Suppose you have to tell the font colour of a word say ‘red,’ and the font colour is the same as the colour name itself, i.e., red (congruent stimuli) you will immediately tell that the font colour is red. Now consider another word say ‘green’ but its front colour is different from the green colour (incongruent stimuli), this may trick your brain and you may take it longer to tell the font colour this time as the word is green but its font colour is yellow. This delay in the reaction time in both the stimuli, i.e., the congruent and the incongruent stimuli is known as the Stroop Effect. The term Stroop effect is named after an American Psychologist John Ridley Stroop, he was the first who publish a paper entitled “Studies of interference in serial verbal reactions” on the Stroop effect in English in the ‘Journal of Experimental Psychology,’ in 1935. Earlier, the strop effect was first published in Germany by the psychologist Erich Rudolf Jaensch in 1929. Erich’s publication on the Stroop effect was based on the work of Wilhelm Maximilian Wundt and James Mckeen Cattell in the 19th century. The phenomenon of the Stroop effect causes behind the Stroop effect, and various real-life examples of the Stroop effect are discussed in this article.
The original English paper on the Stroop effect published by John Ridley Stroop is one of the most cited papers in experimental psychology that leads to more than 700 articles related to the Stroop effect. Stroop used three different elements in his original study, i.e.,
- Colours name printed in black font colour
- Colours name printed in different font colour other than the name of the colour
- Squares patches of all the given colours
He later conducted three different experiments using the above three elements. The first experiment was conducted on 70 undergraduate students, in this experiment, the participants had to read the colour name irrespective of the fact that the given word (colour name) is printed in a different colour than the colour name, for example, the word green is printed in the yellow colour, but you have to read the word green. The second experiment was conducted on 100 college students. On contrary to the first experiment, the participants have to speak the colour of the word (colour name) that it is printed in. For example, if the word ‘red’ is printed in the green colour rather than speaking ‘red’ the participant has to say the ‘green.’ In this experiment, the squares of the colours were also shown to the participants and they had to name the colour given in the squares. The third experiment was conducted on 32 participants, Stroop tested the subjects at different levels of practice of the tasks given in the first and the second experiment to examine the learning of the subjects. In all these three experiments, the congruency of the name and the colour of the font is the Independent variable and the time taken to report the colour is the dependent variable.
Findings of the Experiment
In Stroop’s experiment, the stimuli’s can be divided into three groups, i.e., the neutral stimuli, congruent stimuli, and the incongruent stimuli.
Neutral Stimuli: If only the texts or the colours are displayed to the subjects that do not trigger any responses, it is called the neutral stimuli. For example, the participants just have to read the word displayed on the screen or the colour shown to them, and there is no interference of the word with the colour it is printed in. For example, the word is ‘table’ and it is printed in any random colour.
Congruent Stimuli: If the colour of the font is the same as the word (colour name) it is called the congruent stimuli. For example, The word ‘green’ is printed in the green font colour.
Incongruent Stimuli: If the colour of the font is different from the word (colour name), it is called the incongruent stimuli.
In the Stroop experiment, three experimental findings are generally discussed. The first finding is ‘semantic interference,’ which explains that participant does not take much time to report the font colour in case of the neutral stimuli, while they took a significant amount of time in naming the font colour in case of the incongruent stimuli, this happens due to the interference of the word (colour name) and the colour it is printed in. Semantic facilitation is the second finding, which explains that the response to the congruent stimuli (font colour and the word are the same) is faster than the neutral stimuli (when coloured squares were shown). The third finding includes the disappearance of both the semantic finding and the semantic facilitation when the participants were asked to speak the word rather than the font colour, no matter if the font colour of the word (colour name) is different from the given colour. This phenomenon is often known as ‘Stroop asynchrony.’
Conclusions of the Experiment
The experiment’s findings show the disparity in the time taken in naming the colours and reading the colour’s names. This shows that there is a difference in how our brain processes information when we label the colours or just read the word (colour name).
Theories to explain the Stoop Effect
By using brain imaging techniques such as magnetic resonance imaging (MRI), Positron emission tomography (PET), and functional magnetic resonance imaging (fMRI), it is said that two main areas of the brain, i.e., dorsolateral prefrontal cortex, and anterior cingulate cortex, are involved in the Stroop effect. Dorsolateral prefrontal context is responsible for the execution of functions while resolving the conflicts and finding the errors while for choosing the appropriate response and allocating memory, the anterior cingulate cortex is used. Let us discuss various theories, which are usually known as ‘race models’ that have been proposed by the researchers to explain Stroop’s effect.
1. Processing Speed
According to this theory, the brain takes more time to recognize the colour of the given word because the brain finds it easier to read the words than to recognize the colour of the given word. It is based on the phenomenon that colour processing takes more significant time than word processing in the case of the conflict between the naming the words and the colours, i.e., the Stroop effect. If the subject has to report the colour of the word, the word information enters the decision-making stage before the colour information, which creates confusion. On the other hand, if the subject has to report the word (colour name), the word information enters before the colour information at the decision-making stage so the subject can answer in a lesser time as there is no confusion. This theory is also known as the Relative Speed of Processing Theory.
2. Selective Attention
According to the ‘Selective Attention Theory,’ colour recognition requires more awareness and attention than recognizing a word. The brain needs to be more active to recognize a colour than simply reading a word, which takes a comparatively longer time.
This theory is considered the most common theory to explain the Stroop effect. This theory states recognizing a colour takes longer than reading the text as the former is not an automatic response, whereas due to habitual reading the brain automatically understands the words by immediately linking them to the meaning associated with that word. One does not require controlled attention while reading as it is required in labelling the colour.
4. Parallel Distributed Processing
According to this theory, while analysing the information, our brain develops a distinct and specific pathway for the different tasks. Some pathways (reading) are stronger than the other pathways (naming colours), and hence what important is the strength of the pathway in comparison to the speed of the pathway. During the Stroop effect, the two pathways simultaneously get active, which results in the interference between the stronger pathways such as reading a word and the weaker pathways such as naming the colour.
Real-life Examples and Applications of Stroop Effect
1. Emotional Stroop Test (Larsen et al., 2006)
The principle behind the emotional Stroop test is based on the Stroop effect. This test is used to assess the emotions of people by analysing the way they approach information. In this test, the response time of the subjects in reporting the colour name of the words shown to them is measured. The words presented in this test are either neutral (table, chair, pen, watch, box) or they are related to any disorders or emotional states (headache, pain, love, cancer, death). When this test was conducted on the participants suffering from depression, it was found that they took comparatively more time in reporting the colours of the depressing words in comparison to the time taken in reporting the colours of the non-depressing words. Even when the test was conducted on the non-clinical participants, the time taken for reporting the colour of emotional words was more than the time taken in reposting the colour of neutral words. This may happen due to the emotional relevance of the subject with that word. The negative or emotional words in the emotional Stroop test are carefully selected by the researchers for better emotional analysis of the people.
2. Stroop Test
The Stroop test is one of the most widely used neurological tests. It is used to measure various factors like processing speed, cognitive flexibility, and selective attention. Stroop test shows increased interference in various psychological disorders such as dementia, schizophrenia, ADHD and depression. Different types of Stroop tests are available these days depending upon the number of stimuli, duration of the task, number of tasks and subtasks in the test, and scoring procedure. A study conducted in 1976 showed that the Stroop test was around 88.9 per cent precise in distinguishing between the participants who suffered from brain damage and those without any brain damage.
3. Interference in Numerosity Processing and the Duration (Dormal et al., 2006)
Unlike the standard Stroop effect experiment of the relation between the word and the colour processing, another experiment to find the relation between the numerosity and duration was conducted. In this experiment, ‘two series of dots in successions’ were shown to the subjects and they were asked either of the two questions.
Which series out of the two consists of more dots?
Which series seems longer in appearance from first till the last dot of the series?
The incongruent stimuli occurs when a few dots were flashed longer on the screen and the congruent stimuli refer to the situation when more dots results in the longer series. The results of the experiment show the interference between the numerosity processing and the duration, i.e., it was difficult for the subjects to decide which series appeared for longer on the screen when the few dots were presented for longer.
4. Additional Variations (Mac Leod, 2015)
The Stroop effect is not just limited to the interference of the colour and the words processing, it is also responsible for various other interference. Look at the figure below, this image represents the various additional interferences due to the Stroop effect.
- figure-a represents the interference between word processing and the picture
- figure-b represents the interference between the word processing and the direction
- figure-c represents the interference between the digit and the numerosity processing
- figure-d represents the interference between the identification of central vs. peripheral letter
The Stroop effect is widely applied in marketing. The presentations or the advertisements are carefully designed by considering the font style and the colour it is printed in. In accordance with the Stroop effect, people are generally more mentally attracted towards the specific words and the colours, which is why the colours of the products are carefully chosen by the manufacturers.