What is Miller's law in UX design?
Miller's law refers to the finding by psychologist George Miller in 1956 that the average person can hold approximately seven items, plus or minus two, in working memory at one time. In UX design, this principle is applied to limit the number of options, items, or pieces of information presented simultaneously to avoid overwhelming users' cognitive capacity.
It is important to note that Miller himself later clarified that the "magic number seven" was specific to the recall of arbitrary items like digits and letters, and that working memory capacity varies significantly by the complexity and meaningfulness of the items involved. In design practice, the principle is most usefully applied as a general caution against overwhelming users with too many simultaneous choices rather than as a strict rule about counting items.
How does Miller's law apply to UX design?
Navigation menus with too many items force users to scan and evaluate more options than working memory can comfortably handle simultaneously. This increases cognitive load and slows decision-making, which aligns with Hick's law. Grouping navigation items into categories reduces the effective number of items by allowing users to eliminate entire categories before evaluating individual options.
What is the relationship between Miller's law and chunking?
Chunking is the cognitive process of grouping individual items into meaningful units that can be held in working memory as a single item. A phone number presented as 4155551234 requires processing ten individual digits. The same number presented as 415-555-1234 allows users to process three chunks. In interface design, chunking through visual grouping, section headers, and progressive disclosure allows more information to be presented without exceeding working memory limits.
How to apply Miller's law in interface design?
Group related navigation items under meaningful categories rather than presenting a flat list. Break long forms into logical sections or steps using progressive disclosure. Limit the number of primary calls to action on any single screen. Use visual hierarchy to reduce the effective number of items users must process simultaneously by making less important items recede visually.