ABSTRACT
From its beginnings, psychometrics has had a split personality. On the one hand, it has been concerned with practical means of measurement and prediction, including not only the construction of instruments but also the mathematical and statistical bases for obtaining reliable and valid measurements—or what is commonly called “test theory.” On the other hand, the very notion of validity — particularly the notion of “construct validity” (Gulliksen, 1950)—implies that one be at least somewhat bothered by the problem of what a test measures. Tests of “intelligence” have always been the most prominent type of psychometric instrument. However great their interest in practical matters, all the leading figures in psychometrics—Binet, Spearman, Thurstone, and Guilford (to name but a few)—have had an abiding concern for the nature of intelligence; all of them have realized that to construct a theory of intelligence is to construct a theory of cognition. It is not without significance that one of Spearman’s (1924) major works bore the title The Nature of Intelligence and the Principles of Cognition. The same theme was carried by the titles of books by Thurstone (1924) and Guilford (1967).
