How do we maintain a stable perceptual world despite moment-to-moment variations in input stimulation?

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How do we maintain a stable perceptual world
despite moment-to-moment variations in input
stimulation?

• Distal vs. Proximal Stimulus
• Unconscious inference vs. higher-order patterns
  in the stimulus
• Lightness Constancy
• Shape Constancy
• Size Constancy

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Physical Stimulus
Physical Stimulus
Sensory Experience
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Lightness constancy
Ones judgment of an objects lightness remains
constant under varying levels of illumination.
Shape constancy
Ones judgment of an objects shape remains
constant at varying viewing angles.
Size constancy
Ones judgment of an objects size remains
constant at varying distances.
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The Gelb effect
dim ceiling light
screen
black disk
white disk
observer sits here
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The Gelb effect
dim ceiling light
screen
black disk
white disk
The observer ignorant of the spotlight will judge
the black and white discs to have equal
brightness. A piece of paper thrust into the
light beam, however, makes it obvious that the
left disc is black.
observer sits here
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Reflected light (luminosity)
Albedo

Incident light (illumination)
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Observer has matched this stimulus that is under
low illumination to the target on the left that
is under high illumination
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The observers matched stimulus exactly as
before, now under the same bright illumination
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Cues for distance or depth (depth perception)
1. Binocular cues
Convergence (oculomotor)
Retinal disparity
involves kinesthetic feedback
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Convergence as a binocular depth cue (The role
of kinesthetic feedback)
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2. Monocular cues
Pictorial (static) cues
Interposition Texture gradients Light and
shadow Linear perspective Aerial
perspective Horizon
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Interposition (occlusion)
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Texture gradient as a monocular depth cue
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Light and shadow as a monocular depth cue
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Linear perspective
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Aerial perspective as a monocular depth cue
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