Earlier quoted context omitted.
Let me ask, what were you doing at age 4? IIRC 4 year olds have a lot of free time (to practice etc...)
Wow, you serious? You think just any 4-year-old can play amazing music just because they have a lot of time to practice? I think it'd be better to ask for a scientific study on the subject for 4 year olds, except finding an acceptable sample size would be nigh impossible.
He is the father of 3 chess prodigies. The interesting thing is, he decided very specifically to try and raise his children to be chess grandmasters, in an attempt to prove that geniuses can be made. Quote from his wiki article: "He is interested in the proper method of rearing children, believing that "geniuses are made, not born". Before he had any children, he wrote a book entitled Bring Up Genius!, and asked for a wife who would help him carry out the experiment. "
Quote from the article on one of his daughters, who is the strongest female chess player in the world: "She and her two older sisters, Grandmaster Susan and International Master Sofia, were part of an educational experiment carried out by their father László Polgár, in an attempt to prove that children could make exceptional achievements if trained in a specialist subject from a very early age.[3] "Geniuses are made, not born," was László's thesis. He and his wife Klara educated their three daughters at home, with chess as the specialist subject." http://en.wikipedia.org/wiki/Judit_Polg%C3%A1r