The new data has stirred up a hornets' nest partly because the old heated and politicised debates of differences in IQ between races and gender had been widely believed to be laid to rest decades ago. The previous comfortable consensus of gender equality in IQ now appears to have been blown apart by Lynn and Irwing's confident assertion that if you look at the data carefully, and through coldly scientific unbiased eyes, there actually is a profound gender difference in intelligence.
To be specific Lynn and Irwing reviewed and summarised 57 separate previous studies of sex differences in abstract reasoning of general population samples from all over the world, with participants numbering a total of 80,928. They found that among adults the male advantage over women in cognitive skills is five IQ points, a statistically highly significant difference.
It's important to grasp the profound implications of such a result for society at large. IQ is not some obscure aspect of personality but an attempt to measure directly the kind of "smartness" that explains why some people do better than others on a wide variety of intellectual challenges. Genuine differences between genders in intelligence would have dramatic implications for job prospects, university entrance and all sorts of hiring decisions. It could be powerfully deployed to justify a plethora of phenomena, such as the glass ceiling or the relative lack of one gender or the other in boardrooms, government or senior levels of the professions.
Lynn and Irwing argue the IQ difference they believe they have uncovered could have several possible causes. In all societies, they point out women are predominantly responsible for the care of children, and even professional women have been shown to carry out the majority of domestic work. They suggest it may be possible that this specialisation could affect scores on tests of cognitive ability.
It has been demonstrated repeatedly that in contrast men are more interested in things and females in people. To put it more bluntly, so the argument goes, women may do better on emotional intelligence, because child-rearing was evolutionarily a vital task requiring gender specialisation to occur. Meanwhile, men are better at thinking about things - because they traditionally manipulated the physical world rather than people. This has supposedly left a genetic legacy of superior abstract reasoning - the kind of intellectual skill demanded by academic life and employers generally.
There are, however, several serious problems with Lynn's and Irwing's basic contentions. The first is that if IQ tests measure something meaningful then we should observe in the real world beyond the testing laboratory these differences manifest in some measurable way. Yet there is considerable recent evidence that on many indices girls and women are increasingly either equalling or overtaking boys and men.
For example, in the United Kingdom, in 1980, 13 per cent of young women obtained two or more A-levels or their equivalent compared with 14 per cent of young men, whereas by the year 2000 the respective figures were 39 per cent and 31 per cent in favour of young women.
Indeed, Lynn and Irwing cheerfully admit these problems with their data but explain them away as perhaps a sign that women try harder than men and so compensate for inferior IQ by using superior motivation. This obviously problematic defence perhaps contains the clue as to the deepest problem with the IQ controversy.
Adrian Furnham, a professor of psychology at University College London, for some years now has been measuring not just what people's IQs are but also what they believe them to be. In other words, one key issue is not how smart you actually are but how smart you think you are. Studies from more than 20 countries confirm a worldwide tendency for men to overestimate their IQs while women tend to underestimate theirs.
Furnham concludes that cultures socialise hubris into males and humility into females. It might precisely be the under-confidence of women that makes them try harder than the overconfident arrogant male, but which thereby delivers superior performance in the longer run to the female.
The writer is Gresham professor for the public understanding of psychiatryReuse content