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Stroop Interference and Reading Ability

If you have ever taken an introductory level class in Psychology, chances are you learned about the Stroop task.  For those of you who haven’t, try this activity out for yourself; look at the list of words written below. Simply name the color ink the word is written in. It sounds easy enough, but is actually much harder than you might think.



Undoubtedly you were able to read the first line with ease, but the second line, well that was a different story. Chances are you find yourself inclined to read the word initially and then must pause to actually say the color ink instead. This task can be frustrating! Why is it so hard? Why is the bottom row where color words are written in their inconsistent ink so much harder do than the top row where words are in consistent ink color?

When presented with words we are taught to read them, and have less experience ignoring the word meaning and simply stating the color. This makes this simple task not so simple. Fluent readers have what is know as reading automaticity; for them (and you if you are able to read this easily) reading is an automatic skill. In the Stroop Task however, we are asked not to read the word but state the color instead. The slower reaction time in naming the color when the word is inconsistent with the color is known as Stroop interference. The meaning of words interferes with our ability to name the color. If you presented this task to a young child for whom reading had not yet been mastered, or did it again yourself but this time with the words written in an unknown language, stating the color ink would be very easy to do without word interference.

Typically, Stroop interference occurs when reading is fluent and automatic.  This then raises the question of how individuals with selective reading deficits such as dyslexia perform on this task? Very broadly, dyslexia is a learning disability that impairs an individual’s comprehension accuracy and/or fluency of reading. In a 2006 study, Protopapas, Archonti and Skaloumbakas, observed the relationship between reading skill and Stroop interference (again, that’s slower reaction time at naming inconsistent color/word pairings) in 7th grade students. Some of the 7th graders were at normal automatic reading ability and others were diagnosed with the dyslexia.  Previous research suggests that Stroop interference is greatest among those for whom reading is a strong mastered automatic skill. This study, however, found the greatest Stroop interference among individuals with reading disability, and less interference for individuals with strong reading automaticity (reading fluency).  They found a negative relationship between Stroop interference and reading ability. As reading ability increased, Stroop interference decreased.

One of the possible sources of the increased Stroop effect among dyslexic individuals may be poor cognitive control resulting in difficulty inhibiting the desire to read the word instead of stating the color.  Poor cognitive control means that the individual has a difficult time changing certain behaviors depending on the instructions and situation. In this case, poor cognitive control would reflect the inability to suppress the desire to read (which is the most common response when presented with words), and instead name the color ink. Dyslexic and normal readers both have a difficult time stopping word processing before it acts as interference (as you probably experienced when engaging in the Stroop Task); however, automatic readers can control this interference much better than dyslexic readers can. Researchers Helland and Asbjorsen (2000) said that Stroop interference is due to dyslexic individual’s “impaired executive function” which essentially refers to poor cognitive control. Their ability to select relevant stimuli (in this case the color ink) is impaired. Dyslexic individuals have a harder time selectively paying attention to the color ink and inhibiting the response to the read the word when compared to individuals at normal automatic reading ability and thus show heightened Stroop interference.

In sum, this research suggests that dyslexia is not simply a reading disorder, but a disorder that also affects attentional control and executive function. Individuals suffering from Alzheimer’s Disease are categorized by impaired executive function as well and similarly show heightened Stroop Interference.  Stroop Interference is not a phenomenon simply driven by reading automaticity but more importantly, is a function of attentional control.


Protopapas, A., Archonti, A., & Skaloumbakas, C. (2006). Reading ability is negatively related to stroop interference. Cognitive Psychology, 54(3), 251-282.


  1. April 9th, 2013 at 09:41 | #1

    I think the Stroop task is so interesting because the task sounds so easy, yet it is difficult to do! In my PS215 research group we used the idea of conflicting images to see if stimuli (pictures/words) would be remembered better if they were typical or conflicting (a yellow banana versus a purple banana).

  2. April 23rd, 2013 at 20:26 | #2

    Recently, I had a serious head injury and I had to go through a lot of testing. Included in one of the neurocognitive tests I had to take was the Stroop Test. Although I have a lot of knowledge about the Stroop Test, I still found it hard to do! As I continue to visit more doctors and learn about my injury and the symptoms I am experiencing, it is interesting to hear what they have to say about head injuries/concussions and performance on neurocognitive tests such as the Stroop Test.

  3. April 25th, 2013 at 09:44 | #3

    I remember our teachers in elementary school used to have us do this task. I always thought it was just a fun brain teaser. I never knew at the time that it was such a huge component of cognitive psychology (but then again what fifth grade would), and that it potentially also has practical implications like predicting potential onset of Alzheimer’s Disease.

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