Stop interfering: Stroop task conflict independence from informational conflict and interference.

Performance of the Stroop task reflects two conflicts-informational (between the incongruent word and ink colour) and task (between relevant colour naming and irrelevant word reading). This is supported by findings showing that the anterior cingulate cortex is more activated by congruent and incongruent stimuli than by nonword neutral stimuli. Previously, researchers demonstrated behavioural evidence for task conflict-a reverse facilitation effect under a reduced task conflict control condition. The boundary conditions of this Stroop reverse facilitation effect are not yet clear. The current study aimed to investigate whether task conflict arises, and task control is needed, whenever there are two possible tasks, even if the irrelevant task cannot mislead one to give erroneous responses (i.e., stimuli do not contain an informational conflict). To this end, in both experiments no incongruent stimuli were presented. In Experiment 1, participants conducted a Stroop task with a high proportion of nonword neutrals and with a neutral/congruent cue in 50% of the trials. In Experiment 2, the nonword neutral was replaced by a real non-colour-word. We found the reverse facilitation effect in the noncued trials of Experiment 1. Moreover, as expected, this effect was eliminated when a noncolour neutral word that induced task conflict was used (Experiment 2). We conclude that task conflict control is reactively activated whenever there are at least two possible tasks, even in the absence of any possibility of informational conflict.