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Stroop Test

Answer with the color of the ink, not the word. When the two disagree, people answer more slowly.

Type
Attention
Takes
about 1 min
Result in
milliseconds

Stroop Test

~1 min

  1. A color word appears, printed in a colored ink.
  2. Answer with the ink, not the word: tap its button, or press D F J K for red, blue, green, yellow.
  3. 24 words. Speed counts, and so does the right answer.

This test needs you to tell red, green, blue and yellow apart.

Your result: — ms

How it's measured

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What is the Stroop test?

In the Stroop test you see a color word, such as RED, printed in a colored ink, and you have to name the ink rather than read the word. When the word and the ink disagree, people answer more slowly and make more mistakes. That slowdown is called the Stroop effect, after the American psychologist John Ridley Stroop, who described it in 1935.

What does the Stroop test measure?

The Stroop test measures how well you can attend to one feature of what you see, the ink, while ignoring another that pulls harder, the word. Psychologists call this selective attention and response inhibition, parts of what they call executive function. Your Stroop effect is the cost of that conflict, in milliseconds.

How this test works

There are 24 words, each one of red, blue, green and yellow. In half of them the word matches its ink, and in the other half it names a different color. Answer by tapping the button for the ink color, or by pressing D, F, J, K for red, blue, green and yellow in that order. After each answer there is a pause of 0.5 to 0.9 seconds with a small cross, then the next word. The same ink never comes twice in a row, so you never just press the same button again.

How is your result calculated?

Each word is timed from the animation frame in which it is drawn to the moment your key or finger goes down, using the timestamp your browser gives the press. Your main result is the average time of your correct answers. Wrong answers are left out of the average and counted in your score out of 24.

You also see your own Stroop effect: the average time of your correct answers when the word didn't match the ink, minus the average when it did. It is calculated from your run only, so it tells you how much reading the word got in your way this time.

Why does the word get in the way?

Because reading is automatic for a fluent reader. You can't look at a familiar word and not read it, so the word's meaning arrives whether you want it or not, and it competes with the ink color you are trying to report. Naming the ink takes deliberate attention; reading the word takes none. When the two point to different answers, sorting out the conflict costs time, and sometimes the word wins and you press the wrong button.

Stroop's 1935 paper, "Studies of interference in serial verbal reactions" in the Journal of Experimental Psychology, timed people working through printed cards with a stopwatch. Versions of his task have been used in psychology research ever since; this one is timed by your browser instead, one word at a time.

What can change your result

  • Color vision. The test needs you to tell red, blue, green and yellow apart. If some of these look alike to you, the result will say more about telling the colors apart than about the words getting in the way.
  • Keyboard or touch. Fingers resting on D, F, J, K need no aiming; on a touchscreen your thumb has to travel to the right button.
  • Language. The words are in English. How automatically you read them affects how much they interfere.
  • Practice. Your second run is usually different from your first, so compare runs taken the same way.

What this test does not measure

It measures how quickly and accurately you named ink colors against conflicting words, on your device, in one sitting. Stroop tasks are used in research and in some clinical assessments, but a few minutes in a browser isn't an assessment of anything: this isn't a test for ADHD or any other condition, and the result says nothing about intelligence. For a reaction test without words, try the Choice Reaction Time Test; for another test of attention, the Visual Search Test.

Questions

What is a normal Stroop effect?
About 80 to 100 ms for adults. In a 2024 study of 425 people aged 7 to 88 who pressed colour keys, as here, the average Stroop effect was 83 ms at ages 21 to 34, 103 ms at 37 to 55 and 179 ms at 66 to 88 (Sapienza University of Rome, BMC Psychology). The effect is a difference, so a device's delay mostly cancels out.
Why do half the words match their ink?
So your Stroop effect can be measured: it is the difference between your times on matching and mismatching words. It also means you can't ignore the words and always guess against them.
I'm color-blind. Can I take the test?
You can try, but if any of the four inks look alike to you, your result will mostly reflect that rather than the Stroop effect. The test has no color-blind mode, because the colors are the task.
Why the keys D, F, J, K?
They sit under the index and middle fingers of both hands, so all four answers are ready without looking down. Tapping the buttons works just as well on a phone.
Can the Stroop test diagnose ADHD?
No. Stroop tasks are used in research and are sometimes one part of a clinical assessment, but no single test diagnoses ADHD, and a few minutes in a browser can't. If you're concerned about attention, talk to a doctor or psychologist.
What is the emotional Stroop test?
A research version where the words carry emotional meaning, such as threat-related words, instead of color names. People are often slower to name the ink of emotional words than of neutral ones, and the task is used in studies of anxiety. This page uses the classic color-word version.