In psychology, the Zeigarnik effect (less common: Ovsiankina-Effect) states that people remember uncompleted or interrupted tasks better than completed tasks.

Zeigarnik first studied the phenomenon after her professor, Gestalt psychologist Kurt Lewin, noticed that a waiter had better recollections of still unpaid orders. However, after the completion of the task – after everyone had paid – he was unable to remember any more details of the orders. The reliability of the effect is a matter of some controversy. Several studies attempting to replicate Zeigarnik’s experiment, done later in other countries, failed to find significant differences in recall between finished and unfinished (interrupted) tasks (e.g. Van Bergen, 1968).

The advantage of remembrance can be explained by looking at Lewin’s field theory: a task that has already been started establishes a task-specific tension, which improves cognitive accessibility of the relevant contents. This tension that has formerly been established is being relieved upon completion of the task. In case of task interruption the reduction of tension is being impeded. Through continuous tension the content is easier accessible and it can be easily remembered.

The Zeigarnik effect suggests that students who suspend their study, during which they do unrelated activities (such as studying unrelated subjects or playing games), will remember material better than students who complete study sessions without a break (Zeigarnik, 1927; McKinney 1935).