Matakuliah
Tahun
: O0072 / Pengantar Psikologi
: 2008
Perception
Pertemuan 3
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PERCEPTION(1)
http://en.wikipedia.org/wiki/Perception
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Definition :
– is the process of acquiring, interpreting, selecting, and organizing sensory
information
– The process of organizing and intepreting information received from the outside
world
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Perception is one of the oldest fields within scientific psychology, and there
are correspondingly many theories about its underlying processes. The
oldest quantitative law in psychology is the Weber-Fechner law, which
quantifies the relationship between the intensity of physical stimuli and their
perceptual effects. It was the study of perception that gave rise to the
Gestalt school of psychology, with its emphasis on holistic approach. .
•
Sensory is a system that consists of a sensory cell type (or group of cell
types) that responds to a specific kind of physical phenomenon, and that
correspond to a defined region (or group of regions) within the brain where
the signals are received and interpreted
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•
Stimulus : any aspect of the outside world that directly influences our
1. Visual Perception
2. Multisensory Integration
3. Motivation, Emotion and Perception
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VISUAL PERCEPTION
Perceptual Organization
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VISUAL PERCEPTION
• What We perceive is often based on how sensory
information is processes in our brains than what is in
front of our eyes (Long & Toppino, 2004)
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VISUAL PERCEPTION
Perceptual Organization
1. Figure Ground
Part of visual stimulus will be the center of our attention (figure) and the
rest will be the indistinct ground. Sometimes the figure and the ground
can be reversed in our perception of the same stimulus
2. Continuity
The lines or patterns that follow the smooth contour will be perceived as
part of a single unit
3. Proximity
Parts of a visual stimulus that are close together will be perceived as
belonging together
4. Similarity
Parts of visual stimulus that are similar will be perceived as belonging
together
5. Closure
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The Incomplete figures of familiar objects will tend to be perceived as
FIGURE GROUND
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CONTINUITY
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PROXIMITY
• This that are close together are usually perceived as
belonging together
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SIMILARITY (1)
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SIMILARITY (2)
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CLOSURE
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VISUAL PERCEPTION
Depth Perception
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VISUAL PERCEPTION
Depth Perception (1)
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Retina has 2 – dimensional surface : up – down, left – right
Monocular cues to depth perception can be perceived by one eye
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8 monocular cues :
Texture gradient
Linear perspective
Superposition
Shadowing
Speed of movement
Aerial perspective
Accommodation
Vertical position
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TEXTURE GRADIENT (1)
• The texture of object is larger
and more visible up close and
smaller the far away
• On curve surfaces, the
elements of texture are more
slanted when the surface does
not squarely face us
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TEXTURE GRADIENT (2)
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TEXTURE GRADIENT (3)
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LINEAR PERSPECTIVE
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Objects cast smaller images on the retina when they are more
distant
The parallel line appear to grow closer together the farther away
they are from us
Objects with larger relative size appear to be closer than objects
SUPERPOSITION
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Closer objects tend to be partially in from of, or partially cover up,
more distant objects
SHADOWING
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The shadows cast by objects and highlights of reflected light
suggest their depth
SPEED OF MOVEMENT
Object farther away appear to move
across the field of vision more slowly
than do the closer objects
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AERIAL PERSPECTIVE
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Aerial perspective or atmospheric
perspective is the effect on the appearance
of an object by the atmosphere between it
and a viewer (or the technique of depicting
this effect in a work of art, such as a
landscape painting). As the distance
between an object and a viewer increases,
the contrast between the object and its
background decreases. The contrast of
any markings or details on the object also
decreases. The colors of the object also
become less saturated and shift towards
blue.
•
Aerial perspective was discovered and
named by Leonardo Da Vinci, who used it
in many of his works, such as the Mona
Lisa, in order to suggest distance. In such
early
paintings the distant objects tend to
http://en.wikipedia.org/wiki/Aerial_perspective
be represented as gray-green.
ACCOMODATION
• The shape of the lens of the eye must change to focus
the visual image on the retina from stimuli that are
different distances from the eye.
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VERTICAL POSITION
• When objects are on the ground, the farther they appear
to be below the horizon, the closer they appear to be to
us
• For the objects in the air, the farther they appear to be
above the horizon, the closer they appear to be to us
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VISUAL PERCEPTION
Depth Perception (2)
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Binocular Cues in depth perception can only perceived
using two eyes
1. Convergence
When both eyes are looking at an object in the center of the visual
field, they must angle inward more sharply for a near object
than for a distant object
2. Retinal Disparity
The principle behind the old fashion stereopticon
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CONVERGENCE
• When both eyes are looking at an object in the center of
the visual field, they must angle inward more sharply for
a near object than a distant object.
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RETINAL DISPARITY
• Our eyes are couples of inches
apart, they do not see the same
view of 3-dimentional objects,
especially when the object is close.
• The difference between the images
on the 2 retinas is a key factor in
depth perception
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VISUAL PERCEPTION
Visual Illusion
• Visual stimuli in which the cues used in visual perception
create false perception
• An optical illusion is always characterized by visually
perceived images that, at least in common sense terms,
are deceptive or misleading. Therefore, the information
gathered by the eye is processed by the brain to give, on
the face of it, a percept that does not tally with a physical
measurement of the stimulus source.
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VISUAL ILLUSIONS (1)
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VISUAL ILLUSIONS (2)
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VISUAL ILLUSIONS (3)
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PONZO ILLUSION
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The Ponzo illusion is an optical illusion
that was first demonstrated by the Italian
psychologist Mario Ponzo (1882-1960) in
1913.
• He suggested that the human mind
judges an object's size based on its
background.
• He showed this by drawing two identical
lines across a pair of converging lines,
similar to railway tracks. The upper line
looks longer because we interpret the
converging sides according to linear
perspective as parallel lines receding into
the distance.
• In this context, we interpret the upper line
as though it were farther away, so we see
it as longer – a farther object would have
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to be longer than a nearer one for both to
THE ZOLLNER ILLUSION
• a classic optical illusion named
after its discoverer, German
astrophysicist Johann Karl
Friedrich Zöllner.
• In this figure the black lines
seem to be unparallel, but in
reality they are parallel. The
shorter lines are on an angle to
the longer lines. This angle
helps to create the impression
that one end of the longer lines
is nearer to us than the other
end.
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THE MϋLLER-LYER ILLUSION
• an optical illusion consisting of
nothing more than an arrow.
• occurs because the visual
system processes that judge
depth and distance assume in
general that the “angles in”
configuration corresponds to an
object which is closer, and the
“angles out” configuration
corresponds to an object which is
far away.
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THE AMES ROOM (1)
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The distorted room seen above is
named after the American
ophthalmologist Adelbert Ames,
Jr., who first constructed such a
room in 1946. He based his
design on a concept originally
conceived by Hermann Helmholtz
in the late 19th century.
There are two illusions associated
with the Ames Room. First the
room appears cubic when viewed
monocularly from a special
viewing point (the true shape of
the room is trapezoidal).
Secondly, within an Ames Room
people or objects can appear to
grow or shrink when moving from
one corner to the other.
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THE AMES ROOM (2)
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This diagram shows how the Ames Room forms an identical
image of a normal cubic room on your retina. If a straight
line (representing a ray of light) is drawn from one corner of
an imaginary cubic room to your eye, the corner can meet
this ray at any point along its length and still appear cubic
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When you look (through a
peephole -- to remove any cues
from stereopsis) into an Ames
Room, the room looks normal and
cubic, but its true shape is cleverly
distorted. The floor, ceiling, some
walls, and the far windows are
actually trapezoidal surfaces.
Although the floor appears level, it
is actually at an incline (the far left
corner is much lower than the
near right corner). The walls
appear perpendicular to the floor,
although they are actually slanted
outwards.
POGGENDORF ILLUSION
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The Poggendorf illusion is one of the most
famous distortion illusions known. Although
much has been written about it since its
discovery in 1860, the underlying mechanism
that gives rise to this effect is still not well
understood.
An adequate explanation of the Poggendorf
illusion must take all the above factors into
account, as well as several others. For
example, the Poggendorf illusion is not
confined to two-dimensional representations: It
also occurs with three-dimensional objects.
Secondly, perspective cues can have a drastic
effect on diminishing the effect of this illusion.
While the Poggendorf illusion is over 100
years old (it was discovered in 1860), there
have been no end of theories to try to account
for it. Recently, interactive versions have
revealed new characteristics and variations of
this illusion. There is, unfortunately, no theory
to date that will adequately account for all the
variations perceived.
VISUAL PERCEPTION
Color Perception
• The perception of color is based on more than the
information that reaches the brain about the wavelengths
of light that reach the cones
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COLOR PERCEPTION (1)
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COLOR BLIND
Color blindness, (also known as Dyschromatopsia) or color vision
deficiency, in humans is the inability to perceive differences between
some or all colors that other people can distinguish. It is most often
of genetic nature, but may also occur because of eye, nerve, or
brain damage, or due to exposure to certain chemicals.
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MULTISENSORY INTEGRATION
• Integrate and interpret information from multiple senses
at the same time (Ernst & Bulthoff, 2004)
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MOTIVATION, EMOTION AND PERCEPTION
• Motivation influence perception
– Hungry  taste the food more delicious
• Emotion influence perception
– Anxious  hear the ambiguous statement more threatening
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TUGAS
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Secara kelompok :
1. Jawablah pertanyaan dari Buku Psychology an Introduction,
halaman 152 (Thinking Critically about Psychology)
1. What is the point of studying perceptual illusions ?
2. What is the value of knowing that our perception is influenced by
our emotions?
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