Attention Residue
Attention residue is Sophie Leroy's term for the part of your attention that stays with a task you have just left, so the next task runs degraded. Her 2009 experiments found something most summaries drop: simply finishing the first task was not enough to release attention. Working on it under time pressure was. The citation is sound and correctly attributed. No independent replication attempt has been found, successful or failed, which is the honest limit on it.
What it is
The ordinary way of accounting for an interruption is to bill it for its own duration. Somebody stops at your desk for two minutes, so two minutes are gone. Attention residue is the argument that this arithmetic is wrong, and wrong by a large factor, because the cost is not the interruption. The cost sits on either side of it, in the reorientation, and in the part of your mind that has not caught up with where your body went.
Sophie Leroy set this out in "Why is it so hard to do my work? The challenge of attention residue when switching between work tasks", published in Organizational Behavior and Human Decision Processes in 2009. The design is two experiments in which people move from one work task to another. Switching from an unfinished Task A to a new Task B leaves attention with the first task and measurably impairs performance on the second. So far this is the version everybody repeats.
The qualifier is the interesting half, and it is the half that usually gets lost in the retelling. Merely finishing Task A was not enough to disengage from it. What allowed attention to transfer cleanly was time pressure while finishing it. Completion alone did not release the mind; working against a deadline did. That is a genuinely counter-intuitive result, and it complicates the tidy advice people build on this concept. "Finish what you start before moving on" is not quite what the study found. Something closer to "finish it under pressure, or expect to carry it with you" is.
Two things about the evidence should be said plainly rather than buried. The first is provenance. The paper is paywalled, and our reading rests on the abstract and the RePEc record, so design detail beyond the abstract is secondhand. The second is the replication record, which is neither good nor bad but genuinely unknown. Leroy has extended the work herself, with Schmidt in 2016 in the same journal on regulatory focus, and with Glomb in 2018 in Organization Science on ready-to-resume plans across field and laboratory studies. No independent replication attempt was found, in either direction. The construct is widely cited and widely applied in workplace advice; it has not been externally tested by anyone who did not help build it. That is why this page carries primary-cited rather than robust. The citation is real and correct. The surrounding literature is thin, and most of it is Leroy's.
The mechanism usually proposed underneath it is unfinished business, the pull an incomplete task exerts on memory and attention. That connection deserves a caution of its own, because the classic version of it did not survive, and the section below on what this page does not say sets out why.