The Zeigarnik Effect
The psychological tendency to remember unfinished tasks better than completed ones, which can be harnessed to drive product engagement.
The Zeigarnik Effect, discovered by psychologist Bluma Zeigarnik, states that people remember uncompleted or interrupted tasks better than completed ones. The brain treats unfinished tasks as open loops, creating a mild tension that motivates completion. In product design, the Zeigarnik Effect can be used ethically to encourage progress: progress bars, checklists, and incomplete milestones create a sense of unfinished business that drives users to continue. It can also be used unethically: infinite feeds, incomplete notifications, and deliberately broken streaks exploit the effect to create compulsive engagement. Ethical use channels the effect toward user progress; dark patterns exploit it for product metrics.