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Abstract

Even though shape is the basis of object recognition, there is still an on-going debate about how it is perceived and represented in the brain. An important question is how various visual cues, like disparity and texture, are integrated into a unique shape percept. Different visual information has also been shown to play an ancillary role in shape perception. For example, cast shadows can help disambiguate shape perception (Kersten et al, 1996 Nature 379 31) while 2D retinal motion information can help organize dots into meaningful shapes despite incongruent depth information (Bülthoff et al, 1998 Nature Neuroscience 1 254 - 257).
Shape perception is also important for object categorization. For example, faces varying in shape and texture may be perceptually grouped into different categories (a phenomenon known as categorical perception). Previous studies have shown that faces varying in expressions, identity or race are perceived categorically (e.g. Levin amp;amp;amp;amp;amp; Angelone, 2002 Perception 31 567 - 578). We did not find similar effect for faces varying in masculinity/feminity (Bülthoff amp;amp;amp;amp;amp; Newell, 2004 Visual Cognition 11 823 - 855). This difference in perception for sex and identity is supported by new studies showing a lack of sensitivity to sex changes in familiar faces, while changes in identity are easily noticed. These results have implications for the nature of shape representations of faces in the brain.