What Is the Stroop Effect?

How to Create Your Own Stroop Effect Experiment

Reading a list with the Stroop effect
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The Stroop effect is a phenomenon in which you must say the color of a word but not the name of the word. Blue for example might be printed in red and you must say the color rather than the word. While it might sound simple, the effect refers to the delayed reactions times when the color of the word does not match the name of the word.

In this task, people are asked to say aloud the color of each word that than reading the actual words themselves.

They just say the color in which the words are printed.

This task can be much more difficult than you might initially expect. The Stroop effect refers to a phenomenon in which it is easier to say the color of a word if it matches the semantic meaning of the word. For example, if someone asked you to say the color of the word "Black" that was also printed in blank ink, it would be much easier to say the correct color than if it were printed in green ink.

The task demonstrates the effect that interference can have when it comes to reaction time. The effect was first described during the 1930s by American psychologist John Ridley Stroop for whom the phenomenon is named. His original paper describing the effect has become one of the most famous as well as one of the most frequently cited in the history of psychology. The effect has been replicated hundreds of times by other researchers.

For students of psychology looking for a relatively easy and interesting experiment to try on their own, replicating the Stroop effect can be a great option.

How Does the Stroop Effect Work?

The words themselves interfere with your ability to quickly say the correct color of the word. Two different theories have been proposed to explain this phenomenon:

  • Selective Attention Theory: According to this theory, naming the actual color of the words requires much more attention that simply reading the text.
  • Speed of Processing Theory: According to this theory, people can read words much faster than they can name colors. The speed at which we read makes it much more difficult to then name the color of the word.
  • Automaticity: This theory proposes that automatic reading does not require focused attention. Instead, the brain simply engages in it automatically. Recognizing colors, on the other hand, may be less of an automated process. While the brain registers written meaning automatically, it does require a certain amount of attentional resources, making it more difficult to process color information and therefor slowing down reaction times.

Terms and Key Questions for Background Research

Before you begin your experiment, there are some key terms and concepts you should understand.

Performing Your Own Stroop Effect Experiment

There are a number of different approaches you could take in conducting your own Stroop Effect Experiment. The following are just a few ideas you might explore:

  • Compare reaction times among different groups of participants. Have a control group say the colors of words that match their written meaning. Then, have another group say the colors of words that differ from their written meaning. Finally, ask third group of participants to say the colors of random words that do not relate to colors. Then, compare your results.
  • Try the experiment with a young child that has not yet learned to read. How does the child's reaction time compare to that of an older child who has learned to read?
  • Try the experiment with uncommon color names, such as lavender or chartreuse. How do the results differ from those who were shown the standard color names?


Stroop, J. R. Studies of interference in serial verbal reactions. Journal of Experimental Psychology. 1935; 18: 643-662.

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