The definition and classification of mental retardation.

Problems with current definitions of mental retardation were recognized. Classification systems based on the behavioral capabilities of retarded persons were criticized since there are so many noncognitive determinants of performance. It was proposed that mental retardation be defined solely by IQ scores at least 2 SDs below the population mean. This suggestion was predicated on the view that the behavioral sciences currently have no better way to assess intellectual functioning. Etiology was seen as such a significant predictor of group differences that the organic, familial, and undifferentiated categories would be used in classification. Social adaptation and expected performance were seen as correlates of class membership rather than defining features of retardation, since they have no reliable method of measurement. Problems of labeling were discussed, but the practice was deemed useful if it leads to beneficial services and interventions.