Green Red Blue
Purple Blue Purple
Blue Purple Red
Green Purple Green
the Stroop effect refers to the fact that naming the color of the first set of words is easier and quicker than the second.
In psychology, the Stroop effect is a demonstration of the reaction time of a task. When the name of a color (e.g., "blue," "green," or "red") is printed in a color not denoted by the name (e.g., the word "red" printed in blue ink instead of red ink), naming the color of the word takes longer and is more prone to errors than when the color of the ink matches the name of the color. 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 Germany in 1929.[2][3][4] The original paper has been one of the most cited papers in the history of experimental psychology, leading to more than 700 replications.[4] The effect has been used to create a psychological test (Stroop Test) that is widely used in clinical practice and investigation.
Contents |
Stimuli 1: Purple Brown Red Blue Green
Stimuli 2: Purple Brown Green Blue Green
Stimuli 3: ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀ ▀
Examples of the three stimuli and colors used for each of the activities of the original Stroop article.[1]
The effect is named after John Ridley Stroop, who published the effect in English in 1935 in an article entitled Studies of interference in serial verbal reactions that includes three different experiments.[1] However, the effect was first published in 1929 in German, and its roots can be followed back to works of James McKeen Cattell and Wilhelm Wundt in the nineteenth century.[2][3][4]
In his experiments, J. R. Stroop administered several variations of the same test for which three different kinds of stimuli were created. In the first one, names of colors appeared in black ink. In the second, names of colors appeared in a different ink than the color named. Finally in the third one, there were squares of a given color.[1]
In the first experiment, 1 and 2 were used. The task required the participants to read the written color names of the words independently of the color of the ink (for example, they would have to read "purple" no matter what the color of its ink was). In the second experiment, stimulus 2 and 3 were used, and participants were required to say the color of the letters independently of the written word with the second kind of stimulus and also name the color of the dot squares. If the word "purple" was written in red, they would have to say "red", but not "purple"; when the squares were shown, the participant would have to say its color. Stroop, in the third experiment, tested his participants at different stages of practice at the tasks and stimulus used in the first and second experiments, to account for the effects of association.[1]
Stroop identified a large increase in the time taken by participants to complete the color reading in the second task compared to the naming of the color of the squares in experiment 2 while this delay did not appear in the first experiment. Such interference was explained by the automation of reading, where the mind automatically determines the semantic meaning of the word (it reads the word "red" and thinks of the color "red"), and then must override this first impression with the identification of the color of the word (the ink is a color other than red), a process that is not automatized.[1]
Unlike researchers performing the Stroop test that is most commonly used in psychological evaluation,[5] J.R Stroop never compares the time used for reading black words and the time needed for naming colors that conflicted with the written word.
Stimuli in Stroop paradigms can be divided into 3 groups: neutral, congruent and incongruent. Neutral stimuli comprise those in which only the text (similarly to stimuli 1 of Stroop's experiment), or color (similarly to stimuli 3 of Stroop's experiment) are displayed.[6] Congruent stimuli are those in which the ink color and color name refer to the same concept (for example the "pink" word written in pink). Incongruent stimuli are those in which ink color and concept differ.[6] Three experimental findings are recurrently found in stroop experiments.[6] A first finding is semantic interference, consisting of the fact that naming the ink of neutral stimuli is faster than in incongruent conditions. It is called semantic interference since it is usually accepted that the relationship in meaning between ink color and word is at the origin of the interference.[6] Semantic facilitation defines the finding that naming the ink of congruent stimuli is faster than with neutral stimuli. The third finding is that both semantic interference and facilitation disappear when the task consists in reading the word instead of naming the ink. It has been sometimes called Stroop asynchrony, and has been explained by a reduced automaticitation when naming colors compared to reading.[6]
In the study of interference theory, 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 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.[4] Usually lists of stimuli are used, but time measures for individual words permit more control on research variables.[4] Rather than naming or reading stimuli aloud, subjects have also been asked to sort stimuli into categories.[4] Different characteristics of the stimulus such as ink colors or direction of words have also been systematically varied.[4] None of all these modifications eliminates the effect of interference.[4]
As one of the most referenced papers in experimental psychology, the test has also been further modified to investigate very different phenomena.[4]
The Stroop task has been employed to study frontal function and attention in brain imaging studies.[7] 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.[8] Other examples of derived tasks which show interference effects may include a drawing with an incongruent caption (e.g. a drawing of a bird with the name of another animal as caption, the task being naming the drawing), or the word left in the right of the image (the task being saying where the word is located).[9]
The test has additionally been modified to include other sensory modalities and variables,[10] to study the effect of bilingualism,[11] or to investigate the effect of emotions on interference.[12][13][14] 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.[15]
In the neo-Piagetian theories of cognitive development, several variations of the Stroop task have been used to study the relations between speed of processing and executive functions with working memory and cognitive development in various domains. This research shows that reaction time to Stroop tasks decreases systematically from early childhood through early adulthood. These changes suggest that speed of processing increases with age and that cognitive control becomes increasingly efficient. Moreover, this research strongly suggests that changes in these processes with age are very closely associated with development in working memory and various aspects of thought.[16][17]
| Stroop effect | |
|---|---|
| Diagnostics | |
| MeSH | D057190 |
The Stroop effect has been used to investigate the psychological capacities of a person since its discovery during the twentieth century it has became a popular neuropsychological test.[18]
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.[18][19] 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 four 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 that have to be read.[18] The number of stimuli 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.[18] The number of errors and different derived punctuations are also taken into account in some versions.[18]
This test is considered to measure selective attention, cognitive flexibility and processing speed, and it is used as a tool in the evaluation of executive functions.[18][19] 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.[18][20][21]
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.[19][22] 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.[19] Stroop performance has also been associated with the correct functioning of the hippocampus or posterior brain areas.[19]
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.[23] A Nova episode used the Stroop Effect to illustrate the subtle changes of the mental flexibility of Mount Everest climbers in relation to altitude.[24]