ERP evidence for rapid within-trial adaptation of cognitive control during conflict resolution.

People often have to resolve many conflicts at the same time in their everyday lives. So far, the mechanisms of conflict resolution when multiple conflicts co-occur are not clear. This study examined the neurocognitive mechanisms of cognitive-control adaptation when two sources of conflict co-occur. To this aim, we measured event-related potentials in a task combining the Stroop conflict (the meaning and the color of a word differ) and the word-word conflict (two different words are presented). The word-word conflict was expected to tap the same stage of stimuli processing (i.e., semantics) and to modulate the magnitude of the Stroop conflict. Behavioral data showed that the word-word conflict facilitated the resolution of the Stroop conflict, which indicates the within-trial adaptation of cognitive control. ERP data showed two additive effects (the Stroop conflict and the word-word conflict) in the N450 time window, which suggests that at the neural level these two conflicts were processed in parallel (simultaneously and independently of each other). The N450 finding demonstrates that the control system flexibly and rapidly adapts to different types of conflict by modulating information processing in ways that individually address each source of conflict. Crucially, processing the conflicts in parallel substantially improved the efficiency of the control system. Overall, the study shows that the cognitive-control system can act as a collection of parallel but independent mechanisms; it thereby advances our understanding of goal-directed behavior.