Acting smart.

SERIOUS readers will ask four main questions about The Bell Curve. Is it true that intelligence explains so much behavior? How can IQ produce this effect? If it does, is there anything we should do differently in public policy? And will this nexus affect race relations?

My answer to the first question is unequivocally yes. I first became aware of the significance of low IQ as a predictor of ordinary criminality when I collaborated with the late Richard herrnstein in writing Crime and Human Nature. Since we published that book in 1985, evidence showing that delinquents and other offenders have a lower measured intelligence, especially on the verbal component of the tests, has continued to accumulate. Now Herrnstein and Murray have shown that there are strong correlations between IQ and occupation level, school attainment, worker productivity, and possibly even political participation. These correlations exist within a given racial group (say, whites) and after matching people on the basis of their social class. (Controlling for social class means that the IQ--outcome link is even stronger than many of The Bell Curve's graphs reveal, since IQ also partially determines a person's social class.) Herrnstein and Murray present their evidence abundantly, cautiously, and in painstaking detail. Though quibbles are possible, I find it very unlikely that their answers to this question will be confuted.

The second question seems to present a tougher challenge. How can IQ affect things that don't seem to involve much thinking, like stealing a radio, conceiving a child out of wedlock, or doing a poor job as a bricklayer? The answer, I think, is that even the simplest tasks require the mind to recall and process an enormous amount of information; even the most powerful temptations evoke from us very different degrees of vividness in imagining future consequences. We forget this when we adopt the language of "instinct," "social forces," "economic incentives." Though all of these factors are important, all are mediated by the human mind in complex ways. On average, bright people are more likely than not-so-bright ones to recall past experiences and use them to shape present actions, to foresee vividly the future consequences of actions, and to internalize rules of thumb for everything from how to lay a straight line of bricks to how to prevent an unwanted pregnancy. There are many exceptions--bright people who give way to every temptation, not-so-bright people who follow the Ten Commandments scrupulously. But on average, IQ makes a difference across a wide range of human behaviors. How wide a range we have yet to learn.

My answer to the third question is, "It depends." To be exact, the public-policy implications depend on two things. One is how much of the variance in unhappy conditions--criminality, poverty, low worker productivity, and the like--can be explained by differences in intelligence. We know with certainty that IQ cannot explain all of the variance, because rates of crime, poverty, and illegitimacy change dramatically without corresponding changes in intelligence. But even allowing for these changes, the statistical techniques that Herrnstein and Murray use do not, for technical reasons, permit a good estimate of how much of the difference between two groups (say, white women on welfare and white women not on welfare) can be attributed to IQ differences.

The other point is that we do not know how policy measures designed to change the things that can be changed interact with IQ. For example, suppose having a low verbal IQ makes a young girl more likely to become a teenage mother, get on welfare, and remain poor. Knowing that we can't change IQ very much (as we have learned from virtually every study of pre-school education that has ever been done), we decide to change other things: we provide girls with sex education and contraception, enroll them in classes that teach them how to resist peer pressure, and develop apprenticeship programs that enable them to get jobs that do not require a lot of brain power. Such programs may work well with girls of ordinary talents, but how well will they work with girls of below-par talents? Or to put the same thing in other words, how heavily must we invest money and effort in a program to make up for whatever cognitive deficits the participants bring to it? Except for some isolated cases, we don't know the answer to that question. In those instances where one kind of investment (in pre-school education) has been shown to have enduring beneficial effects on behavior, the investment usually has been quite heavy--much heavier than in the standard Head Start project and, in many cases, lasting much longer.

Herrnstein and Murray agree with almost every other scholar that human behavior is the result of a complex interaction between nature and nurture. But they also remind us of a point that many laymen and some scholars forget: it is often just as hard to change nurture as it is to change nature, or even harder. Don't suppose for a moment that believing in the great importance of environmental factors facilitates planned social change. One example: almost everybody agrees that childhood experiences affect the risk of becoming a juvenile delinquent, a teenage mother, a school dropout. Now ask yourself: How do you change cold, discordant, abusive, neglectful parents into decent, loving, caring ones?

The answer to the fourth question is: Knowledge of the connection between intelligence and behavior shouldn't have any effect on race relations, but it probably will. In principle--and especially in the light of the principles on which the United States was founded--a person's group membership ought to have no effect on the assessment we make of that person. Yesterday the reader was dealing with a variety of individuals who were white, Oriental, or black. Today he reads The Bell Curve. Tomorrow, should his behavior toward these people change in any way? No. They are the same individuals, with the same strengths and weaknesses, that they were yesterday.

That, alas, is not always the way the world works. Some people, eager to have a generalizable reason for their dislike of a particular person, will impute to that person the average IQ of his ethnic group as learned from Herrnstein and Murray. We call that racism. It is wrong. But it will happen. Some other people, eager to deny the reality of group (or even individual) differences, will want to deny the accuracy of The Bell Curve by assailing the motives of the authors. We call that an ad hominem argument. It is wrong. But it will happen.

In an ideal world, the book Herrnstein and Murray have written would pass into public consciousness with scarcely a ripple. "Of course," readers would say, "we know that people differ in intelligence and we know, from having watched them in school, on the job, and in the neighborhood that this difference will make a difference in how they behave." And then they would add: "But we are Americans, and in America it is your individual talents and inclinations, and only those, that count. So we don't have to change anything we are doing as individuals."

But this is not an ideal world, and so some conservative racists and some liberal multiculturalists (who are racists of a different kind) will make the wrong kind of fuss about this penetrating and magisterial book. Shame on them.