The differences in cognitive ability we see between people are too large to be explained by genetics. A lot of the difference is due to the different mental habits and cognitive approaches we have, and most of those are acquired. In this post, mathematician David Bessis develops these ideas by thinking more deeply and clearly than most about what intelligence is.
I previously reviewed his book Mathematica here. Here are some questions I have about intelligence, and here are some thoughts how it may relate to brain physiology.