Individual differences in the impact of mask use on face perception

Abstract

Since protective masks were shown to be effective in reducing the risk of contagious respiratory virus infection, there was widespread use of protective masks during the COVID-19 pandemic. However, with the occlusion of the lower half of the face, mask use disrupts face perception in various dimensions, which can further interfere with daily social interaction substantially. Thus, it is of vital importance to understand how individuals’ face perception is influenced by mask use and possible remedial strategies. Accordingly, this thesis investigated the impact of mask use on face perceptual tasks, including face recognition, facial expression recognition, passive viewing, and social categorization and bias, and whether individual differences in related factors, such as eye movement measures, cognitive abilities, and autistic traits, could predict performance impairment due to mask use. Study 1 (Chapter 3) and Study 2 (Chapter 4) focused on the cultural differences in the effect of mask use on face perception, an important issue in the age of globalization. More specifically, Study 1 examined cultural differences in the mask effect on face and facial expression recognition, and whether individual differences in face scanning patterns could account for performance impairment due to mask use. The results showed that mask use affected Asian and White individuals differentially only in facial expression recognition, but not in face recognition. Interestingly, across groups, individuals whose preferred face scanning pattern was more eyes-focused were less impaired by mask use in both tasks. This suggested that individual differences, rather than culture, may better account for the effect of mask use on performance. Study 2 examined cultural differences in the mask effect on social categorization, social bias, and passive viewing, and whether individual differences in face scanning patterns could account for impairment due to mask use. The results showed that mask use modulated face scanning patterns in passive viewing in White and Asian participants differentially, but not for social categorization accuracy. Nevertheless, across participants, less impairment due to mask use in social categorization accuracy was associated with larger eye movement change towards the pattern associated with better individuation ability. Again, this study showed that individual differences in face scanning behaviors may better predict the impact of mask use than culture. In addition to typical-developing populations, Study 3 (Chapter 5) addressed the needs of vulnerable populations with face perception difficulties, such as autism, and examined how autistic and non-autistic individuals were affected by mask use differentially. The results showed that autistic individuals had a reduced tendency to look at the eyes and reduced change in eye movement consistency than non-autistic individuals when passively viewing masked faces during face learning; this was not observed during face recognition. Across participants, selective attention ability and flexibility to change face scanning behaviors according to mask conditions were two important factors accounting for individual differences in performance. Interestingly, autistic traits accounted for additional variance when recognizing masked faces learned also with a mask. These findings have important implications for identifying vulnerable populations whose face recognition ability may be particularly affected by mask use.