Familial studies of intelligence: a review.
A summary of 111 studies identified in a survey of the world literature on familial resemblances in measured intelligence reveals a profile of average correlations consistent with a polygenic mode of inheritance. There is, however, a marked degree of heterogeneity of the correlations within familial groupings, which is not moderated by sex of familial pairing or by type of intelligence test used.
D005190:Family; D005260:Female; D005826:Genetics, Medical; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D008297:Male; D011247:Pregnancy; D012737:Sex Factors; D014427:Twins