Eye Need to Know: What Is the Stroop Effect?


Try this: name the colors of the words in the box.  Do not read the word; just say the color of word’s letters.

Did you find this difficult? Most people do.  You have just experienced interference.

John Ridley Stroop documented this phenomenon in 1935 in the Journal of Experimental Psychology, therefore it is now known as “The Stroop Effect”.

The words themselves have a strong influence over your ability to say the color. The interference between the different information (what the words say and the color of the words) your brain receives causes a problem.

There are two theories that may explain the Stroop effect:

  • Speed of Processing Theory: the interference occurs because words are read faster than colors are named.
  • Selective Attention Theory: the interference occurs because naming colors requires more attention than reading words.

Try it again, but only look at the last letter of each word instead of the whole word.  Is this easier?

 Something you need to know?  Ask Rebecca

Submitted by guest blogger, Rebecca Johnson, Founder of EyeTrain4You, an ophthalmic staff training and development company.  Contact her at Rebecca@EyeTrain4You.com

Claire Goldsmith MidPage


  1. That’s fun! This reminds me of the trick where the first and last letters of a word are correct, but everything in between is mixed up, yet we are still able to read the words without difficulty. 🙂

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