PSYCHOLOGY
Perceptual
Organization
Perceptual Illusions
http://www.yorku.ca/eye/m-lillu.htm
Objectives
1. Understand how illusions help us
understand perception
2. Understand perceptual organization
principles
Outline


A. Intro & illusions
B. Organizational Principles
1. Form perception
 Figure/Ground
 Gestalt grouping
2. Depth perception
 Binocular cues - retinal dispartity, convergence
 Monocular cues - 8
3. Motion Perception - stroboscopic, phi phenomemon
4. Perceptual Constancy - size & shape, size &
distance, light, color
Perception
What can we learn from looking at the
visual illusions #1-6 in your textbook?
Illusion reveal the ways we normally
organize and interpret sensation.
Perceptual Illusions
Perceptual Organization:
Muller-Lyer Illusion
Illusions
Muller-Lyer Illusion
We interpret the arrows as cues for
distance & length
The arrows at the ends of the lines
make them appear of different lengths
Room Illusion
Room Illusion
Perceptual Organization:
Size-Distance Relationship
Illusions
What assumptions do we make about
rooms?
90 degree angles
Size & distance (we make the false
assumption that they are the same
distance way)
To fool us they distorted the shape of the
room
St. Louis Arch
Taller than wider?
Wider than taller?
Perceptual Organization:
Depth Perception
Relative Height
St. Louis Arch
Explanation:
Relative Height - we perceive objects
higher in our field of vision as farther
away
Perceptual Illusions
Illusions
Hans- Wallach’s - glowing blue worm
Gestalt principles grouping principles lead
you astray in this puzzle
Apply grouping principles like - continuity
Perceptual Illusions
Illusions
Hoffman - ripple illusion
It is a shading technique using light &
shadows
Perceptual Illusions
Illusions
People tend to overestimate distance in
the fog
Light & Shadow issues
Relative Clarity issues
Where can this information be useful in
the real world?
Perceptual Illusions
Perception
What can we learn from looking at the
visual illusions #1-6 in your textbook?
Illusion reveal the ways we normally
organize and interpret sensation.
Which sense dominates?
Visual Capture
 tendency for vision to dominate the
other senses
 Ex. - movie theater, roller coaster
Perceptual Organization:
Gestalt
 Our brains do more then just register
info, we filter & infer to make sense
Gestalt = whole
 tendency to integrate pieces of
information into meaningful wholes
Necker Cube
The whole may exceed the sum of the
parts
8 circles - people tend not to notice the
circles but the whole box
Perceptual Organization:
Illusory Contours
Fig. 15.2
Is there really a line down the middle?
Your eye perceives one
Outline M15
 A. Intro & illusions
 B. Organizational Principles
1.Form perception
Figure/Ground
Gestalt grouping
2.Depth perception
 Binocular cues - retinal dispartity, convergence
 Monocular cues - 8
3.Motion Perception - stroboscopic, phi phenomemon
4.Perceptual Constancy - size & shap, size & distance,
light
Form perception
 Our brains do more then just register
info, we filter & infer to make sense
by discriminating what it is - form
 We organize and interpret meaning
QuickTime™ and a
decompressor
are needed to see this picture.
What is it?
Perceptual Organization
Form perception
 Figure and Ground--organization of the visual
field into objects (figures) that stand out from
their surroundings (ground);
 Reversible figures
What is it?
QuickTime™ and a
decompressor
are needed to see this picture.
What is it?
QuickTime™ and a
decompressor
are needed to see this picture.
Perceptual Organization:
Gestalt
Grouping
 the perceptual tendency to organize stimuli
into coherent groups
Gestalt grouping prin.
Grouping Principles
a)
b)
c)
d)
e)
proximity--group nearby figures together
similarity--group figures that are similar
continuity--perceive continuous patterns
closure--fill in gaps
connectedness--spots, lines, and areas are
seen as unit when connected
PerceptualOrganization:
Grouping Principles
PerceptualOrganization:
Closure
 Gestalt
grouping
principles
are at work
here.
PerceptualOrganization:
Grouping Principles
 Gestalt
grouping
principles
are at
work here
PerceptualOrganization:
Grouping Principles
 Impossible
doghouse
Perceptual Organization:
Depth Perception
 ability to see objects in three dimensions
 allows us to judge distance
 Somewhat innate ability as shown by infants
Perceptual Organization:
Depth Perception
Visual Cliff
Depth perception
1. Binocular cues
a) retinal disparity
images from the two eyes differ
closer the object, the larger the disparity
(floating finger sausage)
b) convergence
neuromuscular cue - two eyes move
inward for near objects
2. Monocular Cues
a) relative size
smaller image is more distant
b) Interposition (overlay)
closer objects blocks distant object
Perceptual Organization:
Depth Perception
Relative Size
Perceptual Organization:
Depth Perception
Interposition
Monocular cues
c) relative clarity
hazy object seen as more distant
d) texture
coarse --> close
fine --> distant
Perceptual Illusions
Monocular cues
e) relative height
higher objects seen as more distant
Perceptual Organization:
Depth Perception
Relative Height
Monocular cues
f) relative motion
closer objects seem to move faster
g) linear perspective
parallel lines converge with distance
h) relative brightness
closer objects appear brighter
Perceptual Organization:
Depth Perception
Light and Shadow
Perceptual Organization:
Depth Perception
Perspective Techniques
Perceptual Organization:
Depth Perception
Illusory Depth
Perceptual Organization:
Depth Perception
Illusory Depth
Explanation
Motion Perception
1. Stroboscopic movement - still
pictures can be perceived as moving (
cartoons & film)
2. Phi phenomenon - 2 adjacent
stationary lights blink on/off in
succession are perceived as moving
Perceptual Constancy
 Perceptual Constancy
 perceiving objects as unchanging even as
illumination and retinal image change
 color
 shape
 size
Size & distance p.239
Monster & Ponzo illusions
Monster - linear perspective, relative
height; cues to distance & size
Ponzo - we perceive the bar as farther
away as being larger based on experience
Moon illusion
Moon looks larger at the horizon then it
does high in the sky
Explanation: cues to objects distances at
the horizon make the moon seem farther
away
Similar to the monster & ponzo illusion
Perceptual OrganizationBrightness Contrast
Perceptional Constancy
1.
2.
3.
4.
Shape
Size & distance
Color
Lightness/Brightness
Concentrate on the 4 dots
in the middle for 30 sec.
QuickTime™ and a
decompressor
are needed to see this picture.
Which is line is longer?
QuickTime™ and a
decompressor
are needed to see this picture.