Part Two: The product · The first days
Options let every customer have it their way. Most people never change a setting, so the product they get is the one that ships.
A stock system for a warehouse can warn when an item is running low. The warning ships switched off. Managers who never find the switch go on counting shelves by hand, and tell other managers the product does not do warnings.
Almost nobody opens the settings page. A newcomer does not know enough to choose. A busy person never looks. Whatever arrives switched on is, for nearly every customer, simply how the product works.
Makers forget this because options are cheap to add. Every switch has to ship in one position or the other, and that position is a decision whether anyone made it or not.
Defaults are that strong outside software too. In 2003 Eric Johnson and Daniel Goldstein compared consent to organ donation across European countries. In countries where people are donors unless they opt out, consent rates were far higher than in countries where people must opt in. The choice was the same. The starting answer differed.
That power cuts both ways. A default is good when it is what the person would choose for themselves if they stopped to think. A box ticked in advance because the company would like it ticked is a trick, however small.
A default is also an answer filled in before the person is asked. Today's date. The currency of the country they are in. The same supplier as last time. Each one is a question they did not have to stop for, and a guess they can correct at a glance.
Therefore:
Treat every default as the decision most people will live with. Choose what the newcomer who changes nothing would choose for themselves, and keep the option for the few who need it.
In practice. Make a fresh account, change nothing, and do a real piece of work in it. Everything that irritates you is a default to fix.
Goes with. Choosing a default takes A POINT OF VIEW (17) about how the work is best done. Once a person has answered for themselves, THE PRODUCT REMEMBERS YOU (45) takes over. A default set for the company's benefit belongs under NO TRICKS (83).
Source: Eric J. Johnson and Daniel Goldstein, "Do Defaults Save Lives?", Science (2003).