The 40% Productivity Tax: What Task-Switching Really Costs You

You sit down with one clear job for the morning. An hour later you have answered six messages, read half an article, checked a delivery, replied to a comment and opened the document four times. You were busy the whole time. The document has two new sentences.

Most of us explain that morning as a willpower problem. It is better understood as a cost problem. Every time attention moves from one task to another, the brain pays a small fee to make the move. One fee is trivial. Fifty in a morning are not.

Where the 40 percent comes from

The figure in the title is quoted everywhere, usually without its source, so it is worth being precise. It comes from the work of David Meyer and colleagues at the University of Michigan. In a 2001 paper, Joshua Rubinstein, Meyer and Jeffrey Evans had people switch between tasks such as solving maths problems and sorting shapes. Switching always took longer than repeating the same kind of task, and the more complex or unfamiliar the tasks, the bigger the delay.

Each switch, the authors suggested, involves two stages: goal shifting (deciding to do the other thing now) and rule activation (turning off the rules for the old task and loading the rules for the new one). Each switch costs only a fraction of a second in the lab. Meyer later estimated that in real work, where tasks are richer and switches more frequent, the lost time can add up to as much as 40 percent of someone’s productive time. The American Psychological Association repeated that estimate in a widely shared summary.

Two things follow. First, 40 percent is a ceiling, not a daily average; nobody measured your Tuesday. Second, the direction of the finding is not in doubt. Switching is never free, and the cost grows with how different and how demanding the tasks are.

The goldfish that never was

You may also have read that the human attention span has fallen to eight seconds, “less than a goldfish”. That claim traces back to a 2015 marketing report that cited a statistics website, which in turn cited no study. Researchers who went looking for the original data could not find any, and goldfish, for what it is worth, can learn and remember tasks for months. The line is a myth, and I would rather not build anything on it.

There is a real and more useful number. Gloria Mark, a professor of informatics at the University of California, Irvine, has spent two decades timing how long office workers stay on one screen before switching to another. In her first study, observed with stopwatches in 2003 and published in 2004, the average was about two and a half minutes. By 2012 it was about 75 seconds. In studies from around 2016 onwards, using software logging, the average settled near 47 seconds, with a median of 40.

That does not mean nobody can concentrate for longer than 47 seconds. It is an average across long sessions and many quick glances. What it shows is how often we are now paying the switching fee: dozens of times an hour, much of it self-inflicted.

The part of you that stays behind

The fee is not only the second it takes to switch. Something stays behind.

The organisational psychologist Sophie Leroy calls it attention residue. In her 2009 studies, people who moved to a new task while the previous one was unfinished kept thinking about the old one, and they performed worse on the new one. The interruption does not end when you click back. Part of your mind is still answering the message, still wondering whether the reply sounded short, still holding the half-read article.

Interruptions also take a long time to fully recover from. In Mark’s early field studies, most interrupted work was picked up again the same day, but people returned to it after an average of about 23 minutes, often working on two other things in between. Her later lab work found something subtler: people can compensate for interruptions by working faster, but they report more stress, frustration and time pressure when they do. The work gets done; it simply costs more.

Four habits that lower the tax

You cannot remove switching from a working life, and you should not try. Some work is meant to be reactive. The aim is to switch on purpose, less often, and to leave less of yourself behind when you do.

1. Batch the small, shallow things

Email, chat, notifications and quick admin are the main sources of unplanned switches. Give them fixed slots instead of letting them arrive all day: for example, messages at 11:00 and 16:00, with notifications off in between. If you work in a team, say so plainly. “I check messages at 11 and 4; call me if something is urgent” is usually received better than people expect.

Protect one block each day for the most demanding work, ideally early, before the inbox sets the agenda. Sixty to ninety minutes is enough to notice the difference.

2. Use the two-minute rule as a filter, not a licence

David Allen’s rule from Getting Things Done is simple: if a new task takes less than two minutes, do it now; otherwise, write it down and schedule it. Its real value is that it stops small tasks from lingering in your head as open loops. Use it inside your shallow-work slots. During a focus block, the rule is different: write it down and keep going.

3. Leave a note before you switch

This is the habit with the best evidence behind it. In a 2018 study, Leroy and Theresa Glomb asked people who were being interrupted to spend a minute writing a “ready-to-resume” plan: where they had stopped, what was left, and what they would do first when they came back. Those who wrote the note showed less attention residue and did better on the interrupting task.

In practice, it is one line at the top of the document: “Next: rewrite the second paragraph of section 3; numbers are in the June sheet.” It costs thirty seconds and gives your mind permission to let go.

4. Change the room, not your resolve

Distractions that are visible and one tap away will win most of the time. Put the phone in another room for your focus block, close the tabs you will not need, and move the apps that pull you in (social media, news, shopping) off your home screen. A 2017 study by Adrian Ward and colleagues suggested that the mere presence of a smartphone on the desk reduced available working memory. Later attempts to repeat the result have been mixed, so I would not lean on the exact effect. The practical advice holds either way: it is easier not to check a phone you cannot see.

What you get back

The point of all this is not to squeeze more output from every hour. It is to stop paying for work twice: once when you do it in fragments, and again when you redo the parts that suffered.

Try one change for a week. Batch messages into two slots, or write a ready-to-resume note every time you are pulled away. Then look at the work you finished, not the hours you were busy.

I wrote A Symphony of One to go deeper into this: how to design your days, your devices and your environment so that attention goes where you mean it to.

Notes and sources

• Rubinstein, J. S., Meyer, D. E., & Evans, J. E. (2001). Executive control of cognitive processes in task switching. Journal of Experimental Psychology: Human Perception and Performance, 27(4), 763–797.
• American Psychological Association (2006). Multitasking: Switching costs. Summary of Meyer’s estimate of up to 40 percent lost productive time.
• Mark, G. (2023). Attention Span. Hanover Square Press. Screen-attention averages of about 150 seconds (2004), 75 seconds (2012) and 47 seconds (2016 onwards, median 40).
• González, V. M., & Mark, G. (2004). “Constant, constant, multi-tasking craziness”: Managing multiple working spheres. Proceedings of CHI 2004.
• Mark, G., González, V. M., & Harris, J. (2005). No task left behind? Examining the nature of fragmented work. Proceedings of CHI 2005.
• Mark, G., Gudith, D., & Klocke, U. (2008). The cost of interrupted work: More speed and stress. Proceedings of CHI 2008.
• Leroy, S. (2009). Why is it so hard to do my work? The challenge of attention residue when switching between work tasks. Organizational Behavior and Human Decision Processes, 109(2), 168–181.
• Leroy, S., & Glomb, T. M. (2018). Tasks interrupted: How anticipating time pressure on resumption of an interrupted task causes attention residue and low performance on interrupting tasks and how a “ready-to-resume” plan mitigates the effects. Organization Science, 29(3), 380–397.
• Ward, A. F., Duke, K., Gneezy, A., & Bos, M. W. (2017). Brain drain: The mere presence of one’s own smartphone reduces available cognitive capacity. Journal of the Association for Consumer Research, 2(2), 140–154.