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Yu-Hao Sun, Zhe Wang, Paul Quinn, Naiqi Xiao, Huimin Shi, Ming Zhong, Haiyang Jing, Liezhong Ge, Olivier Pascalis, James Tanaka, Kang Lee; Face contour is crucial to the fat face illusion. Journal of Vision 2013;13(9):425. doi: https://doi.org/10.1167/13.9.425.
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Thompson (2010) reported a fat face thin illusion that when next to an inverted face an upright face looks ‘fatter’ (Figure 1a). Sun et al. (2012) observed that one of the faces need not be inverted for the illusion to emerge: when two identical faces are presented vertically, the face at the bottom appears ‘fatter’ than the top one (Figure 1b). Neither inverted faces nor clocks induced the illusion.
We conducted three experiments probing the role of face contour in producing the fat face illusion (Figure 2). In Experiment 1, line drawing faces were found to induce the illusion, a result suggesting that face contour is important for producing the illusion. In Experiment 2, faces with scrambled internal features and empty faces devoid of internal features also induced the illusion. These data underscore the importance of face contour for producing the illusion by showing that it does not require the normal layout of internal parts or the internal parts in a face per se. In Experiment 3, a subjective contour additionally induced the illusion. In particular, the response rate of "bottom face is fatter" for the normal layout of internal parts (with a subjective contour) was significantly higher than that for a scrambled layout of internal parts (without a subjective contour), suggesting that top-down processing of contour impacts the illusion; however, the magnitude of the illusion induced by subjective contour was significantly lower than that produced by the whole face (with an objective contour), suggesting that bottom-up processing of contour is also involved.
The findings indicate that face contour by itself is sufficient to induce the fat face illusion. The illusion is robust regardless of reduction or even elimination of internal part information, and is also present with a subjective contour, implicating a top-down contribution.
Meeting abstract presented at VSS 2013
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