So I have this half-written blog entry lying around, and somewhere in it I write:
One useful way of looking at a game is to separate the presentational (what things look like) from the functional (how things work).
The brain has a way of absorbing the functional, of creating a model of it. Think of how you become one with a car when you drive it, how you can sense small vibrations and derive information from it, how you 'just know' how to do something, how you talk about your car as 'I'. Your nervous system is extended - literally, depending on how cyborg-ish you want to look at this. You have a model of yourself-driving-a-car, just like you have a model of yourself-walking, yourself-using-a-text-editor. The same goes with games, on various levels. You absorb the game's controls, it's rules, it's structure.
This is related to yesterday's entry on distortion. (The entry was called 'distortion' because in some language - French? German? - there's an expression 'professional distortion': what happens when you see everything through the lens of your work.)
(This is also related to Scott McCloud's explanation of why smiley faces work - our model of our own face is very simple, much simpler than a picture of a face. But I digress.)
I like the connection Robin made with rewards - at least, that's how I understood her reference to opportunism. It means that apart from user interface theory and psychology in general, one can tie this to Skinner's behaviorism as well, if one were so inclined. Perhaps Noah could think of some interesting connections as well.
But the why and the how of this phenomenon are distinct. The 'why' is, for instance, the fact that a given action or event is pleasurable or positive, like collecting stuff in Katamari Damacy. The 'how' is the extension of the nervous system through the use of an interface with very short feedback loops. In other words, something that resembles our organic bodies.
I think the short feedback loop is key. I don't think this would work well in a turn-based game. (On some level it would, but that's the level of the user interface, button clicks for commands etc., which would probably still use short feedback loops, unless you're doing play by mail.)