Pop-Out Phenomenon

When a strikingly
distinct stimulus,
such as the only
smiling face,
draws our eye.
Perceptual Sets


The tendency for our perceptions to be
influenced by expectations or
preconceptions.
A mental predisposition that greatly
influences what we see.




Devoted fans to science fiction are
more likely to see UFO’s
We may fail to notice writing and
printing errors.
Have also found that emotion,
motivation and culture can influence our
perception.
Is this the letter B or the number 13?
The cat sat on the map and licked its whiskers.
Perceptual Set

What you see in the centre figures depends on the
order in which you look at the figures:


If you scan from the left, see an old woman
If you scan from the right, see a woman’s figure
Schemas


Through experience we form concepts, or schemas,
that organize and interpret unfamiliar information.
Especially strong are out schemas for faces.
Mona Lisa
Form Perception


Gestalt principles describe the brain’s
organization of sensory building blocks
into meaningful units and patterns.
They generated laws of perceptual
organization such as:


Figure and Ground
Laws of Grouping
Figure and Ground

Organization of the
visual field into
objects (figures)
that stand out from
their surroundings
(ground).
Gestalt Laws of Grouping

Proximity: Objects that are
near each other will be
perceived as belonging to a
common set.


Seeing 3 pair of lines in A.
Similarity: Objects that are
similar will be perceived as
belonging to the same group.

Seeing columns of orange
and red dots in B.
Gestalt Laws of Grouping

Continuity: Tendency
to perceive stimuli in
a unified form.

Seeing lines that
connect 1 to 2 and 3
to 4 in C, rather than
four separate lines.
Gestalt Laws of Grouping


Closure: Grouping disconnected
pieces into a meaningful whole.

Seeing a horse in D and
“triangle.”
Connectedness: The tendency to
perceive objects as belonging
together when they are positioned
together or are moving together.
Form Grouping
Impossible
Doghouse
Depth Perception


Seeing objects in three
dimensions enables us to
determine distance.
Visual Cliff experiments

Gibson and Walker
Visual Cliff


A laboratory device for testing depth perception in
infants and young animals.
It suggests that the ability to perceive depth is at
least partially innate.
Binocular Cues

Visual cues to depth or distance
that require the
use of both eyes.


Retinal Disparity: The slight
difference in lateral
separation between two
objects as seen by the left
eye and the right eye.
Convergence: Turning
inward of the eyes, which
occurs when they focus on a
nearby object.

The more the inward strain
the closer the object.
Monocular Cues

Relative Size: The one that casts the smaller
retinal shadow is further away.
Monocular Clues
Interposition:
if one object
partially blocks
another we
perceive it as
closer.
Interposition
Monocular Clues

Relative Clarity: We perceive hazy objects as
farther away than sharp focused ones.
Monocular Clues

Texture Gradient: A gradual change from a coarse, distinct texture to
a fine, indistinct texture signals increasing distance.
Monocular Clues

Relative Height: We perceive objects higher in our field of
vision as further away.
Monocular Clues

Relative Motion: As we move,
objects that are actually stable
appear to move.

The nearer the object the faster
it seems to move.
Monocular Clues

Linear Perspective: Parallel
lines appear to converge
with distance.
Monocular Clues

Light and Shadow: Nearby objects reflect more light
into our eyes than more distant objects. Given two
identical objects, the dimmer one appears to be
farther away.
In or Out?
Distance Cues
The moon just above the horizon
typically appears to be unusually
large because we perceive it as
unusually far away from ourselves.
This is a result of distance cues,
which make the horizon moon
seem farther away. The horizon
moon appears to shrink in size if it
is viewed through a narrow tube
that eliminates the perception of
distance cues. This illustrates the
importance of context effects.
Motion Perception

Phi Phenomenon: When two adjacent, stationary
lights blink on and off in quick succession, we
perceive a single light moving back and forth between
them.

An illusion of movement
Motion Perception


Objects traveling
towards us grow in
size and those moving
away shrink in size.
The same is true when
the observer moves to
or from an object.
Perceptual Constancy

Perceptual constancy enables us to perceive an object as unchanging
even though the stimuli we receive from it change.


Thus, we can identify things regardless of the angle, distance, and
illumination by which we view them.
Constant in terms of color, size and shape
Shape Constancy

Even though these images cast shadows of
different shapes, we still see the quarter as round
Size Constancy

We perceive objects as having a constant size,
even while our distance from them varies.
Lightness Constancy


We perceive an object as
having a constant lightness
even while its illumination
varies.
Perceived lightness depends
on relative luminance.

The amount of light an
object reflects relative to its
surrounding.
The Ames Room
The Ames Room
The Ames Room



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
Visual
Illusions

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
converge
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. Look
beyond your fingers to experience the illusion.
Hearing:The Psychology of Sound




Sound waves are really air
molecules being pushed about.
Frequency: The length of the
sound wave.

Pitch
Amplitude: The height of the
sound wave.

Loudness
Timbre: Complexity of sound,
mixtures of tones

Allows us to recognize a
friends voice on the
phone.
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