- What's a normal reaction time?
- For a simple visual stimulus (a color change) and a mouse click, the median for healthy adults is in the 200 to 250 ms range. Faster than 200 ms is in the fast tail; slower than 300 ms is in the slow tail. None of those bands are diagnostic — they describe a distribution. The fastest human reactions ever recorded (elite sprinters reacting to a starting pistol) are around 100 ms; reactions much faster than that on a mouse-click test usually mean the user got lucky guessing the timing, not that they're superhuman.
- Why is my reaction time slower than I expected?
- A few non-cognitive factors stack up. Your monitor refresh rate is the first floor — a 60 Hz monitor refreshes every 16.7 ms, so on average you wait half a frame (8 ms) before you see the green. Your mouse polling rate adds another 1 to 8 ms depending on the device. Browser frame timing adds another frame. None of that is your reflexes; it's the hardware in the middle. Beyond hardware, fatigue and distraction can add 50 to 100 ms easily. Try the test after coffee, on a 144 Hz monitor, focused on nothing else, and the number will improve without your reflexes actually changing.
- What does this test actually measure?
- Simple visual reaction time — the latency between seeing a stimulus and producing a motor response. It's not a measure of intelligence, cognitive speed, decision-making, or sports ability. The brain pathway is small and well-understood: light enters the eye, signal travels through the visual cortex, motor cortex fires, signal travels to the finger, finger clicks. The whole loop is about 200 ms. Tests that measure choice reaction time (decide between two stimuli), Go/No-Go, or working memory are different and much more cognitive — this one is essentially a hand-eye latency check.
- What's a false start and why doesn't it count?
- If you click before the panel turns green, that's a false start — the test discards it and asks you to retry that trial. The reason is the delay is random; if false starts counted, you could click in a rhythm and shave 50 to 200 ms off your real reaction time. Penalizing them too harshly (adding to your average) would be discouraging for new users. The middle ground is to not count them at all but show you the count so you can see if you're rushing.
- Why 5 trials and not more?
- Five is enough to smooth out one bad luck trial without becoming a chore. Most published reaction-time research uses 10 to 50 trials per subject, but those studies are testing groups, not entertaining individuals. Five gives a reasonable mean for self-comparison and lets you re-run another five if you want a better feel. If you want a serious statistical estimate, run several rounds of five and average the means.
- Does this work on mobile?
- Yes. The panel is a single big touch target and the timing uses performance.now() the same way on touch devices as on desktops. Mobile times tend to run 30 to 80 ms slower than desktop times because touchscreen scan rates are 60 to 120 Hz with extra debouncing latency, and your hand has to travel from a resting position to the screen rather than already hovering over a mouse. Compare yourself to yourself across sessions on the same device; don't compare your phone time to a friend's desktop time and conclude anything about your reflexes.
- Can I cheat?
- Sort of. If you mash the panel during the red phase repeatedly, eventually one click will land just after green and look like a sub-50 ms reaction. The false-start rule catches the obvious case, but a fast clicker could probably squeeze a fake number through with timing luck. The test doesn't try to fingerprint cheating — it's a self-assessment tool, not a leaderboard. The number is whatever you make it; getting an honest one is its own reward.
- Is my data stored?
- No. Every trial runs in your browser and disappears the moment you close the tab. We don't log times, we don't store rankings, we don't have an account system on this tool. If you want to keep a result, screenshot it.
- What's the difference between this and a Stroop test or a typing test?
- A Stroop test measures interference — your brain has to override an automatic response (reading the word) to give the right one (naming the color). That's a cognitive control measurement, much slower (500 to 1000 ms typical) and much more interesting psychologically. A typing test measures motor planning plus language retrieval plus accuracy under time pressure. This reaction-time test is the simplest of the three — see a thing, react. It's a useful baseline before doing any of the others, because if your simple reaction time is unusually slow today, your Stroop result will be unusually slow too, and that tells you something about your state rather than your skill.
