Receptive fields care about size

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Receptive fields care about size shape
But since orientation is important for
identifying objects what about other levels of
organization?
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Receptive fields overlap
Across a collection of receptive fields,
orientation matters to cells in the visual cortex
of the brain.
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Multiple representations of the retina in visual
cortex of the brainin excess of 100,000,000
cells/neurons
Form is not meaninghow do we go from sensations
and neural codes to PERCEPTION?
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Example Exam Questions Multiple Choice
Examples The traditionally defined problem of
perception is that a. distal stimuli are
ambiguous. b. the relation of proximal stimuli to
distal stimuli is ambiguous. c. proximal stimuli
are specific to distal stimuli. d. sensations
are unambiguously related to distal stimuli.
Empiricism a. emphasizes the availability of
concepts and categories given at birth. b.
rejects the notion that sensations are different
form perceptions. c. assumes that associations
acquired through experience can convert
sensations into perceptions. d. assumes that
simple laws of organization can convert
sensations into perceptions.
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Perception - Knowing the World
DISTAL STIMULUS (thing in the world)
PROXIMAL STIMULUS (Image on the retina)

• Inverted
• Ambiguous
• 2-dimensional

PROBLEM Perception does not correspond to
proximal stimulus!!
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HOW CAN THE ENVIRONMENT BE PERCEIVED GIVEN THE
INADEQUACIES OF THE RETINAL IMAGE?
TRADITIONALLY HOW DO SENSATIONS BECOME
PERCEPTIONS?
FOR EXAMPLE (a) INTENSITY OF LIGHT PRODUCES
SENSATION OF BRIGHTNESS (b) WAVELENGTH OF LIGHT
PRODUCES SENSATION OF COLOR
FOR EXAMPLE I PERCEIVE PLACES, OBJECTS,
PEOPLE, EVENTS
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NATIVISM Knowing how to perceive from the start
RETINAL IMAGE (proximal stimulus)
SENSATIONS INBORN RULES AND CATEGORIES
PERCEPTION (know about distal stimulus)
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EMPIRICISM LEARNING TO PERCEIVE
RETINAL IMAGE
SENSATIONS MEMORIES ESTABLISHED THROUGH
EXPERIENCE
PERCEPTION
ASSOCIATIONS
(BERKELEY, 1709)
Associate size of arm movement with retinal
image. Associations become cues (clues) about
the world.
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? For a given object, RI gets smaller with
distance
? When one object hides another, the hider is
closer to me
? Parallel lines converge at infinity
? Texture elements are denser at greater distances

• Aspects become cues
• Cues allow inferences

? This SP was probably caused by a particular SD
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Binocular Disparity
Amount of binocular disparity indicates

• Absolute distance
• Relative distance

more disparity ? closer to me more disparity
? more separation
distance from me distance from each other
If SP has pictorial cues and disparity, its a
real scene (not just a picture of that scene). ?
Given my experience, assign to SP the SD that is
most likely to have caused it.
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Binocular clue (two eyes) Convergence
Different distance away, different angle of
convergence
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Motion Based Cue for Depth
Ever look out the window while riding in a car?