Face processing in humans is compatible with a simple shape-based model of vision
Understanding how the human visual system recognizes objects is one of the key challenges in neuroscience. Inspired by a large body of physiological evidence (Felleman and Van Essen, 1991; Hubel and Wiesel, 1962; Livingstone and Hubel, 1988; Tso et al., 2001; Zeki, 1993), a general class of recognition models has emerged which is based on a hierarchical organization of visual processing, with succeeding stages being sensitive to image features of increasing complexity (Hummel and Biederman, 1992; Riesenhuber and Poggio, 1999; Selfridge, 1959). However, these models appear to be incompatible with some well-known psychophysical results. Prominent among these are experiments investigating recognition impairments caused by vertical inversion of images, especially those of faces. It has been reported that faces that differ Â featurallyÂ are much easier to distinguish when inverted than those that differ Â configurallyÂ (Freire et al., 2000; Le Grand et al., 2001; Mondloch et al., 2002) Â a finding that is difficult to reconcile with the aforementioned models. Here we show that after controlling for subjectsÂ expectations, there is no difference between Â featurallyÂ and Â configurallyÂ transformed faces in terms of inversion effect. This result reinforces the plausibility of simple hierarchical models of object representation and recognition in cortex.