Why your digit span will not match another site's

You held 6 here and 9 somewhere else. Nothing is broken. Here are the five things that differ between two digit span tests, and how much each one is worth.

Version 1.0 · Published 5 September 2026 · Last reviewed 5 September 2026 · About the digit span test

1. How long each digit is on screen

Ours shows each digit for one second, with a 200 millisecond gap, and that is published on the test page. A test that shows digits for two seconds is an easier test. A test that shows them for half a second is a harder one.

This is not a hypothetical difference and we have been caught by it ourselves. Browsers slow timers down in background tabs, so our own test was quietly running at about two seconds a digit for anyone who switched away mid-sequence. We found it, published the correction, and now void any attempt where the tab was hidden. If a timing difference that size can appear inside one test, it can certainly exist between two.

2. How many attempts you get at each length

We give two attempts at each length, and your span is the longest length where at least one attempt was correct. That is a deliberately forgiving rule and it is stated in full.

A test that gives one attempt will usually produce a lower number for the same person, because a single lapse ends the run. A test that gives three will produce a higher one. Nothing about the person changed; the stopping rule did.

3. Where the test starts and how it steps

Ours starts at three digits and adds one at a time. A test that starts at five saves you time and removes the easy trials — which matters if a lapse of attention early on would have ended your run anyway. A test that steps by two lengths at a time will land on a coarser number.

4. Forward, backward, or a blend

Forward span and backward span are not the same task and generally do not produce the same number. Holding a sequence is one thing; holding it while reversing it is another, and it draws on more than storage.

Our result reports a forward span, and offers a reverse phase separately and after the fact — never blended into one figure. A site that reports a single "digit span" without saying which it measured has given you a number you cannot interpret.

5. Whether the scoring rule is published at all

The other four differences are all knowable, but only if both tests say what they did. Most do not. Without the presentation rate, the attempts per length, the starting length and the direction, two digit span numbers cannot be reconciled even in principle — and there is no way to tell whether either was computed sensibly.

Ours is published in full, including the exclusion rules and the fact that band boundaries are a design decision rather than an empirical finding.

What would have to be true for two spans to be comparable

• The same presentation rate, and both actually running at it.
• The same number of attempts per length and the same stopping rule.
• The same starting length and step.
• The same direction — both forward, or both backward, never one of each.
• Both rules published, so the difference can be located rather than guessed at.

So which number should you believe?

Neither, as a statement about you — each describes what you did on one task under conditions that were probably not the same. Ours claims to be the longest sequence you gave back in order, on our task, today. That is all it is.

The comparison that survives is you against yourself: the same test, conditions you can name, and a note of what was different. It costs nothing and it does not require anyone to have been measured.