L. L. Thurstone





  • Cornell University, Master of Engineering (1912)
  • University of Chicago , Ph.D. in Psychology, (1914-1917)
  • Division of Applied Psychology at the Carnegie Institute of Technology, assistantship (1915-1917)


  • Assistant to Thomas A. Edison (1912)
  • Taught descriptive geometry and drafting, College of Engineering, University of Minnesota (1912-1914)
  • Professor, Carnegie Institute of Technology (1917-1923)
  • Institute for Government Research, Washington DC (1923)
  • Professor, University of Chicago (1924-1952)
  • President of American Psychological Association (1932)
  • First President of the American Psychometric Society (1936)
  • Director, Psychometric Laboratory, University of North Carolina (1952-1955)
  • Numerous awards, including:  Best Article, American Psychological Association (1949); Centennial Award, Northwestern University (1951); Honorary Doctorate, University of Göteborg (1954).

Definition of Intelligence

“Intelligence, considered as a mental trait, is the capacity to make impulses focal at their early, unfinished stage of formation.  Intelligence is therefore the capacity for abstraction, which is an inhibitory process (Thurstone, 1924/1973 p. 159).”

Major Contributions

  • Theory of Primary Mental Abilities
  • Developed the statistical technique of multiple-factor analysis

Ideas and Interests

Louis Leon Thurstone made significant contributions in many areas of psychology, including psychometrics, statistics, and the study of human intelligence. He developed methods for scaling psychological measures, assessing attitudes, and test theory, among many other influential contributions. He is best known for the development of new factor analytic techniques to determine the number and nature of latent constructs within a set of observed variables.

The new statistical techniques developed by Thurstone provided the necessary tools for his most enduring contribution to psychology: The Theory of Primary Mental Abilities, a model of human intelligence that challenged Charles Spearman’s then-dominant paradigm of a unitary conception of intelligence. Spearman, using an earlier approach to factor analysis, found that scores on all mental tests (regardless of the domain or how it was tested) tend to load on one major factor. Spearman suggested that these disparate scores are fueled by a common metaphorical “pool” of mental energy. He named this pool the general factor, or g (Spearman, 1904).

Thurstone argued that g was a statistical artifact resulting from the mathematical procedures used to study it. Using his new approach to factor analysis, Thurstone found that intelligent behavior does not arise from a general factor, but rather emerges from seven independent factors that he called primary abilities: word fluency, verbal comprehension, spatial visualization, number facility, associative memory, reasoning, and perceptual speed (Thurstone, 1938). Furthermore, when Thurstone analyzed mental test data from samples comprised of people with similar overall IQ scores, he found that they had different profiles of primary mental abilities, further supporting his model and suggesting that his work had more clinical utility than Spearman’s unitary theory. However, when Thurstone administered his tests to an intellectually heterogeneous group of children, he failed to find that the seven primary abilities were entirely separate; rather he found evidence of g. Thurstone managed an elegant mathematical solution that resolved these apparently contradictory results, and the final version of his theory was a compromise that accounted for the presence of both a general factor and the seven specific abilities. This compromise helped lay the groundwork for future researchers who proposed hierarchical theories and theories of multiple intelligences (Ruzgis, 1994).

Selected Publications

Thurstone, L. L. (1924/1973). The Nature of Intelligence.  London:  Routledge.

Thurstone, L. L. (1934). The vectors of the mindAddress of the president before the American Psychological Association, Chicago meeting, September, 1933. First published in Psychological Review, 41, 1-32.

Thurstone, L. L. (1938). Primary mental abilities. Chicago: University of Chicago Press.

Thurstone, L. L. (1947).  Multiple-Factor Analysis.  Chicago:  University of Chicago Press.

Thurstone, L. L., & Thurstone, T. G. (1941). Factorial studies of intelligence. Chicago: University of Chicago Press.


Ruzgis, P. (1994).  Thustone, L.L. (1887-1955).  In R. J. Sternberg (Ed.).  Encyclopedia of human intelligence (pp. 1081-1084).  New York:  Macmillan.

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

Thurstone, L. L. (1924/1973). The Nature of Intelligence.  London:  Routledge.

Thurstone, L. L. (1938). Primary mental abilities. Chicago: University of Chicago Press.

Image Courtesy of the National Library of Medicine

L.L. Thurstone Psychometric Laboratory