title: Evidence for a low upper limit of heritability of mental test performance in a national sample of twins.
mesh_terms: D002648:Child; D005260:Female; D005823:Genetics; D006801:Humans; D007361:Intelligence Tests; D008297:Male; D011247:Pregnancy; D012737:Sex Factors; D014427:Twins; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic