Constructing the Visual World
Bottom Up & Top Down Processing
Form perception
Depth and distance perception
Visual constancies: When seeing is
Visual illusions: When seeing is misleading
What do you see??
Group A
You are going to look briefly at a picture
and then answer some questions about it.
The picture is a rough sketch of a poster for
a costume ball (formal dance).
Do not dwell on the picture. Look at it
only long enough to “take it all in” once.
After this, you will answer YES or NO to a
series of questions.
Group B
You are going to look briefly at a picture
and then answer some questions about it.
The picture is a rough sketch of a poster for
a trained seal act. Do not dwell on the
picture. Look at it only long enough to
“take it all in” once. After this, you will
answer YES or NO to a series of questions.
In the picture was there . .
A car?
A man?
A woman?
A child?
An animal ?
A whip?
A sword?
A man’s hat?
A beach ball?
A fish?
Top Down processing
 You go beyond the sensory information to try to
make meaning out of ambiguity in your world
 What you expect (your experiences and your
perceptual set) drives this process
Bottom Up processing
 Digesting raw sensory information to make sense
of something.
 Our feelings of pain combine both top down &
bottom up processing. (tickling)
How old is the woman on the
following slide?
Without speaking, write your answer on a
piece of paper.
Perceptual Ambiguity
Your brain tries to make sense of what you
are looking at based on the region you are
focusing on.
To recognize an
object (figure) we
must first perceive it
as distinct from its
Form Perception – Gestalt
Gestalt principles describe the brain’s
organization of sensory building blocks
into meaningful units and patterns.
Proximity occurs when
elements are placed close
together. They tend to be
perceived as a group.
The fifteen figures above
form a unified whole (the
shape of a tree) because
of their proximity.
Similarity occurs
when objects look
similar to one
another. People often
perceive them as a
group or pattern.
Closure occurs when an object
is incomplete or a space is not
completely enclosed. If enough
of the shape is indicated,
people perceive the whole by
filling in the missing
Although the panda is not
complete, enough is present
for the eye to complete the
shape. When the viewer's
perception completes a shape,
closure occurs.
Continuation occurs
when the eye is
compelled to move
through one object and
continue to another
Viewer's eye will
naturally follow a line or
curve. The smooth
flowing crossbar of the
"H" leads the eye directly
to the maple leaf.
Proximity Video
How does the advertising world use Gestalt
Gestalt Principles Gone Awry
Objects located within very
little distance of one another.
become related as a group,
even if they are dissimilar in
almost every way--in form,
texture, value, or color.
Sign is read from top to
bottom because of the how the
words are arranged in
columns. If read as a column,
the words do not make sense,
but if read the correct way, the
sign tells us something
Poorly placed dollar sign…
Gestalt Principles
Seeing columns of
orange and red dots in
Seeing 3 pair of lines in
Seeing lines that connect
1 to 2 and 3 to 4 in C.
Seeing a horse in D.
Depth and Distance Perception
Binocular Cues:
Visual cues to depth or distance that require the
use of both eyes.
 Convergence: Turning inward of the eyes,
which occurs when they focus on a nearby
 Retinal Disparity: The slight difference in
lateral separation between two objects as seen
by the left eye and the right eye.
Relax your eyes and try and focus behind the
computer screen. (Convergence)
11 little candies should “pop” out.
Retinal Disparity – floating finger
Because our eyes receive
different information about an
object, their retinal disparity
provides a binocular cue of an
objects relative distance.
Hold your index fingers about 5 inches in front of
your eyes, with their tips a half-inch apart. Now
look beyond them and note the weird result.
Move your fingers out farther and the retinal
disparity- and the finger sausage- will shrink.
Depth and Distance Perception
Monocular Cues:
Visual cues to depth
or distance that can
be used by one eye
illusion (perceiving
vertical dimensions
as longer than
The Ames Room- vid clip on teacher
A specially-built room
that makes people seem
to change size as they
move around in it
The room is not a
rectangle, as viewers
assume it is
A single peephole
prevents using binocular
depth cues
Perceptual Constancies
The accurate perception of objects as stable
or unchanged despite changes in the
sensory patterns they produce.
Shape constancy
Location constancy
Size constancy
Brightness constancy
Color constancy
Shape Constancy
Even though these images cast shadows of
different shapes, we still see the quarter as round
Color Constancy
Color remains constant even when lighting
and wavelengths shift.
It demonstrates that our experience of color
comes not only from the object, but
everything around it as well.
Illusions are valuable in understanding perception
because they are systematic errors.
Illusions provide hints about perceptual strategies.
In the Muller-Lyer illusion (above) we tend to
perceive the line on the right as slightly longer than
the one on the left.
The Ponzo Illusion
Linear perspective
provides context
Side lines seem to
Top line seems
farther away
But the retinal
images of the red
lines are equal!
Fooling the Eye
The cats in (a) are the same size
The diagonal lines in (b) are parallel
You can create a “floating fingertip frankfurter” by
holding hands as shown, 5-10” in front of face.
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