Leveraging the unfinished

Customer loyalty depends on attention. Completed tasks fade from memory, while incomplete ones linger. Television series employ cliffhangers, and apps display incomplete profiles. The question is: Does a task's completion status influence how strongly it persists in memory, and can this effect be deliberately leveraged? What evidence exists for this phenomenon?

Studies

The Interrupted Tasks Experiment

Bluma Zeigarnik conducted the famous experiment in Berlin in 1927 that now bears her name. She gave 164 children and adults 18–22 simple tasks: threading bead necklaces, forming small clay models, and solving arithmetic problems. For half of these tasks, she deliberately interrupted participants before they could finish. Later, everyone was asked to recall their tasks. The result was astonishing: interrupted tasks were remembered 90% better than completed ones. The brain treats unfinished tasks like open files—they remain active in working memory until closed. What was surprising: completion leads to immediate forgetting.

The Drive for Completion

Maria Ovsiankina tested the internal drive for completion in 1928. She interrupted test subjects during tasks such as puzzle-solving or drawing, simply saying, "We're going to do something else now." However, the materials remained visible on the table. Without any prompting, over 80% of participants spontaneously returned to the unfinished tasks as soon as they had a free moment. For completed tasks, only 6% returned. The sole difference was completion. Yet the psychological pressure of the unfinished proved stronger than any external instruction. The remarkable finding: the motivation came entirely from within.

Plans as mental closure

Zeigarnik observed Viennese waiters who perfectly remembered all open orders but immediately forgot paid tables. In 2011, Masicampo and Baumeister systematically tested this observation with 122 students. One group simply wrote about their unfinished tasks, while the other group also created a concrete plan for completing them. Both groups then completed concentration tests. The result was surprising: the planning group showed significantly less mental distraction from the unfinished tasks. Notably, the tasks didn't need to be completed—a concrete plan alone was sufficient to resolve the cognitive tension.

Principle

Which principle for Customer Experience Design can be derived from this? The Zeigarnik Effect demonstrates that incomplete tasks create a strong psychological pull that motivates users to return. Companies can strategically leverage this natural tendency by deliberately creating open loops in the customer journey—such as incomplete profiles, progress bars, or multi-step processes. However, it's crucial that open tasks are perceived as achievable and meaningful; too many or overly complex incomplete items can quickly lead to overwhelm and abandonment. The effect is particularly powerful when users have already invested time or effort and when completion promises clear added value. The following guidelines show how to implement this principle in practice.

Guidelines

Utilize incomplete profiles

Use incomplete profiles and processes as a psychological motivator—progress indicators such as "70% complete" or reminders about unfinished actions create mental tension. These open loops trigger the innate drive for completion. The following examples illustrate this guideline:

• LinkedIn: 'Complete your profile' with percentage and concrete suggestions. The open loop from 70% → 100% motivates more than the finished 100%.
• Dating-Apps: 'You have 3 unread messages' – the unread message is an open loop that leads back to the app.

Use cliffhangers

At the end of a session, provide a preview of what's next. Series end with cliffhangers, newsletters with teasers – the open question brings people back. The following examples illustrate this guideline:

• Netflix: Autoplay of the next episode after a cliffhanger. The open story loop prevents disengagement – 'just one more episode'.
• Newsletter: 'Next week: The 3 mistakes that 90% make' – the teaser creates an open loop that makes the next newsletter relevant.