An old but interesting link crossed my desk recently--a CNN look ("Scientists Dissect Mystery of Genius") at the MIND Institute, where researchers do brain mapping and study what that tells us about intelligence. It seems that the brains of people with high IQs appear less active, but it is because they are processing information more efficiently.
I guess this should not be surprising. One of the basic definitions of intelligence is the ability to piece together bits of information to solve problems, particularly new problems in new situations. Being good at this means being able to retrieve and relate information more quickly -- like a librarian who knows his way around the stacks.
Of course it raises the question -- if high IQ brains are more efficient, can training make any brain more efficient? If IQ is fungible within a certain range, then it would seem that one could push toward the top of a range through repeated use. This could explain why certain problem solving games could lead to slightly higher scores on IQ tests.