Mental retardation in the United States is currently defined as " ...
signif- icantly subaverage general intellectual functioning existing
concurrently with deficits in adaptive behavior, and manifested during
the development period" (Grossman, 1977). Of the estimated six million
plus mentally retarded individuals in this country fully 75 to 85% are
considered to be "func- tionally" retarded (Edgerton, 1984). That is,
they are mildly retarded persons with no evident organic etiology or
demonstrable brain pathology. Despite the relatively recent addition of
adaptive behavior as a factor in the definition of retardation, 1.0.
still remains as the essential diagnostic criterion (Edgerton, 1984:
26). An 1.0. below 70 indicates subaverage functioning. However, even
such an "objective" measure as 1.0. is prob- lematic since a variety of
data indicate quite clearly that cultural and social factors are at play
in decisions about who is to be considered "retarded" (Edgerton, 1968;
Kamin, 1974; Langness, 1982). Thus, it has been known for quite some
time that there is a close relationship between socio-economic status
and the prevalence of mild mental retardation: higher socio-economic
groups have fewer mildly retarded persons than lower groups (Hurley,
1969). Similarly, it is clear that ethnic minorities in the United
States - Blacks, Mexican-Americans, American Indians, Puerto Ricans,
Hawaiians, and others - are disproportionately represented in the
retarded population (Mercer, 1968; Ramey et ai., 1978).