Integrating global and local aspects of visual occlusion

Rob J. van Lier, Peter A. van der Helm, Emanuel L. J. Leeuwenberg

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Abstract. The phenomenon of visual occlusion has frequently been studied by means of two-dimensional line drawings. These drawings may elicit various interpretations. Sometimes a mosaic of shapes is seen, sometimes a shape than partly occludes another shape. In the latter case, observers often have a clear idea about the form of the partly occluded shape. Local and global pattern aspects both seem to be decisive with respect to the preferred interpretations. An attempt is made to integrate these aspects by applying the global-minimum principle to the perceptual complexity of three distinct components of those pattern interpretations: (i) The internal structure, dealing with each of the shapes separately, (ii) the external structure, dealing with the positional relation between these shapes, and (iii) the virtual structure, dealing with the occluded parts of the shapes. The perceptual complexity of each of these three components can be expressed in terms of stuctural information. The hypothesis that the perceptually preferred interpretation is the one for which the total information load is minimal is tested on many patterns stemming from different studies on pattern completion.

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