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Spearman

Spearman (1904) gave persons tests of many different kinds of cognitive ability. When he examined the correlations of these tests with each other, he found that all the correlations were positive, and called this the "positive manifold." The positive manifold leads to a large first factor derived from factor analysis, dubbed general intelligence, or g. The positive manifold implies that, for example, scores on a vocabulary test will correlate positively with scores on a mathematics test. Therefore, it is unimportant which particular tests are used to assess general intelligence--they all intercorrelate highly anyway (this is called the principle of indifference of the indicator).

"Positive manifold is not the same thing as the first factor or g. Positive manifold is the idea that all the variables are positively correlated. (If you think of them as all vectors in a space, they are all going out in the same quadrant.) That they are positively manifolded allows one to find a g factor on which they all have positive loadings. Not all first factors are general factors (if the data are not positvely manifolded then some of the loadings on the first factor will be negative)" (W. Revelle, personal communication, December 20, 1998).

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	Intelligence A: Elementary Information Processing	Intelligence B: Acquired Problem-Solving Skills	Intelligence C: Artifact of Averaging Unlike Abilities
Spearman	Positive Manifold
Binet			Intelligence Quotient
Cattell	Fluid Intelligence	Crystalized Intelligence
Eysenck	Intelligence A	Intelligence B	Intelligence C
Galton	Neural Processing Speed
Gould			Reified Abstraction
Jensen	Neural Processing Speed
Sternberg		Practical Intelligence	Analytic (Academic) Intelligence
Thurstone		Primary Mental Abilities
Wallach and Wing		Cognitive Vitality
	Intelligence A: Elementary Information Processing	Intelligence B: Acquired Problem-Solving Skills	Intelligence C: Artifact of Averaging Unlike Abilities

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Reference

Spearman, C. (1904). "General intelligence" objectively determined and measured. American Journal of Psychology, 15, 201-293.

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Last modified January 1999
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