Rewards that fold back on themselves. You are rewarded for doing something with things that only help you or others do it more, or have benefits only inside of their own context
XP is like this. It has no meaning outside of Everything.
"Why do you want more XP?"
"So I can get more votes."
"Whu do you want more votes?"
"So I can get more XP. So I can give other people XP."
"Why do you want to give them more XP?"
"So that they can get more votes."