The specificity doctrine, holds that psychometric tests measure nothing other than the specific bits of knowledge and learned skills reflected in the item content of the tests. This prevailing doctrine has influenced the interpretation of test scores and the conceptualization of test validity, as well as the practical use of tests in educational and personnel selection. Opposed to the specificity doctrine is the view that a wide variety of cognitive tests measure in common a few large factors of mental ability, most prominently general intelligence or g. The commonality is not ascribable to common contents of the tests but to common brain processes. Recent massive validity evidence from the use of cognitive tests in personnel selection is consistent with the broad common-factor theory and contradicts the specificity doctrine. The practical and theoretical utility of the construct of g as a general information processing capacity also appears warranted by other lines of evidence independent of factor analysis. (Author)