Viewers perceive shape in pictures according to per-fixation perspective

How viewers interpret different pictorial projections has been a longstanding question affecting many disciplines, including psychology, art, computer science, and vision science. The most-prominent theories assume that viewers interpret pictures according to a single linear perspective projection. Yet, no existing theory accurately describes viewers' perceptions across the wide variety of projections used throughout art history. Recently, Hertzmann hypothesized that pictorial 3D shape perception is interpreted according to a separate linear perspective for each eye fixation in a picture. We performed four experiments based on this hypothesis. The first two experiments found that viewers consider object depictions as more accurate when an object is projected according to its own local linear projection, rather than one consistent with the rest of the picture. In the third experiment, viewers exhibited change blindness to projections in peripheral vision, suggesting that perception of shape primarily occurs around fixations. The fourth experiment found surface slant compensation to be dependent on fixation. We conclude that pictorial shape perception operates according to per-fixation perspective.