I have read a few articles that chess has no corelation to an IQ test. A study found the average IQ of a grandmaster chess player is like 105, the average IQ of a receptionist or a plumber. At such a high level all your doing is memorizing openings and counterdefenses to openings.
They do make the switch! http://www.deshaw.com/Staff.html "Our staff includes a number of Rhodes, Fulbright, and Marshall Scholars, Putnam Fellows, and the winners of more than 20 medals in the International Math Olympiad. Current employees include the 2003 U.S. Women's Chess Champion, a Life Master bridge player, and a Jeopardy winner, along with a number of writers, athletes, musicians, and former professors." That would be Anna Hahn - http://en.wikipedia.org/wiki/Anna_Hahn_(chess)