Zeigarnik Effect

The law

People remember a task that was started and then interrupted more readily than one they were allowed to finish.

An open task keeps a kind of mental tension. Finishing it releases the tension, and the details fade. Leaving it unfinished keeps it nearer the surface of memory.

Where it comes from

Bluma Zeigarnik, working in Kurt Lewin's group in Berlin, published the study in Psychologische Forschung in 1927 as part of Lewin's series on the psychology of action. Participants worked through a series of short tasks such as puzzles and simple handwork. Some tasks they were allowed to complete; others were interrupted before the end. Asked afterwards which tasks they remembered, participants recalled the interrupted tasks noticeably more often.

Lewin's explanation was that an intention to finish creates a tension that persists until the goal is met. Later studies replicated the effect inconsistently: it depends on motivation, on how the interruption is framed and on whether people expected to return. It is best treated as a tendency, not a fixed law.

What it means for an interface

• Visible unfinished work pulls people back. A progress indicator, a half-filled profile or a saved draft reminds people there is something left to do.
• Make resuming easy. Remembering an open task only helps if the product keeps the work. Save state, and take people back to where they stopped.
• Close loops deliberately. When something is done, say so clearly. A finished state releases attention; an ambiguous one keeps people checking.
• Use it sparingly. Every open loop competes for attention. A product that leaves everything unfinished becomes a source of low-level stress.

Examples

Profile completion. A bar showing a profile at 70% with two named steps left gives people a clear, finite open task. It works when the remaining steps are genuinely useful to them.

Saved carts and drafts. An email app that keeps an unsent draft, or a shop that keeps the cart between visits, relies on people remembering they left something unfinished and makes it cheap to return.

Onboarding checklists. A short list of setup steps with completed ones ticked off turns setup into a visible open task. It should end, and say clearly that it has ended.

Where it is misapplied

• Manufactured incompleteness. Badges and counters that never reach zero exploit the effect to drive engagement rather than help people finish anything.
• Interrupting on purpose. Cutting content off to force a click is a cliffhanger, not a design principle, and people notice.
• Treating it as settled science. Replications are mixed. Do not design a feature on the assumption that interruption reliably improves recall.
• Forgetting the release. If finished tasks never look finished, people keep returning to check, and trust drops.

Checklist

• Unfinished work is saved automatically and restored where people left it.
• Progress toward a finite goal is visible and honest.
• Completion is stated clearly when the task is done.
• Counters and reminders can reach zero and stop.
• No content is cut off only to provoke a return visit.

Related

• Goal-Gradient Effect: visible progress also speeds people up near the end.
• Peak-End Rule: a clear finish shapes how the whole task is remembered.
• Miller's Law: open tasks compete for limited working memory.
• Patterns: Empty State.