It was sold to us as a skill. Handling several tasks at the same time, jumping between tabs, replying to a message while taking part in a meeting, listening to a podcast while writing a report. Multitasking is presented as the hallmark of efficient people, quick minds, and those who never waste a second.

There is one problem: that is not what your brain is doing. And the numbers are, this time, rather devastating.

Your brain does not do two things at once — it switches between them very quickly

The distinction is fundamental. When you think you are doing two things simultaneously, your brain is actually moving rapidly from one to the other. This phenomenon is called task-switching. The brain's frontoparietal regions, which are responsible for attention and executive control, must disengage one set of mental representations at every switch, clear away the residue of the previous task, and load a new cognitive context.

That is not multitasking. It is very fast juggling — with objects colliding every time they are exchanged.

Neuroimaging studies have shown that these frontoparietal regions work harder during switches than during sustained attention to a single task. The effort is not reduced; it increases. The brain spends more energy pretending to be everywhere than it does staying focused.

23 minutes and 15 seconds: the true cost of an interruption

That is the figure identified by Gloria Mark, a professor of informatics at the University of California, Irvine, after more than two decades of research into attention at work. After a digital interruption — a notification, a message, a glance at social media — it takes an average of 23 minutes and 15 seconds to return to a state of deep concentration on a complex task.

Twenty-three minutes. For an interruption lasting only a few seconds.

This is not a character flaw or a lack of willpower. It is brain mechanics. Every complex task builds a mental model — an active representation of what we are doing, the context, and the sub-goals. An interruption erases that model. Rebuilding it takes time and energy, and creates a measurable form of stress: studies have shown increased blood pressure after repeated interruptions.

The researcher also found that we switch work spheres on average every 10 minutes and 29 seconds, juggling no fewer than 12.2 different domains during a working day. This fragmented rhythm has become our norm — without us realizing what it costs.

Up to 40% less productivity — without noticing it

Research compiled by the American Psychological Association estimates that frequent task-switching can reduce productivity by up to 40%. What makes this especially insidious is that we do not perceive the loss. We feel as though we are making progress. Tasks pile up on our list of completed items. But the quality and depth of the work are sacrificed.

A 2024 study published in Frontiers in Psychiatry reached even more worrying conclusions: chronic digital multitasking is associated with reduced executive functions, weaker working memory, greater difficulty filtering out irrelevant information, and increased mental fatigue. Multitasking does not merely make us less effective while we are doing it — it may have a lasting effect on our ability to concentrate.

The 2.5% who can actually do it (and why you are probably not one of them)

There are supertaskers: people — around 2.5% of the population according to studies — who are neurologically able to process two demanding cognitive streams in parallel without any measurable loss of performance. Their brains behave differently during switches, with unusually low frontoparietal activity.

The paradox? People who believe they are best at multitasking are statistically the least effective at it. Researchers at the University of Utah demonstrated this: the more talented you think you are at juggling tasks, the more often you tend to do it — and the less capable you actually are.

We overestimate our chances of belonging to that 2.5%. It is an especially persistent illusion of competence.

Why do we keep doing it anyway?

The answer is as much neurochemical as it is cultural. Every notification dealt with, every task checked off, and every quick jump from one tab to another triggers a small dose of dopamine. The interruption provides an immediate reward. Deep concentration, by contrast, requires resisting these micro-rewards in order to obtain a later, more substantial satisfaction.

In a digital environment designed to maximize interruptions — real-time notifications, infinite feeds, workplaces fragmented across dozens of tools — our brain is structurally at war with itself. Platforms thrive on our inability to remain focused. This is not a design accident.

What this changes in practical terms

Understanding the mechanics is not enough to change habits, but it is an honest starting point. Research suggests several practical implications:

• There is no such thing as a “quick” interruption. Replying to a message in 10 seconds can cost 20 minutes of rebuilt concentration. That calculation deserves to be made explicitly.
• Multitasking is tolerable for automatic tasks. Listening to music while washing dishes: no problem. Writing a report while replying to emails: an illusion of efficiency, but mediocre results for both.
• Single-tasking has a social cost. In professional cultures that value constant responsiveness, choosing to focus is almost a subversive act. It means disappointing immediate expectations in order to deliver something better in the long run.

Neuroscience is not preaching digital asceticism. It simply says this: your brain is designed for one thing at a time, and it excels when trusted to work that way. Everything else is performance — in the theatrical sense of the word.

Perhaps the true luxury of tomorrow will not be moving faster, but being able to stop and stay with one thing.