Stroop

The Stroop effect refers to the delay in reaction time when a task requires naming the color of the ink used to print a word whose meaning is the name of a different color. It is a classic demonstration of interference between different cognitive processes, such as automatic reading and controlled color naming. The effect was first described by John Ridley Stroop in 1935 in a series of experiments that showed slower color-naming when the inked word conflicted with the word’s meaning.

In a typical Stroop task, participants view color words (for example, "red," "blue") printed in ink that may be congruent (matching the word), incongruent (mismatching), or neutral (non-color words or colored blocks). They are asked to name the ink color as quickly and accurately as possible. Incongruent stimuli produce longer reaction times and more errors compared with congruent or neutral stimuli, revealing interference from automatic word reading.

The Stroop paradigm has been extended to many variants, including emotional Stroop (emotional or affective words), numerical Stroop, and auditory versions. It is widely used to study cognitive control, selective attention, and conflict monitoring. The task has applications in clinical psychology and neuropsychology, including assessments of ADHD, schizophrenia, aging, and mood disorders, where Stroop performance can reflect executive function and attentional control.

Neural and cognitive accounts attribute the effect to automatic processing of reading competing with intentional color naming, with involvement of brain regions such as the prefrontal cortex and anterior cingulate cortex. The Stroop remains a foundational tool in cognitive psychology and neuropsychology.