", (III) voluntary "action", (IV) "behavior", and (V) "conduct". 2. There were three types of conversions in subjects' behavior; (A) directional conversion (d-c), (B) content conversion (c-c), and (C) qualitative conversion (q-c). 3. About 30 items of behaviors (for example, aimless walking, stealing food) were observed on each of the profoundly retarded subjects. 4. In daily records for ten years, there were 329 kinds of behaviors in a profoundly retarded subject. These were categorised into 30 categories (for example, putting or one's shoes). We found in the records, too, three types of conversions of behavior had beer taking place for these ten years. 5. The author tried to apply the check-list method to evaluate the developmental steps of behavior and types of conversions of behavior to profoundly and severely retarded subjects. 6. It could be said that, we could expect any development of behavior even for the profoundly retarded.
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