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

350 Educability and Group Differences
3. The closest to anything like this that I have been able to find in the
relevant literature on human nutrition and growth is a study, carried
out in Aberdeen, Scotland, which showed a correlation between the
mother’s nutritional status as determined by her height and her
infant’s birth weight and subsequent growth and development; there
were also correlations between mother’s height, child’s height at age
7, and his performance on achievement tests in school (Birch,
Richardson, Baird, Horobin & Illsley, 1970). The possible confounding
of genetic and nutritional factors in determining these
relationships rules out any definite interpretation.
4. The investigation also conducted parallel studies in two rural
samples of poor Appalachian whites in Tennessee. Their nutritional
status was higher than that of the urban samples mainly because
they raised much of their own food. About 70 percent of the rural
samples, as compared with about 50 percent of the urban samples,
had pin worms. The IQs of the rural whites averaged about 6 points
lower than those of the urban whites.
5. An assistant director of the U.S. Department of Agriculture’s human
nutrition research division claimed that 50 percent of children with
IQs in the range from 70-80 are depressed 10 IQ points due to
poor nutrition (Biomedical News, November 1971, p. 14). Despite
repeated efforts, however, I have not succeeded in obtaining from
the official source of this claim any factual evidence that would
substantiate it.
6. If we assume a mean IQ of 100 in the white population, 85 in the
Negro population, and an SD of 15 in each population, and further
assume that all brain-damaged persons are of lower IQ than neurologically
non-damaged persons, what percentage of the Negro
population would have to be screened out as neurologically damaged
in order to bear out this prediction by Amante et al. Calculations
indicate that at least the lower 62 percent of the Negro population
in IQ would have to be screened out for the remaining 38 percent to
have a mean IQ of 100. This surprising conclusion would seem to
cast some doubt on this hypothesis. Have there been any estimates
of the incidence of neurological damage in the Negro population
which come anywhere near such a figure and which are also experimentally
independent of the IQ determination, i.e., based on
criteria that do not include measurement of the dependent variable,
viz., IQ I know of none. The criteria used in the study by Amante
et al. were derived from signs of the Bender Gestalt Test, which
itself has a high g loading, making it difficult, if not impossible,
to distinguish reliably between signs of neurological impairment
and sheer mental immaturity. Among neurologically normal white
middle-class elementary school children, Bender-Gestalt perfor-