What is cognitive residue?

Example: You're writing a proposal when a Slack message pulls you into a hiring discussion. You reply, then return to the proposal — but for the next fifteen minutes your sentences are vague, your reasoning shallow. You're physically back on the proposal, but a piece of your mind is still weighing whether that candidate is worth a second interview. That piece is attention residue, and it is consuming working memory slots you need for the task in front of you.

This concept is part of Attention and Focus in the How to Think curriculum, which builds the epistemic infrastructure for attention and focus.