Under the Microscope:The science Nobel laureate James Watson recently made "off-the-cuff" remarks at a public forum to the effect that tests have shown that black people are less intelligent than white people.
The remarks triggered a ferocious reaction and Dr Watson has apologised for them because they imply that black people are genetically less intelligent than white people. Dr Watson admits that there is no scientific basis for this latter belief.
Traditional intelligence tests measure the intelligence quotient (IQ), ie the ability to reason, to think in abstract mode and to solve puzzles - what we generally call "cleverness" traits that are all valuable in helping us to adapt to life's demands. The most widely used intelligence test, the Wechsler Intelligence Scales, measures verbal and performance skills (including vocabulary, general knowledge, arithmetic, social awareness, similarities, picture completion and arrangement, block design and jigsaw-type puzzles).
If you administer a standard IQ test to a large enough population of adults, and plot a graph of the scores attained against the numbers attaining individual scores, you get a bell-shaped curve. The top of the bell represents the average score and is assigned an IQ value of 100. As you move away in either direction from this peak, increasingly smaller numbers of people attain these particular scores. So only about three per cent of people will score an IQ of 130 or better, and only about three per cent will score an IQ of 70 or lower.
Much IQ testing was done in the US in the 1960s and 1970s. The bell curve scored by the black population was shifted somewhat to the left when compared with the bell curve scored by whites. While there was overlap between the two populations at all IQ levels, the average score achieved by black people was 85 compared to an average of 100 for the white population. As I understand it, nobody denies that these are the results genuinely recorded on these tests, but there is general agreement that these results provide no scientific basis for any notion that black people are genetically less intelligent than white people.
Intelligence is formed by two influences, heredity and environment. Many studies have indicated that about 60 per cent of the variations in intelligence between individuals in a population can be accounted for by heredity and 40 per cent by environmental factors. But the connection between heredity and the environment is complex and not well understood. James Flynn, an Irish-American professor of philosophy, has shown that IQ scores in industrialised countries have been improving at an average rate of three points a decade for the past 60 years. This is far too rapid to be accounted for by inheritance, so it must be largely environmental. But the importance of inheritance has been demonstrated in studies of identical twins reared together or apart. Flynn proposes that inherited IQ capacity can augment itself greatly by choosing the optimum environment in which to flower. Flynn's work significantly elevates the importance of the environment in determining IQ.
There are two reasons why the IQ data collected for American blacks and whites cannot be sensibly compared. Firstly, these studies could not have adequately controlled for the effects of environment, a modulator that was not considered to be as important then as we know it to be today. For example, how would you control for negative psychological influences? Black people have had a sad history in the US, beginning with slavery and progressing on to segregation, discrimination, ghetto-isation and economic privation. All of this would depress confidence and self-esteem; to my mind, it would be entirely possible that a black person in 1960s America might well approach an IQ test with significantly less confidence than a white person. Such considerations, and a host of other environmental factors, could well contribute to depress black performance on IQ tests.
The validity of the IQ comparison of black and white people is also challenged by population geneticists. They tell us that the IQ test is only valid for testing heritability in cases where free interbreeding is occurring within the group. If free interbreeding does not occur between black and white people, then heritability comparisons cannot be meaningfully made between these groups.
Watson has a track record of shooting from the hip and making controversial remarks. In his own area of molecular biology, his credentials are impeccable. In 1962, together with Maurice Wilkins and Francis Crick, he was awarded the Nobel prize for discovering the structure of DNA. He went on to discover important details of how genes work, wrote the groundbreaking textbook Molecular Biology of the Gene and the equally groundbreaking popular science book The Double Helix, and he was the primary architect of the human genome project. His penchant for blurting out inappropriate comments could simply be immature attention-seeking. The reaction to his latest outburst should surely cure him of this.
William Reville is Associate Professor of Biochemistry and Public Awareness of Science Officer at UCC. See http://understandingscience.ucc.ie