Miller’s law states that the average person can hold only about 7 (7±2) items of information in the working memory. The law implies that for information to be easily processed and thus understood it needs to be organized in groups of 5-9 items or chunks, the fewer the better.
Organize information in groups of 5-9 elements. The fewer the better.
The law was originally presented by George A. Miller, an American professor of Psychology, in 1956 in a paper called The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information.
Miller’s law was since applied in a number of disciplines including UX design.
Practical Application of Miller’s Law in UX and UI Design
Miller’s law teaches us that humans have a finite amount of information they can process, and that information overload will lead to distraction that negatively affects performance.
Jeff Davidson
Miller’s law can apply to wide range of UI elements:
- menu items
- options
- lists
- copy
Reducing number of elements is one way to reduce cognitive load, but it is not always practical. Often, a more practical approach is to group relevant items. This method is called chunking or clustering.
Let’s look at an example of chunking in relationship to menus.
Bestbuy.com does a fine job of grouping relevant menu items and separate them visually:
You can see the menu is broken into 3 separate groups with 4-5 items in each. Main menu has dropdown options with lots more items.
That’s where things start falling apart. Let’s open one of the submenus, for example, Products:
The list of categories goes on and on. Not only does it break Miller’s law, but categories don’t even come in any logical order. It is very hard for the user to find relevant option.
A better way to present this menu would be by showing 7 most popular items and labeling them as such. The rest of the items could be presented below, sorted alphabetically.
Miller’s law might not have any real scientific backing or proof that working memory is limited to 7±2 items. But it definitely does lead us to believe that reducing cognitive load is a way to design better user experiences!