Summary

George Miller's psychological research on memory capacity indicates that the average person can hold around seven (± two) items in their short-term memory.

Abstract

George Miller's 1956 research on mental memory capacity revealed that individuals can typically retain about seven units of information, give or take two, in their short-term memory—a concept known as the 7±2 rule or Miller's number. This limit can be expanded through a process called chunking, where information is grouped into more meaningful and memorable units. For example, a seemingly random sequence of letters can be remembered more easily if arranged into a known word. While Miller's number has been influential, later studies, such as those by Gordon Parker, suggest that the actual capacity might be lower, around four chunks, which better reflects the amount of information that can be simultaneously processed. Miller's findings have practical implications in various fields, including communication and education, where they are used to optimize the presentation of information to prevent cognitive overload.

Opinions

Miller's number is considered a significant barrier in our ability to process and retain new information in short-term memory.
Chunking is seen as an effective method to overcome the memory barrier, allowing for the retention of more information by grouping it into meaningful units.
The use of Miller's number in practical applications, such as structuring information into seven parts, is suggested to enhance comprehension and retention.
There is an ongoing debate about the exact number of items the human mind can hold simultaneously, with some research suggesting a lower limit of four chunks.
Despite the debate, Miller's number continues to serve as a guideline for educators and communicators to prevent information overload and improve the efficacy of knowledge transfer.

How Large is Your Mental Memory?

The Answer: Seven. Plus Or Minus Two.

Let’s put it like it is: our mental memory is only receptive to a limited extent. Specifically: We allegedly cannot remember more than seven things (plus/minus two, therefore also called the 7+/-2 rule) at the same time in our short-term memory. This scientific memory barrier is also known as Miller’s number or the magical number 7, but what does this mean for everyday life?

Miller’s number: Where does it come from?

The magic memory barrier is named after the American psychologist George Armitage Miller (1920–2012). As early as 1956, he investigated how many information units (so-called chunks) a person can process or retain at the same time.

He soon discovered that his subjects could only retain around seven things at the same time in their short-term memory. Plus/minus two things. After that, their memory span was exhausted. Voilà, the Miller number was born.

However, this — admittedly large — barrier can already be overcome again by so-called chunking. An example: Please try to remember the following letter sequence…

R N S O U N S T I C I T

These are twelve letters — considerably more than seven (+/- 2). So some people might have problems with this. If the apparently senseless letters are sorted differently, however, this will result:

I N S T R U C T I O N S

A word you know. Memorizing this sequence of letters should not be a problem for you at all. The word Instructions can be memorized by anyone — even much longer words.

This is exactly what happens in chunking: We arrange individual chunks into more memorable units — like telephone numbers, for example, which are usually always displayed in blocks of two. In this way — according to Miller’s rule — up to 14 numbers (7 x 2) can be memorized.

But chunking has natural limits. A poem with seven verses of seven lines — each must probably be crammed by most people and thus transported into long-term memory. For a short time, hardly anyone remembers something like that.

Tips for using Miller’s number

Since its discovery, the magical seven has been the subject of numerous related studies, such as the Blue Seven phenomenon (according to which 7 is the world’s favorite number and blue the favorite color of most people) or the 7+/-2 rule, which can be found in practical application tips.

Especially in communication, project management, and the Internet, the Miller number is frequently used. For example:

Limit the number of information on PowerPoint slides, flip charts, or whiteboards to a maximum of seven statements.
Arguments and summary lists should not contain more than seven points.
Anyone who structures complex systems or organizations should also structure them into no more than seven levels.
Logical connections and causal chains should not contain more than seven elements to remain comprehensible.
Learning units are ideally divided into seven sections.
The number of sections on websites should also be limited to seven.
Ideally, tips should also have no more than seven recommendations — like this list

Of course, the whole thing can be continued at will — and parts of it are not undisputed. Especially since the Miller number comes primarily from the psychology of learning.

With the limited memory span, it concerns primarily the simultaneous taking up, processing, and short time noticing of new information, less around pure perception or even organization.

Nevertheless, it offers a good orientation for all trainers, coaches, teachers, consultants, presenters to always pay attention not to overstrain their audience and not to overload teaching elements. In short: it disciplines and forces you to limit yourself to the essential.

Magic number: seven or four?

When Australian Gordon Parker reviewed Miller’s research in 2012, he came to a different conclusion: Not seven — four is the magic number at which the limit of mental memory is reached.

Parker also cites telephone numbers as evidence, which often has seven digits and is therefore often grouped into two-digit chunks so that we can remember them better. For example, 1234567 becomes 12 34 56 7 — that is, only four chunks, but seven digits.

However, Parker himself admits that this is not to say that our memory cannot store more than four things, but only that it cannot keep more than four things present at the same time.