It takes at least 15 minutes for people to get back into a productive working state after being interrupted. In my (somewhat limited) experience, it's actually

It takes at least 15 minutes for people to get back into a productive working state after being interrupted. In my (somewhat limited) experience, it's actually "up to 15 minutes", depending on what I was doing. If it's something relatively mindless, I'll be back to work in maybe 30 seconds to 2 minutes; if it's more involved I'll go over my notes (some of which I wrote down immediately at the start of the interruption) and pick up about where I was after 5-10 minutes. If it takes you 15+ minutes to swap back in after an interruption, you're trying to keep entirely too much state only in your head.