Face Representation and Perceptual Processing in Mask-making

Abstract

Mask-making is widely distributed in human culture and shows remarkablediversity. How are faces represented in masks, and how are these representations processedin the human brain? Here we asked if masks show systematic differences in structure andprocessing compared to natural faces. First, we assembled a large, diverse database of 138standardized mask images and measured structural features and ratios. We find that masksshow an increased length ratio exaggeration compared to painted portraits and naturalfaces, as well as larger variance in the length ratio compared to portraits and natural faces.Then, in order to understand how mask representations of the human face are processed inthe brain, we used a rapid symmetry detection task to compare upright and inverted stimuli.We predicted that there would be an inversion effect, namely that symmetry detectionaccuracy would be higher for upright compared to inverted stimuli, indicating theinvolvement of high-level face-specific processing. Instead, while performance for uprightand inverted masks was significantly above chance, there was no significant differenceacross subjects in performance for upright versus inverted masks (N=40). This result isconsistent with the notion that masks do not fully engage high-level cortical processingsystems specialized for the human face. Together, these studies suggest that masks aredesigned and processed in a way that may be distinct from how natural faces are processed.We conclude that handmade masks can serve purposes beyond face representation, despitemasks’ superficial functionality as face surrogates.