THE REAL ERROR OF CYRIL BURTing the particular kind of operation. These neural groups would thus
function as alternative "engines" into which the common supply of
"energy" could be alternatively distributed. Successful action would always
depend, partly on the potential of energy developed in the whole cortex,
and partly on the efficiency of the specific group of neurons involved. The
relative influence of these two factors could vary greatly according to the
kind of operation; some kinds would depend more on the potential of the
energy, others more on the efficiency of the engine (1923, pp. 5-6).
The differing g-loadings of tests had been provisionally explained:
one mental operation might depend primarily upon the character
of its engine (high s and low ^-loading), another might owe its sta-
tus to the amount of general energy involved in activating its
engine (highg--loading).
Spearman felt sure that he had discovered the basis of intelli-
gence, so sure that he proclaimed his concept impervious to dis-
proof. He expected that a physical energy corresponding with g
would be found by physiologists: "There seem to be grounds for
hoping that a material energy of the kind required by psychologists
will some day actually be discovered" (1927, p. 407). In this discov-
ery, Spearman proclaimed, "physiology will achieve the greatest of
its triumphs" (1927, p. 408). But should no physical energy be
found, still an energy there must be—but of a different sort:
And should the worst arrive and the required physiological explana-
tion remain to the end undiscoverable, the mental facts will none the less
remain facts still. If they are such as to be best explained by the concept of
an underlying energy, then this concept will have to undergo that which
after all is only what has long been demanded by many of the best psychol-
ogists—it will have to be regarded as purely mental (1927, p. 408).
Spearman, in 1927 at least, never considered the obvious alterna-
tive: that his attempt to reify g might be invalid in the first place.
Throughout his career, Spearman tried to find other regulari-
ties of mental functioning that would validate his theory of general
energy and specific engines. He enunciated (1927, p. 133) a "law of
constant output" proclaiming that the cessation of any mental
activity causes others of equal intensity to commence. Thus, he rea-
soned, general energy remains intact and must always be activating
something. He found, on the other hand, that fatigue is "selectively
transferred"—that is, tiring in one mental activity entails fatigue in
some related areas, but not in others (1927, p. 318). Thus, fatigue