PSYCH%202220

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PSYCH 2220 Sensation and Perception I Lecture 6
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Keywords for lecture 5

Dorsal/ventral streams, action/perception
streams. Grandmother cell hypothesis. Face cells,
hand cells (in ventral stream), prosopagnosia.
Distributed processing.
transient cells
DORSAL
magnocellular layers of LGN
parvocellular layers of LGN
VENTRAL
sustained cells
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SPATIAL VISION
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FOURIERS THEOREM any complex curve can be
mathematically described as the sum of a series
of sine waves Variation of luminance across a
scene can therefore be described as a series of
sinewaves of different SPATIAL FREQUENCIES.
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Just low spatial frequencies.
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all spatial frequencies
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High spatial frequencies here are NOT telling you
about the face but about the annoying squares.
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when the squares are too small to be seen, then
the remaining information (i.e., the face) can be
seen clearly.
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high
low
invisible
Contrast sensitivity
Threshold contrast
visible
low
high
Spatial Frequency
CONTRAST SENSITIVITY FUNCTION
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THE CONTRAST SENSITIVITY FUNCTION
High contrast Low
Low spatial frequency High
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moving
stationary
High contrast Low
Low spatial frequency High
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.. which revises Big rfs ? best for low sf ?
found in periphery Where cells prefer
MOVEMENT (on way to dorsal stream good for
action)
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DEPTH PERCEPTION
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Cues to DEPTH
Stereopsis Parallax Perspective Size Overlay Textu
re gradient Accommodation and convergence
Artists cues
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David Hockney
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The Ames room as conflict between SIZE and
PERSPECTIVE
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Ames room movie
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perspective vs size
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The IMPOSSIBLE TRIANGLE as conflict between
PERSPECTIVE and OVERLAY (or OCCLUSSION)
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The playing card illusion as conflict between
overlay and size
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Perspective and overlay cues
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perspective gt size
overlay gt perspective
overlay gt
size
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Size constancy a given object seems the same
size as its retinal image size varies with
distance from the viewer. Mechanisms of size
constancy can be clarified by looking at when it
breaks down 1 Emmerts Law 2 Moon Illusion
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big thing far
small thing close
EMMERTs LAW If retinal image stays the same then
perceived size will depend on distance
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EMMERTs LAW If retinal image stays the same then
perceived size will depend on distance
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DEMO ONLY!! They have been MADE different sizes
here!!)
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CRITICAL POINT the moon always has the same
visual angle, but different perceived distance.
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Scale demo (from Lord of the Rings)
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Binocular disparities and stereopsis
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(red over left eye)
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The correspondence problem How does the brain
know which dots in the right eye go with which
dots in the left eye?
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Floating Square
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RIGHT EYE
LEFT EYE
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(red over left eye)
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Reversing the glasses opposes stereopsis and
artists cues
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Necker cube
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Cube
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Pyramid (lots of depth)
(red over right eye)
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Checkerboard
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AUTOSTEREOGRAM
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Ames Window Demonstration
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perspective gt size
overlay gt perspective
overlay gt
size
overlay gt stereopsis
stereopsis gt perspective
but only at close distances
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Pulfrich illusion
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Parallax
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parallax video
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Accommodation and convergence
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Accommodation and convergence need someone who
hasnt got stereopsis parallax doesnt know
about artists cues (perspective, overlay,
texture gradients,size) who could this be???
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Accommodation cues can be used to solve the
visual cliff.
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Neural basis of stereopsis
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Ocular dominance bands
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FAR CELL
RIGHT EYE
FAR
NEAR
LEFT EYE
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NEAR CELL
RIGHT EYE
FAR
NEAR
LEFT EYE
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NEAR
FAR
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motion in depth leads us nicely into. VISUAL
MOTION
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My mother by David Hockney
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The scrabble game by David Hockney
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Visual motion
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PREDICTIONS
EXPERIMENTS
OUTFLOW
DATA
INFLOW
No movement
No movement
Active motion of real image
No movement
YES movement
Passive motion of real image
YES movement
YES movement
Active motion of after image
Passive motion of after image
YES movement
No movement
No movement
YES movement
Attempt to move paralyzed eye
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No movement
YES movement
YES movement
No movement
YES movement