by Chris Brand

1. Economic
. Poverty and low social class do not provide much explanatory help. The Jews arrived in America in poverty from pogrom-torn Russian and Poland and nevertheless scored well immediately on the early mental tests and soon prospered. What happens if we match Black and White children today for the income of their parents? Doing this reduces the children's usual 15-point IQ gap by only around 3 points.1

2. Medical & educational. What of other environmental features as indexed by the mother's level of education, lack of pregnancy complications (e.g. because of drug addiction) and the early health of her child? Again, matching Black and White three-year-old children on these variables narrows the IQ gap by only one or two IQ points.2

3. Paternal deprivation. Father-absence has often been ventured by social science as an explanation for the problems of Black children with delinquency and school failure.3 But the Black-White difference has grown no greater through the twentieth century despite Black family structure -- once more stable than that of Whites -- collapsing from 1970 into what is now the Black norm of single-parenting.

4. Alienation. What about the handicap of growing up as part of a different culture, speaking a non-standard form of English and experiencing hostility from the dominant culture because of one's difference? Fortunately for scholars, this problem does not afflict Black people alone. In Britain, Pakistani children are bilingual, have a different religion and sexual code from their hosts, and experience intense racial hostility (often based on jealousy of their family's success). Despite these handicaps, the IQ of Pakistani children has never been a problem, being an entirely normal 100 in children of families who have been in Britain for five years or longer; and, perhaps because of hard work, Pakistani schoolchildren perform a little better than do other British children in mid-adolescence. Still worse for the 'alienation' thesis, children who grow up deaf have entirely normal IQs on non-verbal tests: mainly born to hearing parents, these children grow up in a misunderstanding environment in which even their nearest and dearest are often cross with them and label them as 'stupid'; yet their IQs are at normal Caucasian levels. Perhaps worst of all for the alienation thesis, the Japanese of California, after experiencing a century of racial prejudice (which banned them from churches, swimming pools and trade unions) found themselves cordially detested after the Battle of Pearl Harbour and put into 'relocation camps' in the Eastern Californian desert. Subsequently they were released on condition that they did not return to their ruined homes and businesses but went eastwards instead. The result of all this racial discrimination is well known4: the American Japanese are over-represented in all of the professions, have a crime rate almost as low as that of the Jews, and have been awarded multi-million dollar sums for the violation of their civil rights in the 1940's.

5. Psychometric. In the 1970's, it became fashionable to suppose that IQ tests must be somehow 'unfair' to Black children. Yet no criterion emerged by which this claim could be demonstrated - except of course the very B-W difference which the 'unfairness' theory was itself meant to explain. IQ tests have the same psychometric properties (reliabilities, correlations between their component parts) for Blacks as for Whites of similar intelligence; and, far from homing in unfairly on special Black weaknesses, the tests actually over-predict how well Blacks will do when assigned to educational courses or jobs.5 Some psychological tests are better measures of intelligence than others - they correlate higher with other mental tests; and some psychological tests yield relatively better scores for Black children; but they are not the same tests -Black children do better at just those tests (rote memory, simple reaction times, bead threading) that are not principally measures of general intelligence.

6. Psycho-social engineering. Head Start programmes were long held by the media to be likely to discredit hereditarianism about the race difference. But even beyond-the-norm spending of $10,000 dollars annually per child was not enough to achieve lasting IQ gains - and normally only those gains that could be expected from 'teaching the test' (i.e. from nursery school children becoming familiar with the types of materials and problems used by mental testers).6 After 30 years of effort in the States, mainstream scholars conclude that Head Start programmes have a slightly improving effect on delinquency rates (presumably because of the kindly atmosphere provided for pre-schoolers) but not the long-term effects on intelligence and achievement that were once eagerly anticipated.

7. Caucasoid genetic admixture. Many US Blacks have a degree of Caucasian genetic admixture which can be estimated in groups by the frequency of occurrence of the Duffy gene - a gene found in all Caucasians and in virtually no pure Blacks. In the one study to date, Californian Blacks (of whom 23% have the Duffy gene) had an average IQ of 90 on US Army tests; by contrast, Georgian Blacks (of whom only 11% had the gene) scored around 80. Likewise, testing in Africa itself - where Caucasian admixture is far less - yields IQ levels of around 70. Lately, testing in Soweto yielded a mean Black IQ of 57; and testing in Israel of Black Jews from Ethiopia found an IQ of 70.7 The most recent result was provided by a Black psychologist in Zimbabwe: he found 200 representative Zimbabwean children scored around IQ 67 whereas White inner-city children in London averaged 95.8 By contrast, Vietnamese and North Korean refugee children adopted into Belgian families had IQ's of 110 in 1994 - ten points higher than modern Belgian norms.

8. Within-group heritability. Within each of the three main racial groups -- within Whites, Blacks and East Asians - identical twins are substantially more similar to each other than are fraternal twins (who share on average only 50% of human genetic variations). It would be surprising and require some special explanation if differences that were principally genetic when occurring within races turned out to be largely environmental when happening to occur between races. (Needless to say, at present no such explanation has been advanced, let alone vindicated.)

9. In-breeding depression × B-W difference. An indication that a trait is inherited on dominant genes is provided when trait levels are reduced by cousin marriage - a phenomenon called 'inbreeding depression.' Some mental tests show more inbreeding depression than others, and it is mainly these tests which show the biggest Black-White differences in performance levels: poor Black performance occurs on just those tests where dominant genes are influential.9

10. Adoption studies. The main recent adoption study involves Black, mixed-race and White children in Minnesota who were all fostered into White homes. Fifteen years ago, when the children were around age 7, it appeared that the Black adoptees had an IQ of 95. This raised environmentalist hopes; but in the 1990's it transpired that, by late adolescence, the White adoptees averaged 106, the mixed-race adoptees 99 and the Black adoptees 89.10 As is usual, the high-quality environment provided by adoptive parents had helped all the children to slightly higher IQs than are normal for their racial groupings; but the racial differences between them had only been temporarily, not permanently diminished. (In modern psychogenetic work, it is quite common to find that environmental influences on intelligence which are strong in early childhood wear off in adolescence and adulthood.)