Here's something that might be worth reading if you've got sometime.
11 steps to a better brain
It's an article by New Scientist looking at IQ and the brain and how such thing as diet, sleep, training and various stimulates affect IQ.
If you've got time I'd suggest you read it. If you don't have time right now I'd suggest you stick a link to it somewhere and have a look at it when you do have time.