It's more than just conflict: The functional role of congruency in the sequential control adaptation

According to the conflict monitoring theory (CMT), one of the most prominent theories of cognitive control, the exertion of cognitive control is triggered by the detection of conflicting response tendencies in the anterior cingulate cortex (ACC). Recent research has challenged this emphasis of response conflicts and has debated whether in addition to shielding after incongruent trials the relaxation after congruent trials also contributes to the sequential adaptation of control. To investigate the functionality of facilitative congruent trials in sequential adaptation of control, we conducted two experiments using a visual (Experiment 1) and an auditory (Experiment 2, preregistered) Simon task with stimuli presented laterally to the left or right (creating response congruent and incongruent trials) or without any particular spatial information (creating neutral trials). Both experiments showed converging results: in the error and reaction time data, the Simon effect was smaller following incongruent trials, larger following congruent trials, and the Simon effect following neutral trials was in-between. Results thus suggest that sequential control adaptations can originate from two processes: Increased shielding in response to incongruent trials and relaxation in response to congruent trials. Argumentations for a functional role of congruent and incongruent trials in the sequential adaptation of control suggest a more general theory of fluency monitoring instead of mere conflict monitoring. In addition, such extensions of the CMT provide theoretical explanations of how control is ever relaxed in response conflict tasks after being enhanced by conflict in the first place. Last but not least, the results may also be taken as a further hint that congruent stimuli may provide a positive affective signal for control relaxation just it has already been shown for incongruent stimuli as aversive signals for the up-regulation of control (shielding).