ABSTRACT
Fig. I. (a) Because of how we organize the top scene into figures and background, the ground regions between the figures do not have shape. Notice how the regions of background isolated below are shapes that we do not perceive in the scene above (if this is pars"d as a group of human semaphore signals). This demonstration is based on a similar one in Kanizsa (1979). (b) Two halves of a disk have different shapes, even though they share the same bounding contour. This demonstration is based on Attneave (1974). The positive and negative curvature of the contour has been labelled to show that when polarity changes from A to B (because of a change of where the inside of the figure is) the perceived shape is different.
