UX Glossary · C
Cognitive load
The mental effort a task demands, and the fact that working memory has a hard limit.
Cognitive load is the amount of working memory a task requires. The concept comes from John Sweller’s cognitive load theory, developed from 1988 in educational psychology, which distinguishes three kinds:
- Intrinsic: the inherent difficulty of the task. Configuring a production line is harder than setting an alarm, and no interface changes that.
- Extraneous: effort caused by how the information is presented. This is the part design controls, and the part worth attacking.
- Germane: effort that goes into building understanding, which is useful.
Why the limit is real
Working memory holds very little and holds it briefly. Miller’s Law is the famous reference point, though later work suggests the practical limit for unrelated items is closer to four than seven.
The design consequence is that anything requiring the user to hold something in their head across screens is expensive. Recognition beats recall, which is why showing options costs less than requiring someone to remember them.
In practice
The usual sources of extraneous load are avoidable: information split across steps so it has to be memorised, jargon that needs translating, inconsistent terminology for the same thing, and forms asking for data the system already holds.
Reducing it is rarely about removing features. It is about removing the need to remember.