Number Memory
Memorize a number that grows one digit at a time. Tests pure digit-span capacity. Memorize the number shown, then type it back. Each round adds one more digit. This is the classic digit-span test used in cognitive assessment since the late 19th century.
What this test measures
The digit-span test is one of the oldest measures in cognitive psychology. It was introduced by Sir Francis Galton in the 1880s and standardized by Alfred Binet in the early 1900s. It is part of the Wechsler Adult Intelligence Scale (WAIS) and is widely used in clinical and research settings as a quick measure of verbal working memory capacity.
The test measures how many digits you can hold in short-term memory and reproduce in order. The longest sequence you can reliably repeat is your digit span. There are two variants: forward span (repeat in the same order) and backward span (repeat in reverse order, which is harder because it requires you to hold and reorder). Our version uses forward span.
Typical scores
Published norms (Wechsler, 2008, and later replications) place the average forward digit span for healthy adults at about 7 ± 2 digits, with most people falling between 6 and 9. The famous "magical number seven, plus or minus two" phrase coined by George Miller in 1956 referred to this kind of capacity limit, though Miller was generalizing across several related paradigms. Children's spans are shorter and increase through adolescence.
Worked example
Round 1 shows you the number 4 7 2 for two seconds. The display clears.
You type 472 and click Submit. Correct — the next round shows a 4-digit
number, say 9 3 1 8. You type 9318. This continues until
you fail a round, at which point the test ends and your final score is the longest
sequence you successfully reproduced.
How to improve your span
- Chunk the digits. A 9-digit number like 471933826 is hard to hold as nine items but easy as three chunks: 471-933-826. Chunking effectively multiplies your span.
- Rehearse silently. Sub-vocal rehearsal — silently repeating the digits to yourself — extends how long you can hold them. Preventing rehearsal (e.g., by making you say "the the the" out loud during the delay) collapses span to 3-4 digits.
- Attach meaning. If the digits happen to form a date or a phone number you recognize, encode them as that meaning rather than as a sequence of disconnected numerals.
What the test does not measure
Digit span is a clean measure of verbal short-term storage, but it does not capture the full complexity of working memory. The ability to manipulate stored information (not just hold it) is measured by backward span and by complex-span tasks like the reading span or operation span. Our Dual N-Back tool targets a different working-memory component — the ability to update stored information against an ongoing stream.