The Mismeasure of Man by Stephen Jay Gould

(^256) THE MISMEASURE OF MAN
more than inborn ability? Brigham did not deny a small effect for
education (p. 191), but he presented two reasons for attributing
the higher scores of Northern blacks primarily to better biology:
first, "the greater admixture of white blood" among Northern
blacks; second, "the operation of economic and social forces, such
as higher wages, better living conditions, identical school privileges,
and a less complete social ostracism, tending to draw the more
intelligent negro to the north" (p. 192).
Brigham faced the greatest challenge to hereditarianism on the
issue of immigration. Even Yerkes had expressed agnosticism—the
only time he considered a significant alternative to inborn
biology—on the causes of steadily increasing scores for immigrants
who had lived longer in America (see p. 251). The effects were
certainly large, the regularity striking. Without exception (see chart
on p. 251), each five years of residency brought an increase in test
scores, and the total difference between recent arrivals and the
longest residents was a full two and a half years in mental age.
Brigham directed himself around the appalling possibility of
environmentalism by arguing in a circle. He began by assuming
what he intended to demonstrate. He denied the possibility of
environmental influence a priori, by accepting as proven the highly
controversial claim that Beta must measure unadulterated innate
intelligence, whatever Alpha may be doing with its requirement of
literacy. The biological basis of declining scores for recent immi-
grants can then be proven by demonstrating that decrease on the
combined scale is not an artifact of differences in Alpha only:
The hypothesis of growth of intelligence with increasing length of res-
idence may be identified with the hypothesis of an error in the method of
measuring intelligence, for we must assume that we are measuring native
or inborn intelligence, and any increase in our test score due to any other
factor may be regarded as an error. ... If all members of our five years of
residence groups had been given Alpha, Beta, and individual examina-
tions in equal proportions, then all would have been treated alike, and the
relationship shown would stand without any possibility of error (p. 100).
If the differences between residence groups are not innate,
Brigham argued, then they reflect a technical flaw in constructing
the combined scale from varying proportions of Alphas and Betas;
they cannot arise from a defect in the tests themselves, and there-
fore cannot, by definition, be environmental indicators of increas-
ing familiarity with American customs and language.