Stroop effect

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In psychology, the Stroop effect is a demonstration of interference in the reaction time of a task. When a word such as blue, green, red, etc. is printed in a color differing from the color expressed by the word's semantic meaning (e.g. the word "red" printed in blue ink), a delay occurs in the processing of the word's color, leading to slower test reaction times and an increase in mistakes. The effect is named after its discoverer, John Ridley Stroop, and was first noted in an article Studies of interference in serial verbal reactions published in the Journal of Experimental Psychology in 1935.

In his experiment, Stroop administered several variations of two main tests. Stroop referred to his tests as RCN, to stand for "Reading Color Names", where participants were required to repeat the written meaning of words with differing coloured fonts, and NCW, to stand for "Naming Colored Words", in which participants were asked to verbally identify the color of each printed color name. Additionally Stroop tested his participants at different stages of practice with each task, to account for the effects of association.

Stroop identified a large increase on the time taken by participants to complete the NCW (Naming Colored Words) tasks, an effect still pronounced despite continued practice at each task. This interference is thought to have been caused by the automatization of reading, where the mind automatically determines the semantic meaning of the word, and then must override this first impression with the identification of the color of the word, a process which is not automatized.

Edith Kaplan's (developer of the Delis-Kaplan neuropsychological test battery) group developed the task further by separating the task into four stages: naming color fields, congruent color words, incongruent color words, and combined. In the fourth section, some words have boxes around them. The participant must name the color of the words in boxes and read the words outside boxes. This puts further strain on the executive function of the brain.

The Stroop task is also employed to study frontal function and attention in brain imaging studies. Speaking is not possible in the scanner because it moves the head, so a number theme is often used instead. For instance, three words may be displayed that read "two" and the participant must press three on their buttonbox. Another variant is to present emotional pictures in the scanner (again using the number paradigm) to determine their effect on frontal inhibition. This is especially useful in studying post-traumatic stress disorder.

Since its development, the Stroop task, a measure of the effect of interference on performance of a colour identification task, has utilised the Stroop effect to investigate aspects of such varied psychological disorders as Attention Deficit Hyperactivity Disorder, Schizophrenia, and Anorexia. EEG and fMRI studies of the Stroop effect have revealed selective activation of the anterior cingulate cortex during a stroop task, a prefrontal structure in the brain which is hypothesized to be responsible for conflict monitoring. J. Ridley Stroop's original word colour identification test has additionally been modified to include other sensory modalities and variables.

[edit] Stroop effect in popular culture

The Brain Age: Train Your Brain in Minutes a Day! software program, produced by Ryūta Kawashima for the Nintendo DS portable video game system, contains an automated Stroop Test administrator module, translated into game forms.

A Nova episode used the Stroop Effect to illustrate the subtle changes of the mental flexibility of Mt Everest Climbers in relation to altitude. [1]

[edit] External links

• John Ridley Stroop, Studies of interference in serial verbal reactions from Classics in the History of Psychology.
• Demonstration and definition of the Stroop effect.
• Interactive JavaScript Demonstration of Stroop effect.