¹Some research has shown differences in the relative sizes of the brains of males and
females of the same age, but so far no great differences have been found between people
of the same age but of different ethnic groups. 2Obviously the brain of a small Japanese
teenager is very much smaller than that of a giant Russian boy. But when brain size is
adjusted for size or weight of the body, there does not seem to be great advantage for
either with respect to intelligence. Moreover, in measuring intelligence one has, of
course, to take into account the effects of education and cultural background.