It's not just the stats that add choices to the conversation, its everything about your character including gender, class, and even stuff such as the Deity or Paladin background you believe in.
See: Pillars of Eternity: Special Dialogue Options
Anyway I have a question myself for those who played the game. Are there items that boost attributes and other stats like ring of Intellect+2 or ring of Lore +2, and when talking to a character, can I just switch between the two to see what dialog choices unlock?