Do Genes Explain Social Class?
In a textbook published in 1975, Herrnstein and his colleague Roger Brown argued that the measurement of intelligence has been the greatest achievement of twentieth-century scientific psychology. Psychometricians can make a numerical estimate of a person’s intelligence that remains surprisingly stable after the age of five or so, and much convergent evidence suggests that the variations of this measure of intelligence in a population are determined significantly (at least 60 percent) by inheritable factors. As Herrnstein and Murray demonstrate at great length, measured intelligence correlates with success in school, ultimate job status, and the likelihood of becoming a member of the cognitively entitled establishment. But correlation is not causation, and it is possible that staying in school causes IQ to go up (rather than vice versa) or that both IQ and schooling reflect some third causative factor, such as parental attention, nutrition, social class, or motivation. Indeed, nearly ev
