Games & Puzzles
Stroop Effect Test - Cognitive Interference Experiment
Experience the Stroop effect - identify the ink color of a color word as fast as possible. Measures cognitive interference when the word and color conflict.
Click the ink color of each word - ignore what the word says.
What is the Stroop effect?
The Stroop effect is the finding that it takes longer and produces more errors to name the ink color of a color word when the word and ink color conflict (e.g., the word BLUE written in red ink) than when they match or when neutral stimuli are used. The interference occurs because reading words is a highly automatic process that competes with the slower, more deliberate task of identifying ink color.
History
The effect was described by American psychologist John Ridley Stroop in his 1935 doctoral dissertation, “Studies of Interference in Serial Verbal Reactions,” published in the Journal of Experimental Psychology. It remains one of the most replicated findings in cognitive psychology, with over 700 studies citing the original work.
What it measures
The Stroop test is a probe of three interrelated cognitive capacities:
- Selective attention: the ability to focus on a relevant attribute (ink color) while ignoring an irrelevant but salient one (the written word).
- Cognitive flexibility: the ability to switch between different response rules depending on context.
- Inhibitory control: the ability to suppress an automatic, dominant response (reading) in favor of a less automatic one (color naming).
Interpreting your score
| Metric | What it means |
|---|---|
| Reaction time (congruent) | Baseline naming speed when word and color match. Reflects general processing speed. |
| Reaction time (incongruent) | Your speed when word and color conflict. Higher = more interference. |
| Stroop interference score | Incongruent RT − Congruent RT. The larger the gap, the greater the interference effect. |
| Error rate (incongruent) | How often you named the word instead of the color. High error rates suggest strong automaticity of word reading. |
Typical adults show an interference effect of 100–200 ms. Faster overall times reflect better processing speed; a smaller interference gap reflects stronger executive control.
Clinical uses
The Stroop Color-Word Test has been standardized and is used in neuropsychological assessment to screen for:
- ADHD: individuals with ADHD typically show elevated interference scores reflecting weaker inhibitory control.
- Dementia screening: performance on the Stroop declines in early Alzheimer’s disease and other dementias, correlating with frontal lobe integrity.
- Traumatic brain injury: the test is sensitive to frontal lobe damage affecting executive function.
- Substance use research: modified Stroop variants with drug-related words are used to measure attentional bias.
Typical score benchmarks
| Age group | Congruent RT | Incongruent RT | Interference (gap) |
|---|---|---|---|
| Young adults (18–30) | ~600–700 ms | ~700–850 ms | ~80–150 ms |
| Middle adults (30–55) | ~700–800 ms | ~850–1,000 ms | ~100–200 ms |
| Older adults (55+) | ~800–1,000 ms | ~1,000–1,250 ms | ~150–250 ms |
These are approximate population averages from laboratory studies. Individual performance varies significantly based on prior exposure, fatigue, and testing conditions. Web-based timing includes keyboard/mouse input latency that is absent in lab settings, so your scores may skew ~50–100 ms higher than published norms.
Emotional Stroop variant
A related paradigm replaces color words with emotionally charged words (e.g., threat words, trauma-related words). Participants who have an attentional bias toward those words - common in anxiety disorders and PTSD - show longer reaction times for emotionally relevant words even though the task is still to name the ink color.
The Emotional Stroop test is widely used in clinical psychology research to measure implicit attentional biases without requiring self-report, providing a more objective measure of emotional processing.