Two Views of Perception:•Bottom-up processing:
-Low-level
-Feature driven
•Top-down processing
-Knowledge driven
-Unconscious inference (Helmholtz)
What do you see in this picture?
Vertical Line Stimulating Receptive Field of Single Cell
Stimulation of a Single Cell by Downward Motion
BRIGHTNESS CONTRAST
Stimulus
Luminance Profile
Mach Bands - Edge Enhancement Illusion
How the Eye Accentuates Edges
Recording From a Single Cell of the Visual Cortex
Frequency of Firing of Single Receptor in Response to Stimuli of Different Amplitude
Inhibitory Effects of Stimulating Adjacent Receptor
Simple Cell in Visual Cortex
Complex Cell of Visual Cortex
On-Off and Center Cells (Retina)
How the Visual System Responds to Edges
Lateral Inhibition
Excitatory & Inhibitory Cells
Which column
is largest?
Which Line is Longer?
Which lines are parallel?
Are lines a and b parallel?
Which Line is Longer?
Which central dot is larger?
What is This a Picture of?
Excitatory & Inhibitory Cells
Bottom-up Perception
Which woman is taller?
Binocular Cues for Depth
•Convergence
•Binocular disparity
Monocular Cues for Depth• Interposition• Linear perspective• Height in vertical plane• Texture• Shadow• Relative motion
Interposition. Which is closer? A or B?
B
A
Which column
is largest?
Linear Perspective
Which red line is bigger?
Which red line is bigger?Which red line is bigger?
Linear Perspective
Height in Visual Field
Texture gradients
Which woman is taller?
Direction of Shadow