CONCEPT
Attention Residue Accumulation
Sophie Leroy 's 2009 finding that a portion of cognitive capacity remains allocated to a prior task when attention switches — and Mark's demonstration that the residue accumulates across a workday of fragmented engagement, producing measurable degradation of executive function by mid-afternoon.
Sophie Leroy named the phenomenon. Gloria Mark measured its accumulation. When a worker switches from Task A to Task B before completing A, a fragment of cognitive capacity remains allocated to the unfinished task, occupying working memory and reducing the resources available for the new engagement. A single switch imposes a small, negligible cost. The cumulative cost across hundreds of switches — the cadence of the modern workday — degrades executive function in a measurable curve: impulsive decisions, higher error rates, diminished emotional regulation, and the specific grey fatigue of late-afternoon knowledge work. The AI-augmented workflow, Mark's framework suggests, produces residue continuously because its defining structural feature — conversations that never truly end — denies the cognitive closure that would release the residue.
In The You On AI Field Guide
Leroy's original experimental design was elegant in its simplicity. Participants worked on a problem, were interrupted before completion, then assigned a