General intelligence: is g a real, unitary factor underlying all cognition?

Charles Spearman, answered from the texts and cited to the page.

The position in brief

The universal positive correlation among cognitive tasks — that whoever excels at one tends to excel at all — is a fact, and it demands a cause.1 That cause is g, a general factor entering in some degree into every intellectual performance, alongside a factor specific to each task. g is not a guess; it is what the correlations, rightly analysed, compel.234

Sources

  1. In general, it seems quite as good as, if not better than, that usually reached in determining the mechanical equivalent of heat and thus establishing the law of conservation of physical energy. UNIVERSALITY OF G REQUIRED GENERAL SURVEY OF COGNITION. Use of Fundamental Laws. The Apprehension of One's Own Ex- perience. The Eduction of Relations. The Eduction of Correlates. DETECTION OF G WITH ALL TEN RELATIONS.
    The Abilities of Man, p. 161
  2. At one extreme lay the talent for classics, where the ratio of the influence of g to that of s was rated to be as much as 15 tox. At the other extreme was the talent for music, where the ratio was only 1 to 4." Here at once we have before us the essence of the whole doctrine, the seedling from which all else has sprung.
    The Abilities of Man, pp. 75–76
  3. In scoring, the speed and the accuracy were compounded into a single index of efficiency. The actual scores were as follows: With prescribed letters. No. of letters. With prescribed; 4: 8 relation. Voune-bnentio..gc0.
    The Abilities of Man, pp. 266–267
  4. Such a factoi as this can scarcely be given the title of " intelligence " at all; being evoked to explain the correlations that exist between even the most diverse sorts of c<gnitive performance, it does not deserve a name appropriate to any one particular sort. On this view, accordingly, the name is commonly written in inverted commas, or else replaced bv the simple letter g.
    The Nature of Intelligence and the Principles of Cognition

Where the argument is made

  • "General Intelligence, Objectively Determined and Measured" (1904)
  • The Abilities of Man (1927)

How the argument was received

That SOME general factor is required by the positive manifold I hold firmly; that g is a single "energy" of the mind rather than the summit of a hierarchy of abilities is the stronger claim, and the group factors I long resisted I came in the end to admit alongside it. The fact is the correlation; g is its best, not its only conceivable, explanation.