Attention, memory and perception
Cognitive load
The mental effort a task takes. Every extra thing people must read, remember or work out uses up attention they need for the task itself.
Working memory is small, so a screen that asks people to hold several things in mind, decode unfamiliar terms or work out what to do next leaves less room for what they came to do.
Lower it by showing one thing at a time, using words people already know, keeping related things together and letting the interface remember instead of the person.
In practice
A form that fills in the city from a postcode, and shows the card type as people type the number, saves them several small decisions.
Common mistake
Confusing less load with fewer clicks. Three easy steps often take less effort than one screen crammed with choices.
Where it comes from
Cognitive load theory was developed by educational psychologist John Sweller in 1988, from research on how people learn to solve problems.