SPEARMAN’S MODEL of GENERAL MENTAL ABILITY
Charles Spearman (1904, 1927) advanced the notion of a general mental ability factor underlying all intelligent behavior (see Thorndike, 1990a, 1990b).
According to Spearman’s theory, intelligence consists of one general factor (g) plus a large number of specific factors. Spearman’s referred to as psychometric g (or simply g), was based on the well-documented phenomenon that when a set of diverse ability tests are administered to large unbiased samples of the population, almost all of the correlations are positive. This phenomenon is called positive manifold, which, according to Spearman, resulted from the fact that all tests, no matter how diverse, are influenced by g. For Spearman, g could best be conceptualized in terms of mental energy.
{(General mental ability) g
- S1 (Numerical reasoning)
- S2 (Vocabulary)
- S3 (Mechanical skill)
According to the model, intelligence can be viewed in terms of one general underlying factor (g) and a large number of specific factors (S1, S2, … Sn). Thus, intelligence can be viewed in terms of g (general mental ability) and S (specific factors).}
Spearman developed a statistical technique called factor analysis (Willis, Dumont, & Kaufman, 2011). Factor analysis is a method for reducing a set of variables or scores to a smaller number of hypothetical variables called factors. Through factor analysis, one can determine how much variance a set of tests or scores has in common (Abbott, Amtmann, & Munson, 2003; Lorenzo Seva, 2003; Timmerman & Kiers, 2003). This common variance represents the g factor. The g in a factor analysis of any set of mental ability tasks can be represented in the first unrotated factor in a principal components analysis (Saccuzzo, Johnson, & Guertin, 1994). Spearman found that, as a general rule, approximately half of the variance in a set of diverse mental-ability tests is represented in the g factor. Today, Spearman’s g “is the most established and ubiquitous predictor of occupational and educational performance” (Willis, Dumont, & Kaufman, 2011).
Implications of General Mental Intelligence (g)
The concept of general intelligence implies that a person’s intelligence can best be represented by a single score, g, that presumably reflects the shared variance underlying performance on a diverse set of tests. True, performance on any given individual task can be attributed to g as well as to some specific or unique variance.
The gf-gc Theory of Intelligence
There are two basic types of intelligence: fluid ( f ) and crystallized (c).
Fluid intelligence can best be thought of as those abilities that allow us to reason, think, and acquire new knowledge (Kane & Engle, 2002; Primi, 2002; Stankov, 2003).
Crystallized intelligence, by contrast, represents the knowledge and understanding that we have acquired (Bates & Shieles, 2003; Horn & Masunaga, 2006). You might think of this distinction in terms of the abilities that allow us to learn and acquire information (fluid) and the actual learning that has occurred (crystallized).
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