The Mismeasure of Man by Stephen Jay Gould

222 THE MISMEASURE OF MAN

sons for differences between groups are framed in environmental
terms. Terman presents his old curves for average differences in
IQ between social classes, but he warns us that mean differences
are too small to provide any predictive information for individuals.
We also do not know how to partition the average differences
between genetic and environmental influences:

It is hardly necessary to stress the fact that these figures refer to mean

values only, and that in view of the variability of the IQ within each group

the respective distributions greatly overlap one another. Nor should it be

necessary to point out that such data do not, in themselves, offer any con-

clusive evidence of the relative contributions of genetic and environmental

factors in determining the mean differences observed.

A few pages later, Terman discusses the differences between

rural and urban children, noting the lower country scores and the

curious finding that rural IQ drops with age after entrance to

school, while IQ for urban children of semiskilled and unskilled

workers rises. He expresses no firm opinion, but note that the only

hypotheses he wishes to test are now environmental:

It would require extensive research, carefully planned for the purpose,

to determine whether the lowered IQ of rural children can be ascribed to

the relatively poorer educational facilities in rural communities, and

whether the gain for children from the lower economic strata can be

attributed to an assumed enrichment of intellectual environment that

school attendance bestows.

Autres temps, autres moeurs.

R. M. Yerkes and the Army Mental Tests:

IQ comes of age

Psychology's great leap forward

Robert M. Yerkes, about to turn forty, was a frustrated man in

1915. He had been on the faculty of Harvard University since


1916. He was a superb organizer, and an eloquent promotor of
      his profession. Yet psychology still wallowed in its reputation as
      a "soft" science, if a science at all. Some colleges did not acknowl-
      edge its existence; others ranked it among the humanities and
      placed psychologists in departments of philosophy. Yerkes wished,
      above all, to establish his profession by proving that it could be as