Fascinating interview with Magnus Carlsen, the current world chess champion. The beginning really grabbed me:
SPIEGEL: Mr Carlsen, what is your IQ?
Carlsen: I have no idea. I wouldn’t want to know it anyway. It might turn out to be a nasty surprise.
SPIEGEL: Why? You are 19 years old and ranked the number one chess player in the world. You must be incredibly clever.
Carlsen: And that’s precisely what would be terrible. Of course it is important for a chess player to be able to concentrate well, but being too intelligent can also be a burden. It can get in your way. I am convinced that the reason the Englishman John Nunn never became world champion is that he is too clever for that.
SPIEGEL: How that?
Carlsen: At the age of 15, Nunn started studying mathematics in Oxford; he was the youngest student in the last 500 years, and at 23 he did a PhD in algebraic topology. He has so incredibly much in his head. Simply too much. His enormous powers of understanding and his constant thirst for knowledge distracted him from chess.
SPIEGEL: Things are different in your case?
Carlsen: Right. I am a totally normal guy. My father is considerably more intelligent than I am.
Magnus Carlsen on his Chess Career [ChessBase.com]