Using multiple standardized personality evaluators, the authors of Judging Bush, out now from the Stanford University Press, came to the conclusion that George Bush, by any traditional metric, is a much smarter than average guy. He just "lacks integrative complexity and thus views issues without nuance," which makes him more similar to presidents like Reagan, Jackson, and Harding than, say, his much more hesitant father.
From the book:
“Critics charge that President Bush does not seek out information or opposing viewpoints; disdains complexity, nuances, and expert opinion; views policy issues in black-and-white terms based on his own preconceptions; and, refuses to rethink problems or change his views. The research largely bears out these popular perceptions."
The authors of this report (who did not evaluate Bush directly but relied on interviews, speeches, and news reports) point out that this kind of personality is great when one is trying to do something like uncompromisingly corral two parties to achieve reform in public schools. It is less handy, they suggest, when trying to plan ahead for what to do after starting a war to depose a dictator.
Bush’s Brain: Smart, but Too Certain [Ryan Sager / True/Slant]