How many things can working memory hold?

Around four meaningful chunks for most people, once rehearsal is controlled for, rather than the widely quoted seven. What counts as one chunk depends on what you already know, which is why an expert holds more of their own field than a novice.

Can working memory be trained?

Training programmes reliably improve performance on the trained task and transfer poorly to anything else. Externalising — writing things down, reducing what has to be held — has a much better record than training the capacity itself.

Working Memory: The Desk, Not the Filing Cabinet

Working memory: The system that holds and manipulates a small amount of information in mind while you use it — the desk you work on, not the cabinet you store things in.

Where the idea comes from

George Miller’s 1956 paper gave us "the magical number seven, plus or minus two", which became one of the most quoted findings in psychology. Later work, particularly Nelson Cowan’s, put the figure closer to four items when rehearsal and chunking are controlled for. Miller’s own paper was more cautious than its reputation.

How it shows up

Losing the thread of a task the moment anyone speaks to you
Walking into a room and having no idea why
Needing to restart a calculation every time you are interrupted
Rebuilding the whole plan each time you return to a project

Practical steps to try

Write down the next action before leaving a task, so re-entry does not require reconstruction
Keep one thing in the head and everything else on paper or screen
Chunk: four meaningful groups fit where fifteen loose items do not
Protect the block from interruption rather than trying to recover faster from it

Where the popular version overreaches

The "seven items" figure is still repeated everywhere and is probably about three too high. It also does not mean seven of anything — a chunk can be a digit or an entire familiar concept, which is most of what expertise does.

Common questions

How many things can working memory hold?: Around four meaningful chunks for most people, once rehearsal is controlled for, rather than the widely quoted seven. What counts as one chunk depends on what you already know, which is why an expert holds more of their own field than a novice.
Can working memory be trained?: Training programmes reliably improve performance on the trained task and transfer poorly to anything else. Externalising — writing things down, reducing what has to be held — has a much better record than training the capacity itself.

Sources

Cowan (2001) — the magical number 4

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