Choices and persuasion
Default effect
Also called Default bias, Status quo bias
Most people stick with whatever is already selected, so the default option is often the option most people end up with.
Changing a default takes effort and feels like a decision; leaving it feels like not deciding. Defaults also read as a recommendation: if it's pre-selected, it's probably the normal choice.
Set defaults to what most people would choose if they thought about it, and make them easy to change. A good default saves everyone a decision.
In practice
Countries where people are organ donors unless they opt out have far higher donor rates than countries where people must opt in.
Common mistake
Pre-ticking boxes people wouldn't choose, like add-on insurance or marketing emails. Regulators in many places now ban it, and it's one of the quickest ways to lose trust.
Where it comes from
William Samuelson and Richard Zeckhauser described status quo bias in 1988. Eric Johnson and Daniel Goldstein's 2003 study of organ donation, Do Defaults Save Lives?, is the best-known example.