TEST

Stroop Test

Inhibitory control and color-word interference resolution

Digital version with binary response of the classic Stroop paradigm. Quantifies with millisecond-by-millisecond precision the cognitive cost of inhibiting automatic reading to resolve the conflict between word and color.

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64

TRIALS

50/50

CONGRUENT / INCONGRUENT

4

COLORS

ms

INTERFERENCE PRECISION

WHAT THE TEST IS

The classic paradigm of cognitive inhibition

Described by Stroop (1935), the Stroop effect is the difficulty in naming the color of a word when the word denotes a different color. Its neuropsychological basis is associated with the functioning of the anterior cingulate cortex and the dorsolateral prefrontal cortex, key regions for executive control and conflict management.

The digital version replaces the oral response with a binary response (congruent vs. incongruent), eliminating evaluator dependency and enabling interference cost to be measured with millisecond precision. The sequence is pseudo-randomized to avoid priming and Gratton effects, with equiprobable distribution of words and colors.

HOW IT IS ADMINISTERED

Decide whether the word and color are congruent or incongruent

In each trial, a word (RED, GREEN, YELLOW, or BLUE) appears written in one of those four colors. The user must decide whether the word and color match (e.g., RED written in red) or mismatch (e.g., RED written in blue) and respond using two keys: X for congruent, N for incongruent.

The test consists of 64 trials (32 congruent + 32 incongruent) presented in pseudo-random order, with equiprobable distribution and never repeating the same word or color twice in a row. No feedback is provided during the test.

WHAT THE TEST MEASURES

Indicators and their interpretation

Performance is separated by condition (congruent vs. incongruent) to isolate the specific cost of interference, without contamination from baseline speed.

Correct responses and omissions

Correct responses within the time limit, separated by congruent / incongruent condition. Omissions reflect lapses or excessive slowness.

Cong/incong dissociation: low correct responses only in incongruent trials point to inhibitory deficit.
Many omissions: slowing or lack of understanding.

Commissions (errors)

Responses given but incorrect. In Stroop, most reflect failure to suppress automatic reading.

High commissions: inhibitory deficit, impulsivity (frontal, Parkinson’s, schizophrenia).
Low commissions: robust inhibitory control.

Congruent RT

Mean reaction time in trials without conflict. Baseline speed without inhibitory demand.

High RT: global bradypsychia (MS, Parkinson’s, depression).
Low RT: efficient processing speed.

Incongruent RT

Mean time in trials with conflict. Reflects processing speed under active inhibitory demand.

Very high RT: difficulty resolving conflict.
RT similar to congruent: excellent control over interference.

Interference index

Congruent RT – incongruent RT difference. Direct measure of the extra cost of interference for the user, controlling for baseline speed.

Small (~-100/-200 ms): optimal inhibitory control.
Very negative (<-400 ms): executive deficit in conflict resolution.

Speed-accuracy index (IES)

Composite metric that integrates speed and accuracy. Places the user on a continuum of overall cognitive efficiency.

High IES: unfavorable trade-off (fast and inaccurate, or slow without errors).
Low IES: optimal speed-accuracy balance.

REFERENCES

Bibliography

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.
Lubrini, G., Periáñez, J. A., Ríos-Lago, M., et al. (2014). Clinical Spanish norms of the Stroop Test for traumatic brain injury and schizophrenia. The Spanish Journal of Psychology, 17, E96.
Scarpina, F., & Tagini, S. (2017). The Stroop Color and Word Test. Frontiers in Psychology, 8, 557.
Gratton, G., Coles, M. G. H., & Donchin, E. (1992). Optimizing the use of information: Strategic control of activation of responses. Journal of Experimental Psychology: General, 121(4), 480–506.