Read the word, name the colour.
Four blocks of twelve trials. In the first two you read the word and ignore the ink. In the last two you name the ink and ignore the word. Reading is automatic; naming is effortful. The cost of that asymmetry is the Stroop effect, and you can measure your own in the next ninety seconds.
Classic four-condition design · Stroop 1935 · MacLeod 1991 norms · 4 colours, 12 trials per block
The test
Click the answer or press 1 to 4 on the keyboard. Speed matters; one wrong answer costs less than a slow correct one. Reaction time is measured from the moment the word appears until you respond. Try not to think about the experiment too much while you do it.
Four short blocks. Two minutes total.
Each trial shows a colour word in a colour. Your task changes per block: sometimes read the word, sometimes name the colour. Pick the answer from the four buttons. Press 1 to 4 on the keyboard if you prefer.
Requires colour vision. About 90 seconds. Your data stays in the browser.
What you just measured
The Stroop effect is one of the most reliable findings in cognitive psychology. Over five hundred studies have replicated it across languages, ages and cultures. The effect even survives in patients with prefrontal damage, though the size shifts.
1935 in Nashville
John Ridley Stroop ran the original at George Peabody College for Teachers in 1935. His subjects read columns of colour words printed in conflicting inks, and named the ink colours of those same lists. Naming took on average 74 percent longer when the word disagreed with the colour. The reverse — words slowed down by ink — was barely measurable. The asymmetry is the whole point.
Why reading wins
Cohen, Dunbar and McClelland 1990 modelled the effect as a parallel race between two pathways. Reading is so practised that it runs without intent; naming a colour requires control. The control system can suppress the reading pathway, but not instantly and not for free. The cost shows up as extra milliseconds.
How robust is the effect
MacLeod's 1991 integrative review covered over four hundred studies up to that point. The colour-naming interference shows up reliably in alphabetic, syllabic and ideographic scripts, in monolingual and bilingual subjects, in children once they can read fluently. Mean interference for healthy young adults sits between 100 and 300 milliseconds in standard lab conditions.
What this version is not
A browser test with twelve trials per block is a small sample. Real lab experiments use forty to a hundred trials and control for fatigue, screen luminance and font size. Treat your number as an order-of-magnitude estimate, not a clinical reading. The robustness of the effect is in the population mean, not in any single run.
Sources
- Stroop J.R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology 18, 643–662.
- MacLeod C.M. (1991). Half a century of research on the Stroop effect: an integrative review. Psychological Bulletin 109, 163–203.
- MacLeod C.M., Dunbar K. (1988). Training and Stroop-like interference: evidence for a continuum of automaticity. Journal of Experimental Psychology: Learning, Memory, and Cognition 14, 126–135.
- Cohen J.D., Dunbar K., McClelland J.L. (1990). On the control of automatic processes: A parallel distributed processing account of the Stroop effect. Psychological Review 97, 332–361.