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About this tool
Test your cognitive control — name the color, not the word. Measure your Stroop Effect and reaction time in this classic psychology experiment.
The Stroop Effect Test shows you colour words printed in a mismatched ink colour and asks you to name the ink, not the word — then measures how much slower you are on those conflict trials than on matching ones. That difference in milliseconds is your Stroop effect: incongruent average reaction time minus congruent average reaction time, the standard way the effect is quantified since Ridley Stroop's 1935 experiment. You get 30 trials across six colours, a 5-second limit each, and a breakdown of accuracy, average reaction time and the interference cost at the end.
Open Stroop Effect Test on AltFTool — it loads instantly in your browser.
Press Start the Experiment, read the three instructions, then press Start Test and wait out the 3-second countdown.
For each of the 30 trials, click the colour button matching the ink colour — or press keys 1-6 — within the 5-second limit, ignoring what the word says.
On Your Stroop Test Results, read Accuracy, Avg Reaction, Congruent RT, Incongruent RT and the Stroop Effect, which is incongruent minus congruent in ms.
Splits your reaction times into congruent and incongruent averages and subtracts them, instead of showing one blended score.
Roughly 70% of the 30 trials are incongruent, so the measurement rests on enough conflict data to be meaningful.
Each trial expires after 5 seconds and records the miss, so you cannot slow down to eliminate interference.
Most adults are somewhere between roughly 100 and 200 milliseconds slower on incongruent trials than congruent ones. The size varies with age, tiredness and screen setup, so your own change across repeat sessions is more informative than comparing against a stranger.
It is your mean reaction time on correct incongruent trials minus your mean on correct congruent trials, in milliseconds. Only correct answers count, so a fast wrong guess cannot shrink the number.
Reading is automatic for fluent readers, so the word meaning is processed before you can suppress it, and your response has to override that head start. The extra time is the cost of that override, which is why the task is used as a measure of executive control.
Thirty trials, with a 5-second limit on each; about 30% show a matching word and colour and the rest are mismatched. A full run takes about two to three minutes including the 3-second countdown.