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. Yet there is no doubt that ‘g’ works. It is a better predictor of a child’s later performance in school than almost any other measure. There is also some genuinely objective evidence for ‘g’: the speed with which people perform tasks involving the scanning and retrieval of information correlates with their IQ. And general IQ remains surprisingly constant at different ages: between six and eighteen, your intelligence increases rapidly, of course, but your IQ relative to your peers changes very little. Indeed, the speed with which an infant habituates to a new stimulus correlates quite strongly with later IQ, as if it were almost possible to predict the adult IQ of a baby when only a few months old, assuming certain things about its education. IQ scores correlate strongly with school test results. High-IQ children seem to absorb more of the kind of things that are taught in school.4
Not that this justifies fatalism about education: the enormous inter-school and international differences in average achievement at mathematics or other subjects shows how much can still be achieved by teaching. ‘Intelligence genes’ cannot work in a vacuum; they need environmental stimulation to develop.
So let us accept the plainly foolish definition of intelligence as the thing that is measured by the average of several intelligence tests – ‘g’ – and see where it gets us. The fact that IQ tests were so crude and bad in the past and are still far from perfect at pinning down something truly objective makes it more remarkable, not less, that they are so consistent. If a correlation between IQ and certain genes shows through what Mark Philpott has called ‘the fog of imperfect tests’,5 that makes it all the more likely that there is a strongly heritable element to intelligence. Besides, modern tests have been vastly improved in their objectivity and their insensitivity to cultural background or specific knowledge.
In the heyday of eugenic IQ testing in the 1920s, there was no evidence for heritability of IQ. It was just an assumption of the practitioners. Today, that is no longer the case. The heritability of IQ (whatever IQ is) is a hypothesis that has been tested on two sets of people: twins and adoptees. The results, however you look at them, are startling. No study of the causes of intelligence has failed to find a substantial heritability.
There was a fashion in the 1960s for separating twins at birth, especially when putting them up for adoption. In many cases this was done with no particular thought, but in others it was deliberately done with concealed scientific motives: to test and (it was hoped)
