My HumanIndex

Stroop Test - Measure Your Interference Cost

Name the ink colour, not the word. This test measures how much a conflicting colour word slows your response - the classic Stroop interference effect.

How the scores are spread

Where players land on this test. Take it to see your own mark on the curve.

typical0 ms cost280 ms cost560 ms cost

Lower is better · reference sample of 25,000

What this test measures

A colour word flashes up, printed in a colour that often does not match what it says. You respond with the ink colour and ignore the word, using the on-screen buttons or the keys R, B, G and Y.

Your score is the interference cost: your median response time on incongruent trials minus your median on congruent trials, over correct answers only. Lower is better - it means the word bothered you less.

How to get a clean score

  • Look at the colour, not the letters. Some people find slightly unfocusing their eyes helps.
  • Keep your fingers over the four keys so response movement is not part of your time.
  • Do not slow right down to avoid errors. The test wants your natural pace; a few mistakes are expected and handled.

Can you get better at it?

Barely. The interference effect shrinks a little with heavy practice and then returns after a break, because it rides on years of reading automaticity that a few minutes of a colour game cannot undo. What you can do is keep your fingers over the four keys so movement time is not in the measurement, and take the test when rested - fatigue widens the effect noticeably. The honest read is that this is close to a fixed trait, which is exactly why it has been useful for ninety years.

What the number tells you

The Stroop task is the standard laboratory measure of response inhibition and selective attention. The interference effect is remarkably robust - it survives practice, appears in every literate population, and is sensitive to fatigue, ageing, and conditions affecting the prefrontal cortex.

FAQ

What is a typical Stroop effect?
The interference cost - your response time on mismatched trials minus matched trials - is usually 80 to 150 ms for adults. A smaller cost means stronger control over the automatic urge to read the word.
Why is reading so hard to suppress?
For a literate adult, reading is fast and involuntary. When the word RED is printed in blue ink, the word meaning arrives before you have finished identifying the colour, and you have to actively override it. That override has a measurable time cost.
Does colour blindness affect this test?
It can. The test uses red, blue, green and yellow, which are usually distinguishable, but if colours are hard for you to tell apart your times and error rate will both rise for reasons unrelated to attention control.
Why does slowing down lower my interference cost?
Because the automatic reading response fades over the first few hundred milliseconds. If you wait before committing, the conflicting word has already lost its pull, so the measured cost shrinks - but that is you gaming the measure, not improving your control. Respond at a natural pace and the number means something.

Related tests

Every test feeds your Human Index. See the blog for what the scores mean.

Reference sample: SYNTHETIC. Lognormal, mean 150 ms / sd 78 ms for the incongruent-minus-congruent interference cost in a 4-choice manual colour Stroop. Manual multi-choice Stroop effects run larger than the classic vocal 80-150 ms.