34 & THE MISMEASURE OF MAN
Thurstone on the uses of factor analysts
Thurstone sometimes advanced grandiose claims for the
explanatory scope of his work. But he also possessed a streak of
modesty that one never detects in Burt or Spearman. In reflective
moments, he recognized that the choice of factor analysis as a
method records the primitive state of knowledge in a field. Factor
analysis is a brutally empirical technique, used when a discipline
has no firmly established principles, but only a mass of crude data,
and a hope that patterns of correlation might provide suggestions
for further and more fruitful lines of inquiry. Thurstone wrote
(1935, p. xi):
No one would think of investigating the fundamental laws of classical
mechanics by correlational methods or by factor methods, because the laws
of classical mechanics are already well known. If nothing were known
about the law of falling bodies, it would be sensible to analyze, factorially,
a great many attributes of objects that are dropped or thrown from an
elevated point. It would then be discovered that one factor is heavily
loaded with the time of fall and with the distance fallen but that this factor
has a zero loading in the weight of the object. The usefulness of the factor
methods will be at the borderline of science.Nothing had changed when he revised The Vectors of Mind (1947,
p. 56):
The exploratory nature of factor analysis is often not understood. Fac-
tor analysis has its principal usefulness at the borderline of science....
Factor analysis is useful, especially in those domains where basic and fruit-
ful concepts are essentially lacking and where crucial experiments have
been difficult to conceive. The new methods have a humble role. They
enable us to make only the crudest first map of a new domain.Note the common phrase—useful "at the borderline of sci-
ence." According to Thurstone, the decision to use factor analysis
as a primary method implies a deep ignorance of principles and
causes. That the three greatest factorists in psychology never got
beyond these methods—despite all their lip service to neurology,
endocrinology, and other potential ways of discovering an innate
biology—proves how right Thurstone was. The tragedy of this tale
is that the British hereditarians promoted an innatist interpretation
of dominant g nonetheless, and thereby blunted the hopes of mil-
lions.