Stroop Test

How to take the Stroop test

1. Choose how many words you want in each block. 20 takes about a minute and gives a stable result; 40 is more accurate.
2. Press Start. In block 1 every word is printed in its own color (RED in red). Answer the color as fast as you can with the four buttons, or the keys R, G, B, Y (or 1-4).
3. Block 2 is the real test: the word and the ink never match (GREEN printed in blue). Always answer the ink color, never the word.
4. Keep going until the bar fills. A wrong answer flashes red and is counted against your accuracy; a correct one flashes green.
5. Read your average time for each block and the difference between them, which is your Stroop effect. Press Start again for another round.

What the results mean

The Stroop effect is the extra time you need to name the ink color when the word spells a different color. Reading is automatic for a fluent reader, so the word fights the color and you have to suppress it. The test reports:

• Matching words: your average correct response time in block 1, when word and color agree. This is your baseline speed with these buttons.
• Mismatched words: your average correct response time in block 2, when they disagree.
• Stroop effect: mismatched minus matching, in milliseconds. Larger means the words interfered more.
• Accuracy: correct answers across both blocks. Below about 80% the timing is not meaningful, because you were guessing.

A button version like this one produces smaller effects than the classic spoken version, where people read the words aloud, because speaking a color name is interfered with more directly than pressing a colored button. Compare your result with your own earlier rounds rather than with lab figures.

What the Stroop test measures

John Ridley Stroop published the effect in 1935, and it has been one of the most used tasks in psychology ever since. It measures selective attention and cognitive control: your ability to focus on one feature of a stimulus (the color) while suppressing an automatic response to another (the meaning of the word). Because reading cannot be switched off, every mismatched word requires a small act of inhibition, and the delay it causes is a clean, repeatable number.

Researchers use Stroop-type tasks to study attention, aging, sleep deprivation, multitasking and the effects of stress or caffeine. Clinicians use standardized versions as one part of a neuropsychological assessment. This online version is for curiosity and self-tracking: it is not a diagnostic tool, and a large effect on its own does not indicate any condition. Being tired, reading in a second language, or just not having done the task before all make the effect larger.

Tips for a fair Stroop result

Do a warm-up round and discard it. Keep your fingers resting on R, G, B and Y (or on the four buttons on a phone) so answering takes the same movement every time. Look at the center of the word and try to see it as a colored shape rather than reading it; many people find squinting slightly helps. Do not sacrifice accuracy for speed: an error costs more than a slow answer, and a round under 80% accuracy is reported but not saved as a best. Take the test at the same time of day if you want to compare sessions, because alertness changes the result. For a pure speed measure without the word interference, try the reaction time test.

Common problems and fixes

The keys do not work

Click inside the test box once so it has focus, then use R, G, B, Y or 1-4. The keys only respond while a word is on screen, not between blocks.

I keep answering the word instead of the color

That is the Stroop effect in action. Slow down slightly, focus on the color of the first letter only, and keep your fingers on the keys so the answer is a reflex. Accuracy improves within a round or two.

My times are very slow on a phone

Hold the phone in both hands and use both thumbs on the four buttons, so each answer is a short tap. Turn off battery saver, which slows the browser.

The result says accuracy was too low

Below 80% the timing is not reliable, so the round is not saved as a best. Take the 10 word version first to get used to the keys, then move to 20 or 40.