Read the colors of the words in the first column.
Now read the colors of the words in the other columns, a bit harder isn’t it?
Time yourself on the first column, then again on the second or third.
In psychology, the Stroop Effect is a demonstration of the reaction of a task. When the name of a color (e.g., “blue,” “green,” or “red”) is printed in a color not denoted by the name (e.g., the word “red” printed in blue ink instead of red ink), naming the color of the word takes longer and is more prone to errors than when the color of the ink matches the name of the color. The effect is named aft John Ridley Stroop who first published the effect in English in 1935.