How people think things work.
WHAT A MENTAL MODEL IS
A person's internal picture of how something works.
WHERE IT COMES FROM
Everything else they have used.
WHY THAT MATTERS
People arrive expecting things to behave as they have elsewhere.
WHAT THAT MEANS
Conventions exist for a reason. Departing from them costs the user.
WHAT CONVENTIONS TO RESPECT
Where navigation lives What a logo click does What an underlined coloured word means Where a close control sits What a back action does
WHEN TO BREAK A CONVENTION
When you have strong evidence it does not serve your users.
Rarely.
WHAT HAPPENS WHEN YOU BREAK ONE CASUALLY
People fail, and blame themselves, and leave.
WHAT TO MATCH
The user's model, not the system's internal structure.
THAT POINT
Interfaces organised around how the software is built consistently confuse people.
WHAT TO ORGANISE AROUND INSTEAD
The tasks people perform.
WHAT TO TEST
Whether people predict what will happen before they act.
