Abstract
Recent face perception studies suggest that our representation of faces is closely related to spatial information. This spatial dependency can be revealed in a face-specific illusion, referred to as the “Fat Face” illusion: when two identical faces are aligned vertically and the bottom one is consistently perceived as larger. This illusion suggests that our visual system uses the vertical layout to implicitly infer the proximity of faces. The face lower in the picture plane is perceived as closer, therefore being seen as larger, than the top face. While the “Fat Face” illusion is highly robust in adults, its developmental origins remain largely unknown. The face-specificity implies that there is a developmental change driven by experiences with faces in the environment. Here, we probed the development of this illusion via the impact of face-race information on the illusion in children and adults. Adult participants (N=34, 17 Asian, 17 Caucasian) saw two identical faces vertically aligned and clicked the one they perceived as larger. The faces were morphed from Asian and Caucasian faces at 5 morphing proportions (0%, 25%, 50%, 75%, & 100% of Asian). Overall, adults misperceived the bottom face as larger in 68% of trials (p<.001). Moreover, adults exhibited a larger illusion for faces with higher morphing proportions of other-race faces (p=.007), suggesting that other-race faces were perceived as closer than own-race faces. Children (7.11yrs, 5 to 10yrs, N=49) also had the illusion (70% of trials, p<.001), but their illusion was not affected by face-race (p=.214). The existence of the illusion among children suggests that our sensitivity to face locations might emerge early in human development. The difference in the effect of face-race between children and adults indicated that the tuning to face location undergoes further development, likely driven by growing experience with face categories.