How fast can you work a simple rule?

Six symbols, each paired with a digit. The pairing stays on screen the whole time. A symbol appears, you press its digit, another appears. Ninety seconds.

It is not a memory test — the key never goes away, and you are meant to look at it. What it measures is how quickly you can keep applying a rule you already have in front of you.

It is one task in the Processing Speed domain.

Nothing you do here is stored or sent. The task runs entirely in your browser and your result exists only on your screen.

Ninety seconds. Get as many right as you can, and accuracy counts.

Works with a keyboard, a numeric keypad, or one thumb.

Before you start

It measures one narrow thing — how fast you apply a simple rule you can see, right now, in the conditions you are in.
Keep the tab in front. If you switch away mid-run the attempt is void, because browsers slow down background tabs and that would hand you extra time.
A count on its own does not mean much. We have measured nobody, so there is nothing to compare it against. The part of the result worth reading is the second half against the first.

How this is scored, in full →

Your result

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correct in ninety seconds

What this task tested

How quickly you can apply a rule that is in front of you the whole time. The key never disappears, so this is not asking you to remember the pairings — it is asking how fast you can keep using them. It is one task in the Processing Speed domain.

The half you should actually read

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What this did not measure

This says nothing about how quickly you think in general, how fast you read, or how sharp you are. It measures one narrow thing: the rate at which you applied one visible rule, once, on one screen.

This is a domain score, not a BrainScore. A single task in a single domain does not make a composite, and we are not going to invent the rest of it.

Your seven scores make one shape. Take the other tests and this number becomes one arm of your Cognitive Fingerprint — seven arms and a single number between 0 and 100. That number says how far you got through what these four tasks can measure. It is not a percentile and not a comparison with other people, and every constant behind it is published, including the one we chose rather than derived.

An online test cannot tell you whether something is medically wrong. This one cannot, and neither can we. That is not caution — it is the limit of the task. If your concentration is worrying you, a doctor is the right person to ask. And you do not need a low score here to justify the appointment.

How much should you trust this number? What moved it that is not you, what it legitimately supports, and what it cannot.

Things that moved this number that are not your processing speed

Your device. A phone keypad and a physical keyboard are not the same instrument. This is a count of completed matches, so how fast you can press matters.
This test may work without sight, and one thing was fixed on 6 September 2026 to make that possible. Each symbol is announced by name as it appears, and the key now carries the symbol names in text — before that fix it listed the digits alone, so assistive software could tell you a circle had appeared without ever telling you that circle means 4. We have not tested it with a screen reader and will not claim it works until we have. Odd one out and paper folding cannot be done without sight, and say so.
Repeat attempts. A second attempt tends to raise the count, because the key becomes familiar. Retest gains are well documented across cognitive tasks and keep growing until about the third attempt. A second attempt is not progress.
Your day. Sleep, stress, illness, caffeine, time of day and interruptions are conditions we cannot hold constant and did not measure.

Should you believe this number?

What it legitimately supports: that in ninety seconds, on this device, under whatever conditions you were in, you completed this many matches correctly. That is a real measurement of a real thing, and it is narrow on purpose.

What it cannot support: any statement about how you compare with other people. We have measured nobody, our reference sample is zero, and a count with nothing to compare it against is not a ranking. The methodology page sets out exactly where we are on the norming ladder.

If another site gave you a different number for a symbol substitution task, both can be right. Versions of this paradigm differ in the length of the window, in how you answer, in how many pairs are in the key, and in whether the score counts what was correct or what was attempted. We set out exactly where the difference comes from — with published figures from a study where the same 104 adults took three versions of this task in one sitting.

Why the two halves are the useful part. The split compares you against yourself across two 45-second halves of one run — same person, same device, same sitting, thirty seconds apart. It is the one comparison that needs no reference sample at all, which is why it is the part of this page we put weight on.

What next

Read what this actually measures

Processing speed in the cognitive sense — what it is, what genuinely moves it, and why the way a browser measures it decides what the number is worth.

Processing speed: what it is, what moves it, and what a browser can actually measure

Why this is not a reaction time test

Somebody measured the equipment directly, with the human taken out of the experiment. A touchscreen added 400ms of latency to a true reaction time of 105ms. That result is why this page scores a rate over ninety seconds instead.

Are online reaction time tests accurate?

Try a different demand

This task is about rate. The other two are not — one is about how much you can hold at once, the other about what you notice with no clock running at all.

Digit span — capacity, about two minutes
Odd one out — accuracy, no timer

Check our working

How BrainScore works — what we measure, how a task becomes a score, and what the score cannot tell you
The instrument register — every task, its norming rung, its sample size and its version
Corrections — every change we have made to a published claim, dated

— worth knowing that scores on cognitive tasks tend to rise on a second attempt because the task has become familiar, not because anything about you has changed. Across 122 studies, retest gains are consistent enough to be a standard methodological problem, and they keep growing until about the third attempt — which is a fact about groups of studies, not a forecast for you.

Two questions, if you have twenty seconds

We are trying to find out whether explaining a result is worth doing at all. Nothing is recorded except which buttons you press — no result, no identifier, nothing that could be traced to you. There are no wrong answers here and nothing follows from your choice.

1 · Did the explanation above make sense to you?

Comparing this run with another one

The two halves above compare you with yourself inside one run. This compares two runs — and it is the same idea one level up: name the conditions, take it again, and read the pair rather than either number alone.

You do not have to write it down. Name the conditions for the run you just did and we will hold it on this screen while you do a second one.

How this is scored

Published in full, because a score you cannot check is not worth much.

The task

Six symbols, each paired with one digit from 1 to 6. The pairing is generated fresh for every run, so it cannot be learned between attempts.
The key stays on screen for the whole window. This is a substitution task, not a recall task — you are meant to look at it.
A symbol appears. You press the digit paired with it. The next symbol appears immediately.
No symbol repeats twice in a row, so you cannot get a run of the same answer.
The window is 90 seconds, measured from the first symbol to the last.

The scoring rule

Your score is the number of correct matches completed in the window. Nothing else is added to it.
A wrong press is counted as an attempt and not as a correct match. It does not subtract.
The symbol advances whether the press was right or wrong, so a wrong answer costs you the time it took and nothing more.
Accuracy is reported as two counts — correct, and attempted — never as a percentage on its own.

The two halves

The window is split at 45 seconds. Correct matches are counted separately in each half.
Both halves are the same length, so the two counts are directly comparable without any adjustment.
This is the only comparison on the page, and it is you against yourself in one sitting.

Exclusion rules — when an attempt does not count

If this tab is hidden at any point during the window, the attempt is void and is not scored. Browsers slow timers down in background tabs, which would leave the clock running slower than real time and hand you more of it than the task allows.
An attempt abandoned by navigating away is not scored. You keep whatever you finished.
Nothing is stored either way, so a void attempt leaves no trace.

What is deliberately not here

No band, no label and no threshold on the count. A count means little without a reference sample and ours is zero — inventing a boundary would be inventing a finding.
No percentile, no average, no comparison with anybody. Rung 0. The ladder is published.
No reaction-time measurement. We considered one and rejected it: a browser cannot measure reaction time in absolute terms, because what it records includes display latency and input latency that vary by tens of milliseconds between devices. A rate over ninety seconds is barely touched by that; a single 250-millisecond reading is dominated by it.