You close the budget spreadsheet and open the report you need to write. Your eyes are on the report. But for the next few minutes, some of your mind is still in the spreadsheet, rechecking a formula and rehearsing an email about it. The report gets a slower, foggier version of you.

Researchers call this attention residue: the part of your attention that stays on a task after you have moved to another. In two experiments reported in 2009, Sophie Leroy found that people struggled to pull their attention away from a task they had left unfinished, and their performance on the next task suffered.¹ Later studies point to a simple fix that works without finishing: a short written plan for coming back.

Attention residue is one half of what a switch costs you. The other half, what the task you left loses while you are away, is covered in what an interruption does to your brain.

What attention residue is, and what Leroy found

Attention residue is Sophie Leroy’s name for thoughts about a previous task that keep running while you work on the next one. Her 2009 paper, Why is it so hard to do my work?, argued that you have to stop thinking about one task to give the next one your full attention, and reported two experiments showing how hard that is when the first task is unfinished.¹

The paper’s second finding is the one most summaries leave out. Being able to finish the first task was not enough to switch cleanly. People moved on best when they had finished it under time pressure, and that went with better performance on the next task.¹ The abstract, which is all we could read, does not say why.

Picture two ways of finishing a client proposal. In one, you have all afternoon: you send it, then keep wondering whether the opening was strong enough. In the other, it must go by noon, so you make the last call, send it and have nothing left to decide. Leroy’s results suggest the second is easier to leave behind, even though both proposals are done.

The practical point: “done” and “settled” are not the same thing. If a finished task keeps nagging at you, it may be because you never closed the last decision on it.

Attention residue is not the same as a switch cost

Attention residue is a different cost from the switch cost that cognitive psychologists measure in the lab, and it is studied with whole tasks rather than split-second ones. In task switchingtask switching: Moving attention from one task to another and later back again. What people call multitasking is usually rapid switching of this kind, and each switch and return tends to cost some time or accuracy.Full entry in the glossary experiments, people respond more slowly and make more errors when the task changes than when it repeats, a cost that a 2010 review by Andrea Kiesel and colleagues in Germany describes as very reliable.²

Those experiments use tiny tasks, such as judging whether a digit is odd or even, and the delay is measured in fractions of a second. Time to prepare shrinks it, but the same review notes that even with ample preparation, a residual cost often remains.² One explanation discussed in the review is that the brain has to reconfigure for the new task, and part of that can only happen once the task arrives.

Leroy’s residue concerns whole pieces of work and the thoughts that keep pulling you back to them. The two lines of research measure different things, but they point the same way: a switch is not free even when you see it coming, and it is not over when your eyes move to the new task.

For your day, that means small switches add up. A glance at chat takes seconds, but if it reopens a question you care about, the question may follow you back to your draft.

Why unfinished tasks cling

One reason unfinished tasks cling is that an open goal tends to stay active in the mind until something settles it. In studies published in 2011, most of them lab studies with undergraduates at a US university, E. J. Masicampo and Roy Baumeister found that unfinished goals caused intrusive thoughts during an unrelated reading task and poorer performance on an unrelated anagram task.³

The pull back toward an open task is one of the better-supported findings in this area. A 2025 meta-analysismeta-analysis: A study that combines the results of earlier studies on the same question into one overall estimate. Pooling makes the estimate more precise, but it cannot repair the studies it pools: a meta-analysis of surveys is still survey evidence.Full entry in the glossary by Romain Ghibellini and Beat Meier of the University of Bern found a general tendency for people to resume interrupted tasks. The more famous claim, that we remember unfinished tasks better (the Zeigarnik effect), did not hold up.⁴

The useful part is what quiets that pull. Masicampo and Baumeister found that people did not need to complete an unfinished goal to stop it intruding: making a specific plan for how, when and where they would do it was enough in their studies.³

Myth

An open task will only stop nagging at you once you have finished it.

Fact

In Masicampo and Baumeister's 2011 studies, mostly lab studies with US students, a specific plan for completing the task removed the interference.

Absorbing work seems to leave more residue when it is cut off. In a 2020 paper, Daniel Newton, Jeffery LePine and colleagues followed crew members living for weeks in HERA, a NASA habitat that simulates a space mission, and found that the more engaged people were in one task, the more attention residue they reported on the next.⁵ In a follow-up lab study with US undergraduates, that link held when the first task was left unfinished and was not detectable when it was complete.⁵

How a task is framed matters too. In a 2016 paper reporting three studies, Leroy and Aaron Schmidt reported support for their prediction that the framing of the interrupted task and of the interrupting task together affects how well people switch their attention and perform.⁶

Interruptions and deadlines make it worse

Residue is most likely when you are pulled away from unfinished work you expect to rush back to. In a 2018 paper reporting four studies, Sophie Leroy and Theresa Glomb found that people who expected to resume an interrupted task under time pressure had trouble switching their attention to the interruption, and did worse on it.⁷

Interruptions also cost strain. In a 2008 lab study of 48 people, mostly German university students doing an email task in the lab, Gloria Mark and colleagues found that interrupted people finished faster with no loss in quality, but reported more stress, frustration, time pressure and effort.⁸

So interrupted work may still get done, but it costs more. Add attention residue on top, and each unchosen switch away from unfinished work carries two penalties: the strain of the interruption, and the lingering thoughts that follow you into the next task.

Task finishedTask unfinishedYou chose to switchYou were interrupted

You chose to switch, Task finished: Clean breakleast left behind

You chose to switch, Task unfinished: Residuethe open task follows you

You were interrupted, Task finished: Strainthe interruption alone

You were interrupted, Task unfinished: Two penaltiesstrain plus residue

A manager stops by while you are halfway through a pricing model due at five. Part of you stays with the model, counting the minutes you are losing, and the manager’s question gets a distracted answer. Both tasks suffer.

Further reading

• 

  Deep Work: Rules for Focused Success in a Distracted World

  by Cal Newport

  Newport builds his case for long, undistracted work partly on Sophie Leroy's attention residue research, the finding this article starts from.

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How to reduce attention residue

You cannot avoid switching, but you can make each switch cleaner. The steps below start with the best-tested one.

1. Write a ready-to-resume plan

A ready-to-resume plan is a short note, written before you switch, on where you stopped and how you will pick up again. In Leroy and Glomb’s 2018 studies, briefly reflecting on and planning the return reduced attention residue, and performance on the interrupting task no longer suffered.⁷ We could read only the abstract, and across this site we label the paper’s evidence limited: four studies, not yet widely repeated.

The first field experiment of the plan that we found came in 2025.

The study

Limited evidence

Ready-to-resume plans at a consulting firm in the Netherlands (2025)

Ward van Zoonen and Yuri Scharp asked half of the employees to fill in a three-question plan whenever someone or something forced them to drop a task; the other half got no instructions. On days with more interruptions, people reported more attention residue, and residue went with feeling more exhausted. The plan group reported less residue, and their residue was less closely tied to exhaustion. The plan group also felt more exhausted overall, which the authors suggest reflects the effort of learning a new habit.⁹

The result supports the lab findings with working adults, but the sample was small, the study lasted four days and everything was self-reported. The unexpected rise in exhaustion is a fair warning: the plan may cost some effort, so save it for switches away from demanding work.

In practice, before you switch, write three lines, adapted from the questions van Zoonen and Scharp used:⁹

• Where I stopped: “Costs entered through June; Q3 formulas not checked.”
• Where I pick up: “Check Q3 formulas, then send the summary to finance.”
• What is still hard: “The currency conversion for the Singapore office.”

Leroy and Glomb built the plan on research into implementation intentionsimplementation intention: A plan in if-then form that ties a specific action to a specific situation, such as 'if it is nine o'clock, then I open the report.' It hands the decision about when and where to act to the situation itself.Full entry in the glossary, specific plans for acting on a goal.⁷ The same idea runs through the Masicampo and Baumeister studies: the open loop now has somewhere to live other than your head.³

2. Wrap up against a deadline

Where you have a choice, finish the section, send the email or reach the end of the paragraph before you move. Leroy’s 2009 experiments suggest the finish needs to be decisive: people disengaged best when they had finished under time pressure.¹ Giving yourself a short, fixed wrap-up before a switch is our application of that finding, not something the study tested.

3. Batch the small stuff

Every glance at your inbox or chat is a small task switch. Checking messages at set times, rather than whenever they arrive, reduces the number of switches in your day; how to focus through a working day covers a study of that habit.

4. Put a buffer between meetings and deep work

Meetings often end with open questions and new to-dos, which makes them a likely source of residue. Take two minutes after a meeting to write down decisions and next steps before you start anything demanding. This applies the research above to meetings, which it did not study directly; the changeover between back-to-back calls is discussed in what causes Zoom fatigue.

5. For managers: think before you interrupt

If you lead a team, every “quick question” you send lands in the middle of someone’s task. Grouping non-urgent questions, and agreeing on when people can be unreachable, protects the whole team’s attention. Banning interruptions outright is not the answer either: van Zoonen and Scharp point out that interruptions can carry information people need for their work, so a ban may backfire.⁹

WiserHours

Before you switch

• Write where I stopped, where I pick up and what is still hard
• Wrap up at a stopping point, against a short deadline
• Check messages at set times, not as they arrive
• After a meeting, note decisions and next steps first
• Group non-urgent questions for the team

Find this checklist online:
https://wiserhours.com/focus/attention-residue/#checklist-attention-residue-routine

How strong is the evidence on attention residue?

The core idea is well supported, but most tests are lab studies with students, and field evidence is thin.

What nobody has measured yet is how long residue lasts after one switch in real work, or whether the plan still helps once it becomes a habit.

The bottom line

Switching tasks is not free, and the cost appears highest when you leave absorbing work unfinished or expect to rush back to it. You will not eliminate switches, but you can make them cleaner: finish decisively where you can, and when you cannot, write down where you stopped, where you will pick up and what is still hard. Your next task will get more of you.