An important reason that the average IQ of black people the U.S. is less than that of whites, for instance, is that the grammar and vocabulary of the tests is structured around the norms of the middle class.
譬如美國黑人的智商普遍低於白人，其中一個重要原因括測驗題的語法和字彙全是依中產階級的白人社會習慣所設計的。