There are, however, sex differences in a number of specific abilities. The conclusion that there is no sex difference in “general intelligence” was reached

in the second decade of the twentieth century by Terman (1916, pp. 69–70) on the basis of his American standardisation sample of the Stanford–Binet test. In recent decades this conclusion was endorsed by many leading authorities. Thus “it is now demonstrated by countless and large samples that on the two main general cognitive abilities – fluid and crystallized intelligence – men and ABT-199 molecular weight women, boys and girls, show no significant differences” (Cattell, 1971, p. 131); “gender differences in general intelligence are small and virtually non-existent” (Brody, 1992, p. 323); “there is no sex difference in general intelligence worth speaking of” (Mackintosh, 1996, p. 567); and “sex differences have not been found in general intelligence” (Halpern, 2000, p. 218). The only challenge to this consensus has come

from Lynn (1994, 1998, 1999), who has argued that males have larger average brain size than females, that brain size is positively correlated with intelligence at a magnitude AZD4547 purchase of approximately .40 (Vernon, Wickett, Bazana, & Stelmack, 2000), and hence that there is a theoretical expectation that males should have higher average intelligence than females. To examine this theoretical expectation, Lynn (1994) proposed that the Wechsler intelligence tests could be taken as among the best measures of general intelligence on the grounds that they provide measures of the major cognitive abilities of verbal, numerical, perceptual, reasoning, spatial, immediate memory, perceptual speed and general knowledge. He then examined the sex difference in eight standardization samples of the Wechsler intelligence tests for children aged 6–16 and showed that boys obtained a higher mean Full Scale IQ by an advantage of 2.25 IQ points. He also showed that in six standardization samples of adults, men obtained a higher mean Full Scale IQ by Oxymatrine an average of 3.08 IQ points.

Despite these results, it has continued to be asserted that “females and males score identically on IQ tests” (Halpern, 2012, p. 233) and that “there is no evidence, overall, of sex differences in levels of intelligence” (Sternberg, 2014, p.178). However, Ellis et al. (2008) recently argued in their book that studies have shown that, although small, there are significant sex differences in intelligence over the years throughout the world. It has also been consistently asserted for approximately a century that while males and females have the same average intelligence, males have greater variability of intelligence than females. An early first statement of this proposition was made by Ellis (1904, p.