The relationship between ensemble coding and individual representation of crowd facial emotion

In recent years, the processing mechanism of group expression has gradually gained the attention of researchers owing to its high ecological validity. However, research on the relationship between ensemble coding and individual representation is still in the early stage of the investigation, with many studies remaining at the behavioral level and findings varying widely. Based on our behavioral research (Experiment 1), we used EEG measures (Experiments 2A and 2B) to investigate the relationship between summary and object representations by manipulating the exposure time of crowd emotions. The behavioral results indicated that participants performed better in judging emotions of multiple faces compared to a single face during the shorter exposure time, whereas the reverse occurred during the long exposure time. Furthermore, ERP results revealed that the N2pc effect was not affected by the number of faces in the short exposure time; however, as the exposure time increased, the N2pc increased as a function of the number of faces. The findings of the current investigation align with time-dependent assumption, indicating that during short time of visual processing, although individual representations may not be fully developed, ensemble representations are initially established. With longer processing times, detailed individual representations become complete and take precedence.