as Spearman's hypothesis. They also discuss possible environmental explanations of the gap, such as the observed generational increases in IQ, for which they coin the term Flynn effect. At the close of this discussion, they write: The authors also stress that regardless of the causes of differences, people should be treated no differently. In Part III, the authors also repeat many of the analyses from Part II, but now compare whites to blacks and Hispanics in the NLSY dataset. They find that after controlling for IQ, many differences in social outcomes between races are diminished. The authors discuss the possibility that high birth rates among those with lower IQs may exert a downward pressure on the national distribution of cognitive ability. They argue that immigration may also have a similar effect. At the close of Part III, Herrnstein and Murray discuss the relation of IQ to social problems. Using the NLSY data, they argue that social problems are a monotonically decreasing function of IQ, in other words at lower IQ scores the frequency of social problems increases. Living Together In this final chapter, the authors discuss the relevance of cognitive ability for understanding major social issues in America. Evidence for experimental attempts to raise intelligence is reviewed. The authors conclude that currently there are no means to boost intelligence by more than a modest degree. The authors criticize the "levelling" of general and secondary education and defend gifted education. They offer a critical overview of affirmative action policies in colleges and workplaces, arguing that their goal should be equality of opportunity rather than equal outcomes. Herrnstein and Murray offer a pessimistic portrait of America's future. They predict that a cognitive elite will further isolate itself from the rest of society, while the quality of life deteriorates for those at the bottom of the cognitive scale. As an antidote to this prognosis, they offer a vision of society where differences in ability are recognized and everybody can have a valued place, stressing the role of local communities and clear moral rules that apply to everybody. Policy recommendations Herrnstein and Murray argued the average genetic IQ of the United States is declining, owing to the tendency of the more intelligent having fewer children than the less intelligent, the generation length to be shorter for the less intelligent, and the large-scale immigration to the United States of those with low intelligence. Discussing a