6.5 The Stroop Effect in Psychology: Definition, Test & Experiment

Jan 13, 2020 | Cognitive Psychology, Courses, ch6 Attentional Processes & Theories

This lesson discusses the Stroop Effect. You will learn about the man and original experiment behind it, try it yourself, study the underlying psychology, and also see what we know today.

Who Was John Stroop?

John Ridley Stroop was an American psychologist who studied reaction times in individuals as part of his work. In 1929, he created what would later be called the Stroop Test. This short and simple test could easily show how quick someone’s reaction time was, and in 1935, he was able to publish his findings.

The Stroop Effect

So… what’s so great about the effect? Well, Stroop didn’t know it at the time, but his test and the paper that accompanied it would go on to become one of the most well-known, most cited papers in the history of experimental and cognitive psychology. The Stroop Test (and the resulting Stroop Effect, which is the name given to the experience of an individual who takes the test) shows that our brains process seemingly conflicting information differently than they process more straightforward information.

In other words, when we see the word ‘red’ written in the color red, we process the color of the word more quickly than if the word ‘red’ were written in green and we were expected to just name the color rather than the word. Does that make sense? Essentially, the Stroop Effect studies how interference can affect the way our brains process information and complete tasks.

Trying The Stroop Effect Yourself

Here is an example of a basic Stroop Test. Take a look at it. Seems easy enough, right? All you have to do is say color the word is printed in rather than reading the word itself. Still think the task seems ridiculously easy? Try it!

It’s a little harder than you thought, isn’t it? That’s what Stroop was trying to show. He recognized that processing times slow down when people take this test because our brains take a little more time to assimilate the information. Even though Stroop discovered all of this almost 100 years ago, the Stroop Test is still used today, generally by cognitive psychologists. It is not uncommon for people who have had damage to portions of their brains to be given this test to demonstrate how quick their processing speed is in certain areas of the brain. And, of course, the Stroop Test is also given just for fun in many, many college psychology courses.

The Stroop Experiment

Stroop’s original experiment had three elements to it:

  1. First, there was just a list of color words printed in black.
  2. Second, there was the element that is pictured earlier. Stroop could measure a difference in reaction time by having people initially just read the words in black and then try to say the actual colors of the words.
  3. The third element was a long row of blocks of different colors–no words at all. Evidently, it is very easy for people to just name the colors of the blocks without any words at all being present.

By comparing performance on these three tasks, Stroop could make inferences about the individual’s processing speed and ability.

Underlying Psychology

Psychologists have specific terms for what occurs when people take the Stroop Test. The most commonly-understood term for this is called interference theory, which basically says that there is interference in the brain (and therefore in processing time) when an individual sees a word that is a different color than what the word is naming. Pretty interesting, huh?

And it gets even more interesting than that! Now that we live in the age of technology, doctors and psychologists have been able to use PET Scans (positron emission tomography, which actually look at different parts of the brain), CAT scans (special X-ray tests that show a cross-section picture of the body), and other forms of imagery like MRIs (magnetic resonance imaging, which uses a magnetic fields and radio energy pulses to take pictures of internal organs) to find out exactly which parts of the brain are involved when the Stroop Test is given. What they have discovered is that two areas of the brain work together during the Stroop Test: the part that deals with memory and the part that deals with response resources and attention. So, it really does all make sense. And to think that Stroop knew about this almost 100 years ago!

Lesson Summary

John Stroop was a psychologist who lived back in the 1920’s and 1930’s who studied reaction times in individuals as part of his work. In the 1930s, he figured out that when people see one thing that they expect to associate with something similar, their reaction time is much quicker than if there is a difference between what they see and what their brains ‘expect.’ This phenomenon is called the Stroop Effect, and you can easily see it yourself when you take the Stroop Test, which was a short and simple test that could easily show how quick someone’s reaction time was.

In addition to the simple Stroop Test, the original Stroop Experiment had three components and eventually lead to the development of interference theory, which says there’s interference in the brain when a individual sees a word that is a different color than what the word is naming. Stroop’s work and his test have literally been reproduced thousands of times and are very well-known in the areas of both experimental and cognitive psychology. The Stroop Test is still used today by psychologists to test processing speed, sometimes with modern technology like PET scans, CAT scans, and MRIs.

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