Five Illusions Challenge Our Understanding of Visual Experience

Five illusions suggest that visual experience is not an inferential process: 1. VISUAL INFERENCE (Linton Un-Hollow Face and Morphing Face Illusions): Perceived depth is not inverted in the Hollow-Face illusion: First, objects placed in the hollow of the hollow mask are seen in true (un-inverted) depth relative to the mask. Second, if we put balls on the tip and base of the nose, and morph from a hollow to a protruding mask (by gradually switching the position of the two eyes), we see the balls switch in depth. So priors, top-down information, and cue-integration merely appear to affect our cognition, rather than our perception, of depth. 2. VISUAL SHAPE (Linton Stereo Illusion): The Linton Stereo Illusion (ECVP 2024) demonstrates that perceived stereo depth reflects retinal disparities, not 3D geometry. 3. VISUAL SCALE (Linton Scale Illusion): The ‘Linton Telestereoscope’ decouples horizontal disparities from vergence and vertical disparities in VR. It shows that visual scale is governed by horizontal disparities. When vergence and vertical disparities are increased, and horizontal disparities are toggled between ‘normal’ and ‘increased’, we see a startling effect: the scale of the scene changes from ‘normal’ to ‘miniature’, even though the perceived distance of the scene doesn’t change. This suggests that visual scale relies on a purely cognitive association between accentuated 3D shape (stereo depth) and closer distances. 4. SIZE CONSTANCY (Linton Size Constancy Illusion): Placing a rectangular frame around instances of pictorial and stereo size constancy, and stereo shape constancy, demonstrate that these constancies do not affect perceived angular size. 5. COLOR CONSTANCY (Linton Color Constancy Illusion): We show that if you transition between the two interpretations of Kitaoka’s version of Anderson’s illusion (where a disk’s color is interpreted differently depending on its surround) our color judgements change, whilst the perceptual appearance of the disk does not.