A dual role for shape skeletons in human vision: perceptual organization and object recognition

Shape perception is crucial for object recognition. However, it remains unknown exactly how shape information is represented, and, consequently, used by the visual system. Here, we hypothesized that the visual system represents “shape skeletons” to both (1) perceptually organize contours and component parts into a shape percept, and (2) compare shapes to recognize objects. Using functional magnetic resonance imaging (fMRI) and representational similarity analysis (RSA), we found that a model of skeletal similarity explained significant unique variance in the response profiles of V3 and LO, regions known to be involved in perceptual organization and object recognition, respectively. Moreover, the skeletal model remained predictive in these regions even when controlling for other models of visual similarity that approximate low- to high-level visual features (i.e., Gabor-jet, GIST, HMAX, and AlexNet), and across different surface forms, a manipulation that altered object contours while preserving the underlying skeleton. Together, these findings shed light on the functional roles of shape skeletons in human vision, as well as the computational properties of V3 and LO.

Comparing Sky Shape Skeletons for the Analysis of Visual Dynamics along Routes

The motion of an observer in a given space produces a particular perception called motion perspective. This has been defined by Gibson as the gradual changes in the rate of displacements of contour lines in the visual field of the observer. This paper describes a new approach intended for analysing the motion perspective in order to quantify the morphology of urban open spaces along routes. It is based on spherical projections, which provide the shape of the sky boundary around the observer. The projections are studied through their skeletons, which are continuous sets of curves obtained by a progressive thinning down of the shapes around their main saliencies. The proposed method uses these skeletons to follow the variations in the shape of the sky boundary between the successive views. Measures of these variations have been developed and applied in a range of simplified theoretical examples and a real field example in order to show that they succeeded in capturing significant variations in spherical projections.