Percep Lec
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Transcript of Percep Lec
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VII. Perception
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Sensation:
- raw material for perception- started at entry level, data driven
bottom-up processing
Perception: top-down processing- concept driven, use preexisting knowledge
to interpret information.
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VII. PERCEPTION Recallwe are bombarded with possible energy
from environment...
A. To what sensations do we attend? In order to perceive something, we must attend or pay
attention to it (consciousness).
Selective Attention:
Ability to focus awareness on a single stimulus to theexclusion of other stimuli.
(We focus our awareness on only a limited aspect of
all that we are capable of experiencing.)
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B. How do we organize stimuli? We tend to organize stimuli into wholes.
Origin: Gestalt Psychology
Gestalt: means whole or form in German.
Proposed nervous system is predisposed torespond to patterns in stimuli according to
certain rules. Whole is different from its parts
Example from videowooden triangle
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C. FORM PERCEPTION One of these basic rules...
1. Figure vs. Ground
To see an image, need to be able to distinguishbetween figure and ground.
Sometimes, they can be reversible.
But, at one time, we can focus on only one or other.
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ging Distance
an
ve
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C. FORM PERCEPTION What stimuli are grouped together?
2. Grouping- We automatically imply order by grouping
things together according to certain rules.
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D. DEPTH & DISTANCE PERCEPTION
How do we perceive depth/distance?
- Image on retina is 2-d.
- Need the brainuses certain cues.
1. Depth perception:
a. Binocular Cues:
Cues for perceiving depth that require both eyes.
- Retinas receive slightly different images of world.
- Brain compares those 2 images.
- Retinal Disparity: difference between 2 images.
- Key to judging depthSHORT DISTANCES.
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D. DEPTH OR DISTANCE
PERCEPTION But, when at a distance, there is very little
retinal disparity.
2. Distance perception
a. Monocular Cues
Cues for distance that require one eye.
Example from video.
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Judging Distance
Which is closer, the man
or the house?
How can you tell?
-- Interposition
-- Relative size
-- Relative height
-- Linear perspective
-- Relative Clarity
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Linear Perspective
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D. DEPTH OR DISTANCE
PERCEPTION 3. Nature or nurture?
When would ability to perceive depth be
important in terms of development?
Gibson & Walk (1960):
Visual Cliff Experiments
But, is evidence for nurture also. Use it or lose it
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E. MOTION PERCEPTION Another possible innate ability.
Speculated to have evolved more for survival
than other types of perception. Why?
Brain makes sense of cues:
Shrinking objects are retreating.
Enlarging objects are approaching.
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Perceptual Constancy
Perceptual constancy:
We perceive objects as unchanging eventhough the stimuli we receive about those
objects change.
Importance of experience and expectations?babies vs. Pygmies
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Connecting the cues....
Distance
Size
Motion
Perceptual Constancy
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Insert slide of Muller-Lyers Illusion
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INTERPRETATION IN
PERCEPTION Folk, croak, soak...
1. Perceptual Set:A mental predisposition to perceive one
thing and not another.
- Power of our expectations, predispositionparticularly when interpreting ambiguous
stimuli.
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3. Where do our expectations (schemas)
come from?
a. Experience
b. Culture
Vulnerability to illusions
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G. INTERPRETATION AND
PERCEPTIONc. Context
- Context Effects: We often discern the
meaning of something by using the context
in which it is placed.
- rat/man study- Kulechov effect
Importance of EXPECTATIONS
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G. Interpretation in Perception
How adaptive is our ability to interpret and
organize stimuli into perceptions?
4. Perceptual Adaptation:
In vision, the ability to adjust to an artificially
displaced or even inverted visual field.
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Conclusions Perception: The top-down part of understanding
environment and processing information. Braininterprets and organizes information.
Amazing feats of grouping stimuli & using cues.
But that can also cause illusions...
Individual differences based on experience andexpectations.
All of these rely on taking in physical energy fromenvironmentsensations.
Assumption: our experiences are tied to actual,physical events occurring in environment.... see text
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H. Perception without Sensation?
ESP -Extrasensory perception:
Perception without sensory input.
Types of ESP: Telepathy, Clairvoyance, Precognition
More than Americans believe in some type ofESP.
Parapsychologists:
Psychologists who study psychic phenomenathrough case studies and experiments.
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H. Perception without Sensation?
Rhines Research
Conclusion about ESP:
No sound evidence for para-psychological
phenomena
No single individual who can demonstratepsychic powers to independent investigators
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Impossible Figures
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Example:
Cocktail Party Effect:
The ability to selectively attend to one voice
among many.
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