I remember an interview from current #1 chess grandmaster Magnus Carsen about why John Nunn never became World Champion because he is too intelligent:
> 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 intelligent 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.