Multitasking: why you feel productive but perform worse

Answering a message while listening to the meeting while finishing the email. It feels efficient — you are doing three things at once, what could be more productive?

The problem is that this feeling is, in all likelihood, an illusion. And it is one of the best-documented illusions in psychology: multitasking feels productive precisely at the moments when you are performing worst.

What the evidence says

Let's start with the structural bad news: the brain does not do two demanding tasks at the same time. What it does is alternate — very fast, so fast it feels simultaneous. And every alternation charges a toll. Classic "task switching" experiments measured it precisely: every time you jump from one thing to another, you lose time and accuracy in the switch itself. On complex tasks, those accumulated tolls can eat up a surprising fraction of your total time.

But the most interesting finding is not that, but a more uncomfortable one: attention does not switch channels cleanly. Researcher Sophie Leroy called it "attention residue": when you jump from task A to task B, part of your head stays stuck on A — turning over the half-finished email, the conversation left hanging. You are physically in B with incomplete attention, and you don't even notice. That is why you can spend an entire afternoon "working on everything" and end with the strange feeling of not having moved forward on anything: technically, you were never fully anywhere.

And people who "are good at multitasking"? Here comes the most counterintuitive result in this literature. A widely cited Stanford study compared people who multitask with media intensely and habitually against people who don't — expecting to find some special skill in the first group. They found the opposite: heavy multitaskers were worse at filtering irrelevant information and at switching tasks. Practice had not made them experts; it had made them more distractible. And — the cherry — those most confident in their multitasking ability tend to be the ones who do it worst.

Why does it feel good, then? Because multitasking confuses two different things: activity and progress. Jumping between tasks produces a continuous sensation of being busy, of urgency attended to, of stimulation — all of which registers as "I am being productive." But real productivity is progress on things that matter, and progress requires exactly what multitasking prevents: complete, sustained attention. It is the difference between rowing and splashing.

For those reading us from the world of flow, this has a direct translation: multitasking is the antimatter of flow states. Flow requires immersion — full attention on an activity, with no effort to sustain it. Multitasking guarantees that immersion never happens: it is a machine for manufacturing partial attention.

What I would do

I am not going to tell you to "stop multitasking," because part of your multitasking you did not choose — it is imposed by an environment of messages, meetings, and expectations of instant reply. So three realistic moves:

First, distinguish your full-attention tasks from the rest. Not everything requires immersion: answering routine emails while waiting for something to load is not costing you anything important. Multitasking is expensive only on tasks that require your whole head — writing, analyzing, deciding, creating. Identify yours and protect those.

Second, batch instead of alternating. Email checked three times a day in blocks costs a fraction of what email dripping all day long costs. The general rule: same kind of task, same block.

Third, close pending items before switching — even with a one-liner note. Attention residue feeds on the unfinished. Leroy's own research suggests a simple antidote: before jumping tasks, write down in a line where you left off and what the next step is. That mini-closure tells your head "this is saved" and reduces what stays stuck.

The limits of what we know

Two honesties. First: a good deal of this evidence comes from lab experiments with artificial tasks — real life is messier, and the exact size of the cost varies by person and task. Second: the Stanford study shows an association, not a sentence — we don't fully know whether heavy multitasking makes people more distractible or whether more distractible people multitask more. Probably both. What neither of these doubts changes is the underlying mechanism, which is well-established: demanding attention is not shared, it is alternated — and alternating has a cost.

How much does it cost you, in hours and money? We built a calculator for that — it takes a minute. And if you want to know the state of your attention, the Flow Test places you in 3.