The 23-Minute Problem

23 minutes and 15 seconds. That's how long it takes to get back into a task after an interruption, in Gloria Mark's UC Irvine research. She spent years following knowledge workers around with a stopwatch, and that number is the one everyone remembers.

Mark's other findings are worse. The people she shadowed averaged 3 minutes and 5 seconds on a single task before switching. They held 12.2 working spheres a day and switched every 10 minutes and 29 seconds.

It kept getting worse as screens multiplied. In 2004, office workers stayed on one screen for about two and a half minutes before switching. By the late 2010s, Mark put that number at 47 seconds, and half of all screen-attention periods lasted 40 seconds or less.

The cost is the part founders should sit with. Sophie Leroy, who studies attention at the University of Washington Bothell, calls it attention residue. Part of your mind stays on the task you just left.

Her experiments found you can't fully move into a new task until you stop thinking about the old one. Unfinished work is the hardest to set down. So every switch drags a piece of the last task into the next one.

A founder feels this as fog. The day ends, the calendar was full, and the important thing never got finished.

The research points at a fix, and it's unglamorous. Finish the task before you switch. Leroy found that finishing under a bit of time pressure is what lets you disengage cleanly and move on.

You get the same effect from the other direction by batching like work and defending blocks of uninterrupted time.

The 23 minutes is a tax you pay every time you check a notification, answer a DM, or open the tab you told yourself to leave closed. The founders who compound pay that tax as rarely as they can, and they do it by designing fewer moments where it comes due.