What is the Stroop test?
In 1935, John Ridley Stroop published "Studies of interference in serial verbal reactions" in the Journal of Experimental Psychology. That paper — today among the most cited in experimental psychology — introduced the paradigm that bears his name, and which became the standard instrument for measuring inhibitory control: the brain's capacity to suppress an automatic response (reading) in order to execute a less automatic one (naming the ink colour).
Our version follows the same classic design: words naming colours, written in four ink colours. Your task is to respond based on the ink colour, ignoring the word's meaning. "Congruent" trials (word and colour match) are easy; "incongruent" trials are the ones that truly test inhibition.
What does this game test?
- Inhibitory control — suppressing an automatic response (reading) to execute a controlled one (naming the colour).
- Selective attention — focusing on one feature (the colour) and ignoring another (the word's meaning).
- Frontal executive function — coordinated by the prefrontal cortex, which declines more rapidly in cognitive ageing and frontotemporal dementia.
The Scarpina & Tagini 2017 review (Frontiers in Psychology) describes clinical applications of the Stroop test for cognitive screening, evaluation in dementia, ADHD, major depression, and frontal lesions. The study is freely available on PMC — recommended reading for professional context.
Frequently asked questions
▶What is the Stroop effect?
The Stroop effect, described by John Ridley Stroop in 1935 in the Journal of Experimental Psychology, is the response delay that occurs when an automatic task (reading the word) interferes with a controlled task (identifying the ink colour). Healthy adults read words much faster than they name colours, and the conflict between the two processes forces the brain to suppress the automatic response — a process called inhibitory control.
▶What does a low score on the Stroop test indicate?
A much longer response time on incongruent trials (word differs from colour) and a high error count suggest difficulties with inhibitory control and selective attention. These deficits appear in multiple conditions: frontal lesions, ADHD, frontotemporal dementia, major depression. It is NOT a diagnostic test in itself — a low isolated score can also be caused by fatigue, stress, or reading difficulties.
▶How often should I do the Stroop test?
For self-assessment, once every 1–2 weeks is sufficient. More frequent testing adds no information (the learning effect is large). What matters is the trend over time — if latency on incongruent trials increases consistently over 1–2 months, it is worth discussing with your GP.
▶Why are there fewer colours in the online version?
The original clinical test uses four colours (red, green, blue, yellow) — exactly as in our version. Some research versions use 5–6 colours. The small number of colours is due to working memory limits: with more than 4 alternatives, errors increase for a different reason (forgetting the key mappings), confounding the result.