Stroop test online
The famous word–colour conflict: the word “blue” is written in red — the right answer is “red”. The test measures interference — how much the conflict slows you down — and trains attention control. Free, no sign-up.
Two series of 12 cards. First neutral: press the button matching the colour of the swatch — that is your base speed. Then the conflict series: the word is written in the “wrong” colour — answer by the COLOUR OF THE LETTERS, not the meaning. A card waits for the correct answer: errors cost time.
Interference norms
Adult reference points: how much slower, on average, a conflict card is answered compared with a neutral one (interference per card). The smaller the difference, the better the attention control.
- under 100 msExcellent — the conflict barely throws you off
- 101–200 msGood result — control above typical
- 201–350 msTypical range for adults
- 351–500 msAbove typical — possibly fatigue or lost focus
- over 500 msHigh interference — mind your sleep and state
What the Stroop effect is
For an adult, reading is automatic: seeing the word “green”, the brain reads it faster than it recognises the colour of the letters. When the word and the colour disagree, the automatic response has to be suppressed — and that takes measurable time. John Ridley Stroop described this delay in 1935, and his test became one of the most cited methods in experimental psychology.
The Stroop test measures what psychologists call cognitive control: the ability to suppress an automatic but wrong reaction in favour of the right one. This skill works everywhere — from not answering “on autopilot” in a conversation to impulse control at the wheel.
How to take the test
The test has two series:
- a neutral series — coloured cards without conflict: it measures your base speed;
- a conflict series — colour names written in the “wrong” colour: answer by the COLOUR of the letters, not the meaning;
- interference = how much slower the conflict series is — that is your result;
- don’t trade accuracy for speed: errors count too.
What affects the result
Interference grows with fatigue, sleep loss and stress — attention control is the first thing to get “expensive” when resources are low. It also increases moderately with age, which is normal.
Consistently high interference along with everyday distractibility is a reason to check sleep and physical causes: iron, B12, thyroid. And if attention control has been hard “all your life” — the adult ADHD screener is worth taking.
Attention control suffers from overload
Chronic stress, high cortisol and poor sleep hit the prefrontal cortex first. Upload your labs — AI explains every value and tells you what to check.
The Stroop test on this page is a trainer and a reference point, not medical or neuropsychological diagnostics. The final assessment of cognitive function is up to a professional.