The Bell Curve: Intelligence and Class Structure in American Life.

• Author: Heckman, James J.

Charles Murray and the late Richard Herrnstein have produced a controversial and well-written book about human differences, the sources of human differences, and how we should respond to those differences. The early reactions to the book in the popular press have been emotional and denunciatory, focusing almost exclusively on the authors' discussion of racial differences and the genetic basis for those differences. This is unfortunate. The book is not devoted exclusively to a discussion of racial differences, although it certainly considers them in detail. It is obvious that most reviewers of the book have not read it as a whole, if they have read it at all. It is also clear that in an age of rampant egalitarianism, discussion of differences in cognitive skills remains taboo. The authors deserve much praise for discussing a forbidden subject and thereby initiating a public discussion that challenges the egalitarian presumptions of our day.

Like Robert Reich in The Work of Nations and Mickey Kaus in The End of Equality, the authors are concerned about the growth of economic and social inequality in American society, a topic that dominates many contemporary political discussions. Unlike those authors, Murray and Herrnstein probe more deeply into the personal sources of inequality, devoting considerable attention to the genetic component of personal differences and presenting fresh empirical evidence about an important relationship between their measure of IQ and success in society at large. Like Reich and Kaus, Murray and Herrnstein worry about the consequences for the social order of the growing inequality in economic and social success between the "haves" and the "have nots," and the social and economic partitioning of high-skill, high-IQ persons away from low-skill, low-IQ persons.

This 845-page book covers an enormous and impressive range of topics. Its numerous tables and charts make close reading a challenge. Indeed, all but trained social scientists will be intimidated by the statistical details and by the complicated arguments used by the authors. Even more forbidding to most readers will be the hundreds of pages of footnotes and appendix tables that document the statistical analysis underlying the arguments in the text. Despite all this, the book is organized in easily summarized sections. It is accessible at one level to all readers who are willing to skip the details.

The book contains four parts. Part I updates Herrnstein's 1973 book IQ and the Meritocracy and documents that American society has become more stratified on the basis of intelligence than it was even one generation ago. Merit - treated here as synonymous with IQ - has become concentrated in schools and the workplace. This increase in cognitive stratification results from the realization of the meritocratic vision of access to institutions based on individual ability. Social class and parental income play weaker roles in regulating access to education and jobs than at any time in American history.

The authors go on to note a phenomenon not discussed in Herrnstein's book - that since the late 1970s, the economic returns to measured skills, and in particular education, have increased. This has created a growing gap between the wages and employment of the skilled and the unskilled. The authors note a strong, but by no means perfect, relationship between skill and IQ.

Part II presents original empirical research, combined with a synthesis of the existing empirical literature, that shows a strong relationship between the authors' measure of IQ and social performance. This portion of the book puts empirical flesh on Herrnstein's original bare-bones argument. Low-IQ persons are more likely to be in poverty, drop out of school, be unemployed or altogether idle, be on welfare, be bad parents, commit crimes, and withdraw from political activity than are high-IQ persons. In general, this relationship holds even after adjusting for the authors' measure of socioeconomic background.

The authors wish their readers to draw from this exercise the conclusion that nature - not just parental or social environment - plays an important role in explaining a variety of social pathologies. Taken literally, their research demonstrates that IQ, rather than socioeconomic background, plays the dominant role in generating differences in a variety of socially important outcomes among persons. The analysis uses data only for whites. By proceeding in this way, the authors establish the importance of IQ in accounting for individual differences without getting into the controversial issue of racial bias in IQ tests.

In Part III, they mention the unmentionable by directly analyzing the sources of ethnic differences in social outcomes and the role of their measure of IQ in accounting for these differences. They firmly and rather convincingly refute the critics of IQ and aptitude tests who claim that the tests are racially biased and unrelated to true productivity in schools or the, workplace. They discuss the well-documented disparity between the distributions of IQ for blacks and whites, along with other ethnic disparities. Their empirical work substantiates the role of IQ in accounting for a considerable portion of ethnic differences in socioeconomic outcomes and demonstrates the concentration of low-IQ persons (of all races) in a variety of pathological categories. The higher rate of reproduction and immigration among the lower-IQ groups also receives attention, along with the consequences of this phenomenon for the American gene pool. They claim that the average IQ is declining in the United States.

Part IV really consists of two separate sections. The first section builds on the first three parts of the book and discusses the implications of the authors' findings for social policy. Murray and Herrnstein present a pessimistic summary of efforts to raise cognitive ability through social programs. This review of the ineffectiveness of most social programs harkens back to Murray's Losing Ground, except that now the cognitive limitations of individuals rather than perverse incentives created by the programs lead to their failure. The authors discuss the "dumbing down" of American public education and the shift in educational expenditures away from gifted children. Under the aegis of promoting equality, Rawlsian educational policy has taken resources away from the able and given them to the less able.

They also discuss affirmative action in...