Stephen Jay Gould's argument against IQ testing is based on his critique of the factor analytic derivation of g (a unitary quality underlying all mental cognitive activity) as the principal component which can resolve the greatest amount of information from a battery of tests. Gould does not really argue against the cultural or class and race biases of the test--a more suitable topic for what is supposed to be a popular critique of the IQ industry--but the attempt to resolve test information into a principal component, instead of rotating factor axes from their principal component to new positions until multiple clusters of intelligence are identified and g has disappeared. That is, Gould argues that g is a reification, an artefact of a statistical technique, and the attempt to simplify test information into a principal component is ideologically (or metaphorically) driven.
But on these grounds his argument is shaky. As Clark Glymour puts it, "Gould claims that factor analysis produces conjectures about the existence of unobserved properties solely because the properties, if they existed, would explain features of data; in his phrasing factor analysis 'reifies' unobserved quantities, and he thinks 'reification' is a Big Mistake. I wonder whether he thinks atoms and molecules and their weights are Big Mistakes as well, and if not, why not." (Scientists Respond the Bell Curve, p. 259)
[Justin S then argued persuasively that Glymour had simply dropped the ball in terms of this specific criticism; Justin showed that Gould argues specifically against the reification of g, not the postulation of any unobservable causal mechanism.]
What makes Gould's argument fascinating is his explication of the metaphor of the mind which drove Spearman to discover a method--factor analysis-- by which to derive from a battery of tests g.
"Thus caught up in physics envy again, Spearman described his own 'adventurous step of deserting all actually observable phenomena of the mind and proceeeding instead to invent an underlying something which --by analogy with physics--has been called mental energy.'. Spearman looked to the basic property of g--its influence in varying degree, upon mental operations--and tried to imagine what physical entity best fitted such behavior. What else, he argued, but a form of energy pervading the entire brain and activitating a set of specific 'engines,' each with a definite locus. The more energy, the more general activation, the more intelligence...If g pervades the entire cortex, as a general energy, then the s-factors for each test must have more definite locations. They must represent specific groups of neurons, activating in different ways by the energy identified with g. The s-factors, Spearman wrote (and not merely in metaphor), are engines fueled by a circulating g." (Mismeasure of Man, 296). -------------
The most comprehensive defense of the factor analytic derivation of g is in Arthur Jensen's new book, originally titled, The G Factor ( a book surprisingly inept in its evolutionary account of deep racial differences in cognitive abilities, an account moreover which makes no attempt to state with what level of certainty that hypothesis can be put forward). The best introductions to factor analysis are in a textbook, ed. Joseph Hair An Introduction to Multivariate Analysis (if anyone has a spare copy of this textbook they want to sell, I'll pay a fair price) and An Introduction to Factor Analysis by Paul Kline. But Gould's chapter is truly a wonderful summary of what factor analysis attempts to do; he himself claims that it is among the best popular scientific writing he has ever done.
yours, rakesh