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(1954) Structural and functional organization of the mammalian cerebral cortex. The correlation of neurone density with brain size. Cortical density in the finwhale with a not on the cortical neurone density in the Indian elephant. Journal of Comparative Neurology 101:19-53. [TWD] von Economo, C. & Koskinas, G. N. (1925) Die Cytoarchitektonik der Hirnrinde deserwachsenen Menschen. Springer. [rllG] Zilles, K. & Rehkamper, G. (1988) The initial brain concept: A work in progress. Behavioral and Brain Sciences 11:105-6. [TWD] Commentary on Camilla Persson Benbow (1988) Sex differences in mathematical reasoning ability in intellectually talented preadolescents: Their nature, effects, and possible causes. BBS 11:169—232. Abstract of the original article: Several hundred thousand intellectually talented 12- to 13-year-olds have been tested nationwide over the past 16 years with the mathematics and verbal sections of the Scholastic Aptitude Test (SAT). Although no sex differences in verbal ability have been found, there have been consistent sex differences favoring males in mathematical reasoning ability, as measured by the mathematics section of the SAT (SAT-M). These differences are most pronounced at the highest levels of mathematical reasoning, they are stable over time, and they are observed in other countries as well. The sex difference in mathematical reasoning ability can predict subsequent sex differences in achievement in mathematics and science and is therefore of practical importance. To date a primarily environmental explanation for the difference in ability has not received support from the numerous studies conducted over many years by the staff of Study of Mathematically Precocious Youth (SMPY) and others. We have studied some of the classical environmental hypotheses: attitudes toward mathematics, perceived usefulness of mathematics, confidence, expectations/encouragement from parents and others, sex-typing, and differential course-taking. In addition, several physiological correlates of extremely high mathematical reasoning ability have been identified (left-handedness, allergies, myopia, and perhaps bilateral representation of cognitive functions and prenatal hormonal exposure). It is therefore proposed that the sex difference in SAT-M scores among intellectually talented students, which may be related to greater male variability, results from both environmental and biological factors. "Small" | scenario John G. Borkowski Department of Psychology, University of Notre Dame, Notre Dame, IN 46556 Benbow (1988a) has provided a provocative account of various possible developmental origins for sex differences in mathe- matical reasoning. Her thesis boils down to the following ques- tion: Do biological or social explanations account for the 30- point spread on the SAT-M that differentiates boys and girls? One point to keep in mind in locating the origin of this difference is that the standardized data amount to about 2 items (of 40) on the SAT-M. The point here is not to trivialize the sex differences reported by Benbow, Stanley, and colleagues - for they predict later achievements better than other indicators - but rather to focus attention more on test items per se and then to identify plausible reasons for differential performance. It is doubtful that highly complex cognitive interpretations - such as advanced solution planning, speed of access, spatial abilities, or working memory capacity - will prove useful in explaining the consistent but rather small behavioral differences (found on a few items) in the SAT-M. Because the additional errors on unattempted answers, characteristic of highly compe- tent girls, are spread across many types of items — each requir- ing a different set of interactive cognitive components - it is unlikely that current approaches to task analysis could ever explain the cognitive correlates of sex differences in mathe- matical reasoning (assuming that stable correlates exist at all). Cognitive science is not yet up to the challenge of explaining diverse error patterns found on the SAT-M. Nor do the interpretations based on physiological correlates and prenatal hormonal differences appear to be plausible sources of the 2-item difference on the SAT-M that distinguishes boys and girls. First, none of the potential biological correlates has been strongly linked to the Study of Mathematically Pre- cocious Youth (SMPY) population studied by Benbow, Stanley, and colleagues. Furthermore, testosterone differences detected at birth do not predict a wide range of social and academic behaviors in later life. It is hence speculative to assert that small differences on the SAT-M would be related to early hormonal differences. In addition, the cortical bases of handedness and myopia seem only tangentially related to the substrates that underlie mathematical ability, as previous commentators have noted. Perhaps a more important question is whether socialization hypotheses have yet been adequately tested. For example, 190 BEHAVIORAL AND BRAIN SCIENCES (1990) 13:1