Reaction Time Test,
how fast are your reflexes?

Science guide

The neuroscience of reaction time.

What actually happens when you react

A visual reaction involves a precise chain of neurological events. Light hits your retina; photoreceptor cells convert it into an electrical signal; the signal travels along the optic nerve to the visual cortex at the back of your brain; the visual cortex identifies the change; the signal travels forward to the motor cortex; the motor cortex fires the command; the electrical impulse travels down the spinal cord and out through the ulnar nerve to the muscles in your hand. The absolute minimum time for this chain — even with perfect efficiency — is approximately 100 ms.

The "extra" time above 100 ms is where training matters: how quickly does your brain classify the stimulus as the target, and how quickly does it commit to the motor command? Experienced athletes and gamers reduce this decision overhead through familiarity with the task, not through faster nerve conduction.

Factors that affect your score

• Alertness and sleep: Reaction time worsens by up to 10–15% when sleep-deprived. Even a single bad night measurably impairs performance.
• Caffeine: A moderate dose (100–200 mg) reduces reaction time by approximately 15–40 ms in non-habituated users. Regular coffee drinkers see smaller effects, as tolerance reduces the benefit.
• Alcohol: Even small amounts impair both reaction time and accuracy, with effects lasting well beyond when a person feels intoxicated.
• Fatigue and distraction: Performing two tasks simultaneously adds 50–200 ms to reaction time, which is why driving while distracted is so dangerous.
• Device and display lag: Monitors and touchscreens introduce 10–50 ms of input lag. This test measures your true reaction time minus whatever your device adds — results are best compared on the same device.

Simple vs. choice reaction time

This test measures simple reaction time — one stimulus, one response. Real-world scenarios typically involve choice reaction time, where you must decide between multiple possible responses. Choice reaction time follows Hick's Law: it increases logarithmically with the number of choices. A two-option decision adds ~150 ms; four options adds ~300 ms. Athletes train to reduce choices by reading situations early and pre-committing to likely responses — which is why pattern recognition matters more than raw reflexes in most sports.

Tips to improve your score

• Take the test when well-rested and not fatigued
• Eliminate distractions — close other browser tabs, silence notifications
• Keep your clicking finger lightly hovering — don't move it from the mouse/trackpad between rounds
• Focus on the screen, not your hand — let peripheral motor control do the work
• Avoid watching for patterns in the timing — the delay is randomized 2–5 seconds precisely to prevent anticipation