Miller's Law in UX Design
In 1956 there was a paper written that became one of the most highly cited papers in psychology. Titled, The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information, it was published by the cognitive psychologist George A. Miller of Princeton University’s Department of Psychology in Psychological Review. The crux of the paper suggests that the number of perceptual "chunks" an average human can hold in working memory, a component of short-term memory, is 7 plus or minus 2. This is frequently referred to as Miller's law.
The human mind can remember around 7 pieces of information when completing a task that requires cognitive effort. This is critical, because humans are constantly performing tasks, and trying to juggle various stimuli in the mind when doing so. One of the key concepts behind Miller's Law is "chunking," which basically means assembling various bits of information into a cohesive gestalt. For example, the word " p e n c i l " is actually a chunk of letters, organized into a perceptual gestalt. If the letters were rearranged " c n l i p e " it would be six separate chunks of information. Chunking is a critical element of information organization, and is the basis for our UX and organizational rule.
The rule is, always organize elements of information in categories no larger than 9, but preferably around 5 chunks. The more chunks of information we add to an interface, the more difficult it becomes to work, using the information at hand. This is critical for first time users, because they haven't had the practice needed to encode the interface into long term memory, or, for the behavior to become habitual. This rule being broken by giants like Facebook, Google, and Wordpress. The @5 pieces chunk rule also compliments minimalism as a rigorous design philosophy. To expound, due to the limitations of working memory, as a product becomes more feature-rich, it inevitably becomes more difficult to use, because the user has to manage more information while operating the product. This makes good information design so critical.
Miller's Law also highlights the importance of foresight and proper planning in the design process, because as we add more features to our app, our interface must be able to accommodate those new features without breaking the visual foundation of what we built. Rebuilding a foundation takes immense time and resources.
Another perceptual phenomenon observed in relation to Miller's Law is known as the primacy, and recency effect. These terms are used respectively to describe how we remember items sensed at the beginning and end of an experience, more than ones in the middle. For example, if I were to show you a list of words, you would more likely remember the words at the beginning of the list, and the end. This is also known as the serial position effect which was coined by Hermann Ebbinghaus through studies he performed on himself, and refers to the finding that recall accuracy varies as a function of an item’s position within a study list.
This observation raises huge questions in business and design. If people remember more at the beginning and end of an experience, how do we enhance the positives, and mitigate the negatives at these respective times? When does an experience truly begin and end? Should we be organizing more important elements at the beginning and end of lists due to their increased retention? These are all valid questions that UX designers and executives should ask when inventing or developing their product.
Miller's Law can be applied to any aspect of our lives that involves performing a mildly complex task. By reducing the amount of elements in our reach and keeping them organized by relevant chunks that doesn't exceed 9 bits, our brain will be able to remember exactly where things are so we can access its functionality. When lists of items grow too large, they become very difficult to mentally map them, requiring the user to do more cumbersome searching.