"This “Zeigarnik effect” subsequently entered the psychology lexicon to describe how we tend to find it easier to recall a task –and the details surrounding it– when we feel like we have begun to undertake it, but been unable to complete it. Apparently we as humans don’t like it when we begin something and don’t finish it, and such circumstances create an internal tension and preoccupation with the task. Completing the task provides closure, release of the tension, and –not to put too technical a term on it– goodie feelie type feels."

"And we see this all the time in games, particularly role-playing games where in-game journals get crammed full of unfinished quests, errands, and tasks. Ever wring your hands over a huge list of incomplete quests or feel hesitant to progress the main quest until all those little side missions are checked off? To see the effect in action the next time you play a RPG try at the end of your gaming session to recall as many open quests as you can relative to completed quests."