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

210 Educability and Group Differences
the correlation between race and the genetic component, rRG
= 0*18, is small - and it could be zero or even a negative correlation,
given somewhat more extreme values of rRX and rR2.
Taking the example further, suppose that these correlations
were reversed, that is, the mean racial difference is greater for the
test with the higher heritability. Then
0-4 = 0-7rRG+0‘7rRE
0-5 = 0-9rRG + 0-45rK£
And here we see that the racial difference is largely accounted for
by the correlation of race with the genetic component of test
variance. It would be desirable to obtain the relevant data on more
than two tests differing from one another in heritability and in
their correlations with race, so that the system of equations
would be overdetermined, thereby permitting a test of the
adequacy of this model in accounting for the empirically obtained
correlations.
At present we have no ideal data for this kind of analysis.
However, it can be noted that such data as do exist seem to be
less in accord with the first example above than with the second.
Tests that appear to be more culture-loaded, contrary to popular
belief, usually show smaller racial mean differences than tests
which are designed to be more culture-fair. For example, Negroes
do less well, relative to whites, on Raven’s Progressive Matrices
Test than on the much more obviously culture-loaded Peabody
Picture Vocabulary Test. (Although the reverse is true for another
socioeconomically disadvantaged group, the Mexican-Americans.)
Also, contrary to popular belief, scholastic achievement tests,
which have generally been found to have h2 values around 0-4
to 0-6 (as compared to 0-7 to 0-8 for intelligence tests), generally
show a smaller mean Negro-white difference than is found with
intelligence tests. Comparison of large representative samples of
Negro and white children in grades 1 through 8 in a California
school district, for example, showed an average race difference of
0-66(7 on a battery of scholastic achievement tests and a difference
of 1-08(7 on a set of non-verbal intelligence tests (Jensen, 1971).
The cultural contents of the two sets of tests differ strikingly, yet
both sets of tests have their largest factor loadings on the g factor