Anthony J Greene 1

The Role of Experience

1. Perceptual Development

2. Effects of Learning and Cognition

3. Development Vs Hardwiring

Perceptual Development

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The Measurement of Infant Perception

• A reliable tendency to stare at new stimuli

• Comfort responses and preferences for familiar stimuli

• Reliable surprise reactions when configurations are altered

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The Development of Visual Acuity

• Vary spatial frequency and contrast compared to a gray swatch

• The highest frequency and smallest contrast that produce a response determine the acuity of infant perception

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The Development of Visual Acuity

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The Development

of Visual Acuity

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Stereopsis: Use it or lose it• At Birth, the nerve fibers at the edge of column

boundaries are poised to cross over and make connections with columns from the opposite eye that have similar receptive fields

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Stereopsis: Use it or lose it• With normal development, corresponding inputs

from different eyes cause nerves to overlap

• As with phase detectors, different eccentricities are detected in slightly different regions of cortex. Such regions then discern different disparities.

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Stereopsis: Use it or lose it• If the inputs do not correspond (e.g. child may be

cross-eyed or have a wandering eye), the inputs do not overlap and stereopsis does not develop.

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Object Constancy

• By 2 months of age, most children can detect that an object is missing

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The Time Course of Perceptual

Development

Newborn 1. Recognize mothers face2. Discriminate mothers voice3. Intermodal matching

2 Weeks 1. Moving stimuli1 Month 1. 20/600 Vision

2. Can discern speech from othervoice noises

2 Months 1. Some color vision2. Object constancy

3 Months 1. Perception of Facial Expressions2. Good color vision3. Binocular fixation4. Smooth eye movements

4 Months 1. Object Categories2. Biological Movement3. Binocular Disparity

5 Months 1. Pictorial Depth Cues6 Months 1. High Visual Acuity

2. Hearing threshold close to adult3. Speech Classification

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The Development of Myopia (childhood into adulthood)

• With excessive up-close viewing, the strain on the lens and cilia eventually cause the eyeball to shorten to accmodate more easilly – The Air Force Academy

– Eskimos

– Chicks

• This process can be prevented and reversed by using reading glasses and engaging in distance viewing (e.g., lots of outdoor activity)

COGNITIVE ASPECTS OF PERCEPTION

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Top-Down Aspects of Perception

1 Categorization2 Attention3 Identification &

Recognition4 Competition Between Top-

Down & Bottom-Up Information

5 Resolving Ambiguity 6 Context7 Imagery8 Perception & Action9 Perception is Malleable10 Is Perception Modal?11 Concepts

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1 Categorization

Memory

Grouping like objects - category exemplars

Generalization

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2 Attention

Behavioral and Physiological phenomenon

Acquisition of Sense Data : Cognitive gating of sensory/perceptual input -- Guides Acquisition of Sense Data

Competition between Top-Down & Bottom-Up information

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Cognitive Gating

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Cognitive Gating

There are benefits to keeping your mind on what you’re doing

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The Physiology of Attention

• Amplification (the Pulvinar of the Thalamus)

• De-amplification

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3 Identification & Recognition

• Perceptual systems learn to recognize

• Identification for previously seen items is faster and more reliable, regardless of whether or not you consciously remember

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Disorders of Identification or Recognition

• V3: Visual agnosia

• IT: Associative agnosia

• Fusiform gyrus of IT: Prosopagnosia

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4 Process Competition

Irrelevant Information

Facilitation and Interference

Stroop Interference

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Stroop Interference

TTRRUUCCKK BLUE GGRRAAYY

PLATE GREEN BLUE

TREE RREEDD PURPLE

DDEESSKK YELLOW RED

BUCK PURPLE GREEN

STRAW GGRRAAYY YYEELLLLOOWW

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5 Resolving Ambiguity

Purpose of perception is unambiguous information

Gibson- perception is a behavior which actively resolves ambiguity

Perception can be viewed as a probability funnel

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6 Context and Perception

Context can serve to constrain or resolve ambiguity - source of additional information (associative) and clues.

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7 Imagery

• What color is your neighbors house?

• Perception in the absence of the stimuli - an aspect of memory

I Mental Rotations

II Activation of Perceptual Areas

III Damage to Perceptual Areas Disrupts Imagery and Memory

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Mental Rotation

Reaction Time (RT) Study

1 Shepard Mental Rotation - Internalized Perception

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Mental Rotation (cont.)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

15 30 45 60 75 90 105 120 135 150 165 180

•Straight slope line indicates mental rotations of 600/sec

•If it weren’t a rotation, the slope would be either flat or irregular

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Mental Rotation (cont.)

• The fact that the result is a straight line indicates that the subjects must be rotating through the intermediate positions.

• Analog Process - Analogous to Physical Rotations; mental rotation is constrained in the same way that our physical interaction with the environment in constrained

• The further apart the objects are, the longer it takes to mentally rotate them.

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Mental Rotation (cont.)

Can blind people do mental rotation? (i.e. Is vision necessary for mental rotation?)

2 Marmor & Zaback - 2-D mental rotation in the Picture Plane

• Subjects:– Sighted Blindfolded

– Congenitally Blind

– Blind (Late Blindness; have a visual frame of reference)

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Mental Rotation (cont.)• Stimulus:

– The figures used here are simpler than those used by Shepard.

– Wooden objects fastened to a larger, flat piece of wood.– Present one object to the Left Hand.– Present another (possibly different) object in a different

orientation to the Right Hand.

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Mental Rotation (cont.)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

15 30 45 60 75 90 105 120 135 150 165 180

2330/sec 1140/sec 590/sec

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Mental Rotations (cont.)

• Because all of the lines are straight subjects are constrained to the physical/mental rotation through intermediate positions.

• Vision is NOT necessary to do rotation; vision just makes for faster mental rotations.

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8 Perception & Action

• Recall Gibson’s theory that perception is a behavior

• As such, part of action must be to help constrain perception (e.g., exploration) or inform (foraging)

• Similarly, action is directed and updated by perception

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9 Perception is Malleable

• Prism Effects on reaching

• Facilitation

• Perception is influenced by expectation

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10 Is Perception Modal?

Do the senses influence one another?

1. Synesthesia

2. Barn Owl: Optic Tectum (Colliculus)

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11 Concepts• Pigeons can learn complicated concepts• From some points of view, concepts are no

more than configurations of perceptual information

• Or, at least, conceptual processes evolved for the purpose of making the best use of perceptual information

• What you perceive depends upon what you know

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Do Concepts Help Us Figure Out What We’re Looking At?

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Innate Vs. Developed Nature Vs. Nurture

Two Species on Their Day of Birth

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Is Perception Innate?

Nature vs. Nurture

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Turn That

Frown Upside-Down

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Facets of Perception That Are Hardwired

1. Bottom-Up Processes

2. Neural Organization

3. Reflex Mechanisms1. The Reflex Arc

2. Visual and Auditory Orientation Reflex

4. Range of Perception

5. Capacities of Perception 1. Attention?

2. The Ability to Learn Perceptually and Conceptually

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Facets of Perception That Are Hardwired

1. Bottom-Up Processes?

2. Neural Organization?

3. Reflex Mechanisms1. The Reflex Arc

2. Visual and Auditory Orientation Reflex

4. Range of Perception

5. Capacities of Perception ?1. Attention?

2. The Ability to Learn Perceptually and Conceptually?

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Facets of Perception That Require Development

1. Top-Down Processes1. Attention2. Learning

2. Fine-Tuned Functioning1. Acuity2. Stereopsis3. Perceptual Facilitation (Priming)4. Generalization vs. Discrimination

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Conclusion

•Evolution favors what?•Speed versus flexibility trade-off

It favors both, but under different circumstances.  In rapidly changing environments, or in species that occupy varied habitats (like humans:  everything from the equator to near the poles, including jungle, desert, plains, citys, farm, etc.) then flexibility is favored.  In species where the lifespan is short and/or mortality rate is high, speed is favored.