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

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

The Stroop Test

The Stroop test is a psychological test especially linked 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 to value aspects like the selective attention and of inhibitory control , when observing that the people who knew to read tended to take more time the color in which the words were written that in reading the name of these colors (because they had more automated the reading). It also allows for the assessment of processing speed

The duration of the application of this test is relatively short , of about five minutes, and is designed for people between seven and eighty years of age.

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

The three phases or tasks

A total of three different tasks are performed during the Stroop test, using three slides in which five columns of 20 elements appear. Each of the tasks is carried out for a certain time (for example, forty-five seconds), and the hits are noted for later evaluation.

1. Reading words

First, the subject is given a list of 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 the identification of colours , in which the observer is provided with a list of coloured meaningless symbols. The subject is asked to identify and name the colour 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 previously mentioned colors, but this time written with a different color than the one referred to by the word . 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 the stimulation are evaluated, paying attention to what is reflected in each of the sheets 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 capacity to resist it, the management of cognitive and attention resources or the persistence and repetition of behaviour.

Effect of interference

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

If we subtract the estimated score from the actual score obtained in the interference task, we can see whether the person correctly inhibits the response (values above 0, positive) or if there are significant interference problems (if it is a negative value). Usually most people get scores between 10 and -10.

However, it is possible that this estimation is biased if the subject has a very low or very high level of experience in reading (the value of the answers in the first test and the performance in the third test may vary depending on whether we are more or less accustomed to reading)

Possible indications of brain damage

In addition, each of them can provide important information regarding brain functioning, although the test in question does not allow a specific interpretation if there are a large number 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 injuries 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 all the population, but e sometimes it can be observed the existence of perseverance in the realization of errors that could be indicating an affectation in the frontal or basal ganglia.

Scope of application

The main field of application of this test is neuropsychological evaluation. This is because allows us to obtain a measure of attention and of executive functions such as inhibitory control of behaviour.

In particular, it is often used to observe the effects of a brain injury or to assess whether certain brain areas such as the frontal lobe are affected. In addition to injuries, it can assess the executive functions of patients with dementias such as Alzheimer’s and Huntington’s disease.

Although it is not as common as in the previous cases, it can also be used in the assessment of the abilities 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 Ediciones.
  • Almond tree, M.T. (2012). Psychotherapies. Manual CEDE de Preparación PIR, 06.