# Toward a New Theory of Stereopsis Dhanraj Vishwanath **Keywords:** stereopsis, depth perception, distance perception, tangible depth, 3-D Supplemental materials: http://dx.doi.org/JO. 1037/a0035233.supp **Opening (not a real abstract):** Toward a New Theory of Stereopsis Dhanraj Vishwanath Humans can obtain an unambiguous perception of depth and 3-dimensionaJity with 1 eye or when viewing a pictorial image of a 3-dimensional scene. However, the perception of depth when viewing a real scene with both eyes is qualitatively different: There is a vivid impression of tangible solid form and immersive negative space. This perceptual phenomenon, referred to as "stereopsis," has been among the central puzzles of perception since the time of da Vinci. After Wheatstone's invention of the stereoscope in 1838, stereopsis has conventionally been explained as a byproduct of binocular vision or visuaJ parallax. However, this explanation is challenged by the observation that the impression of stereopsis can be induced in single pictures under monocular viewing. Here I propose an alternative hypothesis that **Authors:** [[Psychological Review]]