How the Stroop test works
A colour word, RED, BLUE, GREEN or YELLOW, appears in coloured ink. Your job is to name the colour of the ink, not the word, as fast as you can, using the four colour buttons or the keys 1 to 4. There are twenty-four words. In half of them the word and the ink match; in the other half they clash, like the word GREEN printed in yellow.
The clashing words are the real test. You read so automatically that the word arrives in your mind before the colour does, and you have to push it aside to answer. That small fight is called the Stroop effect, after John Ridley Stroop, who described it in 1935. It is one of the most studied effects in psychology, and a standard measure of selective attention: the ability to focus on what matters and ignore what does not.
Your score is your average time on the clashing words, with each mistake counting as its time plus 600 milliseconds. The result also shows your Stroop effect, the gap between your matching and clashing averages, so you can see exactly how much the clash cost you.
What counts as a good score
| Average on clashing words | Standing |
|---|---|
| Under 520 ms | Exceptional focus |
| 520 – 640 ms | Sharp |
| 640 – 760 ms | Above average |
| 760 – 920 ms | About average |
| Over 920 ms | The words are winning |
These ranges are a first estimate based on published keypress versions of the test, and will be refined as more people take this one. Response times include your screen and your input device, so compare yourself with other browser scores.
How to beat the Stroop effect
- Look at the colour, not the shape of the word. Some people blur their focus slightly, so the letters stop reading as a word.
- Learn the keys. Once 1 to 4 are automatic, the only thing left to think about is the ink.
- Slow down a little. Mistakes cost 600 milliseconds each, far more than a moment’s care.
- Do not say the word in your head. Saying the ink colour silently instead helps hold the word back.
- Practise. The Stroop effect shrinks with practice, though it rarely disappears completely.
For more tests of attention, try Dot Count, the Drift Test or the Rhythm Test.
This test depends on telling colours apart. If you have a colour vision difference, your score will not compare directly with other people’s.
Frequently asked questions
What is the Stroop test?
A test of selective attention, first published by John Ridley Stroop in 1935. You see colour words printed in coloured ink and name the ink. When the word and the ink clash, such as the word RED printed in blue, people are slower and make more mistakes, because reading happens automatically and has to be held back.
What is the Stroop effect?
The extra time it takes to name the ink when the word names a different colour. This test measures it directly: the result shows your average on matching words, your average on clashing words, and the gap between them.
What is a good Stroop test score?
On this test, an average under about 600 milliseconds on the clashing words is quick, and most people land between 650 and 850. A Stroop effect under 100 milliseconds means the clash barely slows you down. These ranges are a first estimate and will be refined as more people take the test.
Can I take the Stroop test if I am colour blind?
The test depends on telling red, green, blue and yellow apart, so colour vision differences, especially between red and green, will affect your score and the result will not mean what it does for others. The colour buttons also carry the numbers 1 to 4 to help, but the words themselves can only be told apart by colour.
Why do mistakes add time?
Without a cost, the fastest strategy would be to press anything. Each wrong answer counts as its own time plus 600 milliseconds, so accuracy matters as much as speed, which is what the real test measures.