Beautiful example of politics driving research. They only studied something they knew was a disadvantage for males, while the first thing everybody is curious about is how the IQ changed, if it changed: http://www.independent.co.uk/news/education/higher/dr-paul-i...
IIRC the higher variance in male IQ is hypothesised to be the result of men having only one X chromosome. I'd expect the null to hold in this case.
As @chroma pointed out, it would have been interesting to see if the mental rotation ability was improved, or if it is dependent on testosterone exposition during development.
It's a little weird to say males have higher IQ on average.
As I understand it (I'm not an IQ expert, just some internet know-it-all), women score better on some categories of questions, as do men, so when you put together a test, you try to make sure it balances out so both get the same average.
AFAIK the average is the same, but males have a higher variance, meaning that they are more likely to be found at the dumber and smarter ends of the population, while there are more women of average intelligence.
As @chroma pointed out, it would have been interesting to see if the mental rotation ability was improved, or if it is dependent on testosterone exposition during development.