The item-specific proportion congruent (ISPC) effect is the observation that the Stroop effect is larger for words that are presented mostly in congruent colours (e.g., BLUE presented 75% of the time in blue), and smaller for words that are presented mostly in a given incongruent colour (e.g., YELLOW presented 75% of the time in orange). One account of the ISPC effect, the modulation hypothesis...