(Also called sociocultural or cultural-familial retardation)

Mild mental retardation attributed to environmental causes and generally involving some degree of psychosocial disadvantage.

The majority of persons suffering from mental retardation fall into the category of familial retardation rather than that of clinical retardation, which usually has neurological or other organic causes. Persons with familial retardation typically have IQs ranging from 55-69 and show no signs of physical disability. Environmental causes thought to contribute to familial retardation include the quality of the mother's prenatal care, maternal and child nutrition, family size, the spacing of births within a family, disease, and health risks from environmental toxins such as lead. The 1994 publication of The Bell Curve, an analysis, by Richard J. Herrnstein and Charles Murray, of the relative importance of heredity and environment in determining IQ scores, and the 1995 release of the most in-depth study to date on retardation among...