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

Race Differences in Intelligence 169
quantized racial dichotomy (Negro = 0 v. white = 1) and SES
(if the Negro and white groups are of equal size) is +0-53. (The
median SES of the Negroes and whites differs by about one SD.)
The usual argument is that SES does not measure the most
important environmental variables, which, if included in the SES
index, would greatly increase the correlation between the quantized
racial variable and the improved SES index. It is most likely,
however, that a 12-point SES index pulls along with it many other
more subtle environmental factors which are not explicitly
measured by the index. Thus many other environmental indices
combined along with SES in a multiple regression equation will
raise the multiple correlation (R) between ‘environment’ and race
(or between ‘environment’ and IQ) only slightly.
There are a few environmentally relevant variables on which we
can express the (United States) Negro-white difference in terms
of standard deviation units, assuming an approximately normal
distribution of the variable in both populations. These estimates
have been made by Shockley (1969, p. 1432). Based on statistics
for all family annual incomes in the U.S. population from $3,000
to $15,000 from 1947 to 1966, the mean family income of Negroes
was —0-80±0*15 SDs below that of whites. The SD units by
which the Negro mean falls below the white on other variables is:
—0-33 for unemployment rate, —0-52 for completing high school,
—0-87 for children living with both parents, —1*0 for rate below
‘poverty line’. None of these SD differences comes near the 3-2
SDs (for total environmental effects) or 4-48 SDs (for betweenfamilies
environmental effects) derived from the twin studies as
being the environmental difference required to produce a 1 SD
mean IQ difference between two genetically identical populations.
Does a variable seemingly as non-psychological as family
income pull along with it enough other factors reflecting the
qualities of the environment that would affect children’s mental
development such that taking family income into account as an
environmental index would improve the prediction of children’s
IQs (from the parental IQs) over the prediction that would be
derived from a genetic model alone
Data which may help to answer this question are found in
Terman’s (1926) monumental study of gifted children. In 1922,
over 1,500 children with Stanford-Binet IQs of 140 or above were
selected from California schools; their educational and occupational