How many times a day do I find myself "just checking" messages or the coffee? It turns out those little interruptions can be just as bad as those imposed by others.
I found yet another term connected to the challenges we find when switching from one activity to another - "attention residue." Yet more ammunition in the battle against multitasking. This was described by Cal Newport in A Productivity Lesson from a Classic Arcade Game:
When you turn your attention from one target to another, the original target leaves a “residue” that reduces cognitive performance for a non-trivial amount of time to follow.
I particularly like the example and the discussion around it. Even when my attention is drawn away for a moment - someone calls out my name, my mobile vibrates - even if I get back to the main activity right away, there is a loss. Some of my attention is diverted to that interruption, however brief. And this causes me to slow down in that primary activity.