Click when the screen turns green. The average person scores about 250ms, can you beat it?
This measures visual reaction time, the delay between seeing the green screen and clicking. A typical result is 200 to 300 milliseconds; fast reflexes land under 200ms. Scores under about 100ms mean you jumped early and guessed. Try five rounds for a fair average, and note how sleep, focus and screen lag change your numbers.
Reaction time is how long it takes you to respond to something you did not know exactly when to expect, and the test above measures it by timing how fast you click once the signal appears. For a simple visual signal like this, a typical adult reaction time is around 200 to 300 milliseconds, roughly a quarter of a second. Anything consistently under 200ms is quick, and the average creeps up slowly with age and drops when you are tired.
What affects the number. Alertness is the big one: fatigue, alcohol and even mild dehydration slow you down measurably, while being warmed up and focused speeds you up. Caffeine gives a small lift. The type of signal matters too, as reacting to a sound is usually a touch faster than reacting to a light. Because a single go can be a fluke (a lucky early click or a distracted slow one), take several attempts and look at your average rather than your best.
Can you improve it? Simple reaction time is mostly fixed by biology, but you can shave a little off by being rested, focused and warmed up, and by practising the specific action, which is why gamers and athletes drill their responses. What training really improves is decision speed, choosing the right response among several, more than raw reaction to a single cue. Treat the score here as a fun benchmark, not a medical measure.