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Demonstration
Say aloud the colors of each of these words, as fast as you can:

Green Red Blue
Yellow Blue Yellow

Blue Yellow Red
Green Yellow Green

If naming the first group of colors is easier and quicker than the second, then your performance exhibits the Stroop effect.

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 John Ridley Stroop who first published the effect in English in 1935.[1]

The effect had previously been published in 1929, but only in German.[2][3][4] The original paper has been one of the most cited papers in the history of experimental psychology, leading to over 710 replications.[4]

Contents

Original experiment

In his experiment, J. Ridley 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 colored fonts, and NCW, to stand for "Naming Colored Words", in which participants were asked to orally 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.[1]

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.[1] This interference was explained by the automation 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.[1]

Clinical use

Since its development, the Stroop task, a measure of the effect of interference on performance of a color identification task, has utilized 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 (see frontal lobe) in the brain which is hypothesized to be responsible for conflict monitoring.

Further development and usage

Edith Kaplan's group (developer of the Delis-Kaplan neuropsychological test battery) developed the task further by separating the task into four different stages: naming color fields, congruent color words, incongruent color words, and combined. The additional strain on the executive function of the brain allows for a more precise diagnosis.citation needed

The Stroop task is also employed to study frontal function and attention in brain imaging studies.[5] 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.[6]

The test has additionally been modified to include other sensory modalities and variables,[7] to study the effect of bilinguislism,[8] or to investigate the effect of emotions on interference.[9] 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.[10]

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 form.

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

References

  1. ^ a b c d Stroop,, John Ridley (1935). "Studies of interference in serial verbal reactions". Journal of Experimental Psychology 18: 643-622. Retrieved on 2008-10-08. 
  2. ^ Jaensch, E. R. (1929). Grundformen menschlichen Seins. Berlin: Otto Elsner.
  3. ^ Jensen AR, Rohwer WD (1966). "The Stroop color-word test: a review". Acta psychologica 25 (1): 36–93. PMID 5328883. 
  4. ^ a b MacLeod CM (March 1991). "Half a century of research on the Stroop effect: an integrative review". Psychological bulletin 109 (2): 163–203. PMID 2034749. 
  5. ^ Pujol J, Vendrell P, Deus J, et al (January 2001). "The effect of medial frontal and posterior parietal demyelinating lesions on stroop interference". NeuroImage 13 (1): 68–75. doi:10.1006/nimg.2000.0662. PMID 11133310. 
  6. ^ Kaufmann L, Ischebeck A, Weiss E, et al (October 2008). "An fMRI study of the numerical Stroop task in individuals with and without minimal cognitive impairment". Cortex; a journal devoted to the study of the nervous system and behavior 44 (9): 1248–55. doi:10.1016/j.cortex.2007.11.009. PMID 18761138. 
  7. ^ Roberts KL, Hall DA (June 2008). "Examining a supramodal network for conflict processing: a systematic review and novel functional magnetic resonance imaging data for related visual and auditory stroop tasks". Journal of cognitive neuroscience 20 (6): 1063–78. doi:10.1162/jocn.2008.20074. PMID 18211237. 
  8. ^ Rosselli M, Ardila A, Santisi MN, et al (September 2002). "Stroop effect in Spanish-English bilinguals". Journal of the International Neuropsychological Society : JINS 8 (6): 819–27. PMID 12240746. 
  9. ^ Kampman M, Keijsers GP, Verbraak MJ, Näring G, Hoogduin CA (2002). "The emotional Stroop: a comparison of panic disorder patients, obsessive-compulsive patients, and normal controls, in two experiments". Journal of anxiety disorders 16 (4): 425–41. PMID 12213037. 
  10. ^ Ramachandran, V.S. and Edward M. Hubbard. "More Common Questions about Synesthesia. Scientific American online. April 14, 2003. URL accessed 2007-03-12.
  11. ^ "NOVA Online".

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