Number memory test: method

What it measures

Short-term memory span for digits (forward order): the longest digit string recalled correctly right after presentation.

Procedure

A random number is shown on screen all at once (first digit 1 to 9, the rest 0 to 9; repeats allowed), with a shrinking bar, for 1,000 ms plus 600 ms per digit. It is then hidden and the player types it into a field (numeric keypad on phones; non-digits are removed) and submits. Feedback shows right or wrong and the number. A right answer adds one digit; a wrong one repeats the same length with a new number. Two misses at one length end the test. The start length is 3 and the maximum 25. There is no practice and no time limit for typing.

Parameters

Scoring

Primary metric: span = the longest length typed back exactly right (0 if none); higher is better. Also reported: longest length tried, number of trials and number correct. An answer is right only if it matches the number exactly (leading and trailing spaces ignored). No percentile or norm is shown.

Valid-run rules

Only digits up to the maximum length are accepted; the trial log has an abuse cap. The run is not stopped when the player leaves the tab. Every scored run is stored with its input device class (touch, mouse, keyboard), page language, scorer version and runner-config hash. Quality flags (for example many runs from one connection within an hour, a missing visitor id, an automated browser, impossibly fast answers) and earlier attempts by the same visitor, account or connection are recorded with the row. Such runs are kept, but they are left out of any comparison with other players. Flags never change the player's own result.

Differences from the classic task

Clinical digit span tests read digits aloud at one per second, test forward and backward order, and usually start at 2 or 3 digits with two trials per length and a stop after two failures at one length. This version shows all digits at once on screen and asks for typed recall, forward only, so its span is not the same as a clinical digit span score.

Limitations

Visual presentation allows chunking and rehearsal strategies that change the score; players can also write the number down. Strategy, tiredness and practice move scores from day to day. The setting is unsupervised and has no norms. No clinical or diagnostic use.

Languages and review status

Digits only (Western Arabic digits, shown left to right on all pages); instructions in all site languages.