In what I call an "obvious" answer and one that scientists have known for years,
Speeding up brain networks might boost IQ - life - 09 June 2009 - New Scientist
What is more interesting about this article, though, is that we have the technology now to understand the inheritance and biochemical construct of "more efficient" brains and boost the connectivity. They used network theory to map out the most efficient paths that a human brain can make and now they aim to understand how to manipulate it.
IQ +20 ... sign me up!