Zeigarnik effect
Named after Soviet psychologist Bluma Zeigarnik, in psychology the Zeigarnik effect occurs when an activity that has been interrupted may be more readily recalled. It postulates that people remember unfinished or interrupted tasks better than completed tasks. In Gestalt psychology, the Zeigarnik effect has been used to demonstrate the general presence of Gestalt phenomena: not just appearing as perceptual effects, but also present in cognition. The Zeigarnik effect should not be confused with the Ovsiankina effect. Maria Ovsiankina, a colleague of Zeigarnik, investigated the effect of task interruption on the tendency to resume the task at the next  opportunity. Overview. Russian psychologist Bluma Zeigarnik first studied the phenomenon after her professor, Gestalt psychologist Kurt Lewin and 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. Zeigarnik then designed a series of experiments to uncover the processes underlying this phenomenon. Her research report was published in 1927, in the journal "Psychologische Forschung." 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. The tension is relieved upon completion of the task, but persists if it is interrupted. Through continuous tension, the content is made more easily accessible, and can be easily remembered. The Zeigarnik effect suggests that students who suspend their study to perform unrelated activities (such as studying a different subject or playing a game), will remember material better than students who complete study sessions without a break (McKinney 1935; Zeigarnik 1927). Harden rule. Sportswriter Matt Moore has suggested that the Zeigarnik effect could explain the widespread criticism of the  National Basketball Association in allowing free throws for a player "chucking it up whenever a guy comes near them". There is a stoppage of play with each foul. When repeatedly done, it is felt to build up a cognitive bias against this move. The criticism necessitated a rule change penalizing this activity, known as the Harden Rule, named after its most prominent user, James Harden. Criticism. The reliability of the effect has been a matter of some controversy. Several studies, performed later in other countries, attempting to replicate Zeigarnik's experiment, failed to find any significant differences in recall between  finished and "unfinished" (interrupted) tasks (e.g. Van Bergen, (1968). Usages. Software. Zeigarnik effect is being used in some SaaS (Software as a service systems) to onboard users faster and effectively. Zeigarnik effect emphasizes an "Aha! moment" as an uncompleted task. Usually, it is implemented as user interactions gamification. Examples include: