Number Memory

How to play

A number appears for a few seconds, then disappears. Type it back exactly. Every round the number grows by one more digit, so round one is a single digit and round ten is ten digits long. One wrong answer ends the run, and your score is the longest number you repeated correctly. Most adults stop somewhere between seven and nine digits, which is the classic digit span result psychologists have measured since the 1880s.

Tips

• Chunk the digits. Reading 4 8 1 5 9 2 as 481 592 turns six things to remember into two.
• Say them under your breath. The phonological loop holds sound better than it holds shapes.
• Look at the whole number at once instead of scanning left to right. You get more from one glance.
• Type immediately. Every second you wait, the tail of the number fades first.
• Do not try to picture the digits. Rehearsing the sound beats visualising for strings this short.

Digit span, the oldest memory test

Repeating back a string of digits is one of the earliest formal tests of memory, in use since the 1880s, and it is still part of standard intelligence assessments today. The result is called digit span, and for adults it lands around seven digits, give or take two. That figure is where the phrase seven plus or minus two comes from, and it is the reason phone numbers were designed the length they are.

The game grows the number by one digit each round and gives you a little more time per round to read it, but the time is capped, so long numbers really do have to be held rather than transcribed. The first digit is never zero, so a number always has the length it claims.

Extending your span

• Chunk. Reading 481592 as 481 and 592 turns six items into two.
• Rehearse in sound, not sight. The phonological loop holds a spoken string better than a picture of digits.
• Take the number in one glance rather than reading left to right. A whole view encodes faster than a scan.
• Type immediately. The tail of a number fades first, and every second of delay costs the last digits.
• A score in the range of 7 to 9 is normal. Well beyond that usually means you have found a chunking system that works for you.

Common questions

What is a normal digit span?

Around seven digits for adults, give or take two. A run of 9 or more here is a good result.

Does the number stay on screen longer as it grows?

Yes, by a little each round, but the display time is capped so long numbers must be remembered rather than copied.

Can the number start with zero?

No. The first digit is always 1 to 9, so a ten digit number really has ten digits.