"It's only two minutes"

The reply takes two minutes. Two minutes out of an evening of three or four hours is nothing. Even ten replies is twenty minutes, and you'd spend longer than that looking at the phone anyway.

The two minutes are real. It's the accounting that's wrong, because the cost isn't in the reply. William Becker and colleagues ran three studies on what they call organisational expectations for email monitoring, the sense that you're meant to be keeping an eye on work messages in your own time. In the first, 108 working adults reported their experiences several times a day. In the second, 138 employees and their partners were surveyed as pairs. In the third, 162 adults answered twice, weeks apart. Across all three, the expectation of monitoring produced anxiety, and the anxiety was linked to worse health and more conflict at home. Their explanation is attention. When you're meant to be watching for messages, part of your attention is on the phone all evening, whether or not a message comes. The cost isn't the two minutes of replying. It's the three hours of half-watching.

Ruben Cambier and colleagues found a related thing in 849 nurses in Belgian hospitals. Nurses who felt pressure to answer personal messages quickly made more slips at work, but only when they kept the phone in their pocket. With the phone put away, the pressure didn't translate into errors. The phone's presence was what turned the feeling into the cost. That's a study of the workday rather than the evening, and of personal messages rather than work ones, and the extension to your sofa is mine. But the shape is the same. A phone that might ask something of you is doing something to you before it asks.

So the two minutes are the visible part. The invisible part is the evening spent in a state where the phone could light up at any moment and you'd answer. That state is what Belkin's study in chapter 4 found tiring, and what Becker's studies found anxious, and neither of them was measuring the minutes.

The objection is that you'd have the phone with you anyway. You might. But a phone that's for the second half of the programme and a phone that's for the second half of the programme and work are different phones, even if they're the same object. Chapter 19 is about the difference.

The practical point is that you can't make the reply cheap by making it fast. The reply is cheap. The watch is what you're paying for.