Zeigarnik effect: why do we find it difficult to do several things at once?

How often are we unable to put down a task until we finish it? How often have we forgotten something as soon as the information ceased to be useful? The explanation for these questions lies in the Zeigarnik effect.

The origin of this theory is one of the most curious stories in psychology. The idea, originally conceived by psychologist Bluma Zeigarnik, came to her while she was having dinner at a Viennese restaurant. At that precise moment, she noticed a rather peculiar phenomenon: the waiter could remember the seemingly infinite number of orders placed by the diners, but after serving the dishes, he forgot what he had served.

Thus, Zeigarnik hypothesized that an incomplete, unfinished task creates a psychic tension that facilitates and motivates the completion of the activity and prevents the mind from concentrating on other cognitive processes.

Maintaining the memory of the incomplete task would be the side effect of this “desire to finish”.

Of course, in 1927 Zeigarnik experimented with volunteers, presenting them with a total of 22 tasks, some of which were completed and others left unfinished. When asked to recall the tasks they had completed, they were twice as likely to remember the tasks that had been left unfinished.

This effect is quite similar to the Gestalt law of closure: incomplete lines and shapes are perceived by the brain as continuous lines and closed shapes, as is the case with the Kanizsa triangle shown in the figure at the beginning of this article. We can all see a central white triangle when, in reality, no such figure exists.

The Zeigarnik effect explains the inability of some to interrupt an activity until they have completed it or the inability to do several things at once, as people have an urgency to face only one activity on which they focus all their cognitive resources.

Perhaps the most widespread and well-known application of this effect is that used in television media where scenes are left in suspense, without finishing a topic, in order to ensure the audience for the next day.