How to use this test
Start when ready
Choose Start and keep your attention on the target.
Wait for the change
Do not click before the target changes.
Click once
Click as soon as it changes, then compare the result with another attempt.
What we check
The test records the interval between a browser-driven visual change and your click using a high-resolution browser timer.
A result reflects this page, your device, your input method and your attention during that attempt.
What this test can’t tell you
It is not a diagnosis, a measure of driving fitness, or a comparison against a population average.
Something not working?
I clicked too soon
Start a new attempt and wait for the colour change.
My result varies
That is expected. Try a few relaxed attempts rather than drawing a conclusion from one.
Common questions
Is this a medical test?
No. It is a simple browser timing exercise.
Does it save results?
No. Results stay on the page until you reset or leave.