Stroop test online

Free Stroop test online: name the ink colour, not the word, across 40 trials. Get accuracy, matching and conflicting median times and your interference score.

BEFORE YOU BEGIN

How this test works

40 trials · about 2 minutes

Choose the ink colour, not the word. Use the labelled buttons or keys 1–4. After Start, 40 trials mix 20 matching and 20 conflicting word/colour pairs. Each trial allows 8 seconds. A wrong choice or timeout counts as an error. A break or hidden tab interrupts the run; restart for a comparable result.

Check that you can distinguish all four ink colours on your screen:

1 · Red2 · Blue3 · Green4 · Purple

I can distinguish these colours.

This visual task depends on colour perception. If the colours are hard to distinguish, try the digit span test.

The timer begins only after you press Start. No signup. Full results are free.

What the Stroop test measures

The Stroop test is the classic demonstration of interference between two mental processes. You see colour words printed in coloured ink and must name the ink, not read the word. When the word and the ink match, the task is easy. When the word RED appears in green ink, reading the word happens automatically and competes with naming the colour, so you respond more slowly and make more errors. The difference between the two conditions is the Stroop effect, and it is used in research on attention, response inhibition and cognitive control.

This version measures three things: how accurately you name the ink, how fast you respond in each condition, and the interference between them.

How this free test works

40 trials in about 2 minutes: 20 matching and 20 conflicting word and colour pairs in a random order, using red, blue, green and purple.
Respond with the labelled buttons or the keys 1 to 4. Each trial allows 8 seconds; a wrong choice or a timeout counts as an error.
Accuracy is correct responses out of 40.
Median response times, calculated from correct trials only, separately for matching and conflicting trials. The median is used so that one distracted trial does not swing the result.
Interference is the conflicting median minus the matching median, shown when you have at least five correct trials in each condition.
An optional shareable result with a permanent link, preview image and an Add to LinkedIn profile button.

Sample Stroop trial

The screen shows the word BLUE printed in red ink, with four buttons: Red, Blue, Green, Purple. The correct response is Red, because the task is the ink colour. Most people feel the pull towards Blue on exactly this kind of trial, and that hesitation is what the conflicting median records.

On the next trial the word GREEN appears in green ink. The correct response is Green, and it usually comes faster. That is a matching trial.

How to get a comparable Stroop result

Use the keys, not the mouse. Moving a pointer adds variable time to every trial. Keys 1 to 4 keep the response method constant.
Say the colour in your head before you press. Naming the ink silently blocks the word from taking over.
Keep the tab in front. A hidden tab or a break interrupts the run and the timings; restart for a comparable result.
Run it three times on the same device before reading anything into a number. The first run includes learning the key positions.
Expect the interference figure to move. With 20 trials per condition it is a rough estimate. The direction is more informative than the exact milliseconds.

Reading your result

Your result shows accuracy, both medians and the interference in milliseconds. The result guide explains how each is calculated and why device latency and reading familiarity affect it. This is a demonstration and practice task, not a clinical Stroop assessment, and it has no norms or pass mark.

Reaction time test: simple response speed without the interference, for a baseline.
Digit span test: working memory for sequences, another classic laboratory task.
Attention to detail test: sustained checking of records and codes under time pressure.

Frequently asked questions

Is this Stroop test free?

Yes. All 40 trials, the accuracy score, both median response times, the interference figure and a public result link are free, with no account or email address.

What is the Stroop effect?

Reading a word is faster and more automatic than naming a colour, so when the word RED is printed in blue ink, the word interferes with naming the ink. The extra time you need on those conflicting trials is the Stroop effect, first reported by John Ridley Stroop in 1935.

What is a typical Stroop interference score?

On a computer version with a keyboard response, most adults are tens of milliseconds to a few hundred milliseconds slower on conflicting trials than on matching ones. The exact figure depends on the device, the response method and practice, so compare your own runs on the same setup rather than a published norm.

Can the interference score be negative?

Yes. With only 20 trials per condition, a few fast conflicting trials or slow matching ones can produce a small negative difference. It is shown only when you have at least five correct trials in each condition.

Is this a clinical or diagnostic test?

No. Clinical Stroop tests are administered and scored under controlled conditions with published norms. This is a demonstration of the effect and a practice task for attention and response control.