Stroop Test: Why Words Get in the Way of Colors
Try naming ink colors while the words pull you toward a different answer. Compare your response times and errors, explore the research, and learn what a small result can tell you. Five short chapters, eight checks and five stamps, in about twelve minutes, at your own pace.
BySeph Fontane Pennock
Reviewed byMichael Callans, MSW
Stroop test: when words compete with colors
The Stroop test asks you to respond to one feature of a stimulus, usually its ink color, while ignoring another, usually the word it spells. If RED is printed in blue, the color answer is blue. The word can get in the way: this is called the Stroop effect, a widely studied example of interference in attention.
Stroop effect examples
Matching, or congruent: BLUE in blue ink points toward the same answer twice. Mismatching, or incongruent: RED in blue ink points toward two different answers. A plain blue patch provides a neutral comparison without a competing word.
In his 1935 experiments, J. Ridley Stroop found that naming the ink colors of conflicting words took longer than naming colored patches. The reverse comparison, reading words in conflicting colors rather than in black, showed much less interference (Stroop, 1935).
Progress stays on this device.
Your passport: 0 / 5 stamps
20 points for running the demonstration or exploring sample data. Each completed check earns 10 points, including retries. First-attempt accuracy is separate from points and task errors.
Chapter 1 / 5
Try the Color Rule
At a print studio, Mira sorts ink samples. A label names one color, while its ink shows another. Try the conflict yourself: respond to the ink color, not the written word.
This is an educational demonstration, not a clinical or neuropsychological test. There is no pass mark for speed, and your task errors do not affect course points.
Before you try: make a prediction
Which block will take longer? This prediction is unscored.
Try the Stroop task
Choose a response method and keep it for both blocks. Practice has six trials with feedback, followed by two blocks of 12. Aim to be both quick and accurate. There is no countdown or response deadline.
If these colors are hard to distinguish, English color words are unfamiliar, or you use a screen reader, choose sample data. You can complete every chapter without a timed visual task.
The sequence of blocks is randomly assigned. Stay on this tab; leaving it restarts only the unfinished block. Reloading also discards an unfinished block.
Practice
Choose the ink color. 1 = red · 2 = blue · 3 = green
Chapter 2 / 5
The Stroop effect: two competing responses
The ink and the word arrive together. Your goal favors one, but reading a familiar word is so practiced that the other response can become active too. Selecting the color response may then take extra work.
This is not a contest between a good part and a bad part of your brain. The same reading skill that helps you read a sign can interfere when the rule changes. “Automatic” here does not mean entirely outside the influence of attention.
One stimulus, two routes
In a matching trial, the word and color support the same choice. In a mismatching trial, they support different choices. Keep the instruction fixed so the comparison means something.
MacLeod’s 1991 review of Stroop research brings together evidence on attention, practice and competing explanations. A familiar shorthand, “reading is faster,” does not explain every finding.
Chapter 3 / 5
Meet the original experiment
Stroop’s participants worked through printed lists and responded aloud. In the color-naming comparison, they named the colors of patches and the ink colors of conflicting words. This page instead presents individual words and records a keypress or button click.
That difference matters. You are also learning where the response keys are. Our matching block can make responses easier, whereas Stroop’s patches contained no helpful word. Treat this as a demonstration inspired by the research, not a reproduction of the original procedure.
What does your gap contain?
Mismatching median minus matching median is the gap we report. Without a neutral condition, it cannot separate interference in the mismatching block from facilitation in the matching block.
Another way to practice examining evidence is the Endowment Effect course’s ownership experiment. Its task also shows why a difference in responses needs careful interpretation.
Chapter 4 / 5
Read the Numbers with Care
Mira gets faster at the keys during practice. Later, a message interrupts her. Either change could affect a small set of times even if the words had no effect at all.
That is why you see an error rate beside each time. We use the median of correct responses between 150 and 10,000 milliseconds, which reduces the influence of extreme times. Every wrong response still counts toward errors, including responses outside that time window.
The block order is randomized once per attempt. Each block has four target trials of each color, and each mismatching word-color pairing appears twice. This improves the comparison, but does not remove practice, fatigue, language, input-device or display-timing effects for one person.
A result is not a personal label
A small, zero or reversed gap can happen. A large gap is not evidence of poor intelligence. Standardized clinical tasks have procedures and reference data that this browser demonstration does not use (Scarpina and Tagini, 2017).
Chapter 5 / 5
Explain what you learned
Imagine explaining the studio task to a friend. Start with the rule, describe what happened, then name one limitation. “The word competed with my color response” is more useful than “my attention is bad.”
You have practiced separating an observation from an explanation. That habit travels further than any particular number on this page.
Optional. Saved only in this browser. You may leave this blank and finish.
For another everyday experiment, explore how ownership can change what something feels worth.
Stroop test questions
What is the Stroop effect?
The Stroop effect is interference between competing information, commonly seen when naming the ink color of a word that names a different color. Responses are often slower or less accurate than in a comparison condition.
What does the Stroop effect demonstrate?
It shows that a familiar but irrelevant word can compete with the response a task requires. It helps researchers study selective attention and cognitive control; it does not show that attention always fails.
How does this Stroop test online work?
Choose the ink color using three buttons or the 1, 2 and 3 keys. After six practice trials, complete two blocks of 12 trials each. The page compares median correct response times and error rates. An untimed sample-data route is also available.
Why does the Stroop effect occur?
Reading familiar words is highly practiced, so the word can activate a response even when the instruction is to name its ink color. Researchers study several contributors, including how competing responses are selected; no single simple explanation accounts for every version of the task.
Can a Stroop effect test diagnose an attention problem?
This course cannot diagnose a condition or rate your cognitive health. Clinical versions have standardized procedures, reference data and professional interpretation. Device timing, language familiarity and color perception all limit what this short demonstration can tell you.
Sources
- Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18(6), 643-662.
- MacLeod, C. M. (1991). Half a century of research on the Stroop effect: An integrative review. Psychological Bulletin, 109(2), 163-203.
- Scarpina, F., and Tagini, S. (2017). The Stroop Color and Word Test. Frontiers in Psychology, 8, 557.
Cite this source
Psychology.com. (2026, September 16). The Stroop Test. Psychology.com. https://psychology.com/courses/stroop-test
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- Anchoring Bias (12 to 15 minutes): Spin a random wheel, compare your estimate with its anchor, and practice using evidence to make better judgments.
- Confirmation Bias (12 to 15 minutes): Try the 2-4-6 number puzzle, inspect your test choices, and learn to look for evidence that could change your mind.
- Hindsight Bias (12 to 15 minutes): Make five predictions, then compare your remembered answers with the record. Learn why a known ending can make uncertainty disappear.