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The Stroop effect is a phenomenon which can show how the brain processes words and colors differently. Discovered by John Ridley Stoop in the 1930s, this effect is typically triggered by printing words that express a different color than they actually are. If the word green is printed in blue, for example, most people will read what the word says, while it is usually more difficult to read out the colors of the text instead. Different tests for the Stroop effect can involve words that have one letter that is different in color, words that do not have meaning, or that identify emotions. Research using Stroop experiments has shown that most people identify words quicker than colors.
A basic test of the Stroop effect includes a list words that say what color they are, while a second list includes words printed in a different color than what they mean. Readers are typically asked to say the color instead of the meaning of the word. Another variety of the Stroop effect is to use shapes outlined in different colors. Usually, people identify the colors and shapes regardless, in contrast to the general difficulty of reading what color a word is. The Stroop effect, however, can be reduced and even eliminated by changing the color of just one letter.
Slowed brain processing can also be tested by manipulating words in other ways. Some Stroop effect tests rotate words, or arrange the letters in a clockwise or counterclockwise pattern. These can provide insight into whether the brain processes the word patterns or the colors faster, and some varieties of the test even reverse letters or scramble them altogether.
Researchers often test brain processing using multiple tasks. Up to 150 items may be used in a clinical test; scores can be derived by counting how many of these are read during a specific period of time. Sometimes tests are scored based on the amount of time it takes to complete each sub-task, while other versions focus more on counting one’s mistakes.
The Stroop effect is often used to gauge brain development in school children. Higher levels of interference are often present in conditions such as brain damage, dementia, or Attention-Deficit Hyperactivity Disorder (ADHD). The effect can also be used to determine the severity of these problems, as well as schizophrenia, addictions, and other common mental disorders. Many experiments, however, are used to demonstrate brain function as part of a school science fair, while interactive online tests, in different variations, can be taken and scored automatically.