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

238 Educability and Group Differences
thus more heavily weighted with scholastic achievement than with
intelligence. As was noted previously, achievement scores (a) have
lower heritability than IQ, (b) are more susceptible to family
environmental influences, and (c) generally show smaller racial
differences than does IQ, as is also true in Tulkin’s study when the
social and family variables are not controlled. Controlling these
variables, therefore, should make a greater impression on achievement
than on IQ tests. Even among the several achievement tests
the magnitude of the difference between the upper SES white and
upper SES Negro groups is greater for the less culturally loaded
subject matter. The upper SES white sample exceeds the Negro
upper SES sample, for example, by only 0-18 SD on the language
achievement test but by 0-51 SD on the arithmetic test, a highly
significant difference. When we compare the upper and lower
SES white samples on these two achievement tests, on the other
hand, the reverse occurs: the SES difference is greater for language
than for arithmetic. These results, then, are consistent with the
general finding, which is reviewed in a subsequent section, that
the largest differences between Negroes and whites appear on
tests that are the least culturally loaded. Tulkin’s study also shows
the composite achievement score to be more highly correlated
with verbal IQ than with non-verbal IQ, and the overall Negrowhite
difference is greater on non-verbal IQ. Tulkin’s investigation
might have been more interesting if he had also applied the
covariance control of family variables to non-verbal IQ alone
rather than only to a composite score heavily weighed with
achievement tests.
But as was pointed out, the method of matching racial groups
for SES or other environmental variables and then comparing
their mean IQs cannot tell us anything of importance, except that
the SES matched groups are usually more alike in IQ than
unmatched groups, for some indeterminate combination of genetic
and environmental causes. We can go a step further, however, and
seek a set of circumstances in which environmentalist and genetic
theories should predict opposite results. The environmentalists’
emphasis on equating for SES, and even for parental intelligence,
is based on the idea that the SES variable has a predominantly
causal connection with IQ, and therefore racial IQ differences will
be eliminated to the extent that we are successful in equating SES
and other environmental factors. The logic at least is clear, even