How long does a thought take? We timed it

We asked readers to try a simple experiment: when a word appears on screen, say it out loud as fast as you can. More than two thousand people took part, using the microphone on their phones. The average time from word to voice was 540 milliseconds.

That half second hides a remarkable relay race inside your head.

The relay, step by step

• About 100 ms: light from the screen reaches the back of the brain and the shapes are detected.

• About 200 ms: the shapes are recognised as letters and then as a familiar word.

• About 350 ms: the brain retrieves the sound of the word and plans the movements to say it.

• About 540 ms: muscles in the throat and mouth start moving, and the microphone hears you.

Half a second is slow for a computer and astonishingly fast for a brain.

What changed the time

Common words like “house” were said about 60 ms faster than rare ones like “quay”. Readers who took the test in the morning were slightly faster than those who took it late at night. Age made less difference than most people expected.

Try it yourself with a friend and a stopwatch app. You will not match lab precision, but you will feel how long half a second really is.

Why it matters

Reaction time tests like this one are used in research on reading, ageing and the effects of tiredness. They are simple, cheap and surprisingly sensitive: a night of poor sleep can add tens of milliseconds, which is roughly the difference between a common word and a rare one.

Our readers’ results also showed how much individuals vary. The fastest ten percent averaged under 450 milliseconds; the slowest ten percent were over 650. Neither group was doing anything wrong. Brains simply differ, as feet or voices do.

We plan to repeat the experiment next year with a larger set of words and a version for children, with parents’ permission. If you took part, thank you; your half seconds are now part of a very large and rather beautiful chart.