SHAPE CONSTANCY IN PICTORIAL RELIEF

Pictorial relief was measured for a series of pictures of a smooth sol id object. The scene was geometrically identical (ie the perspective o f the three-dimensional scene remained the same) for all pictures, the rendering different. Some of the pictures were monochrome full-scale photographs taken under different illumination of the scene. Also incl uded were a silhouette (uniform black on uniform white) and a 'cartoon '-style rendering (visual contour and key linear features rendered in thin black line on a uniform white ground). Two subjects were naive an d started with the silhouette, saw the cartoon next, and finally the f ull-scale photographs. Another subject had seen the object and did the experiment in the opposite sequence. The silhouette rendering is impo verished, but has considerable relief with much of the basic shape. Th e cartoon rendering yields well-developed pictorial relief, even for t he naive subjects. Shading adds only small local details, but differen t illumination produces significant alterations of relief. It is concl uded that shape constancy under changes in illumination is dominant th roughout, but that the (small) deviations from true constancy reveal t he effect of cues such as shading in a natural setting. Such a 'pertur bation analysis' appears more promising than either stimulus-reduction or cue-conflict paradigms.