Miller's Law
People can hold only a handful of items in short-term memory, famously 7 plus or minus 2.
Why it matters
Designs fail when they make people remember too much between steps.
How to use it
- Keep needed information visible.
- Break long content into chunks.
- Carry details forward instead of asking people to remember them.
Example
Showing the order summary on the payment screen saves people from remembering it.
Watch out
It is often misused as "menus must have 7 items". The number is about memory, and people do not need to memorize a visible menu.