Stroop test: psychological evaluation of attention

The human being tends, through learning, to get used to performing certain actions. Eating, writing, reading or cycling: all are processes that initially require our full attention, but that we end up automating.

In general, this automation helps us save resources, but the truth is that it can sometimes be disadvantageous. This is what happens when we are asked for a task in which stimuli appear that elicit the automated response, but asking us to do something else. We must stop the automatism to carry out the real task. One way to measure this interference is the Stroop test..

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The Stroop test

The Stroop test is a psychological test linked especially to neuropsychology that allows to measure the level of interference generated by the automatisms in the accomplishment of a task.

Also called Test of Colors and Words, it was elaborated by Golden with the intention of assess aspects such as selective attention and inhibitory control

, when it was observed that people who knew how to read tended to take longer for the color in which they were written the words than in reading the names of those colors (because they had more automated the reading). It also allows assessing the processing speed 

The duration of the application of this test is relatively short, about five minutes long, and is intended for people between the ages of seven and eighty.

Although it consists of three phases, the best known part and the one that has the most use is the one that is based on the reading of the word that designates a color written in a different color than the one it expresses, so that the subject has to inhibit automatic response from reading in order to correctly designate the color with which the words are written.

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The three phases or tasks

Throughout the Stroop test, a total of three different tasks are done, by means of three sheets in which five columns of 20 elements appear. Each of the tasks is carried out for a specified time (for example, forty-five seconds), and the correct answers are recorded for later evaluation.

1. Reading words

First, the subject is provided with a list with the names of three colors (red, blue and green) written in black, and is asked to read them.

2. Color identification task

The second of the tasks is color identification, in which the observed is provided with a list of colored symbols without meaning. The subject is asked to identify and name the color of each of the elements.

3. Interference task

Finally, the third and most representative task of the Stroop test is based on the principle of interference, offering the subject a list of words with the name of the aforementioned colors, but in this chance written in a different color than the word refers to. For example, the word BLUE appears written in red. The subject must name the color in which each element is written.

Interpretation of the Stroop test

The data collected by the Stroop test must be analyzed. The successes that the subject has had during the test or by the time it takes to react to stimulation, paying attention to what is reflected in each of the pictures or tasks.

In the third of the tests we can observe the reaction time of the subject, which indicates aspects such as the interference produced by different aspects of the same stimulation, the ability to resist it, the management of cognitive and attentional resources or the perseverance and repetition of behaviors.

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Effect of interference

The estimate of the approximate score that a subject should obtain in the third test can be calculated from of the quotient of the product of the words read in the first test by the color of the second one divided by their sum.

If we subtract the estimated score from the real score obtained in the interference task, we can see if the person correctly inhibits the response (values ​​greater than 0, positive) O well if there are significant interference problems (if it is a negative value). In general, the majority of the population scores between 10 and -10.

However, this estimate may be biased whether the subject has a very low or very high level of reading experience (the value of the responses in the first test the performance in the third can vary depending on whether we are more or less used to read)

Possible indications of brain damage

In addition, each of them can provide important information regarding brain function, although the The test in question does not allow a specific interpretation if there are a lot of errors in all of them.

In the reading task, errors usually appear in those subjects with problems in the left hemisphere, specialized in language. Especially in the case of lesions in the supramarginal and angular gyrus.

On the other hand, the color naming task allows to detect if there are problems in the right hemisphere.

The interference task usually shows lower results than the previous ones in almost the entire population, but it can sometimes be observed the existence of perseverance in making mistakes which could be indicating a frontal or basal ganglia involvement.

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Area of ​​application

The main area of ​​application of this test is the neuropsychological evaluation. And is that allows to obtain a measure of attention and executive functions such as inhibitory control of behavior.

Specifically, its use is frequent to observe the effects of a brain injury or to assess whether there is involvement of certain brain areas such as the frontal lobe. In addition to injuries, it can assess the executive functions of patients with dementia such as Alzheimer's and the Huntington's chorea.

Although it is not as common as in the previous cases, it can also be used in the assessment of capabilities of people with different mental disorders, such as schizophrenia or, more frequently, ADHD.

Bibliographic references:

• Golden, C.J. (2005). Color and word test (Stroop). Madrid: TEA Editions.

• Almendro, M.T. (2012). Psychotherapies. CEDE PIR Preparation Manual, 06. CEDE: Madrid.