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Within the narrow limits of two hundred and six pages, Dr. Halstead has compressed a report of twelve years of investigation of the relation between lesions of the brain and "biological" intelligence, which he feels is superior to psychometric, clinical and neurologic concepts of intelligence. Through intensive testing of 237 patients, and through factorial analysis of his results with twenty-seven tests (many of them devised by him for this purpose), he finds "biological" intelligence to consist of four factors: the central integrative field factor, C; the abstraction factor, A; the power factor, P, and the directional factor, D. These are measurably reduced through extirpation of cerebral tissue, and this reduction is expressed in quantitative terms as an impairment index. Part II discusses localization of function in the cerebrum through an analysis of the degree of impairment found after lobectomies in the several lobes, the greatest degree being found in the
Brain and Intelligence: A Quantitative Study of the Frontal Lobes. JAMA. 1948;137(14):1266. doi:10.1001/jama.1948.02890480086045