Challenges to g
Viewpoints and theories antithetical, or in some cases mistakenly thought to be antithetical, to the large body of psychometric evidence supporting the presence of a predominant general factor, g, in the domain of mental abilities are reviewed. The proponents of the specificity doctrine, which holds that mental tests measure only a collection of bits of knowledge and skills that happen to be valued by the dominant culture in a society, as well as those who hold that individual differences in mental abilities reflect only differences in opportunities for learning certain skills, largely of a scholastic nature, or the contextualists who claim that mental ability is not general but is entirely specific to particular tasks and circumstances, have not produced any empirical evidence that contradicts the existence of the ubiquitous g factor found in any large and diverse collection of mental tests. There are, however, more rigorous critiques of g.
Guilford's Structure-of-Intellect (SOI) model, which claims 150 separate abilities, is supported only by a type of factor analysis that mathematically forces a large number of narrow factors to be uncorrelated, even though all the various ability tests that are entered into the analysis are correlated with one another. Guilford's claim of zero correlations between ability tests is unsupported by evidence; the few zero and negative correlations that are found are attributable to sampling error and other statistical limitations.
Cattell's theory of fluid intelligence (Gf) and crystallized intelligence (Gc) is reflected as second-order factors in tests that are either highly culture-reduced (Gf) or highly culture-specific (Gc) and is particularly valid in culturally and educationally heterogeneous populations. The greater the homogeneity in the population, however, the higher is the correlation between Gf and Gc. The correlation