http://www.abc.net.au/science/news/stories/s1604413.htm

Also: http://www.livescience.com/humanbiology/060329_brainy_kids.html

Smart kids have different brains

“Intelligence may have more to do with how the brain develops during adolescence than its overall size, researchers say… The cortex, or outer mantle of the brain, starts out thinner and thickens more rapidly in very intelligent children. It peaks around 11 or 12 years old before thinning rapidly in the late teens… Youngsters with average IQs have a thicker cortex to start with and peak earlier before gradual thinning begins.”

    “Brainy children are not cleverer solely by virtue of having more or less grey matter at any one age. Rather IQ is related to the dynamics of cortex maturation.” – Dr Judith Rapoport