Digit Span: How Many Numbers Can You Hold in Mind?

Try to remember a phone number someone reads out, without writing it down. That short struggle is your working memory at work. Digit Span measures how much of it you have for numbers.

How to play

A whole number appears for a few seconds. When it hides, type it back with your keyboard or the keypad. Level 1 has 2 digits and each level adds one, up to 20. One wrong answer ends the test, and your answer time is measured too.

Where it comes from

Digit span tests have been part of intelligence and memory testing for over a century. In 1956, George Miller wrote a famous paper about "the magical number seven, plus or minus two", the rough number of items people can hold at once. Later research by Nelson Cowan suggested the true limit is closer to four chunks when people cannot group or rehearse.

Why groups help

A chunk is a group your brain treats as one item. "1 9 4 7" is four digits, but "1947" can be one chunk if it is a year you know. That is why phone numbers are written in groups. Our version shows the whole number at once, so you can chunk it, which is different from the classic test where digits are read out one by one.

What practice can change

People can become dramatically better at digit span with practice, mostly by learning chunking strategies. That shows improvement at this task, not a bigger memory in general. Reviews of working memory training find little evidence of benefits beyond the trained tasks.

A worked example

Suppose the number is 4 7 1 9 2 6 8. Seven separate digits is near the limit for many people. Split it into groups: 471, 926, 8. Now you are holding three chunks instead of seven digits. If part of it is meaningful to you, like a year or a familiar number, that part becomes even easier.

Common mistakes

Trying to see the number as a picture rather than saying it silently is a common one; for most people, saying it in their head works better. Waiting too long before typing lets the memory fade. Another is changing strategy halfway through a long number.

Questions people ask

Is seven the limit? The famous "seven plus or minus two" is a rough guide. With grouping, people can do more; without it, the true limit may be nearer four chunks.

Why is backwards harder? You must hold the number and also reverse it.

Does practice increase my memory? It mostly teaches better strategies for this task.

Tips

Split the number into groups of three or four and say them silently. Not medical advice.