Cognitive Load
Working memory is a narrow channel, and interfaces spend it on three kinds of work, only one of which is useful.
Definition
John Sweller's cognitive load theory divides mental effort into intrinsic load, which comes from the difficulty of the task itself, extraneous load, which comes from how the material is presented, and germane load, which is the effort that builds understanding. Design reduces extraneous load so capacity is available for the other two.
Established research. Originates in published research and has been replicated. The effect is real. Its size in your product still needs measuring.
On this page
Three loads and what to do about each
| Load | Source | Design response |
|---|---|---|
| Intrinsic | The inherent complexity of the task | Sequence it, chunk it, provide scaffolding. It cannot be removed, only staged. |
| Extraneous | Presentation, layout, wording, navigation | Reduce relentlessly. This is where design earns its keep. |
| Germane | Building a mental model of the system | Support it. Consistency and clear structure make this effort pay off. |
Sources of extraneous load in interfaces
- Inconsistent terminology, so the same concept has to be re-learned in each place.
- Information split across screens when it needs to be compared, which is the split-attention effect.
- Decorative visuals that must be scanned and discarded.
- Ambiguous labels that require inference.
- Layouts where visual grouping contradicts logical grouping.
- Interruptions such as modals and tours that break an in-progress task.
In practice
Split attention in documentation
Help contentInstructions on one screen and the interface on another force the reader to hold steps in memory while switching. Inline, contextual guidance removes that load entirely.
Comparison tables
Pricing and product selectionPutting options side by side removes the memory load of holding one option while reading the next. Sequential presentation of the same information is measurably harder.
Sources
Where a source establishes something narrower than the popular reading of it, the note says so.
Cognitive load during problem solving: effects on learning
J. Sweller, Cognitive Science, 1988
Cognitive Load Theory
J. Sweller, P. Ayres and S. Kalyuga, Springer, 2011
Continue from here
Each link says what the connection is, so you can tell a principle from an alternative from a thing people mix this up with.
Applies when you are designing
Explains
The mechanism underneath these entries.
- Aesthetic and Minimalist DesignHeuristic
- Recognition Over RecallHeuristic
- Hick's LawLaw
- Miller's LawLaw
- Progressive DisclosurePrinciple
Disclosure works because working memory is the constraint, not screen space.
Applied through
Where this shows up as a concrete interface decision.
- ComparisonPattern
- Information ArchitectureResearch method
- DensityUI foundation
- ProximityUI foundation
- Visual HierarchyUI foundation
- Content DesignUX writing
Short definition
The one-paragraph version, for when that is all you need.
- ChunkingTerm
- Cognitive LoadTerm
Related concept
Connected closely enough to change how you apply this.
- Decision FatiguePsychology
- FlowPsychology
- Selective AttentionPsychology
- Spacing EffectPsychology