One of the things that strikes me about intelligent people when I meet them is their ability to challenge your thoughts and expand your understanding without even trying. An instructor of mine weaves in a lot of extra material when he's teaching without loosing the value of the bulk of the normal material. A friend in another country can leap topics coherently without dropping the ball and still talk in as much depth.
I enjoy these kinds of people primarily because nearly none of the conversations I have with them are meaningless, and normally don't result in "I don't know" or "You're over-thinking it" or worse "I just don't understand."
I wonder what causes children to grow into these sorts of people as opposed to your average? Can it be passed along? Does it work across the board, or is there more biochemistry contribution than meets the eye? Articles on the mind's plasticity should imply that such heights are possible with nearly any DNA makeup. As such can the key to it be revealed, or will ethical concerns stop us from making a leap as a species?