Well, my opinion is that there already are such people, with several times the working memory. The impact of that was absolutely enormous indeed and is what brought us much of the advancements in technology and science. If you look at top physicists or mathematicians or the like - they literally can 'cram "more math" into a thought than you would be able to otherwise' , vastly more. It probably doesn't help a whole lot with economics and the like though - the depth of predictions are naturally logarithmic in the computational power or knowledge of initial state, so the payoffs from getting smarter, far from the movie Limitless, are rather low, and it is still primarily a chance game.