IIF Certified Assessment
Start IQ Test
IIF Certified Assessment
Brain Games · Attention
4 practice words, then 24 for real: about 1 minute. Press the button for the ink colour, not the word.
In short
The Stroop test asks you to name the ink colour of a word while the word spells another colour, like RED printed in blue. You slow down, because reading is automatic. That delay is the Stroop effect. In J. Ridley Stroop’s 1935 experiment, naming the ink took 74% longer than naming plain colour squares.
Below: three ways to take the Stroop test online, how every word is timed, the classic instructions and what your score says.
How to play
Pick a mode at the top, then Quick (about 1 minute) or Standard (about 2 minutes). Every run starts with a few practice words with feedback.
Holding back the urge to read.
How little the ink disturbs reading.
The same clash, with place instead of colour.
Fair timing
The same timing in every run, so your runs compare fairly. The clock starts on the screen frame that shows the word.
| Step | Time |
|---|---|
| A cross before each word | 0.4–0.7 s |
| The word stays until you answer | up to 3 s |
| A gap after each answer | 0.3 s |
| Too quick to count, shown again | under 0.2 s |
Answers slower than 3 seconds count as too slow. If you leave the page during a word, it is shown again.
Your score
Your Stroop effect is your middle (median) time for clashing words minus your middle time for matching words, counting right answers only.
Instructions
The Stroop test instructions are simple: name the colour of the ink, not the word, as fast and as accurately as you can. In our test you tap the button for the ink colour.
The clinical paper version (Golden, 1978) has three pages of 100 items and gives 45 seconds for each. The score is how many items you name in that time.
Online, the computer times each word to the millisecond, so a short run is enough. Our Classic mode times 48 words after 8 practice ones.
The experiment
In the original Stroop experiment of 1935, a clashing word slowed colour naming far more than a clashing colour slowed reading. Naming 100 ink colours took 110.3 seconds on average, against 63.3 seconds for colour squares.
The usual explanation is that reading is so practised that the word arrives first and has to be held back. Researchers still argue about the details (MacLeod, 1991).
Psychologists still use the Stroop task to study attention and self-control. A 1991 review already covered some 400 studies of the effect.
Our article Stroop test explained covers what it measures, how clinics use it and what it cannot tell you.
Scoring
The clinical paper version is scored on three cards, with 45 seconds for each, and each score is the number of items done. The interference score compares the colour-word card with what the first two predict.
| Card | What you do | Score |
|---|---|---|
| Word (W) | Read colour words printed in black | Items read in 45 s |
| Colour (C) | Name the colour of patches | Items named in 45 s |
| Colour-word (CW) | Name the ink of clashing colour words | Items named in 45 s |
| Interference | CW − (W × C) ÷ (W + C) | Below 0: more slowing than predicted |
Clinicians read these against age norms and never on their own.
There is no single good score. Here, a smaller Stroop effect in milliseconds means the clash slows you less. Compare with yourself, on the same device.
Our online version is free to play. The clinical Golden version is a paid test with a manual, given by trained professionals.
Uses and types
Psychologists use it to study attention and self-control. Clinicians use it, alongside other tests, when they assess attention and executive function.
Emotional Stroop uses charged words, the numerical version clashes size with value, and spatial versions clash direction with position, like our Arrows mode.
Brain scans link the task to the anterior cingulate cortex and the prefrontal cortex, the areas that handle conflict (Pardo and colleagues, 1990).
Young children can’t read yet, so researchers use a day-night version: say “night” for a sun card and “day” for a moon card (Gerstadt, Hong and Diamond, 1994).
A large effect can come from slow reading, colour-vision differences or a second language, not poor attention. That is why it is never used alone.
Skills
Picking out the one feature that matters, the ink, the word or the place, and ignoring the rest.
Holding back an automatic habit. Reading is so practised that the word comes to mind before you can stop it.
How fast you see, decide and press, on every word.
And IQ
Only loosely. The Stroop test looks at attention control, one of the executive functions: holding back a habit to give the right answer. It is not built to measure intelligence, and a large Stroop effect is normal.
Its closest IQ area is processing speed, because both reward quick, accurate simple work. To see speed next to reasoning and memory, take the IQ test.
The five areas of a modern IQ test
The five primary index areas of the WISC-V (children, 2014) and the WAIS-5 (adults, 2024). See WAIS-5 index scores explained.
FAQ
Naming the ink colour of a word is slower when the word names a different colour, such as BLUE printed in red ink. Reading is so automatic that the word gets in the way. J. Ridley Stroop described it in 1935.
There are no fair norms for online versions: devices, colours and timing differ from site to site. Research finds that clashing words are reliably slower than matching ones; the size depends on the method. Compare your own runs on the same device.
No. Clinical Stroop tests are one part of a full assessment by a professional, with set materials and norms. This game is not one of them.
No. It looks at one part of attention: holding back a habit. A full IQ test measures reasoning across many kinds of questions.
Touch screens add time to every answer, and the buttons sit in different places. That is why your bests compare runs on the same kind of device only.
Practice makes you faster at the task and can shrink the gap a little, but it rarely disappears: reading stays automatic.
Play Arrows: it uses place instead of colour, so nothing depends on seeing colours. Classic also has a colour-vision friendly palette: blue, orange, black and white on grey.
Reading the word is automatic, so it is quick either way. Naming the ink means holding back that habit, which is what the test looks at. Play Reverse to see the difference in your own numbers.
That your clashing words were not slower than your matching ones this time. In a short run chance plays a part; try a Standard run.
The American psychologist J. Ridley Stroop, in a 1935 paper in the Journal of Experimental Psychology. Colin MacLeod’s 1991 review gathered over 50 years of research on it.
The clinical paper version, published by Charles Golden in 1978: three pages of 100 items (words, colours, and colour words in clashing ink), with 45 seconds for each. Clinicians use it alongside other tests, never alone.
Yes. After a run, send the link: your friend gets the same words in the same order and sees both gaps. The smaller gap wins.
Yes. It is free to play, with no signup, and your results stay in your browser.
Sources
The full picture
Each game looks at one skill. The IQ test brings speed, reasoning and memory together in one score, with your percentile and a certificate.
