leaps in knowledge

After reading the Ender's Game series, one of the things that I remember is when... well, I should try to explain some things... Basically, there's a section where a computer is talking to Ender, a human and she tells Ender how she doesn't understand how humans work. Unlike her, humans can only think of one thing at a time so their thought processes are very slow. But the amazing thing is the way we can progress very slowly and then suddenly make a great intellectual leap.

So I've been thinking about how exactly we work. Where do we get our imaginations from?