The theory of fluid and crystallized intelligence propounded 20 years ago by the author has since accumulated support. However, the crucial issue of whether 1 or 2 general factors subtend intellectual performances has lacked an experiment adequately designed for accurate, determinate, simple-structure rotation at the 2nd order. By factoring culturally embedded with culture-fair intelligence measures on a background of pure personality primaries (N = 277 7th and 8th grade boys and girls), it is shown that 2 general factors indeed exist. A review, with some mathematical formulations, is given of the theory's implications for the nature-nurture ratio, brain injury, standard deviaiton of the IQ, growth curves, the concept of a relational difficulty hierarchy, test standardization, and the relative validities of traditional and culture-fair intelligence tests. (PsycINFO Database Record (c) 2019 APA, all rights reserved)

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