Completeness and incompleteness in visual perception

[ A special edition on "Psychological Approaches to Image Understanding" ]

Abstract

  When a figure is partly covered by another, amodal completion is seen, that is, the former is perceived to continue behind the latter or perceived in an overlapping form lying behind the latter. The amodal completion is produced according to the one-sided contour function of a line enclosing an area. When a line separates two stimulus areas, it appears taking a role of the contour at either side of the areas, not at both sides. and the rest, left enclosed incompletely, becomes complete in an amodalous manner. The amodal completion effect indicates the mental activities of making incomplete complete, by which the things not so as to be seen are seen. In rotation of the Metelli figure, an amodal disc appears clearly behind a moving window. If the figure is not completed in an amodalous manner, it is only seen as a crescent-shaped area adjacent to a lemon-shaped one which rotate on a 2-D plane. In the present paper, how the "making incomplete complete" processes sre highly productive mentally and how it makes our perceptual contents fruitful and rich, is discussed.