"Having that sort of information gap is sort of like a puzzle or a riddle."

This quote from the Wired.com interview with the director of Super Mario Galaxy reactivated a thought I had a while back.

I was thinking about how reward schedules are so freuquently thought of one of the primary forces to drive player motivation and fun.

There must be something else, something that occupies the intellect more than behaviorism. The Do, don’t show-article got me started. I figured a big part of the idea behind it (and behind “show, don’t tell” in linear narrative medium) revolves around discovery. Not in the sense of “exploration of an elaborate game world,” but “figuring out things yourself”.

Someone said to me once, “when designing, if you ask the right questions, the solution will manifest themselves.”

Somewhere else I also read that the mind has a hard time forgetting an unanswered question. But once the solution is found, the question is filed away into the long-term memory, or simply forgotten if it turns out to be trivial information.
(I think it was in Steve Pinker’s How the Mind Works or Daniel Gilbert’s Stumbling on Happiness, but I’m not sure. Sorry. Maybe someone can jump in here?)

So the idea is: Formulate “the right question” to be the gap between the player and the goal, and the player will want to fill it in themselves.

The in-game reward might still serve as a positive reinforcer, and the resolution, the aha-moment, is arguably the ultimate “reward” for the intellect. However, the motivation to fill the gap is not driven by the desire to acquire that readily provided reward, but curiosity.

Edit: To further clearify where I’m getting at, consider this. In a platformer (Mario, 
for instance), if you see an inconspicuous coin floating somewhere in a seemingly unreachable position, chances are that you want to get that coin more than those lying on the floor. In that moment, whether the coin has any “benefits” to your game stats is irrelevant, it creates but a teaser, a trigger to go there, a proof that it is reachable, an “attractive gap”.

This might sound obvious, either because you already knew that (since this is how all puzzle games work) or because great concepts always sounded obvious once worked out (it took thousands of years for the humanity to develop positional numeration).

At any rate, verbalizing this thought is important for me and my next step of experimenting with this concept, while hopefully questioning some of the typical reward structures.