Stroop Test

In psychology, the Stroop effect demonstrates the interference in the reaction time of a task. When a word such as blue, green, red, etc. is shown in a colour differing from the colour what the word actually says (i.e. the word “red” shown in blue letters), a delay occurs in our brain in the processing of the word's actual colour, leading to slower test reaction times and an increase in mistakes. The effect is named after its discoverer, John Ridley Stroop in 1935. See Wikipedia