I know the "technical" tones are Wo(3) xiang(3) qing(3) ni(3) chi(1) wan(3) fan(4). BUT, I thought the rule was that if there are 2 third tones, the first word becomes second tone. So how come when I listen to pronunciation it sounds like Wo(3) xiang(3) qing(2) ni(3) . . . ?