  The introduction of face masks during COVID-19 presents a potential challenge
for human face perception and recognition. Face masks possibly hinder the
holistic processing of faces leading to difficulty in facial recognition. Our
present study aims to investigate this issue by probing the neuropsychological
mechanisms of face recognition, while also exploring a possible learning effect
observed in regularly seen (personally familiar) masked faces. Our stimuli
consisted of personally familiar, famous, and unfamiliar Indian faces in masked
and unmasked conditions. Subjects participated in a 2-back task wherein trials
were balanced within and across blocks to represent all conditions identically,
while behavioral and EEG responses were recorded. Statistical analyses revealed
significant main effects of familiarity and mask-conditions on performance
accuracy and reaction time (RT). The highest performance accuracy was observed
for familiar and unmasked faces and the least for unfamiliar and masked ones,
whereas RTs followed expected reverse trends. Notably, the difference in
performance accuracy between unmasked and masked famous faces was more
prominent than that for personally familiar faces. These observations are
suggestive of a beneficial effect of visual experience found for frequently
seen masked faces. Masked unfamiliar faces contributed to the highest
proportion of false-positive errors, indicating the inherent difficulty in
processing novel masked faces compared to known ones. EEG analysis revealed
effect of face masks on N250 for both famous and personally familiar faces and
N170 for only personally familiar faces. Our study suggests that personal
familiarity aids perceptual learning of masked faces, and this learning may not
generalize across familiarity levels.
