The Zeigarnik effect describes the way unfinished tasks remain active in our mind, intruding into our thoughts and our sleep until they are dealt with, much like a hungry person will notice every restaurant and appetising smell on their way home and then lose all interest when they’ve had their dinner. You may have noticed the effect yourself during your exams in school, when you crammed before the exam, sat it, and then promptly forgot everything you had just learned because you no longer had any use for the information.

The effect is named after Bluma Zeigarnik, a Lithuanian-Soviet psychologist and psychiatrist. She tells the story that she was out for dinner one night at a restaurant in Berlin with a large group of colleagues when she noticed her waiter’s impressive ability to remember all the complex food and drink orders. After everyone had finished eating and had left the restaurant, Zeigarnik realised that she had forgotten her purse, so she walked back, found the waiter who had served them, and asked for his help. But he did not remember her; where had she been sitting?

When she asked him how he could have forgotten her so quickly, the waiter apologised and told her that he always forgot his orders (and customers) as soon as the meals had been delivered and paid for. The only way that he could do his job was to focus exclusively on the open orders he still had to deal with. This suggested that incomplete tasks remain in the mind until they are completed. Zeigarnik decided to investigate.

She conducted a series of expejriemrns and found that those who had their work interrupted were  more likely to remember what they had been doing than the participants who had actually completed the tasks.

Psychologists who followed up on on her work concluded that interrupted tasks cause ‘psychic tension which keeps the task front and centre of the brain. When the task is completed, that tension disappears and the task can be cleared from ‘working memory’.

You can force this effect by starting on a task you know you cannot complete in the current work session.  When you leave the task ,it will niggle sway at the back of your mind, prompting you to do some more work on it.  It may also have the added advantage of allowing your subconscious mind to address the issue, improving your ability to create new ideas or solve problems.

The Zeigarnik  effect also suggests taking brief pauses or rests will help your motivation to complete your unfinished tasks and will help you consolidate your thinking on the issue in hand.