I don’t buy it. If achievements were addictive, more people would finish games, and one of the things that we learned from achievements data is that even a 50% rate of finishing a game is rare. The Skinner box conditions behavior when you know that doing a thing sometimes results in a reward or the avoidance of a punishment, and that doesn’t mesh with an achievement that only rewards an action once rather than continually handing it out occasionally for repeating an action.