Lo, Perception Abhors Not a Contradiction

Abstract

Subjective contours are divisions seen crossing homogeneous regions (see Fig. 28.1a,b). They can resemble lines on paper (that is, lines made of pigment flush with the surface bearing them). They can also look like edges of opaque or semitransparent surfaces (that is, occluding boundaries of surfaces overlapping a background). Further, they can also look like boundaries of shadows (perceptible phenomena flush with the surface bearing them) or like highlights (perceptible phenomena that can appear recessed behind a surface). And they can look like corners (that is, convex and concave dihedral angles, dividing surfaces with different slants). In short, they mimic all the main sources of optic structure to which the eye is sensitive, not just occluding edges (Kennedy, 1975).