📜 History

History of the Stroop Test: From 1935 to Today

February 5, 2025 · 8 min read

Few psychological experiments have had as enduring an impact as those described in a 1935 doctoral dissertation by a relatively unknown graduate student. John Ridley Stroop's study of "Studies of Interference in Serial Verbal Reactions" would become one of the most cited papers in psychology, referenced in over 700 studies per year.

👨‍🔬 Who was John Ridley Stroop?

John Ridley Stroop (1897–1973) was an American psychologist who published his seminal work in the Journal of Experimental Psychology in 1935. Remarkably, after publishing this landmark study, Stroop largely left academic psychology to become a minister and Bible teacher. He likely had no idea his dissertation would define a century of cognitive research.

📄 The original 1935 experiment

Stroop's original study had three conditions: (1) naming colors of solid patches, (2) reading color words in black ink, and (3) naming the ink color of words printed in conflicting colors. The results were dramatic: naming ink colors of incongruent words took 74% longer than reading the same words in black ink. The effect was massive and has been replicated thousands of times since.

📅 Key historical milestones

1935
J.R. Stroop publishes his doctoral dissertation — the foundational Stroop paradigm in Journal of Experimental Psychology
1960s
Researchers begin systematic study of the cognitive mechanisms underlying the Stroop Effect
1978
Charles J. Golden publishes standardized clinical Stroop Color and Word Test — still widely used today
1991
MacLeod's landmark review of 50 years of Stroop research catalogues 18 empirical findings
2000s
Neuroimaging (fMRI) studies identify anterior cingulate cortex and prefrontal cortex as key brain regions
2012
EncephalApp Stroop Test validated as a smartphone tool for hepatic encephalopathy screening
2020s
Online Stroop testing surges; used in remote neuropsychological assessment, UX research, and gaming studies

🏥 Clinical standardization: Golden (1978)

The most widely used clinical version is the Stroop Color and Word Test by Charles J. Golden (1978). It provides three standardized scores: Word (W), Color (C), and Color-Word interference (CW). T-scores normalized for age and education are used in clinical neuropsychological practice to assess frontal lobe function, dementia, ADHD, and TBI.

📱 The digital age: EncephalApp & online Stroop

The EncephalApp Stroop Test (2012) marked a pivotal moment: a validated smartphone application using the Stroop paradigm to screen for minimal hepatic encephalopathy in liver disease patients. Today, online Stroop tests are used for remote cognitive assessment, UX attention research, sports performance monitoring, and consumer brain training applications.