The Code, remember the digits

What it asks of you

The Code asks for verbal working memory, the inner voice that repeats a phone number long enough to dial it. You see digits, you hold them, you give them back.

Each level adds one digit, so the game always works at the edge of your span.

How to play

1. A code of three digits shows on the screen, a little longer for longer codes.
2. It hides, so type it back on the keypad or your keyboard.
3. Right, and the next code has one more digit.
4. Wrong, and you lose one of your two lives and get a new code of the same length.
5. Your score is the longest code you typed back right.

The research behind it

Joseph Jacobs measured digit span in 1887, which makes it one of the oldest tests in psychology (Jacobs, 1887). George Miller later made the span famous with his magical number seven, plus or minus two (Miller, 1956).

The span is not a fixed wall. Grouping digits into chunks, three then four, lets you hold more, a strategy Miller described (Miller, 1956). Practising The Code is practising exactly that.

On your weekly card

The Code is the game of season 3, in free play from the start of the season.

It joins your Memory stat only if its reliability, measured during the beta, reaches a test retest correlation of 0.60. Until then it never counts on your card.

Questions

How many digits can people hold?

Around seven is the classic answer (Miller, 1956). The number memory test places your span in a distribution of public games (Human Benchmark, 2026).

Should I say the digits in my head?

Yes if it helps. Repeating and grouping are the natural tools of verbal working memory.

Why two lives?

One slip should not end a good run. The second life gives you a new code of the same length.

Sources

1. Jacobs J. (1887). Experiments on prehension. Mind 12(45), 75 to 79. doi.org/10.1093/mind/os-12.45.75
2. Miller G.A. (1956). The magical number seven, plus or minus two. Psychological Review 63(2), 81 to 97. doi.org/10.1037/h0043158
3. Human Benchmark, score distributions embedded in humanbenchmark.com, read on 13 October 2026. Reaction time n 70 940, sequence memory n 35 868, chimp test n 27 233, number memory n 24 084. humanbenchmark.com