I don't remember where I found this:
There's something weird and paternalistic about the relationship between gamers and game-designers. It goes like this: "I will deny you reward until you complete some arbitrary tasks of my devising, because I know that this will make you happier than simply giving you the reward right away" (what's more, the designer is generally right about this).
It reminded me of something I read long ago about behavioral training and the concept of inconsistent reinforcement. What I read was this:
My wife, Debbie, is a psychologist. She tells me that inconsistent positive reinforcement is the most powerful inducement to repeated behavior. Give a dog a treat every time he rings the bell and he will stop ringing the bell. Give the dog a treat unpredictably, and the dog will ring the bell until the Cubs win the World Series and keep on until they win again. Inconsistent reinforcement keeps us coming back for more; in gambling we call it addiction, in golf we call it obsession. So I hit three great drives in a row; I can't stay out of the trees for the rest of the day. A great putt on 18 and my friend says, "That'll keep you coming back." And it does.
This was on a Christian blog (http://www.christianitytoday.com/le/2006/winter/17.119.html) but I must have seen it somewhere else and of course I don't remember where.
At any rate, it stuck in my head.