English Psychologist



  • Studied engineering in college
  • University of Leipzig , Ph.D. in experimental psychology (under Wilhelm Wundt) (1906)


Major Contributions

  • “First systematic psychometrician” and father of classical test theory (Jensen, 1994)
  • Pioneer of the statistical technique called factor analysis
  • Discovered a general factor (g) in correlations among mental tests

Definition of Intelligence

“As regards the delicate matter of estimating ‘Intelligence,’ the guiding principle has been not to make any a priori assumptions as to what kind of mental activity may be thus termed with greatest propriety. Provisionally, at any rate, the aim was empirically to examine all the various abilities having any prima facie claims to such title, ascertaining their relations to one another and to other functions (Spearman, 1904, p. 249-250).”

Ideas and Interests

Charles Spearman started his psychology career relatively late in life, beginning his Ph.D. studies at age 34 and accepting his first university position at age 42. Yet, his technical and theoretical contributions to the development of intelligence research as a scientific enterprise cannot be overstated. He was the first to offer a tenable psychometric definition of intelligence, and is therefore considered to be the father of classical test theory (Jensen, 1994). In a famous article, “General Intelligence’ Objectively Determined and Measured” (1904), Spearman proposed the idea that intelligent behavior is generated by a single, unitary quality within the human mind or brain. Spearman derived this theoretical entity, called the general factor, or simply g, through a new statistical technique that analyzed the correlations among a set of variables. This technique, called factor analysis, demonstrated that scores on all mental tests are positively correlated; this offered compelling evidence that all intelligent behavior is derived from one metaphorical pool of mental energy. Although proponents of multiple intelligence theory reject this interpretation, factor analysis remains one of the most important tools in 21 st century intelligence research.


Like his predecessors James McKeen Cattell and Francis Galton, Spearman had been a student in William Wundt’s experimental psychology laboratory, and like Cattell and Galton, he found the idea of a single, biologically-based source of human intelligence appealing. However, earlier researchers had failed to discover any statistically meaningful relationships between mental tests; since the tests did not correlate with one another, it appeared that they could not be measuring the same thing; that is, they could not all be measuring “intelligence.” (See the Wissler Controversy Hot Topic). Spearman was able to demonstrate that uncorrected correlation coefficients will always underestimate the true degree of the relationships among any set of variables, and that this underestimation is particularly severe when the scores on the tests have a restricted range of values, as was the case with Cattell’s anthropometric tests. Spearman derived a statistical formula to correct for this underestimation. When he applied his corrective procedure to Cattell’s data, he found substantial positive correlations among all the variables measured by the mental tests, and also between the mental tests and other variables that could be considered measures of mental ability. Through an extended formula, he was able to demonstrate that a common source of variance accounted for the correlations among all the mental tests, and he called this the general factor, or g. This finding reinvigorated the idea that intelligent behavior arises from a single metaphorical entity, and it forms the foundation for many present-day theories of human intelligence (Jensen, 1994).

Selected Publications

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

Spearman, C. (1923). The nature of ‘intelligence’ and the principles of cognition (2 nd ed.). London: Macmillan.

Spearman, C. (1927). The abilities of man. London: Macmillan.

Spearman, C. (1930). Autobiography. In C. Murchison (Ed.), A history of psychology in autobiography (Vol. 1, pp. 199-333). Worcester, MA: Clark University Press.

Spearman, C., & Jones, L. W. (1950). Human ability. London: Macmillan.


Jensen, A. R. (1994). Spearman, Charles Edward. In R. J. Sternberg (Ed.), Encyclopedia of intelligence (Vol. 1, pp. 1007-1014). New York: Macmillan.

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