<P> Louis Leon Thurstone was born in Chicago, Illinois, to Swedish immigrant parents . Thurstone originally received a masters in mechanical engineering from Cornell University in 1912 . Thurstone was offered a brief assistantship in the laboratory of Thomas Edison . In 1914, after two years as an instructor of geometry and drafting at the University of Minnesota, he enrolled as a graduate student in psychology at the University of Chicago (Ph. D., 1917). He later returned to the University of Chicago (1924--1952) where he taught and conducted research . In 1952, he established the L.L. Thurstone Psychometric Laboratory at the University of North Carolina at Chapel Hill . </P> <P> Thurstone was responsible for the standardized mean and standard deviation of IQ scores used today, as opposed to the Intelligence Test system originally used by Alfred Binet . He is also known for the development of the Thurstone scale . </P> <P> Thurstone's work in factor analysis led him to formulate a model of intelligence center around "Primary Mental Abilities" (PMAs), which were independent group factors of intelligence that different individuals possessed in varying degrees . He opposed the notion of a singular general intelligence that factored into the scores of all psychometric tests and was expressed as a mental age . In 1935 Thurstone, together with EL Thorndike and JP Guilford founded the journal Psychometrika and also the Psychometric Society, going on to become the society's first President in 1936 . Thurstone's contributions to methods of factor analysis have proved valuable in establishing and verifying later psychometric factor structures, and has influenced the hierarchical models of intelligence in use in intelligence tests such as WAIS and the modern Stanford - Binet IQ test . </P> <P> The seven primary mental abilities in Thurstone's model were verbal comprehension, word fluency, number facility, spatial visualization, associative memory, perceptual speed, and reasoning . </P>

Who proposed the concept of primary mental abilities
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