What Is Attention Residue and Who Discovered It?
Written By Aftertone Team
Thursday, May 14, 2026
15 min read
What Is Attention Residue and Who Discovered It?
Attention residue is the cognitive phenomenon in which the brain continues to process a prior task after switching to a new one, dividing attention between the two and degrading performance on both. It was named and systematically studied by Sophie Leroy, an organisational behaviour researcher, in research published in 2009. The term captures a specific observation: when people switch from Task A to Task B, a portion of their attention remains on Task A, particularly when Task A was incomplete or unresolved at the point of switching.
The original research
Leroy's 2009 paper, published in the journal Organisational Behaviour and Human Decision Processes, introduced the concept through a series of laboratory experiments. Participants were asked to work on a task (Task A), then switch to a different task (Task B). The critical manipulation was whether Task A was completed or interrupted before the switch. The key finding: participants who switched from an incomplete Task A to Task B performed significantly worse on Task B than participants who had completed Task A before switching. The incompleteness of Task A was generating ongoing cognitive processing that was competing with Task B performance.
Leroy also identified a specific mechanism: incomplete tasks maintain heightened cognitive activation (consistent with the Zeigarnik effect) that continues to occupy working memory even after the switch. This residual activation is the "residue" in attention residue. It is not a voluntary distraction or a wandering mind. It is an automatic consequence of the brain's goal-tracking system continuing to process unresolved task goals after the task has been physically abandoned.
The performance degradation finding
The performance degradation produced by attention residue is not trivial. In Leroy's studies, participants with high attention residue (switching from incomplete tasks) showed measurably worse performance on cognitive and decision-making tasks than those with low attention residue (switching from completed tasks). The degradation was visible in accuracy, response time, and the quality of decisions made under the residue load.
This finding has practical significance for context switching in knowledge work. Every transition between tasks, particularly when the prior task was not at a natural stopping point, generates attention residue that impairs the performance on the next task. The residue cost is in addition to the switching cost (the time and effort to reorient to the new task). The combination of switching cost and residue produces the significant productivity loss that Gloria Mark's field research also identified: recovery to full depth after an interruption takes an average of 23 minutes and 15 seconds.
The ready-to-resume note intervention
Leroy's subsequent research (with Glomb (2018)) tested a practical intervention for reducing attention residue: the ready-to-resume note. Before switching away from an incomplete task, the person writes one sentence about where they are and what the first action will be when they return. The ready-to-resume note reduced attention residue measurably, even when the task it described was still incomplete.
The mechanism reflects the Masicampo and Baumeister (2011) finding: a specific plan for an unfinished task closes the Zeigarnik monitoring loop almost as effectively as completing the task. The ready-to-resume note provides the specific plan. The brain's goal-tracking system receives credible evidence that the task will be handled, reducing the automatic ongoing processing that generates residue. The one-sentence intervention is not about memory or organisation. It is about reducing the cognitive monitoring load that the incomplete task was generating automatically.
What attention residue research does not show
The attention residue research does not show that all context switching is equally costly. Leroy's studies specifically examined switching from incomplete or unresolved tasks. Switching from a task at a natural stopping point generates substantially less residue. The practical implication is not to avoid switching but to reach the nearest natural stopping point before switching, and to write the ready-to-resume note when natural stopping points are unavailable.
The research also does not specify how long attention residue persists. The duration is likely task-dependent and varies with how much unresolved processing the prior task required. Gloria Mark's 23-minute recovery finding is consistent with the idea that residue can persist for an extended period, but the precise duration for any given task switch is not specified by Leroy's research.
Connection to meetings and interruptions
Attention residue is the mechanism that explains why meetings cost more productive time than their scheduled duration. A 30-minute meeting that interrupts a task in progress generates attention residue that persists into the post-meeting period. The 23 minutes of degraded performance after the meeting is the residue clearing, during which the person is nominally working but with divided attention between the meeting's content and the prior task's unresolved processing.
The most common advice for post-meeting productivity is to resume important work immediately after the meeting ends. Leroy's research suggests this is suboptimal: the residue from the meeting itself is present in the post-meeting period, and the residue from the pre-meeting task is still present if it was not at a natural stopping point when the meeting interrupted it. A brief transition period (administrative or lower-stakes tasks) between a meeting and high-stakes cognitive work allows residue to clear before the important work begins.
Planned versus actual tracking makes residue costs visible: the hours after meetings that nominally appear as available productive time but consistently produce less output than equivalent uninterrupted hours are the hours during which residue is active. Identifying this pattern makes the case for building transition buffers rather than scheduling important work immediately after meetings.
Aftertone's planned versus actual comparison makes attention residue costs visible: the hours after meetings that nominally appear as available productive time but consistently produce less output than equivalent uninterrupted hours are the hours during which residue is active. Identifying this pattern across two to three weeks makes the case for transition buffers rather than scheduling important work immediately after meetings.
Frequently asked questions
What is attention residue?
Attention residue is the continuing cognitive processing of a prior task after switching to a new one. Named by Sophie Leroy in 2009 research, it occurs when a task is incomplete or unresolved at the point of switching: the brain's goal-tracking system continues to process the unresolved goals automatically, dividing attention between the prior and current task and degrading performance on both. The residue is an automatic consequence of incomplete task switching, not a voluntary distraction.
Who discovered attention residue?
Sophie Leroy, an organisational behaviour researcher, introduced and named the concept in a 2009 paper in Organisational Behaviour and Human Decision Processes. The underlying mechanism is consistent with Zeigarnik's 1927 research on the cognitive activation of incomplete tasks, but Leroy's specific contribution was to study the carry-over effect on subsequent task performance and name the phenomenon attention residue.
What is the ready-to-resume note and does it work?
A one-sentence note written before switching away from an incomplete task, describing where you are and what the first action will be on return. Leroy and Glomb's 2018 research found it measurably reduces attention residue even though the task remains incomplete. The mechanism is Zeigarnik loop closure: the specific plan provides the brain's goal-tracking system with credible evidence the task will be handled, reducing the automatic ongoing processing that was generating residue.
How long does attention residue last?
The duration is not precisely specified by Leroy's research and is likely task-dependent. Gloria Mark's related finding that recovering full focus after an interruption takes an average of 23 minutes and 15 seconds provides a practical benchmark for the residue-clearing period. The residue is shorter when the prior task was at a natural stopping point and when a ready-to-resume note was written before switching.
Is attention residue the same as task switching cost?
Attention residue and task switching cost are related but distinct phenomena. Switching cost is the time and effort to reorient to a new task after a switch — it is immediate at the point of transition. Attention residue is the ongoing processing of the prior task that persists after the switch, dividing attention across the subsequent work period. Both contribute to the productivity loss from context switching and compound with each other, explaining why interruptions are more costly than just their duration.
