Digit Span Test Guide: How Working Memory Span Works
A digit span test shows a string of numbers and asks you to enter them back in order. In this free online version the string grows by one digit when you succeed and shrinks after a miss, so it settles on the longest sequence you can hold: your digit span. Miller (1956) put the typical limit near seven.
The theoretical foundation of digit span began with George A. Miller's seminal 1956 paper, 'The Magical Number Seven, Plus or Minus Two', which identified human immediate memory span as approximately seven discrete informational items. David Wechsler (1939, 1955, 2008) incorporated forward, backward, and sequencing digit span into the Wechsler Adult Intelligence Scale (WAIS), establishing it as the clinical gold standard for the Working Memory Index (WMI).
According to Alan Baddeley's multicomponent working memory model (Baddeley & Hitch, 1974; Baddeley, 1986, 2000), numerical strings are temporarily maintained in the Phonological Loop. The phonological store holds acoustic traces that decay within 1.5 to 2.0 seconds unless refreshed by the articulatory rehearsal component ('inner voice'). Furthermore, Nelson Cowan (2001, 2010) demonstrated that when rehearsal is controlled, pure unchunked focal capacity is strictly $4 \pm 1$ items; reaching higher digit spans relies entirely on strategic chunking.
Featuring high-precision digital chronometry (Woods et al., 2015), this drill tests your raw capacity and response cadence, converging on your true span through an adaptive psychometric staircase.
How this is measured: every event is timestamped with the browser's performance.now() high-resolution clock, entirely on your device -- no score is uploaded. Browser timers are deliberately coarsened as a Spectre mitigation (typically to about 1 ms), and your display quantizes each change to its refresh interval, about 16.7 ms per frame at 60 Hz (Woods et al., 2015). Treat differences smaller than about 5 ms as measurement noise, and compare your own runs on the same hardware rather than against someone else's setup.
Data transparency: SkillDrills collects no aggregate data. Your scores and settings live only in your browser's localStorage and are never uploaded, so this site publishes no user averages, percentiles or player counts. Every figure quoted here comes from the published work in the References panel below.
This drill is a free browser game for practice and interest. It is not a medical device, a diagnostic instrument, or a screening or treatment tool for any condition, and no score here says anything about your health or your memory in a clinical sense. If you have concerns about your memory or thinking, speak to a qualified clinician.