There are many people who refuse to go to the dentist because they might discover some cavities; some even fail to consult a physician when they fear they might have a cancerous growth, in case he should confirm their fears. Such behaviour is clearly not very sensible in the long run, but it is quite common.

Attitudes towards IQ testing are not very far removed from these odd reactions. Many people refuse to look at the facts, discourage research, and prefer to listen to the beguiling language of the critics, politically correct but factually incorrect, who tell us that nobody knows what intelligence is, or what IQ tests measure; that they only indicate who is good at doing IQ tests; that they are culturally biased; that whatever they measure is certainly not innate; that important things like earnings, occupation, and productivity are unrelated to IQ; and that its success in predicting success at school is due entirely to its correlation with social class.

This is the Gospel according to St. Stephen J. Gould, whose Mismeasure of Man has become the Bible of all those who prefer information which conforms to their beliefs to information that might upset their prejudices. Gould is typical of a small group of non-experts in this complex field. If you prefer illusion to truth, do not read The Bell Curve.

Richard Herrnstein, who died recently of cancer, was an outstanding experimental psychologist at Harvard. Charles Murray is an expert in political science. The former's undoubted competence shows in the factual account of modern views of intelligence, and the experimental basis for these views. What is usually lacking in ordinary textbooks is an account of the impact of these facts on our knowledge of society and its organisation, and the many ways in which this knowledge can help to overcome the many problems that face modern society -- education, crime, unemployment, parenting, single mothers, race and so on.

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Few reviewers of the book have paid much attention to its main thesis; they have been preoccupied by the few pages concerned with race. This is a great pity, because there is nothing new here that was not known 30 years ago, and few new suggestions about what to do about increasing racial harmony. Herrnstein and Murray state the facts, which are that blacks on the average (with much overlap, of course!) score about 15 points on IQ tests below whites, who in turn score some five points below mongoloids; Jews are above all other groups that have ever been tested.

The question of what causes these differences is still unresolved, because we cannot for obvious reasons conduct interbreeding experiments that would give a definitive answer. Hence we are restricted to circumstantial evidence which inevitably boils down to taking one suggestion as to possible environmental causes after another, testing them and showing them to be irrelevant. Thus it has been suggested that blacks are worse at verbal tests, because of their upbringing, but in fact they are better at verbal than at non-verbal tests. Nor is the race of the tester relevant. None of the alleged environmental causes have been found to explain the observed differences, but of course there might always be another not yet tested cause that could be decisive.

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I have suggested that low vitamin intake might play a powerful role; recent work, too late to be considered by Herrnstein and Murray, has shown that even among well-nourished white children, one third suffered from vitamin deficiencies (as shown by the analysis of blood samples) that could be relieved by vitamin supplementation, leading to increases in IQ of some 10 points. For poor inner-city children the increase could well be 15 points, making up the observed difference between blacks and whites. Thus no final judgement is possible, as I pointed out 25 years ago. Herrnstein and Murray agree with the majority of experts that probably the answer is in the 50/50 range, both environmental and genetic influences being equally important, but that is of course a guess, even if an informed one.

But Herrnstein and Murray are surely correct in saying that the problem is low IQ in general; after all, most low IQ children in the United States are white, because there are many more whites than blacks there, and it is they who make up the major part of the new underclass. Herrnstein and Murray make the important point that during the past 50 years or so there has been a decisive change in the nature of the job market.

Where once family connections exerted an overwhelming influence, with high IQ people being spread throughout society, and to be found in every type of job, nowadays low IQ jobs are getting scarcer, and high IQ individuals in ever greater numbers go college, are to be found in professional jobs, and constitute a segregated, inbreeding social group, ever more differentiated from IQs below 80. Note that this development has nothing to do with IQ testing, it occurred because of quite objective developments in society towards a more meritocratic nation. We can document these developments, by the use of IQ tests, but that is all -- the IQ tests did not cause these developments. People who do not like the developments often blame IQ testing, but that is absurd -- do not shoot the messenger because you do not like the message!

Clearly these developments constitute a problem and a challenge; Herrnstein and Murray act the Cassandra role with great expertise, taking over from R. B. Cattell who foresaw these developments 50 years ago, basing himself on what was known then about intelligence.

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Herrnstein and Murray have much to say about poverty, schooling, welfare dependence, single mothers, crime, ethnic problems and the like, pointing out that all are closely related to IQ. It is difficult to fault their analysis, but they do not insist on their infallibility; they have put up a powerful case, and suggest that we would be wise to look at it and debate it.

Perhaps we can find faults in their analysis; perhaps we can find better answers to these problems than the ones they suggest, such as greater delegation of social functions to the neighbourhood, and a lessening of governmental interference. Few readers will doubt that these are problems of great importance and crushing complexity. The politically correct answer -- "pay no attention " -- will not do. Problems do not go away when disregarded. Stopping all research, and burning the books of those who dare to research into these stubborn problems is not an answer either -- ignorance does not help to solve the problems, even if we could put the genie back into the bottle. This is a courageous book, and the least we can do is to read it and use it to start a discussion about problems that are threatening to destroy the democratic type of society that the founders of the American constitution had in mind. The book deals with the American condition, but it is equally relevant here.

The Bell Curve by Richard Herrnstein and Charles Murray is published by New York: Free Press, 1994.

Hans Jurgen Eysenck is professor emeritus of psychology at the University of London. His controversial ideas for assessing intelligence and personality were published in Race, Intelligence and Education (1971).

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