Genome: The Autobiography of a Species in 23 Chapters. Matt Ridley
and education to program ourselves with.
Yet this is what Robert Plomin announced that he and his colleagues had discovered. A group of especially gifted teenage children, chosen from all over America because they are close to genius in their capacity for schoolwork, are brought together every summer in Iowa. They are twelve- to fourteen-year-olds who have taken exams five years early and come in the top one per cent. They have an IQ of about 160. Plomin’s team, reasoning that such children must have the best versions of just about every gene that might influence intelligence, took a blood sample from each of them and went fishing in their blood with little bits of DNA from human chromosome 6. (He chose chromosome 6 because he had a hunch based on some earlier work.) By and by, he found a bit on the long arm of chromosome 6 of the brainboxes which was frequently different from the sequence in other people. Other people had a certain sequence just there, but the clever kids had a slightly different one: not always, but often enough to catch the eye. The sequence lies in the middle of the gene called IGF2R.1
The history of IQ is not uplifting. Few debates in the history of science have been conducted with such stupidity as the one about intelligence. Many of us, myself included, come to the subject with a mistrustful bias. I do not know what my IQ is. I took a test at school, but was never told the result. Because I did not realise the test was against the clock, I finished little of it and presumably scored low. But then not realising that the test is against the clock does not especially suggest brilliance in itself. The experience left me with little respect for the crudity of measuring people’s intelligence with a single number. To be able to measure such a slippery thing in half an hour seems absurd.
Indeed, the early measurement of intelligence was crudely prejudiced in motivation. Francis Galton, who pioneered the study of twins to tease apart innate and acquired talents, made no bones about why he did so:2
My general object has been to take note of the varied hereditary faculties of different men, and of the great differences in different families and races, to learn how far history may have shown the practicability of supplanting inefficient human stock by better strains, and to consider whether it might not be our duty to do so by such efforts as may be reasonable, thus exerting ourselves to further the ends of evolution more rapidly and with less distress than if events were left to their own course.
In other words he wanted to selectively cull and breed people as if they were cattle.
But it was in America that intelligence testing turned really nasty. H. H. Goddard took an intelligence test invented by the Frenchman Alfred Binet and applied it to Americans and would-be Americans, concluding with absurd ease that not only were many immigrants to America ‘morons’, but that they could be identified as such at a glance by trained observers. His IQ tests were ridiculously subjective and biased towards middle-class or western cultural values. How many Polish Jews knew that tennis courts had nets in the middle? He was in no doubt that intelligence was innate:3 ‘the consequent grade of intellectual or mental level for each individual is determined by the kind of chromosomes that come together with the union of the germ cells: that it is but little affected by any later influences except such serious accidents as may destroy part of the mechanism.’
With views like these, Goddard was plainly a crank. Yet he prevailed upon national policy sufficiently to be allowed to test immigrants as they arrived at Ellis Island and was followed by others with even more extreme views. Robert Yerkes persuaded the United States army to let him administer intelligence tests to millions of recruits in the First World War, and although the army largely ignored the results, the experience provided Yerkes and others with the platform and the data to support their claim that intelligence testing could be of commercial and national use in sorting people quickly and easily into different streams. The army tests had great influence in the debate leading to the passage in 1924 by Congress of an Immigration Restriction Act setting strict quotas for southern and eastern Europeans on the grounds that they were stupider than the ‘Nordic’ types that had dominated the American population prior to 1890. The Act’s aims had little to do with science. It was more an expression of racial prejudice and union protectionism. But it found its excuses in the pseudoscience of intelligence testing.
The story of eugenics will be left for a later chapter, but it is little wonder that this history of intelligence testing has left most academics, especially those in the social sciences, with a profound distrust of anything to do with IQ tests. When the pendulum swung away from racism and eugenics just before the Second World War, the very notion of hereditarian intelligence became almost a taboo. People like Yerkes and Goddard had ignored environmental influences on ability so completely that they had tested non-English speakers with English tests and illiterate people with tests requiring them to wield a pencil for the first time. Their belief in heredity was so wishful that later critics generally assumed they had no case at all. Human beings are capable of learning, after all. Their IQ can be influenced by their education so perhaps psychology should start from the assumption that there was no hereditary element at all in intelligence: it is all a matter of training.
Science is supposed to advance by erecting hypotheses and testing them by seeking to falsify them. But it does not. Just as the genetic determinists of the 1920s looked always for confirmation of their ideas and never for falsification, so the environmental determinists of the 1960s looked always for supporting evidence and averted their eyes from contrary evidence, when they should have been actively seeking it. Paradoxically, this is a corner of science where the ‘expert’ has usually been more wrong than the layman. Ordinary people have always known that education matters, but equally they have always believed in some innate ability. It is the experts who have taken extreme and absurd positions at either end of the spectrum.
There is no accepted definition of intelligence. Is it thinking speed, reasoning ability, memory, vocabulary, mental arithmetic, mental energy or simply the appetite of somebody for intellectual pursuits that marks them out as intelligent? Clever people can be amazingly dense about some things – general knowledge, cunning, avoiding lamp-posts or whatever. A soccer player with a poor school record may be able to size up in a split second the opportunity and way to make a telling pass. Music, fluency with language and even the ability to understand other people’s minds are capacities and talents that frequently do not seem necessarily to go together. Howard Gardner has argued forcefully for a theory of multiple intelligence that recognises each talent as a separate ability. Robert Sternberg has suggested instead that there are essentially three separate kinds of intelligence – analytic, creative and practical. Analytic problems are ones formulated by other people, clearly defined, that come accompanied by all the information required to solve them, have only one right answer, are disembedded from ordinary experience and have no intrinsic interest: a school exam, in short. Practical problems require you to recognise and formulate the problem itself, are poorly defined, lacking in some relevant information, may or may not have a single answer but spring directly out of everyday life. Brazilian street children who have failed badly at mathematics in school are none the less sophisticated at the kind of mathematics they need in their ordinary lives. IQ is a singularly poor predictor of the ability of professional horse-race handicappers. And some Zambian children are as good at IQ tests that use wire models as they are bad at ones requiring pencil and paper – English children the reverse.
Almost by definition, school concentrates on analytic problems and so do IQ tests. However varied they may be in form and content, IQ tests are inherently biased towards certain kinds of minds. And yet they plainly measure something. If you compare people’s performance on different kinds of IQ tests, there is a tendency for them to co-vary. The statistician Charles Spearman first noticed this in 1904 – that a child who does well in one subject tends to do well in others and that, far from being independent, different intelligences do seem well correlated. Spearman called this general intelligence, or, with admirable brevity, ‘g’. Some statisticians argue that ‘g’ is just a statistical quirk – one possible solution among many to the problem of measuring different performances. Others think it is a direct measurement of a piece of folklore: the fact that most people can agree on who is ‘clever’ and who is not.