What is the Stroop effect?

The Stroop effect is the delay in reaction time when the name of a colour is printed in a different ink colour. Reading is automatic for fluent readers, so the word meaning interferes with naming the ink colour.

Why does naming the ink colour feel slower than reading the word?

Word recognition is heavily practised and becomes automatic, while colour naming is not. Your brain must inhibit the automatic reading response, and that inhibitory control costs 50 to 150 milliseconds per trial.

What is a good Stroop test score?

Most players score between 10 and 13 out of 15 on a timed round. Scoring 15 out of 15 with an average response under 800 milliseconds indicates strong executive control and sustained attention.

Does the Stroop effect change with age or practice?

Interference is typically largest in childhood and older adulthood, and smallest in the twenties. Practice reduces the effect substantially, so repeated play measurably improves your score.

Why does every round use a mismatched word and colour?

Congruent trials (the word RED printed in red) remove the interference effect entirely. Lekuno only generates incongruent trials so every one of the 15 rounds measures real cognitive control.

Stroop Color Clash

A colour word appears in a mismatched ink colour. Read the prompt rule, then pick the right colour before the 4-second timer expires.

Press Start to begin the Stroop Color Clash.

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How to play

Every round shows a colour word printed in a different ink colour, so the interference effect is always in play.

When the rule says Name the INK colour, pick the colour of the letters. When it says Name the WORD, pick the colour the word spells.

Tap a swatch or press a number key from 1 to 6. Rounds time out after 4 seconds.

Complete all 15 rounds to see your accuracy, average response time, fastest round, and personal best.

Step-by-Step Test Guide

Read the Prompt Rule
Each round tells you whether to name the ink colour or the literal word. The rule changes unpredictably between rounds.
Inhibit the Automatic Response
Suppress the urge to read the word when the rule asks for ink. This inhibitory control is exactly what the Stroop effect measures.
Answer Before the Timer
You have 4 seconds per round. Tap a colour swatch or press its number key 1 to 6 on a keyboard.
Review Your Interference Cost
The result screen shows accuracy, average response time, fastest round, and a tier from Warming Up to Executive Master.

Stroop Interference Benchmarks

Your score reflects both raw processing speed and the extra cost of suppressing an automatic reading response:

Executive Master: 15/15 with an average under 800 ms
Focused Mind: 13 or more correct out of 15
Colour Confident: 10 to 12 correct out of 15
Interference Fighter: 6 to 9 correct out of 15
Warming Up: Fewer than 6 correct

Published Stroop experiments report an interference cost of roughly 50 to 150 milliseconds per incongruent trial compared with a neutral control.

Why the Effect Happens

Two competing processes run in parallel every time you see a colour word:

Automatic reading: Fluent readers decode words without effort, and this pathway is extremely fast and difficult to switch off.
Controlled colour naming: Identifying and naming a colour requires deliberate attention and uses a slower, capacity-limited pathway.
Response conflict: The anterior cingulate cortex detects the conflict and the prefrontal cortex resolves it, which is the measurable delay.

Frequently Asked Questions

What is the Stroop effect?: The Stroop effect is the delay in reaction time when the name of a colour is printed in a different ink colour. Reading is automatic for fluent readers, so the word meaning interferes with naming the ink colour.
Why does naming the ink colour feel slower than reading the word?: Word recognition is heavily practised and becomes automatic, while colour naming is not. Your brain must inhibit the automatic reading response, and that inhibitory control costs 50 to 150 milliseconds per trial.
What is a good Stroop test score?: Most players score between 10 and 13 out of 15 on a timed round. Scoring 15 out of 15 with an average response under 800 milliseconds indicates strong executive control and sustained attention.
Does the Stroop effect change with age or practice?: Interference is typically largest in childhood and older adulthood, and smallest in the twenties. Practice reduces the effect substantially, so repeated play measurably improves your score.
Why does every round use a mismatched word and colour?: Congruent trials (the word RED printed in red) remove the interference effect entirely. Lekuno only generates incongruent trials so every one of the 15 rounds measures real cognitive control.

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