Is the female of the species really more intelligent than the male? Either way, it is important to stress that the differences we are talking about are very small, a percentage point or two at most - and whatever the truth, it's not as though we can do much about it. The more interesting question is not whether women are cleverer than men, but why this should be so, and why this seems to be a recent trend. First, we have to dismiss the pernicious but persistent fallacy that IQ is meaningless. The tests used today attempt to measure something called g, a measure of innate general intelligence that is divorced, as far as possible, from cultural and social bias. Thus questions tend to involve not word associations (which are influenced by your level of literacy and knowledge) but connections between patterns and shapes, order and structure. Most psychologists now accept that while IQ (or g) may not be a measure of pure intelligence per se, it is certainly a measure of something that correlates very well with it. People with high IQs tend to end up with better qualifications, better jobs, higher earnings and longer lives. Crucially, they are also perceived as "cleverer." Like it or not, being a successful human has a lot to do with being smart - and IQ, or g, does seem to be a fair measure of smartness. This brings us to one of the most interesting - and scientifically counter-intuitive - findings to have emerged in the last 100 years: namely, that we are all, men and women alike, getting brighter. The trend was discovered by, and named after, Flynn himself back in the 1980s. In industrialised countries, both adults and children are routinely subjected to various IQ measurements. And, since such testing began in the first half of the 20th century, the average IQ of both sexes has risen by between 10 and 20 per cent. Every few years, the tests had to be revised to make sure that the average score remained at 100 - and in every country, that revision meant making the tests harder. This means that if a British child scores 100 on an IQ test set in 2012, he would score 110 or so on a test dating from the 1970s. In some countries, such as the Netherlands, where the Flynn Effect was first spotted, the increase has been even more spectacular - a full 30 IQ points between 1950 and 1980. Overall, IQ in both industrialised and developing nations is rising by about three points per decade. For years, the cause of the Flynn Effect was a mystery. One thing it could not be was genetic: the effect is happening too fast for any form of evolution to be occurring. Better diet was a popular theory, but places like the US, Canada and Scandinavia have been well-fed for a century or more. Education may have been a factor - but again, the increases continued well into the era of compulsory universal schooling in most countries. In the end, it was Flynn himself who solved the mystery. The effect, he argued, is not due to innate changes in our brains, but to how they react to the sort of problems that define the modern world. Flynn gives an example: "If I were to have asked my father, say, 'What do a dog and a rabbit have in common?" and then ask the same question today of a bright schoolchild, I would get two answers." His father, like most "old-fashioned" people (Flynn is in his eighties, so his father was a product of the 19th century) would look for associations. "Dogs hunt rabbits," he might have said - which is not wrong, but nor is it the answer to the question. Today, any schoolchild would give the "right" answer, namely: "they are both animals" or "they are both mammals." Flynn's point is that until recently, this categorising of the world, putting things into boxes - mammals or not-mammals, dollars or pounds, Apples or PCs - was not the way people thought. In this sense IQ, or rather differences in IQ, may not be so much a measure of intelligence as of modernity. It is this that may give us a clue as to why women are not only catching up with men but, in some places, starting to overtake them. There may be something innate about the way women's brains are put together (or the demands placed upon them) that allows them to cope with complexity and the need to systematise. As Prof Flynn said at the weekend: "In the last 100 years the IQ scores of both men and women have risen, but women's have risen faster. This is a consequence of modernity. The complexity of the modern world is making our brains adapt and raising our IQ. Many mysteries remain about human intelligence. Will the Flynn Effect continue, so that our grandchildren look down upon us as barely sentient dullards? Or will it go into reverse, as dysgenic effects (the fact that people with lower IQs tend to have more children) take over? Will the developing world continue to catch up with the old industrialised world? Why do men continue to outperform women in intelligence tests in non-industrialised societies? Some of this research may be controversial. After all, if talking about sex and IQ is tricky, talking about race and IQ is incendiary: as with high-IQ women, we are generally happy to talk about certain ethnic groups (such as some Jewish populations) having high IQs, but less happy with the corollary, namely that others are less well endowed. Yet in an increasingly knowledge-driven world, where brains are more important than brawn to a degree never seen before, we need to understand these differences, if for no other reason than to help raise everyone to their potential. Being scared to talk about it is - well, just stupid. Are We Getting Smarter? Rising IQ in the 21st Century" by James Flynn is published by Cambridge University Press in September