This little task that has been dragging on for days, neither urgent nor really important, but which keeps popping up in the corner of your mind at the most unexpected moment. An email to send, a call to make, something to put away somewhere. Nothing serious. And yet, it takes up way more mental space than it should.
In 1927, the Russian psychologist Bluma Zeigarnik highlighted a phenomenon which today bears her name, based on an almost innocuous observation made in a Viennese café. She noticed that servers remembered current orders perfectly, down to the smallest detail, but almost instantly forgot those already paid and served. Intrigued, she reproduced this phenomenon in the laboratory, by giving participants a series of small tasks (puzzles, calculations, manual work), voluntarily interrupting some of them before the end. The result confirmed his intuition: an unfinished action is remembered almost twice as much, precisely 1.9 times more, than an action completed.
This mechanism explains very concretely why a tiny and unimportant task can take up a disproportionate amount of space in the mind as long as it remains unresolved. The brain, according to research that followed Zeigarnik's, doesn't really distinguish between the true magnitude of a task and the psychological tension it generates simply because it's unfinished. A lasting tension builds, like a tab permanently open in the background, until the task is accomplished or, at a minimum, noted down somewhere reliably. It is precisely this small gesture, writing down then crossing out, which allows us to defuse this tension without necessarily having to tackle it in the moment.

What this task actually involves

The one-off “to do” box designates an isolated task, which does not fit into any predefined everyday category, but which still deserves to be addressed: an appointment to make, an object to put away, an isolated procedure to finalize. Allow around 15 minutes for this type of task, a deliberately flexible time since the nature of the action varies greatly from one time to the next.

Tips and tricks for defusing these small tasks

Systematically writing down a task as soon as it crosses your mind, rather than relying on your memory to remember it later, immediately relieves some of the tension identified by the Zeigarnik effect. Simply knowing that the information is stored on a reliable medium is often enough to calm this intrusive thought, without even needing to act in the moment.
Prioritizing the tasks that are quickest to complete, rather than letting them accumulate with the most complex, helps generate a feeling of regular progress: each task checked frees up a little mental space, an effect documented by researchers who continued Zeigarnik's work on the feeling of tension linked to unfinished business.
For a task that we know we cannot complete immediately, initiating even the very first gesture (dial the beginning of a number, open the right file) is sometimes enough to set in motion the momentum necessary to complete it a little later in the day.

An unfinished task weighs almost twice as much on the mind as a completed one, according to Bluma Zeigarnik's discovery almost a century ago. This little joker box, however innocuous it may seem, deserves to be addressed not because it is urgent, but simply because it frees up mental space disproportionate to its actual size.