8 THE FACTORS OF THE MIND

and therefore only a few unitary traits in the mind ; but
types exist in great numbers.35 *•

It is frequently implied that these * factors of the mind '
are innate factors—fundamental elements in the individual's
mental endowment handed on to him at birth. 'Thus, in
one of the earliest investigations on intelligence tests, an
attempt was made to show that the factor which they tested
was not only general but also inborn ([16], pp. 169 f.).
And some of the earlier investigations into type-factors,
particularly those that appeared to be associated with
temperament, race, or sex, suggested the possibility that the
most fundamental of all would be those attributable to
genetic elements, obeying Mendclian laws and producing
traits either linked or segregating freely.* It is, however,
somewhat unfortunate that the term c factor ' is used for
both conceptions—the statistical factors that we are dis-
cussing here and the genetic factors responsible for heredi-
tary resemblances : the common name tempts the lay render
and the student to identify the two.

1 Stephenson [96], p. 209.

2 Cf. Burt,£ The Inheritance of Mental Characters' ([22], pp, iH8 /*/ .^/,)
and * The Mental Differences between the Sexes' ([23], pp. 380 ?t .t/y.). The
experimental data reported in these early papers gave, so it seemed to nn% a
strong support to the notion of inheritable group-factors, at a time when the
existence of group-factors was generally doubted by psychological faetorists.
The most obvious but by no means the only instances appeared to be certain
well-marked sensory anomalies, such as colour blindness, for which (at any
rate in certain forms) the pedigrees show a distribution very similar to that of
haemophilia and other sex-linked recessives. Red-green vision h obviously
not a general factor, nor yet a specific factor peculiar to a single test. Nor
could it be explained away by arguing that u most so-called group-factors
would appear to be the result of education or experience, and so fonn only
apparent exceptions to the two-factor theory," Similar hints of a possible
sex-linkage were found in other forms of sensory capacity, in imagery,
memory, the verbal factor, the manual factor, the numerical factor, ami
certain temperamental tendencies traceable to sex-differences in the en-
docrine glands—characteristics closely related to recognisable group-factors
found in other factorial inquiries. The studies of racial types, combining
physical with temperamental traits, also suggested the probability of an
ultimate discrete basis. But in all such cases the relation between the
* manifest types' and the (latent genetic typesy appeared extremely indirect
and complex, so that for all practical purposes it seemed safer to talk " not
of mental types, but rather of mental tendencies " (see below, p. 246),