**3.1 Behavioral evidence**

Holistic face processing, a typical hallmark of perceptual expertise for faces, refers to that participants tend to deal with face parts as a whole, rather than as separate features [34, 35]. Numerous studies have demonstrated that Asian adults outperformed Western adults in holistic face processing [36–39]. For instance, Miyamoto et al. found that the Japanese performed more holistic, rather than featural, strategies in comparison with Americans in choosing to match the prototype faces [37]. Furthermore, Rhodes et al. found that, with the face inversion paradigm in which there is an impaired recognition in inverted compared to inverted faces [40], Chinese subjects exhibited a larger face inversion effect than European counterparts. Some studies used the complete composite face paradigm to tap the holistic face processing, in which the top and bottom parts of two faces are constructed to form a new composite face. In this paradigm, two factors were manipulated. The first manipulation is whether the study face is aligned, meaning that the position of the bottom part of the face is shifted right or left from the top part (misaligned) or not (aligned). And the second is consistency: the consistent trials refer to which the top and bottom parts of the study face are the same as the test face or changed simultaneously; In inconsistent trials, the study face is different from the test face in either the top part or the bottom part. And observers are asked to attend to the target part (such as the top part of the face) and meanwhile to ignore other parts (such as the bottom part of the face). Results showed that the recognition accuracy was better in consistent than inconsistent conditions when faces were aligned, while the consistency effect became weak or disappeared when faces were misaligned [41]. Using the composite face paradigm, Michel et al. showed that Asians had stronger holistic processing (indexed by the composite face effect) as compared to Caucasians [42]. Employing the part-whole paradigm, Tanaka et al. asked Caucasian and Asian observers to recognize facial features of Caucasian and Asians in isolation or in the whole face, showing that Caucasians processed own-race faces holistically compared to Asian faces, while the pattern of holistic processing was observed for both Caucasian and Asian faces in Asians [43]. In summary, converging evidence from different experimental paradigms reaches a consistent agreement that Asians were superior to Westerners in the holistic face processing.
