For the last 80 years, the Stroop task has been used totest theories of attention and cognitive control and ithas been applied in many clinical settings. Most theo-ries posit that the overwhelming power of written wordsovercomes strict instructions to focus on print color andignore the word. Recent evidence suggests that trials inthe Stroop task could in fact be a mixture of readingtrials and non-reading trials. Here we conduct a criticaltest of this mixture hypothesis, where a mixture of pro-cesses should satisfy the fixed-point property (Falmagne,1968).
