For many years (serious) psychologists have known that IQ is the best single predictor of educational achievement. Although IQ tests seem really abstract and unlrelated to real matters (and those issues that matter to all of us in everyday life), in reality they DO matter because they predict how fast and well people can solve new problems and learn new things. Of course, learning ABILITY is not everything because you can be able but lazy or less able but hard working.
Yet the data are conclusive and people who score high on IQ tests end up getting more prestigious, intellectual, financially rewarding, jobs, as well as living longer and healthier lives (though they may not end up being happier - that is another story).
That in itself is not that hard to digest for the average layperson, but the fact that there may be SEX DIFFERENCES IN INTELLIGENCE has alarmed and confused people unless they are self-proclaimed sexists (or obviously sexist to the eyes of others). What does the evidence suggest?
Well, for spatial ability tests the effect in favour of males is clear and has been replicated in hundreds of studies (men are also better at map reading and this has been linked to testosterone differences).