Advances in Visual Perception PSYC 526 Fall Profs

Advances in Visual Perception PSYC 526 Fall Profs. Fred Kingdom & Kathy Mullen

Lecture 3 “Seeing Objects” Readings Goldstein, 5 th ed: Ch. 7; 6 th, 7 th ed: Ch. 5. Bruce et al. , "Visual Object Recognition" Ch. 9 in Visual Perception. Hove: UK. (1996), Web. CT. Tovee "Object perception and recognition" Ch 8 in An Introduction to the Visual System, Cambridge University Press (1996), Web. CT.

Edges in cave paintings

Cartoon drawings

Children’s drawings

‘Two-tone’ image High-pass filtered

‘Two-tone’ image High-pass filtered

Effects of bandpass filtering Unfiltered Lowpass filtered Highpass filtered

Zero-crossings in filter output

Zero-crossings at different scales

‘Blocked’ image

‘Blocked’ images & zero crossings

Seeing contours

Straightish path Curvy path Field, Hayes & Hess (1993)

Common fate Courtesy of Tony Movshon, New York University

Symmetry

Visual completion

Ambiguous figure

Salvador Dali

Penrose staircase

Escher

Spatial frequency (SF)

‘Light-comes-from-above’ assumption

Colour shading effect

Courtesy of Dan Kersten, University of Minesota

Courtesy of Dan Kersten, University of Minesota

Kanizsa triangle

Muller-Lyre illusion

Muller-Lyre illusion

Gregory’s explanation

Illusions of perceived size

Zollner illusion

“Prior knowledge and/or top-down processing ? ” 1. Gestalt law of good continuation 2. The motion after-effect 3. The ‘light-comes-from-above’ assumption 4. Colours of the rainbow 5. Orientation-selective neurons in the cortex 6. Illusory contours, as in the Kanizsa triangle 7. Mirror-symmetry ‘pops-out’ 8. Insensitivity of cortical neurons to uniform 9. illumination 10. 9. Common fate