Digit Span
Repeat sequence forward or backward
About this trainer
Digit Span shows you a sequence of digits one at a time, then asks you to type them back. In the forward version you reproduce them in the same order; in the backward version you reverse them. The sequence grows by one digit each time you succeed, so the game keeps pushing right up to the edge of how much you can hold.
What it develops
It trains verbal short-term and working memory: how many items you can keep active at once, and, in the backward version, your ability to manipulate that material in your head rather than just store it.
History
The task comes from early experimental psychology, where measuring the limits of memory was a central question. It was absorbed into the first standardized intelligence batteries in the early 1900s and has stayed in clinical use ever since, which is why almost everyone who has taken a formal IQ or memory assessment has done some form of it.
Who created it — and when
The method is credited to British psychologist Joseph Jacobs, who published it in 1887 to measure how much information short-term memory could hold. It was later built into the Binet-Simon scale and then the Wechsler scales (WAIS and WISC), where Digit Span Forward, Backward, and later Sequencing remain standard subtests.
How to train
The core trick is chunking: group a long string into pairs or triples (4 7 1 9 3 8 becomes 47, 19, 38) so you hold three units instead of six. Sub-vocally rehearsing the sequence as it appears and giving it a rhythm both help, and for backward span it is often easier to picture the digits written out and read them off in reverse.
How long to practise
Short, frequent sessions beat long ones: 5 to 10 minutes a day is plenty, since once the sequence exceeds your span you are mostly accumulating errors, not learning. A few sessions a week is enough to see your reachable length climb over a couple of weeks.
Evidence base
What is solidly shown is narrow: with practice you get better at digit span itself, and your measured span on similar recall tasks rises. The bigger claims are weak. Multiple meta-analyses, including Melby-Lervåg, Redick and Hulme (2016), found that working memory training of this kind does not produce reliable far transfer to general intelligence or everyday cognition, and several high-profile transfer effects failed to replicate. Treat it as a sharp tool for one specific skill, not an IQ booster.
Recommendations
Use chunking deliberately from the start, and push backward span as well as forward, since reversing the sequence is the part that exercises working memory rather than plain storage.
FAQ
Is a higher digit span the same as being smarter?
Span correlates modestly with measures of intelligence, but it is one narrow ability, not a measure of overall intelligence. Training your span up does not reliably raise your IQ.
What is a normal digit span?
Most adults can repeat about seven digits forward, give or take two, and a couple fewer backward. Your trainable ceiling sits a little above your relaxed average.
Is using chunking cheating?
No. Chunking is a real memory strategy that the task is partly designed to reveal, and it is exactly how skilled performers extend their span. It is worth learning rather than avoiding.
Variants
Common variations include forward span, backward span, and digit sequencing (recall the digits in numerical order). Related tasks swap digits for letters, words, or spatial positions, as in the letter-number sequencing and Corsi block-tapping tests.