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.

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Presentation transcript:

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