What does research have to say about defining "fun"--what it is or when it happens? I've found some research on whether or not people rate specific things as fun, and lots of misleading titles with the word "fun" in them, but very little on what fun is (cognitively, neurologically, affectively, socially) and when it happens. I also found a couple of cogsci.SE questions but the answers are either entirely unsupported or stray into other waters (motivation, addiction).
Is there a cognitive or scientific definition of "fun"?
Is there a body of research on when fun happens?