ABSTRACT
Having described the biological factors that can influence intellectual development, we now shift to “psychological” ones. By these are meant the caregiving environment to which the infant and young child is exposed. Related research is presented in terms of six general topics. They are the general relationship between certain kinds of childhood experiences and cognitive development, children raised under conditions of gross deprivation, children reared by parents who are themselves retarded, adopted and foster children, twin studies, and the prevention of mental retardation through early childhood education. Crocker (1992) attributes about 12% of mental retardation to nonbiological causes (e.g., deprivation), but if we add the environments of families in which both genetic and environmental factors are assumed to be operative (cultural-familial or psychosocial retardation), the environmental contribution is much greater.
