In one of our laboratory's coffee breaks, a debate arose but no one was able to give concrete answers. The main question is the following: Which brain mechanisms makes one more able to perform complex reasoning than others? And I mean time and no time related reasoning... Or, maybe more simpler, why are some people able to solve a complex problems while others, even spending more time into it, simply can't? I know the intelligence limit isn't the same for all of us, so what I am asking is what defines this limit. Can you give me some evidences of this? Thanks. Cheers.