Stroop effect

The Stroop Effect is when a word such as blue, green, red, etc. is printed in a color differing from the color expressed by the word's semantic value (e.g. the word "red" printed in blue ink), naming the color of the word takes longer and is more prone to errors than when the meaning of the word is congruent with its ink color. The effect is named after John Ridley Stroop who first published the effect in English in 1935.Cite error: Closing </ref> missing for <ref> tag. J.R Stroop never compared the time used for reading black words and the time needed for naming colors that conflicted with the written word.

Modifications

The original paper of the Stroop effect has been one of the most cited papers in the history of experimental psychology, leading to over 710 replications.^[1] The test has been further modified to investigate very different phenomena.

In the study of interference the most commonly used procedure has been similar to Stroop's second experiment, in which subjects are tested on naming colors of incompatible words and of control patches; however the first experiment (reading words in black versus incongruent colors) has received much less interest. In both cases the interference score is expressed as the difference between the times needed to read each of the two types of cards.^[1] Usually lists of stimulus are used, but time measures for individual words permit more control on research variables.^[1] Rather than naming or reading stimuli aloud, subjects have also been asked to sort stimuli into categories.^[1] Different characteristics of the stimulus such as ink colors or direction of words have also been systematically varied.^[1] None of all these modifications eliminates the effect of interference.^[1]

The Stroop task has been employed to study frontal function and attention in brain imaging studies.^[2] 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 button box.^[3]

The test has additionally been modified to include other sensory modalities and variables,^[4] to study the effect of bilingualism,^[5] or to investigate the effect of emotions on interference.^[6] A similar effect has also been observed in individuals with grapheme-color synesthesia - people who perceive colors when seeing certain numbers and letters. If a number or letter is presented to such an individual in a color other than what they would perceive, there is a delay in determining what color the character actually is.^[7]

Clinical use

The Stroop effect has been used to investigate the psychological capacities of a person since its discovery; while during the twentieth century it also became a popular neuropsychological test.^[8]

There are different test variants commonly used in clinical settings; with differences between them in the number of subtasks, type and number of stimulus, times for the task or scoring procedures.^[8][9] Regarding the number of subtasks all versions have at least two: there are written color names differing from the ink used and in the first trial the participant has to say the written word and the ink in the second. However there can be up to 4 different subtasks adding in some cases stimulus consisting of groups of letters "X" or dots printed in a given color with the participant having to say the color of the ink, or names of colors printed in black ink which have to be read.^[8] The number of stimulus varies between less than twenty items to more than 150; being closely related to the scoring system used. While in some variants the score is the number of items from a subtask read in a given time; in others it is the time that it took to complete each of the trials.^[8] The number of errors and different derived punctuations are also taken into account in some versions.^[8]

This test is considered to measure selective attention, cognitive flexibility and processing speed, and it is routinously used as a tool in the evaluation of executive functions.^[8][9] An increased interference effect is found in disorders such as brain damage, dementias and other neurodegenerative diseases, attention-deficit hyperactivity disorder, or a variety of mental disorders such as schizophrenia, addictions and depression.^[8][10]

Anatomical basis

The cingulate cortex has been related to the processing of the Stroop effect

EEG and functional neuroimaging studies of the Stroop effect have consistently revealed activation in the frontal lobe; and more specifically in the anterior cingulate cortex and dorsolateral prefrontal cortex, two structures hypothesized to be responsible for conflict monitoring and resolution.^[9] Accordingly patients with frontal lesions obtain lower punctuations in the Stroop test when compared to those with more posterior lesions. However these frontal regions are not the only ones implicated in the effect.^[9] Stroop performance has also been associated with the correct functioning of the hippocampus or posterior brain areas.^[9]

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 form.^[11] A Nova episode used the Stroop Effect to illustrate the subtle changes of the mental flexibility of Mount Everest climbers in relation to altitude.^[12]

References

External links

• [1] Interactive Stroop Test