How to take the Stroop test
- Press Start. A colour word appears, printed in a coloured ink.
- Tap the button that matches the ink colour, ignoring what the word says. On a keyboard press R, G, B or Y.
- After 20 rounds you see your average response time, accuracy, and your personal Stroop effect: how much slower you are when the word and the ink disagree.
Why the Stroop effect happens
Described by John Ridley Stroop in 1935, the Stroop effect is one of the most famous findings in psychology. Reading is so automatic for fluent readers that you cannot help reading the word, even when you are told to name the colour instead. When the word says BLUE in red ink, the two answers compete and your brain has to suppress the wrong one, which takes extra time and causes mistakes.
Psychologists use Stroop tasks to study attention, cognitive control and the effects of fatigue, stress and ageing. A typical Stroop effect is around 50 to 150 milliseconds; with practice it shrinks, but it rarely disappears. It is a fun way to warm up your focus, and a reminder of how much happens automatically in the mind. Results are calculated in your browser and nothing is stored online.
What is a normal Stroop test score?
Most people answer in about 600–900 ms per item with over 90% accuracy, and are 50–150 ms slower on mismatched items.
Why is the Stroop test hard?
Reading is automatic, so the word interferes with naming the colour, and you must override it.
Is it a test of intelligence?
No. It measures attention and inhibition, which vary with tiredness, practice and age.