Transcript Where is it going? Motion Perception

Where is it going?
Motion Perception
Motion Perception
•Neural pathways in the brain combine information
about eye-muscle activity, the changing retinal image,
and the contrast of the moving object to the stationary
background.
•Brain views larger objects as moving more slowly
than smaller objects
•Brain assumes shrinking objects are retreating and
enlarging objects are approaching
Stroboscopic Motion
• The illusion of motion by the rapid projection
of slightly changing images
• The concept a motion picture (movie) uses
Phi Phenomenon
• The illusion of motion when fixed lights are
turned on and off in a sequence
To see how this works click below:
Stare at the X in the middle and notice what happens. Is
the Green Dot Moving?
Lilac Chaser Illusion
OR goto
http://www.weeville.com/eyetest.htm
Want to know more about this? Click here to find out.
Induced Motion
• Karl Duncker studied this with the dot and
moving rectangle.
• Rectangle moved but people thought it was the
dot moving.
• This because of top-down processing (people
expected the dot to move) and our assumption
that the background is stationary.
Induced Motion Demo
Click below to view video
The “Flying” Airplane
The plane is stationary, the background is what is moving.
Check out more Induced Motion at the link below:
Induced Motion
Spiral Motion Detectors
• Research shows that different neural pathways in the
cerebral cortex process information about the depth
of objects, movement, form, and color.
• As you view the spiral motion your spiral motion
receptors are being used. When you look at a
stationary object, they are still on for a brief instant
causing the illusion.
Spiral Motion
Check it out by clicking on video below:
Spiral Motion & Buddha
Stare without blinking at the center of the spiral.
To view an even better spiral motion demo click on :
Spiral Motion Detectors Demo
Motion Blindness
• Look steadily at one stationary point, such as one of the
white discs. Don’t blink as blinks and sudden eye
movements destroy the illusion. Notice that one, two or
all of the white discs will disappear and reappear.
• Deals with your selective attention
Click on the link to view:
Motion Blindness Demo
Perceptual Constancy
Perceptual Constancy
• Perceiving objects as stable or constant (having
consistent lightness, color, shape, and size) even as
illumination and retinal images change
• Example: as a person walks away from you their
retinal image decreases in size
• Example: A car in the distance is still known to be
the same color and size as it was when it was
driving past you.
• Important function of the perceptual system is to
represent constancy in our environment even when
the retinal image varies
Perceptual Constancy:
Size Constancy
Size Constancy
• A person’s understanding that as an object moves
further or closer to them its actual size stays the
same
• As an object appears to become larger we realize
it is getting closer, not bigger.
• As an object appears to become smaller we
realize it is moving farther away, not getting
smaller.
• Perceptions of the world depend on our
experience - Colin Turnbull’s experiment with
Kenge
Relationship Between Perceived
Size and Perceived Depth
• To perceive the
size of objects
accurately we must
also perceive their
distance accurately
• Thus, many visual
illusions occur
simply because a
particular image
lacks sufficient
depth cues
Retina
Image
Image
Pupil
A
B
A
This figure shows that image size depends
upon both object size and distance
Size
Constancy
• People are the same
size even though
their image sizes
differ
• The depth cues such
as linear perspective
and relative size
help the visual
system judge the
size accurately
Size Distance Relationship
Size Distance Relationship
Size Distance Relationship
Perceptual Constancy:
Shape Constancy
Shape Constancy
• The understanding that an object’s shape
remains the same even though the angle of
view makes the shape appear changed
Shape Constancy
• It is hard to tell if the
figure on the upper
right is a trapezoid or
a square slanted
backward.
• If we add texture, the
texture gradient helps
us see that it is
actually a square
Perceptual Constancy:
Lightness Constancy
Light (Brightness) Constancy
• The ability to see an object as having a
constant level of brightness no matter how the
lighting conditions change
• If you look at a sheet of paper in bright
sunlight it looks blazingly white. View the
same sheet in a dimly lit room, and it appears
gray.
• Has the paper changed? Of course not!
• We know the paper stays “white” no matter
what the lighting conditions are.
Brightness Contrast
• Perceived lightness stays
roughly constant as long as
the context or surroundings
stay the same.
• When the context changes
you may perceive the color
as changing.
• Although the interior squares
are in fact identical, we
perceive the one as lighter or
darker because of the
contrast with its
surroundings.
•Want to see more of these perceptions? Goto
http://www.skidmore.edu/~hfoley/Perc4.htm#lightcon
Brightness Constancy: Example
• Obviously A is a dark square
in light and B is a light square
in shadow, right?
•Both A and B are identical shades of
gray! Can you believe that they are
sending the identical level of light
energy to your retina? The organization
of the scene into lighted areas and
shadowed areas must play a role in
determining the perceived lightness of
the squares.
•The white square (Square B) is
reflecting so little light that it is
reflecting the same amount of light as a
black square in direct light (Square A).
Illusion of the Camera
• Play “Lights, Camera, Magic!”
(12:53) Segment #10 from Scientific
American Frontiers: Video Collection
for Introductory Psychology (2nd
edition).
Perceptual Interpretation
• To what extent do we learn to perceive?
• If our eyes were covered with blinders during our
early years, would we enjoy normal perception if
they were later removed?
• The adaptation goggles show us that our brain can
adapt to changes that occur later in life.
Sensory Deprivation & Restored Vision
• Early visual experience can have a profound effect
on perception. Blakemore & Cooper’s restricted
environment with kittens.
• Do the kittens ever fully regain normal sensitivity
to horizontal or vertical lines? NO.
• The “Use it or lose it” phenomenon.
From the time their eyes first opened, and until the
age of 5 months, these kittens were removed from
darkness each day to spend 5 hours alone in a
black-and-white striped cylinder with a clear glass
floor. A stiff collar prevented the kittens from seeing
anything else, even their own bodies. Afterward,
these kittens had difficulty perceiving horizontal
forms, compared with other kittens exposed only to
horizontal forms.
Sensory Deprivation & Restored Vision
• These experiments show that lacking stimulation,
the cortical cells had not developed normal
connections making them functionally blind to
shape.
• A sensory restriction does no permanent damage if it
occurs later in life. This suggests that visual
experiences during infancy are a critical period for
normal sensory and perceptual development.
Experience guides the organization of the brain’s
neural connections.
• If deafness or blindness is corrected as an infant, it
awakens the pertinent brain area. Nurture sculpts
what nature has endowed.
Perceptual Set
Perceptual Set
• A mental predisposition to perceive something one
way and not another
• If we believe we are going to see or hear something,
we often do
• Example of top-down processing
• Influence of the “power of suggestion” (subliminal
perception)
• Guided by schemas: concepts or mental frameworks
that organize and interpret information
Schemas
Children’s drawings reflect their schemas of
reality, as well as their abilities to represent
what they see. This drawing by 4-year-old Anna
illustrates that the face has far greater
importance than the body in young children’s
schemas of essential human characteristics.
Face Schemas
• Which is the real Margaret Thatcher?
• We don’t have a schema for upside down faces.
• As it rotates you’ll find out when you cannot
assimilate her mouth and eyes to into your schema
for faces
Click to below to view:
The Thatcher Illusion
Perceptual Set
The influence of prior assumptions and expectations
on perceptual interpretations
Perceptual Set
What do you see in the center picture: a male
saxophonist or a woman’s face? Glancing first
at one of the two unambiguous versions of the
picture is likely to influence your interpretation.
Subliminal Perception
• Play “Studying the Effects of Subliminal
Stimulation on the Mind” (4:46) Segment #9
from The Mind: Psychology Teaching
Modules (2nd edition).
Context
• The setting or environment in which we interpret sensory
stimuli
• Culture can also influence how we perceive information.
– Nativist Position – people throughout the world view the world the
same way because they share the same biological perceptual rules.
– Empiricist Position – People actively construct their perceptions by
drawing on their prior learning and cultural experiences.
– Carpentered-World Hypothesis – People living in urban and
industrialized environments where there are more right angles and
straight lines will be more susceptible to the Muller-Lyer Illusion
than people in non-carpentered natural environments.
Context & Culture
What is above the woman’s head? In one study, nearly all the East
Africans who were questioned said the woman was balancing a
metal box or can on her head and that the family was sitting under
a tree. Westerners, for whom corners and boxlike architecture are
more common, were more likely to perceive the family as being
indoors, with the woman sitting under a window.
Context Effects
The magician’s cabinet: Is the box in the
far left frame lying on the floor or
hanging from the ceiling? What about the
one on the far right? In each case, the
context defined by the inquisitive rabbits
guides our perceptions.
Illusions
Illusions
• When we misperceive the true
characteristics of an object or image.
• Help researchers understand how sensation
and perception normally works
Müller-Lyer Illusion
• Perceptual psychologists
have hypothesized that the
top horizontal line looks
longer because it also looks
farther away
• Specifically, the inward
pointing arrows signify that
the horizontal line is closest
to you, and the outward
pointing arrows signify the
opposite case
Müller-Lyer Illusion
Müller-Lyer Illusion
Most people think segment AB equals BC.
In reality AB is much longer than BC.
Müller-Lyer Illusion
Müller-Lyer Illusion
Müller-Lyer Illusion
Müller-Lyer Illusion:
Click below to view a video of how this works:
Muller-Lyer Illusion Explanation
Ponzo Illusion
• Converging lines indicate that top line is
farther away than bottom line
• The interplay between perceived size and distance (a) The
monocular cues for distance make the pursuing monster look
larger than the pursued. It isn’t. (b) This visual trick, called the
Ponzo illusion, is based on the same principle as the fleeing
monsters. The two red bars cast identical-sized images on our
retinas. But experience tells us that a more distant object can
create the same-sized image as a nearer one only if it is actually
larger. As a result, we perceive the bar that seems farther away as
larger.
Moon Illusion
• Moon appears larger when it is on the horizon than when it
is directly overhead.
• Objects on the horizon are perceived as farther away than
those above us
• The moon appears to be behind those objects on the
horizon. Since it is bigger than those object it is perceived
as huge! (click on box below for explanation)
Click Below to View an
Explanation:
Moon Illusion
Ames Room Illusion: Secret
Revealed
We perceive the room to be as
we are used to, a perfect square
or rectangular.
When in fact it is a trapezoid!
Poggendorff Illusion
Impossible Figures
• These grouping principles help us construct reality
but perceptual contradictions can lead us astray
See how this and
others like it are
done
More Impossible Figures
More Impossible Figures
Escher’s Impossible Scenes
Chrysanthemum
Is this 3-D?
Toying with your Perception
Want to see more Optical Illusions?
Optical Illusion Montage 1
Optical Illusion Montage 2
Contrast Asynchrony Illusion
Contrast Asynchrony illusion
Water or Monks?
Heads or Houses?
Rocks or Horses?
In or out of the picture?
Ghost Perceptions?
• Watch the car commercial closely. What perceptual concept
causes you to see the faint image of the “ghost?”
Click Below to view:
Ghostly Car Ad