Number memory

The rules, precisely

You start with a single digit. It stays on screen for a length of time that grows with the number: 900 milliseconds per digit plus a 600 millisecond buffer, so a 5 digit number shows for just over 5 seconds and a 10 digit number for about 9.6. Then it vanishes and you type it back. An exact match advances you to the next level with one more digit; the first wrong answer ends the run, and your score is the number of digits you last recalled correctly. There are no lives and no retries at a level, which is exactly how a classic digit span test works.

Two small mercies are built in. The generated number never starts with a zero, so you will not lose a run to a leading digit you reasonably ignored. And any spaces you type are stripped before checking, which means you can enter the number in groups, like 1492 1776, and still be scored on the digits alone.

Chunking is the whole game

Raw rehearsal, repeating digits in your head at speed, carries most people to somewhere between 5 and 9. Past that, the winning move is chunking: recode the string into fewer, larger units. Years work brilliantly, so does reading pairs as two digit numbers, 8 3 1 9 becomes eighty-three nineteen, four items down to two. Since the space-stripping rule lets you type in groups, chunk at memorization time and type in the same groups at recall time. The rhythm you encode with is the rhythm you retrieve with.

The tip that grinders learn: spend the last second of display time on the final three or four digits, not re-reading from the start. The front of the number benefits from the primacy effect and tends to survive on its own; it is the middle and end that die. Say the tail once, deliberately, right before the digits disappear, and type immediately while it is still echoing.

What your score means

The famous finding this style of test produced is 7 plus or minus 2: most adults land between 5 and 9 digits. Reaching double digits is strong. Scores above 12 nearly always reflect a practiced chunking or mnemonic system rather than a bigger working memory, which is not cheating, it is the skill the test rewards. Fatigue, distraction, and background noise cost a digit or two, so a bad score at midnight is a bad measurement, not a diagnosis.

Design notes

The pacing of roughly one second per digit matches standard digit span administration, where digits are read aloud at one per second. The test shows the whole number at once rather than sequentially, which is slightly easier and slightly friendlier to chunkers, worth knowing if you compare against a psychology-lab score. After a miss the screen shows the true number next to what you typed, so you can see whether you dropped a digit, swapped a pair, or lost the tail; those are different failures and chunking fixes them differently. Your best is stored only in this browser. Nothing is uploaded, and there is no way for the page to tell an honest 11 from a screenshot, so the number is for you.