Context-dependent hierarchical categorization of human faces: behavioral and EEG/MEG evidence

Social categorization of faces provides a key cognitive basis of human behavior and may occur along various dimensions of facial attributes. The present study investigated a potential hierarchical structure of social categorization of faces based on a superordinate (Species) versus a subordinate (Race) level of abstraction of facial attributes. We recorded behavioral performances in a face classification task and found faster responses to the same set of Asian faces when presented alternately with dog faces (a species context) relative to Black faces (a race context). In addition, using a repetition suppression (RS) paradigm, we recorded electroencephalography (EEG) and magnetoencephalography (MEG) signals to Asian faces in the species and race contexts, respectively. Our analyses of the RS effects on EEG/MEG signals revealed earlier neural encoding of similarity of Asian faces in the right fusiform gyrus at 140-200 ms and in the left temporoparietal junction at 317-413 ms after stimulus onset when Asian faces were displayed in the species (vs. race) context. These behavioral and EEG/MEG findings unravel the neurocognitive mechanisms of context-dependent social categorization of faces by highlighting its hierarchically organized structure based on different levels of facial attributes.