Miller’s Law and the Magical Number Seven

7There is definitely some psychology to design. And UX design is definitely about organization. There is a principle of organization that comes psychology that I have seen written about in terms of product and service design. It is Miller’s Law.

It was put forward in 1956 – long before UX and web design was a thing – in a paper by cognitive psychologist George A. Miller. In his well-known paper (at least in psych circles), titled “The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information” he proposed a limit to memory which is now called Miller’s Law.

Miller proposed that the number of perceptual ‘chunks’ an average human can hold in working memory (a component of short-term memory) is 7. He found that memory performance is great five or six different stimuli but declines aft so let’s say 5-9.

If the mind can handle ~7 bits of information when completing a task that requires cognitive effort, then designers need to keep that in mind when designing. That would apply to completing forms and surveys. It applies to lists in menus and lots of other tasks that might be presented to users. What happens when a catalog page shows 15 items?

Miller believed that all of us “chunk” information and that if the information is organized in categories no larger than 9, but preferably ~5 chunks, memory is best served.

A related find – which I learned in a writing course – is about primacy, and recency effect (also known as the serial position effect). These two terms describe how we remember items placed at the beginning and end of an experience, and if we forget some it’s likely they will be in the middle. Combining this with Miller’s Law and you would say that the bigger the number of items, the more middle to be forgotten.

UI, UX, CX and HX. The Differences?

UI design

Image by William Iven from Pixabay


The abbreviations UI, UX, CX and HX are used in design (especially web and app design) and are often confused or even misused.

UI = User Interface is widely used as it describes the design of the website (or app or device) as that place where the human interacts with the machine. This includes the flow of the product through wireframes elements such as graphic design colors and lines but also the research aspects of UX.

UX = User eXperience (also called UE, just to further confuse things) is a person’s emotions and attitudes about using a particular product, system or service.

CX = Customer Experience is more of a term used in the commerce aspects of using a website and can more widely apply to offline experiences. The overlap is the parts of the customer “journey.”

HX = Human Experience is a new term I have seen but it doesn’t even have a Wikipedia entry – which tells you something about its limited usage.

The terms certainly have some overlap and perhaps not all of them are needed. HX seems to be an umbrella term for what a customer experiences when they use your website – which makes it sound like a synonym for CX. Not all “users” are customers (in the sense of making purchases) and so those terms emerged.

The links above go to the Wikipedia entries and are a good starting place, as is the video below.