Reaction Time

On a phone or tablet, tap the large panel to begin. It turns dark and asks you to wait. When it flashes amber, tap it immediately. Your time appears in milliseconds; tap again to start the next attempt.

On a computer, click the panel or press Space or Enter whenever you would tap. Using a key is often a little faster than clicking a mouse.

After five valid attempts you see your average and whether it is a new personal best. Your previous attempts are listed beneath the panel so you can see how consistent you were.

1. Each session has five attempts.
2. After you start an attempt, the panel waits for a random time between 1.5 and 4.5 seconds before turning amber.
3. Your reaction time is measured from the moment the amber signal is drawn on screen until your tap, click or key press is received.
4. Pressing while the panel is still dark counts as “too soon”. That attempt is cancelled and you simply try it again; it does not count towards your five.
5. Presses faster than 80 milliseconds after the signal are also treated as “too soon”, because nobody can genuinely react that quickly — they are almost always lucky guesses.
6. Switching tabs or apps in the middle of an attempt cancels that attempt.
7. Your score is the average of your five valid attempts, rounded to the nearest millisecond. Lower is better.

Watch, don’t predict. Because the delay changes every time, trying to anticipate the signal mostly produces “too soon” results. Relax your eyes on the centre of the panel and respond to the change itself.

Keep your finger ready. Rest your fingertip just above the screen or on the key before the signal appears. Moving your hand into position after you see amber costs tens of milliseconds.

Use a key on desktop. Space and Enter usually register faster than a mouse click, which has to travel through more hardware and software.

Reduce delays you can control. Close busy apps, turn off battery-saving modes that reduce the screen’s refresh rate, and play on a wired or responsive keyboard if you can.

Warm up. Your first session of the day is rarely your best. A couple of practice runs help you settle into a rhythm.

Compare like with like. Every device adds its own small input and display delay. To track improvement, use the same device and the same input method each time.

Measuring reaction time is one of the oldest experiments in psychology. In the 1850s and 1860s, Dutch physiologist Franciscus Donders used simple and choice reaction tasks to estimate how long mental processes take, an approach later called mental chronometry. Earlier still, astronomers had noticed that different observers recorded the passage of stars at slightly different moments — the so-called personal equation. Today, reaction tests are used in sports training, driving research and, increasingly, as quick games played in a browser.

• Choice reaction. Several signals appear and you must respond to the right one, which adds decision time.
• Sound reaction. Respond to a beep instead of a colour change; auditory reactions are often slightly faster than visual ones.
• Go / no-go. Respond to one signal but hold back for another, testing self-control as well as speed.
• Streak mode. Keep going until you make a “too soon” mistake and see how many valid attempts you can string together.