APA Dictionary of Psychology

in choice reaction tasks, the interference of an irrelevant stimulus or stimulus feature such that choice reaction time to produce the correct response is slowed. For example, in the Stroop Color–Word Interference Test, in which participants are asked to name the color of letters that spell the name of another color, reaction time is slowed because response activation from the irrelevant information (what the letters spell) conflicts with that from the relevant information (the color of the letters). Also called response competition.