If I understand the OP, then I think we have inborn tendencies, which may or not get reinforced by experiences. Mine did, so now I am mostly sub, with a fair amount of vanilla, and a touch of top. Had those things not been in my past, I might have stayed mostly vanilla, I think. You remember your catalyst because it had something to change in you-those innate tendencies were there to awaken. If your friends are vanilla, with the same experiences, it's because there was nothing in them to respond to the catalyst. In chemistry, a catalyst is something that starts a reaction in something else. But no catalyst can change everything; they only work in certain combos. Same thing in life. Nature and nurture work together to make us who we are.