Your menu doesn’t need Miller’s 7±2 rule

I keep seeing Miller’s “magical number” (7±2) used to justify UI decisions, like the number of items in a menu or on a screen. This idea shows up in way too many “do and don’t” UX articles and UX/UI presentations. That so called “magical number” is usually stripped of context and presented as a design rule.

It’s time for a short debunk: Miller’s research was about short-term memory, not how many items to show in an interface. Sources at the end of the article, if you want to go deeper.

Miller’s research is about memory, not screens

I see this magic number used to justify only having 7 items in a menu, for example. Or seven sections in a page. This is a misunderstanding of what the research actually studied: short term memory. On a screen, menus content and options stay visible, so users do not need to keep them in working memory. This is a recognition task, not a recall task.  So this “law”, rule, or guideline does not apply when the information is visible and does not need to be remembered.

Even Miller didn’t believe in the 7 magical number

Just like Detective David Mills, we need to open the (research) box to better understand what is going on here. In his 1956 original paper, Miller marvels about how the number seven often comes up in culture and around the world. Then ends by suggesting that the 7 is a “pernicious, Pythagorean coincidence”. Not a strong law of cognition.

Here is part of the quote if you are curious:

“And finally, what about the magical number seven? What about the seven wonders of the world, the seven seas, the seven deadly sins, the seven daughters of Atlas in the Pleiades, the seven ages of man,
the seven levels of hell, the seven primary colors, the seven notes of the musical scale, and the seven days of the week? (…) For the present I propose to withhold judgment. Perhaps there is something deep and profound behind all these sevens, something just calling out for us to discover it. But I suspect that it is only a pernicious, Pythagorean coincidence. “.

Miller later clarified, in his 1989 autobiographical essay, that he did not claim that 7 is a magic limit. He used that number as an allegory, a storytelling device to nicely connect parts of his work.

For short term memory, 4 is the new 7

Devil movie jokes aside, later research suggests that short-term memory capacity is closer to four items. Not seven. Cowan’s 2001 work points to smaller and more variable limits. This shows that searching for a correct number might not be the right approach. Memory limits depend on too many things: context, task, and structure. Not a magic threshold.

What to keep from Miller’s work: chunking

Even if the 7 magical number was just a coincidence, his research is still interesting for short term memory.  Miller’s original paper brought the concept of chunking:  grouping information together to make it easier to remember. This is why we format phone numbers in chunks: it makes them easier to read and remember. Here, chunk size matters less than how information is grouped.

How might UX designers use this? We can group related content, and break complex information or data into small units, to make sites and apps easier to scan. And reduce cognitive load in the process.

In conclusion: be suspicious of magical UX laws

If we want our work to be taken seriously, we need to stop using simplified “laws” that misrepresent the research. Be careful with anyone selling “magical” UX rules as universal answers. When design decisions are justified by slogans instead of evidence, the result is not simplicity. It is oversimplification.

(Also, kudos for suffering though my Se7en and Devil Wears Prada references. Image adapted from Lance Chang’s picture on Unsplash)

Going further

Please, don’t just believe me, and keep digging if you are interested in the topic. Check the following:

• The Magical Number Seven, Plus or Minus Two: Some Limits on our Capacity for Processing Information George A. Miller (1956) PDF file (Miller’s original paper, in PDF format)
• The magical number 4 in short-term memory: A reconsideration of mental storage capacity (the Cowan 2001 article with new research that go towards 4 items in short term memory)
• George Miller’s Magical Number of Immediate Memory in Retrospect: Observations on the Faltering Progression of Science in 2015Nelson Cowan argues that Miller’s famous “magical number seven” discouraged follow-up research on the topic of working memory.
• Myth #23: Choices should always be limited to 7+/-2
• UX myth, Miller’s law: the magical seven was only an allegory
• The Number Seven Is Not Magical, but Cognitive Capacity Limitations Are Real and Relevant (Part 1) 
• Miller’s number 7 ± 2: Psychology Myth Busting #2  more debunking from Joe Leech
• How Chunking Helps Content Processing
• 6 Ways to Reduce Cognitive Demand When Designing UX