THE REAL ERROR OF CYRIL BURT 343
the same argument and ask whether this correlation reflects some
higher or more basic cause? The oblique axes of a simple structure
for mental tests are usually positively correlated (as in Fig. 6.11).
May not the cause of this correlation be identified with Spearman's
g? Is the old general factor ineluctable after all?
Thurstone wrestled with what he called this "second-order" g.
I confess that I do not understand why he wrestled so hard, unless
the many years of working with orthogonal solutions had set his
mind and rendered the concept too unfamiliar to accept at first. If
anyone understood the geometrical representation of vectors, it
was Thurstone. This representation guarantees that oblique axes
will be positively correlated, and that a second-order general factor
must therefore exist. Second-order g is merely a fancier way of
acknowledging what the raw correlation coefficients show—that
nearly all correlation coefficients between mental tests are positive.
In any case, Thurstone finally bowed to inevitability and admit-
ted the existence of a second-order general factor. He once even
described it in almost Spearmanian terms (1946, p. 110):
iere seems to exist a large numbei of special abilities that can be identi-
fied as primary abilities by the factorial methods, and underlying these
special abilities there seems to exist some central energizing factor which
promotes the activity of all these special abilities.
It might appear as if all the sound and fury of Thurstone's
debate with the British factorists ended in a kind of stately compro-
mise, more favorable to Burt and Spearman, and placing poor
Thurstone in the unenviable position of struggling to save face. If
the correlation of oblique axes yields a second-order g, then
weren't Spearman and Burt right all along in their fundamental
insistence upon a general factor? Thurstone may have shown that
group factors were more important than any British factorist had
ever admitted, but hadn't the primacy of g reasserted itself?
Arthur Jensen (1979) presents such an interpretation, but it
badly misrepresents the history of this debate. Second-order g did
ot unite the disparate schools of Thurstone and the British fac-
orists; it did not even produce a substantial compromise on either
'de. After all, the quotes I cited from Thurstone on the futility of
nking by IQ and the necessity of constructing profiles based on
nmary mental abilities for each individual were written after he