The Brain Mechanism Of Automatic Processing Of Facial Ethnic Information

The processing of racial information of faces is crucial for human survival,development and social interaction.However,it is still controversial that whether the racial processing under unattended condition can be realized,it is still unclear that the result of the former is the own-race bias or the labeled other-race advantage,moreover,it is less explored that whether the degree of its automatic processing is partially or completely.In this study,the event-related potentials(ERPs)technology with high temporal resolution was adopted as a main method,and the ERP index---visual mismatch negativity(vMMN)which reflecting the brain’s automatic processing was used to investigate the neural mechanisms of automatic processing of racial information(own-race and other-race)under unattended condition.In two studies,by combining the task-irrelevant oddball paradigm(80% of standards and20% of deviants)and the deviant-standard-reverse paradigm,all facial stimuli were presented on both sides of the fixation in blocks,and the vMMN was obtained by subtracting the ERPs to standards from the ERPs to deviants.In study 1,completely normal faces were used as stimulus materials.Subjects were required to response to single attribute(low-load attention)and double attributes(high-load attention)of the fixation in the center of the screen while ignoring the faces on both sides.The results showed that the automatic processing of racial information was asymmetric and had labeled other-race advantage.Other-race faces elicited vMMN in 140-200 ms which wasn’t modulated by attention load and belonged to completely automatic processing,while own-race failed to elicit vMMN and belonged to control processing.Furthermore,attentional load seemed to had a slight moderating effect on the relationship between the racial processing and electrodes distribution.In study 2,the research paradigm,procedure,and parameters were consistent with the study 1,only through misaligning the top and bottom parts of faces to disrupt the configural information.The aim of it was to explore whether the neural mechanisms of automatic processing of racial information remained stable,and what information(configural or featural information)was the basis for the other-race’s automatic processing.The results showed thatthe automatic processing of racial information after spatial misalignment was still asymmetric and had labeled other-race advantage.Other-race faces elicited conspicuous vMMN in140-200 ms while own-race faces elicited no vMMN.Meanwhile,attentional load still only had a weak modulation on racial processing.Comparing the data from the above two studies,we found no significant differences in main outcomes but only a slightly decreasing trend in the amplitude of vMMN elicited by other-race.This prompt that the asymmetry and labeled other-race advantage of automatic processing of racial information were relatively stable and hardly affected by the way that faces were presented.In addition,the automatic processing of other-race faces depended more on featural information.Therefore,the processing of racial information under unattended condition was automatic,asymmetric and stable to some extent.The automaticity of other-race faces processing were basically complete,and depended more on the featural information,while the processing of own-race faces belonged to control processing.Besides,attentional load had a weak modulation effect on the racial processing in the early stages of visual processing.