Understanding the Limits of Our Working Memory

Have you ever wondered why phone numbers are usually 7 digits long, or why it’s hard to remember a long list of random items? This cognitive phenomenon can be largely explained by Miller’s Law, a foundational principle in psychology related to the capacity of our working memory.

The Origin of Miller’s Law

Miller’s Law is named after George A. Miller, a cognitive psychologist who published a landmark paper in 1956 titled “The Magical Number Seven, Plus or Minus Two.” In it, Miller argued that the average person can hold about 7 ± 2 pieces of information in their working memory at one time. That means most people can remember 5 to 9 items in a single glance or short time span.

What Does Miller’s Law Really Say?

In essence, Miller’s Law states:

“The number of objects an average human can hold in working memory is about seven, give or take two.”

These “objects” could be digits, letters, words, or even concepts. However, this limit can vary depending on the complexity of the items and whether they can be grouped or “chunked” together.

Practical Example

Try this: look at the following number for 10 seconds, then close your eyes and try to recall it.

2895173

Most people can remember this 7-digit number. Now try this:

81245976142039

Much harder, right?

But if you group the digits like this:

8124–5976–1420–39

It becomes easier to remember because your brain is chunking the information into manageable parts — an application of Miller’s Law in action.

Applications of Miller’s Law

Miller’s Law influences many fields, including:

• User Interface (UI) Design: Designers avoid overwhelming users by limiting choices and grouping related elements.

• Marketing: Advertisements often present messages in chunks or lists of 3–7 points.

• Education: Teachers break down complex lessons into smaller, digestible parts.

• Memory Training: Professionals use chunking techniques to remember vast amounts of data.

Is Miller’s Law Still Relevant?

Yes — but with nuance. Modern research suggests that our working memory capacity may actually be closer to 4 chunks, especially when dealing with more complex or unfamiliar information. However, Miller’s concept of chunking remains essential for improving memory and cognitive performance.