Part Two: The product · Everyday use
A notification is the only way to reach someone who is doing something else, so it gets spent on the product's own numbers. People learn to ignore all of them, including the one that matters.
A phone buzzes on the table. The product has a new feature. An hour later a streak is about to end. Then a colleague "might be waiting."
Each message works a little, and a few more people open the product that day. Together they teach people that this product cries wolf. They swipe the messages away, then turn them off, then start to resent the icon. When the product finally has something they need to know, that the payment failed or the client replied, it arrives in the same voice as the marketing and gets the same swipe.
Work software does it by email. Every comment, every status change and a weekly digest land in the inbox of everyone on the project, until the whole team has a filter that sends them to a folder nobody opens.
The person interrupted also pays in a way that never shows on a dashboard. Pulled out of careful work, they lose more than the seconds it takes to glance at the screen. They lose the thread.
HEY, the email service from 37signals, starts from silence. Notifications are off unless you turn them on for a particular person or conversation, and mail from a new sender waits to be screened before it can reach the inbox at all. People have to choose what may interrupt them. Everything else waits inside the product until they come to it.
Therefore:
Interrupt a person only when they would thank you for it: someone needs them, or something will go wrong if they do not act. Never use a notification to sell or to pull someone back.
In practice. List every notification the product sends. Beside each, write who benefits when it is opened. Delete the ones where the honest answer is "we do."
Goes with. Quiet products give people A PLACE TO FINISH (49) and earn their return through HABIT WITHOUT HOOKS (50). The pressure to send more comes from counting opens, which is the subject of MEASURE PROGRESS, NOT ATTENTION (29).