ILLUSIONS What are they? What can we learn from them? D.J. Aks 11/10/09 Proseminar Lecture for Z. Pylyshyn, RUCCs Photo credit: Andy Goldsworthy
ILLUSIONS Correspondence Problem Appearance vs. Reality
ILLUSIONS Discrepancy between… physical & perceptual stimulus Mueller-Lyer Illusion
ILLUSIONS Discrepancy between physical & perceptual stimulus Poggendorff Illusion
ILLUSIONS Discrepancy between 2D & 3D info Andy Goldsworthy
Experiments & Illusions illusions/Pogg/HalfCircDrag.html
ILLUSIONS Discrepancy between….? 2D & 3D info
ILLUSIONS Discrepancy between….? 2D depiction of 3D info i.e., conflicting perspective of parts of object
SIZE CONSTANCY - the stability of perceived size despite changes in objective distance and retinal image size. CONSTANCY SCALING - Our mind adjusts retinal size to correct for registered viewing distance = Size Distance Scaling
SIZE CONSTANCY - the stability of perceived size despite changes in objective distance and retinal image size. CONSTANCY SCALING - MOON ILLUSION - moon appears larger near the horizon than when high in the sky Depth cues (on land) give impression that moon is at a "far" distance.-- Thus, we ‘expect’ a far object (moon) to appear small on the retina - but when it does not, the mind compensates and we see the object (moon) as large
Size-contrast
Violation of assumptions We tend to assume: 1) overhead lighting SHADING 2) regularity of.. SHAPE
Shading & Structure Rodin
ILLUSIONS THAT VIOLATE ASSUMPTIONS Overhead lighting SHADING - we perceive convex shape when top is lit & concave when lit at bottom
ILLUSIONS THAT VIOLATE ASSUMPTIONS Overhead lighting SHADING - we perceive convex shape when top is lit & concave when lit at bottom
ILLUSIONS THAT VIOLATE ASSUMPTIONS Overhead lighting & Shading
ILLUSIONS THAT VIOLATE ASSUMPTIONS SHAPE & SIZE CONSTANCY - apparent shape of an object remains constant despite changes in the shape of the retinal image - –REGULAR SHAPES –AMES ROOM
ILLUSIONS THAT VIOLATE ASSUMPTIONS SHAPE & SIZE CONSTANCY –REGULAR SHAPES –AMES ROOM ILLUSION
Occlusion & Shape Perception Does shape of occluder drive shape percept of ‘occludee’? How about orientation of edges w/in occluder shapes?
Camouflage & Occlusion
Occlusion & Shape Perception
Motion & Shape Perception Kinetic Depth Effect
Motion & Shape Perception Johansson
Neuronal Interactions, Attention & Eye-movements
Visual-Auditory Integration Sound localization & ventriloquism Kevin Johnson on David Letterman
Experiments & Illusions illusions/Pogg/HalfCircDrag.html