Digit symbol test — free substitution speed test in your browser

A key across the top of the screen pairs each digit from 1 to 9 with a simple symbol. A digit appears; you tap its symbol. Then the next digit. You get ninety seconds, and your score is how many you get through.

The key is reshuffled every run and stays on screen the whole time, so there is nothing to learn between attempts and nothing to remember during one. Free, no download, no sign-up, and it plays the same with a thumb as with a mouse.

How to play

• Read the key at the top. Each digit sits above the symbol it stands for.
• A digit appears in the yellow box. Find it in the key, then tap that symbol on the pad below.
• A wrong tap costs 1 second and moves on to the next digit anyway. You cannot work through the pad until something sticks.
• On a desktop the number keys 1 to 9 press the pad buttons, reading left to right, top to bottom.
• Your score is correct substitutions in 90 seconds, and your top 5 is kept on this device.

Why the penalty is one second, and why the key never hides

The digit symbol substitution task is one of the oldest items in cognitive testing. Versions of it have been in the Wechsler adult intelligence scales since the 1930s, and a standalone ninety-second variant has been used in multiple sclerosis research for decades. It survives because it is quick, needs no language, and mostly measures one thing: how fast you can carry out a simple lookup over and over without the process falling apart.

Two decisions here follow directly from that, and both are deliberate departures from what a game designer would otherwise do.

The key stays visible. Hiding it after a few seconds would make a better-looking game and a worse test, because it would stop measuring lookup speed and start measuring short-term memory. The site already has three games that measure memory span. This one is about throughput, and the moment the key disappears it is a different task.

A wrong answer costs one second, not three. Most timed games here charge three seconds, because in those games a wrong answer is a guess and guessing needs to be expensive. Here a heavy penalty would push you toward being careful, and carefulness is exactly the variable the test is trying to hold still. One second is enough to make accuracy worth having without turning the task into a different one. The wrong tap also moves on to the next digit, which closes the obvious exploit: if a miss left the same digit up, you could simply work along the pad until one of the nine landed.

The interesting thing to watch in your own scores is not the total. It is the shape of the run. Almost everyone starts slowly, speeds up over the first fifteen or twenty items as the more distinctive symbols stop needing a lookup, then flattens. The plateau is where the score actually comes from, and it moves surprisingly little from day to day.

Worth saying plainly: this is a browser game, not a clinical assessment. The real instruments are administered on paper under controlled conditions and scored against age norms. Nothing here diagnoses anything. Chase your own best.

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