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

Negro parents regress toward the lower mean of the Negro population,
which makes for a larger regression effect than for white
children, who regress toward the white population mean (which
is about 1 SD higher). High SES Negro parents are more deviant
from their population mean than high SES white parents, and
therefore, because of regression, the high SES Negro children will
resemble their parents less in ability than will the white children.
The same thing holds true for siblings of high IQ Negro children.
Criticisms of studies that control for SES argue that SES, as
it is usually measured in terms of parental education, occupation,
income, etc., is too crude a variable to reflect adequately the
important variables of the environment influencing mental development.
But SES is crude mainly in the sense that it is non-specific;
it summarizes within it many other environmental variables, and
adding more refined variables does not markedly increase a multiple
correlation with either IQ or with race. SES seems to summarize
the larger part of those environmental factors that are most
frequently mentioned as the causes of racial IQ differences.
Actually, rather than controlling too little of the variance, SES
probably controls too much, since within racial groups, at least,
there is undoubtedly a correlation between SES and genetic
factors. Matching racial groups for SES thus matches them not
only for some environmental factors but also to some unknown
extent for genetic factors as well. It is interesting also that when
such matching is carried out, it is noted that the average skin color
of the Negro groups becomes lighter in the higher SES categories,
indicating that genetic factors co-vary with SES, for whatever
reason. Genetic SES intelligence differences are firmly established
within the white population. Matching Negro and white groups
on SES, therefore, is certain to minimize genetic as well as
environmental differences. For this reason, studies that control for
SES are probably biased in favor of the environmentalist hypothesis
and can contribute little or nothing to elucidating the naturenurture
problem, except in those instances where the direction of
the environmental difference between two groups is opposite to
the direction of the IQ difference.
Negative Correlations between Environment and Ability
Recapitulation 359
A number of environmental factors which correlate positively with
mental ability within various population groups were shown to