Educability-and-Group-Differences-1973-by-Arthur-Robert-Jensen

Physical Environment and Mental Development 341
of lead poisoning, and the apparent increase in reported cases is
due to better diagnosis and record keeping. In a population of
over 8 million, the annual number of reported cases in the mid
1950s was about 100 (Jacobziner, 1966), and this figure rose to 727
in 1969 and 801 in the first half of 1970 (Guince, 1970). Two
deaths were attributed to lead poisoning in 1969. The fact that
there are many post-World War housing areas in which leaded
paints have never been used and yet in which the majority of
children reared in them have IQs a standard deviation or more
below the national average suggests that lead poisoning, though
undoubtedly serious when it occurs, is an insignificant factor in
relation to average racial or social class differences in IQ and
educability.
REPRODUCTIVE CASUALTY
The association between social class, race, and lower IQ, and the
much higher incidence of mental retardation among low SES
groups, have been attributed in varying degrees to brain impairments
incurred prenatally and perinatally. There is a continuum
of reproductive casualty, going from fetal and neonatal death to
behavorial symptoms referred to as ‘minimal brain damage’. The
prevalence of reproductive casualty, most students of the problem
agree, is much higher among Negroes than among other groups
of similar socioeconomic status. Reproductive casualty is thus
frequently mentioned as a major cause of Negro deficits in IQ
and scholastic performance. Typical is the statement by Bronfenbrenner
(1967, p. 913):
Though the Negro infant is not biologically inferior at the
moment of conception, he often becomes so shortly thereafter.
The inadequate nutrition and prenatal care received by millions
of Negro mothers result in complications of pregnancy which
take their toll in extraordinarily high rates of prematurity and
congenital defect. Many of these abnormalities entail neurological
damage resulting in impaired intellectual function and
behavioral disturbances, including hyperactivity, distractibility,
and low attention span. Of particular relevance is the significant
role played by perinatal and prenatal factors in the genesis of
childhood reading disorders.