The Cognitive And Neural Mechanism Of Conflict Adaptation Triggered By Conflict Level

The ability to flexibly exert cognitive control to adapt to dynamic environments is crucial to successful goal-directed behavior,in which selective attention to information includes both the enhancement of task-relevant stimuli and inhibition of task-irrelevant stimuli.As the saying goes,“The remembrance of the past is the teacher of the future”.Prior knowledge and experience can help solve current problems better.Therefore,adaptive behavior is of great significance to human survival and development.Conflict adaptation is an important phenomenon,as the interference effect on the current trials is reduced following incongruent versus congruent trials.Moreover,conflict adaptation effect(CAE)is thought to measure adaptive control on a trial-by-trial basis.There are two main theories explaining the mechanism underlying CAE: conflict monitoring theory and adaptation by binding theory.Based on conflict monitoring theory,adaptation by binding theory argued that locus coeruleus(LC)serves as a mediator between conflict monitoring and conflict resolution.However,both theories have not explicitly proposed a clear relationship between conflict strength and cognitive control adjustment.Previous studies have mostly focused on the type of conflict that triggers conflict adaptation,which reflected qualitative analysis.Hence,it is still unclear whether conflict levels of the same conflict type affect conflict adaptation.This research attempts to study this issue from behavioral and electrophysiological perspectives to deepen understanding of the mechanism of conflict adaptation.Study 1 consisted of two behavioral experiments to verify each other.Experiment 1explored whether conflict level trigger conflict adaptation.And the variant of the letter flanker task was adopted without feature repetitions.Each stimulus was composed of“F/H/N/P” letter components and arranged in a way that a central target letter was flanked by symmetric arrays of two distracter letters.Experiment manipulated the level of conflict by parametrically varying the target-distracter compatibility.Flankers were 100%compatible with the central target for congruent condition(e.g.,NNNNN),50% for incongruent-low condition(e.g.,HNNNH),and 0% for incongruent-high condition(e.g.,HHNHH).The results of experiment 1 showed that reaction times(RTs)increased with the number of incompatible flankers,suggesting a correlation with the level of conflict.Moreover,congruency of previous trials affected the interference effect of current trials.Follow-up analyses revealed that there were classic conflict adaptation phenomena between congruent and incongruent-low,and congruent and incongruent-high,and incongruent-low and incongruent-high conditions.These results showed that conflict adaptation was also triggered by conflict level in addition to the occurrence of conflict,which supporting that more conflict led to more adjustment of cognitive control.However,it is still unclear how the function of conflict-induced cognitive control is realized.We speculated that the range of attention regulated by cognitive control gradually focuses on task-relevant information.To further verify attention adjustment mechanism of experiment 1,experiment 2 changed the incongruent-low condition(e.g.,HNNNH)to the incongruent-new(e.g.,NHNHN)without varying the target-distracter compatibility,so that the participants cannot use the attentional focusing strategy flexibly.The results of experiment 2 showed that RTs of congruent was significantly shorter than those of incongruent-new and incongruent-high conditions.Besides,there was no significant difference between incongruent-new and incongruent-high conditions,indicating that the conflict level of these two conditions was similar.Accordingly,there were classic conflict adaptation phenomena between congruent and incongruent-new,and congruent and incongruent-high,but not between incongruent-new and incongruent-high conditions,verifying the role of attentional focusing in conflict adaptation.Overall,the study 1demonstrated that more conflict led to more adjustment of cognitive control,and the function of conflict-induced cognitive control may be realized by attentional focusing.Based on study 1,study 2 used electroencephalogram(EEG)to explore the neural mechanism of conflict adaptation induced by changes in conflict levels.The design of experiment 3 was the same as experiment 1 which included three conditions of congruent,incongruent-low,and incongruent-high.The results of experiment 3 were as follows.(1)For interference effect,there were significant congruency effects on behavioral indices(RTs),event-related potential(ERP)components(N2,early P3 and late P3)and theta band power.These indices all increased with conflict level(congruent/incongruentlow/incongruent-high)except early P3 whose average amplitudes showed the opposite pattern.(2)For conflict adaptation effect,RTs and the average amplitudes of early P3 showed that the congruency of previous trials affected the interference effect of current trials.Follow-up analyses revealed that there were classic conflict adaptation phenomena between congruent and incongruent-low,and congruent and incongruent-high,incongruent-low and incongruent-high conditions.These results indicated that conflict level trigger conflict adaptation,and conflict resolution relied on the adjustment of selective attention and the allocation of cognitive resources.Besides,the CAE between congruent and incongruent-high conditions on the amplitudes of early P3 showed a negative correlation with RTs,indicating an intrinsic link between these neural and behavioral indices.Moreover,the conflict adaptation between congruent and incongruent-high triggered the power adjustments of alpha band.In conclusion,the present research based on the Flanker paradigm found that conflict adaptation was also triggered by the level of conflict in addition to the occurrence of conflict,which supporting that more conflict led to more adjustment of cognitive control.In addition,the function of conflict-induced cognitive control may be realized by attentional focusing.These results indicated that conflict monitoring was sensitive to the level of conflict,and then adjusted the level of cognitive control to facilitate conflict resolution,which provided more direct support for attention adjustment mechanism of conflict monitoring theory.In the future,we need to verify the attentional focusing mechanism of conflict adaptation with eye tracker or functional magnetic resonance imaging(f MRI).More importantly,the exploration of this issue will provide references for how people adapt to the complex and dynamic environment in real life.