Mackworth Clock Test — The Job Is To Notice
The Mackworth Clock Test was built in 1948 for a practical problem: radar operators kept missing contacts after a while on watch, and nobody could say how much or why. Its design is deliberately empty — a dot moves one position round a blank dial every second, and every so often it moves two. Nothing else happens. Play it online for free, no download and no sign-up required to start.
Not a diagnostic tool. The original version ran for thirty minutes to an hour, with signals appearing less than once a minute. This one runs about two minutes with skips roughly one step in twelve, because a two-minute round has to contain enough of them to score at all. That trade-off has a real consequence: the vigilance decline this test is famous for takes far longer than two minutes to appear, so you will not see it here and your score cannot be compared with published figures. Like everything on this site it is a practice and self-tracking exercise, not validated, not normed, and it cannot screen for or indicate any condition.
A quiet round of Mackworth Clock Test — Standard. When you start, everything else fades — just you and the task.
No sign-up needed. Press Esc to exit anytime.
Tip
The skip is a distance, not a flash. Nothing lights up and nothing changes colour — a skip is just the dot landing further round than it should. That means you are comparing this step against the rhythm of the last few, not reacting to an event. People who stare at one spot on the dial do worse than people who let the dot lead their eye.
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How to play
- A dot steps clockwise round the dial, once every second.
- Now and then it skips — moving two positions instead of one.
- Press space, or tap the dial, as soon as you notice a skip.
- Most steps are ordinary. Doing nothing is the correct response to those.
Mackworth Clock Test tips
Ways to play it better — each one comes from how this version actually scores, not from general advice about concentration.
The skip is a distance, not a flash
Nothing lights up and nothing changes colour — a skip is just the dot landing further round than it should. That means you are comparing this step against the rhythm of the last few, not reacting to an event. People who stare at one spot on the dial do worse than people who let the dot lead their eye.
You will miss one right after you settle in
The rhythm is easy to follow, and following it is not the same as watching it. The moment it starts to feel automatic is the moment a skip goes by unremarked, which is exactly the failure this task was built to catch in radar operators on a long shift.
Doing nothing is most of the job
On Standard the dot takes 120 steps and only a handful of them skip, so almost every second calls for no response at all. That is the task, not dead time — a version where something happened constantly would measure how fast you react rather than whether you are still watching.
One caveat worth knowing: a change of strategy moves your score for reasons that have nothing to do with attention. Your dashboard reads each session against your own recent ones, so if you adopt something from this list, give it a few sessions before reading anything into the trend.
Frequently asked questions
Why is the dial blank, with no numbers or marks?+
Because marks would let you count positions instead of noticing the movement, and counting is a much easier task than watching. The original apparatus was a plain dial with a moving spot of light for the same reason.
How is this different from the Go/No-Go or SART tests here?+
Those two first build a habit of pressing and then ask you to interrupt it, so the difficulty lives in stopping. This one never gives you a habit at all — you sit still for most of it, and the difficulty lives in noticing. They are different demands even though all three involve rare events.
Is this the same length as the original experiment?+
No, and the difference matters. The original ran for thirty minutes to an hour with far rarer signals. The decline in detection over a long watch is the finding this test is famous for, and it needs much more than two minutes to show up — so a short round like this one measures how well you notice, not whether you fade.
Can this tell me whether I have an attention problem?+
No, and no online test can. This is a practice exercise, not a screening instrument: not validated, not normed, and not administered under controlled conditions. If something about your attention concerns you, that is a conversation for a professional rather than a score on a website.
Where this fits
- Mind Wandering — Built in 1948 because radar operators on a long watch kept missing contacts — the first serious attempt to measure drifting rather than complain about it. Nothing here builds a habit for you to interrupt: you sit still and the only demand is to keep noticing.
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