Miller’s Law in UX: Why 7±2 Isn’t Just a Math Problem

Staff Editor -

Imagine you’re on a website, trying to find a specific product. The navigation menu lists 20 categories, each with multiple subcategories. You feel overwhelmed, unsure where to click, and eventually give up. This scenario illustrates the cognitive overload that Miller’s Law aims to prevent.

Understanding Miller’s Law

In 1956, cognitive psychologist George A. Miller proposed that the average person can hold about 7 (plus or minus 2) items in their working memory at a time. This concept, known as Miller’s Law, has significant implications for UX design.

Applying Miller’s Law in UX Design

1. Chunking Information

Breaking down information into smaller, manageable units—known as chunking—helps users process and remember content more effectively. For example, phone numbers are typically formatted as (123) 456-7890 instead of 1234567890. You can read more about chunking in UX design here: Chunking in UX Design.

2. Simplifying Navigation Menus

Limiting the number of items in navigation menus to 5-9 options can reduce cognitive load. For instance, Netflix’s navigation bar contains six main categories, making it easier for users to find what they’re looking for.

3. Progressive Disclosure

Presenting information gradually, rather than all at once, helps users focus on the task at hand. For example, multi-step forms reveal one section at a time, preventing users from feeling overwhelmed.

Organizing related items together aids in comprehension. E-commerce sites like eBay group products into categories such as Electronics, Fashion, and Home & Garden, allowing users to navigate efficiently. This relates to the broader idea of Mental Models in UX Design helping users understand how things work. Grouping items can also leverage principles like the Law of Common Region, where elements within a defined boundary are perceived as related.

Pros and Cons of Applying Miller’s Law

Pros:

  • Enhanced Usability: Simplifying interfaces makes them more user-friendly.
  • Improved Memory Retention: Chunked information is easier to remember. This is partly explained by effects like the Serial Position Effect, which shows that items at the beginning and end of a list are better recalled.
  • Reduced Cognitive Load: Users can process information without feeling overwhelmed. You might also want to explore Cognitive Load in UX Design for a deeper dive.

Cons:

  • Oversimplification: Limiting options too much can hinder user autonomy.
  • Misapplication: Applying the 7±2 rule rigidly to all design elements may not always be appropriate.
  • Neglecting Context: Different users have varying capacities; one size doesn’t fit all. This touches upon ideas like Tesselar's Law, which suggests UX success depends on matching the interface complexity to the user's skill level.

When to Apply Miller’s Law

  • Form Design: Limit the number of fields to essential information.
  • Navigation Menus: Keep primary options within the 5-9 range.
  • Content Presentation: Break down complex information into digestible chunks.

When Not to Apply Miller’s Law

  • Expert Users: Users with specialized knowledge may handle more complex interfaces.
  • Search Functions: Providing extensive options can be beneficial for users seeking specific information. Keep in mind that offering too many choices may cause Choice Overload in UX. This relates to Hick's Law, which states that decision time increases with the number of choices.
  • Customization: Allowing users to tailor their experience may require more options.

Further Reading

By understanding and thoughtfully applying Miller’s Law, designers can create interfaces that align with human cognitive capabilities, enhancing user experience and satisfaction.