In psychology, the Stroop effect is the delay in reaction time between congruent and incongruent stimuli. The effect has been used to create a psychological test (the Stroop test) that is widely used in clinical practice and investigation. A basic task that demonstrates this effect occurs when there is a mismatch between the name of a color (e.g., "blue", "green", or "red") and the color it is printed on (i.e., the word "red" printed in blue ink instead of red ink). When asked to name the color of the word it takes longer and is more prone to errors when the color of the ink does not match the name of the color. The effect is named after John Ridley Stroop, who first published the effect in English in 1935. The effect had previously been published in Germany in 1929 by other authors. The original paper by Stroop has been one of the most cited papers in the history of experimental psychology, leading to more than 700 Stroop-related articles in literature. Original experiment The effect was named after John Ridley Stroop, who published the effect in English in 1935 in an article in the Journal of Experimental Psychology entitled "Studies of interference in serial verbal reactions" that includes three different experiments. However, the effect was first published in 1929 in Germany by Erich Rudolf Jaensch, and its roots can be followed back to works of James McKeen Cattell and Wilhelm Maximilian Wundt in the nineteenth century. In his experiments, Stroop administered several variations of the same test for which three different kinds of stimuli were created: Names of colors appeared in black ink; Names of colors in a different ink than the color named; and Squares of a given color. In the first experiment, words and conflict-words were used. The task required the participants to read the written color names of the words independently of the color of the ink (for example, they would have to read "purple" no matter what the color of the font). In experiment 2, stimulus conflict-words and color patches were used, and participants were required to say the ink-color of the letters independently of the written word with the second kind of stimulus and also name the color of the patches. If the word "purple" was written in red font, they would have to say "red", rather than "purple". When the squares were shown, the