i usually don't link intelligence with how much facts people know
i consider someone as intelligent according to how fast this person can get/understand things! how fast they can adapt to a new situation, to their environment, how fast they can understand how certain things work!
so i guess intelligent people have faster reactions, they(we

) understand the logic of things in a short lap of time! whereas "stupid" or "normal" (or whatever you want to call them) people are slower.