DISTAL STIMULUS

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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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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 clue (two eyes) Convergence
Different distance away, different angle of
convergence
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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
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Motion Based Cue for Depth
Ever look out the window while riding in a car?
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Problem of Perceiving Motion
Emphasize Retinal Image pattern
BUT
Compare proximal stimulus with commands to
muscles Did I tell myself to move?

• ambiguity if Im being moved passively
• ambiguity if were both moving

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Problem What happens when perception is
different from sensation? Perceptual
Constancies Perception same/Sensations
different E.g., Size constancy
Proximal stimulus is inadequate, does not capture
all aspects of the distal stimulus.
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The Helmholtzian Solution to the Problems of
Perception
Use knowledge of which configurations are likely
Principle of maximum likelihood.
Make Unconscious Inferences about the world.
Figure vs. Ground What does the edge belong to?
Of the alternatives allowed by the proximal
stimulus, infer the more likely.
Howeverare there cases in which this solution
doesnt really work?
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SUBJECTIVE CONTOURS
such illusions used by GESTALTISM to indicate
how Perceptual experience often involves simple
laws of organization.
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Grouping or organization laws that are not in the
proximal stimulus.
Seen as 3 pairs of lines Not dictated over
Law of Proximity
Seen as alternating columns Not dictated over
Law of Similarity
Seen as intersecting curves does not favor
Law of Good Continuation
Gestaltism In general, solution to the problem of
perception is that we are endowed with Laws of
Simplicity that enable us to organize proximal
stimulation into meaningful perceptions.
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GESTALTISM Knowing how to perceive from the start
RETINAL IMAGE (proximal stimulus)
SENSATIONS INBORN LAWS OF ORGANIZATION
PERCEPTION (know about distal stimulus)
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Perception How we are aware of properties of
world One way to phrase the problem How to get
around the problems of the retinal image?
Empiricism Helmholtz Learning and
Inference Nativism Gestaltism Endowed
organizational laws
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Information processing in perception.

• Perception is not just data driven or bottom-up

• Perception can be knowledge-driven or top-down

Context affects interpretation
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The Phenomena of ATTENTION
Orienting
What is the girl feelingemotion?
What is the information for making these
judgments?

• Attention drawn to most informative aspects of
  picture.
• Conscious Unconscious processes sample the
  information and use knowledge about emotions to
  make judgments.

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The Phenomena of ATTENTION
Goal Directed vs. Stimulus Driven
Search for the letter c
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The Phenomena of ATTENTION
Goal Directed vs. Stimulus Driven
Does the number of white T-shirt players change?
Any Gorillas???????
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Traditionally Perspectives of Perception Assume
Perception is a problem given the inadequacies of
the proximal stimulus information
thus, theories of perception must
involve the brain or mind reconstructing a
representation of the world.
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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.
Correct Answer B
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Example Exam Questions Multiple Choice Examples
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.
Correct Answer C