organizing the perceptual world – module 13 intro psych mar 8-10, 2010 class #20-21
TRANSCRIPT
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Organizing the Perceptual World – Module 13
Intro Psych
Mar 8-10, 2010Class #20-21
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Gestalt Psychology
Based on the assumption that the whole is greater than the sum of its parts… Basic principles:
Figure-Ground Processing In a noisy environment, we pick out
features that are important (stands out from the rest) this is the figure
The ground is the less relevant stuff
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Figure and GroundFigure and Ground
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Gestalt Principles of Perceptual Grouping
Having discriminated figure from ground, we then try to organize the figure into a meaningful form
Our minds seem to follow certain rules for grouping stimuli together
Several rules of perceptual organization identified by Gestalt psychologists illustrate their idea that the perceived whole is different from the mere sum of its parts
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Gestalt Principles of Perceptual Grouping
Proximity If figures are near each other we tend to group them
together Similarity
If figures are similar to each other we tend to group them together
Continuity We tend to perceive smooth, continuous patterns
rather than discontinuous ones Closure
When a familiar figure is interrupted we imagine the rest of the figure (we finish the picture)
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Gestalt Principles of Perceptual Grouping
Texture When basic stimuli have the same texture people tend to
group them together Simplicity
People tend to group features of a stimulus in a way that provides the simplest interpretation of the world
Common Region Elements located within some boundary tend to be
grouped together
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Gestalt Principles of Perceptual Grouping Common Fate
Sets of objects that are moving in the same direction and at the same speed are perceived together (example: marching bands)
Connectedness When they are uniformed and linked, we perceive
spots and lines, etc. as a single unit
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Depth Perception
This is our ability to transform two-dimensional retinal images into three dimensional perceptions… Seeing objects in three dimensions enables us to
estimate their distance from us
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Nativist-Empiricist Debate
Nativists (inborn trait) vs. Empiricists (learned trait) Nativists:
Mind doesn’t rely on experience for meaning but innately organizes sensations into perception
Depth perception emerges too early in life to have been learned
Even adults with limited experience (e.g., handicapped) experience depth
Empiricists: Infants learn depth through feedback from their tactile and
motor experiences They associate eye movements with hand and arm
movements.
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Gibson and Walk (1960)
These researchers tried to solve this dispute in their “visual cliff” experiment
Exp 1: human infants
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Gibson and Walk (1960)
They designed a “visual cliff”, which was actually a glass-top table
A checkered pattern was positioned close to the glass under one half of the table (the “shallow” side) and far below the glass under the other half (the “deep” side)
Infants between the ages of 6 months and 14 months were placed on the shallow side of the table, and encouraged to crawl over the edge of the visual cliff on to the deep side by being offered toys or having their mothers call them
Most failed to respond to these incentives, suggesting that they possessed at least some of the elements of depth perception
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Gibson and Walk (1960)
What do you think was the main criticism of this experiment???
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Gibson and Walk (1960)
Experiment 2: Day-old goat Newly hatched chickens
Again, as with the human infants they displayed depth perception
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But…
In other studies, new-born chickens are seen pecking at corn that is in fact ten centimeters away until they are forcibly removed, no matter how many times they peck air
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Bertenthal & Campos (1978) Nine-month-old infants had faster heart rates
than normal when placed on the deep side, presumably because they were frightened
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Held and Hein (1963)
Experiment 1: Kittens raised in darkness until at least six
weeks of age They did not retreat from visual cliff
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Held and Hein (1963) Experiment 2:
Placed two kittens in the 'kitten carousel' a device which let one cat move it while the other followed around but was not in control of the motion
This meant that both cats had the same visual experience
The immobile kittens were unable to blink and didn't stretch out their paws when lowered to the ground
However, when allowed free movement they quickly learned the ability, implying that the perception of depth is learned and related to the motor system
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So how are we able to develop depth perception? Has to do with the use of certain cues…
Binocular Cues These cues require the use of both eyes
Monocular Cues These cues are available to each eye separately
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Binocular Cues: The Pencil Tests Binocular (Retinal) Disparity
The difference between the two retinal images of an object (pencil test #1)
Granrud (1987) – felt that this cue appears to develop after three months of age thereby conflicts with Gibson and Walk (1960)
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Binocular Cues: The Pencil Tests Binocular Convergence
A muscular cue that indicates the extent to which our eyes turn inward when we look at an object (pencil test #2)
Goldstein (1999) – we have basic building blocks of convergence at birth but with maturation of our visual systems these further improve with age
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Monocular Cues for Perception of Depth and Distance Interposition
Depth cue derived from the overlapping position of objects
Relative Size When object gets larger on the retina we assume they
are closer Textural Gradient
This is provided by our proximity to an object Linear Perspective
Cue provided by the convergence of lines towards a single point of the horizon
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Monocular Cues for Perception of Depth and Distance Motion Parallax
The result of changing positions of an object in space due to the motion of the object Accommodation
Feedback we receive from the muscles in the eye that causes the lens to bulge or get thinner (pencil test #3)
Haze Aerial perspective acts as a depth cue over long distances when we are outside
Relative Height We perceive objects higher in our field of vision as farther away (St. Louis Gateway Arch)
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Monocular Cues for Perception of Depth and Distance
Light Nearby objects reflect more light in our eyes therefore
given two identical objects, the dimmer one seems farther away
Shadow This also produces a sense of depth consistent with
the assumed light source
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Perception of Motion
Looming The rapid expansion of the size of an image so that
it fills the retina If this expansion is equal in all directions then its
coming right at you – if its more to one side it will miss you
Sports Psych – could it be that “expert catchers” unconsciously are able to detect these angles better?
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Perception of Motion
Stroboscopic Motion (phi phenomenon) Occurs because of our tendency to interpret as
continuous as series of still images flashed in succession Videotapes show 30 per second – memory of one
is long enough so that we don’t notice any gaps
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Perceptual Constancies
Size Constancy A nearer object will have a larger retinal image
but we don't interpret the object as being larger Without size constancy people would appear to
grow as they walked towards you and shrink as they walk away
Our visual system appears to estimate distance and size together
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Perceptual Constancies Shape Constancy
Objects viewed from different orientations have different forms but we don't interpret them as different objects
Experience is important determining shape constancies Lightness Constancy
No matter how the amount of light striking an object changes, the object’s perceived brightness does not change
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Optical Illusions
A misinterpretation of a visual stimulus… When the "real" and the perceived do not match Illusions mislead us by playing on the ways we
organize and interpret our sensations
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“Visual-capture” phenomenon When there is a conflict between visual and other
sensory information, vision seems to dominate or capture the other senses Examples:
When the sound of a movie comes from the projector behind us, we still perceive it as coming from the screen (we “see” the actors talking)
Same as we perceive the voice from the ventriloquist's dummy
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Optical Illusions
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Which Line Is Longer?Which Line Is Longer?A-C on the Left or A-B on the A-C on the Left or A-B on the
Right?Right?
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How many faces do you How many faces do you see?see?
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Are the horizontal lines parallel or Are the horizontal lines parallel or
do they slope?do they slope?
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Count the black dots...Count the black dots...
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What’s going on here?What’s going on here?
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How many pandas are there in How many pandas are there in this picture?this picture?
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The Impossible TridentThe Impossible Trident
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Crossing Circles IllusionCrossing Circles Illusion
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Well, we all know how many legs Well, we all know how many legs elephants have...elephants have...
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Read this...Read this...
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Very strange...Very strange...
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Baby In Picture IllusionBaby In Picture Illusion
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Expanding Cushion Expanding Cushion IllusionIllusion