1887–1955 · psychometrician, Chicago and Chapel Hill

he engineer Louis Leon Thurstone came to psychology after a spell as an assistant in Thomas Edison's laboratory, and spent his career turning judgments into numbers. He was at the University of Chicago for most of it, and moved to the University of North Carolina in 1952.

what he did

His law of comparative judgment (Thurstone, 1927) treated each judgment as a comparison between noisy internal values. If two weights, or two crimes, or two handwriting samples each produce a spread of impressions, the proportion of times one is judged greater tells you how far apart the spreads are. That is d′ by another route, decades early. He then used the same thinking to argue, in the title of a paper, that attitudes can be measured.

Later he developed multiple factor analysis and argued that intelligence is better described by several primary mental abilities than by one general factor (Thurstone, 1938) [paraphrase, not a quotation]. He was a founder of the Psychometric Society and its journal Psychometrika, and president of the American Psychological Association in 1932.

why he is here

Thurstone's noisy comparisons sit underneath signal detection, and under the pairwise preference judgments used to train reward models today; see reward model.

in the tour: the psychophysics hall has a placard called "A law of comparative judgment" ···

Primary works and sources

1. Thurstone (1927). A law of comparative judgment. Psychological Review. doi:10.1037/h0070288
2. Thurstone (1928). Attitudes Can Be Measured. American Journal of Sociology. doi:10.1086/214483
3. Thurstone (1938). Primary Mental Abilities. Psychometric Monographs no. 1. Chicago: University of Chicago Press.

Try it yourself. [playful] Small toys on the toy shelf that show this in action:   • the line judge — find your Weber fraction for line length

see also

	signal detection — the theory his law anticipates
	annotated: signal detection — where his paper sits
	sycophancy — what pairwise human preferences can teach a model