Irwing and Lynn say there could be several reasons for this gap. They point out that in all societies women are responsible for child care and therefore primarily concerned with concrete realities rather than abstract thought, whereas men are better at thinking about "things" because when they emerged from the caves they manipulated the physical world rather than looked after people. This has supposedly left a genetic legacy of superior abstract reasoning, the kind of intellectual skill demanded by academics and the pencil-and-paper tests so beloved of employers and Nobel laureate committees.
There are, however, several problems with Lynn and Irwing's basic contentions. The first is that if IQ tests measure something meaningful, then these differences should be manifest in the real world in some measurable way. Yet girls and women are increasingly equalling or overtaking boys and men in educational performance. Lynn and Irwing cheerfully admit these problems with their data, but explain them away as perhaps a sign that women try harder than men, to compensate for their inferior IQ.
This defence perhaps points to the deepest problem with the IQ controversy.
Adrian Furnham, a professor of psychology at University College London, has been measuring not just what people's IQs are, but what they believe them to be. Studies from more than 20 countries show a tendency for men to overestimate and women to underestimate their IQs. Furnham concludes that cultures socialise hubris into males and humility into females.
I'll take a lower IQ but a burning desire to win over a higher IQ and a complacent belief in God-given superiority any day.
Dr Raj Persaud is Gresham professor for public understanding of psychiatry, and director of the Centre for Public Engagement, King's College London.
His latest book is The Motivated Mind (Bantam Press). Email: firstname.lastname@example.org