Transcript Sensation and Perception pt. 1

http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/index.html
Unit 4 Perception
Perception pt. 2
http://www.eyetricks.com/scary_optical_illusion2.htm
Perception
a process of organizing and interpreting
sensory information, enabling us to recognize
meaningful objects and events
https://www.youtube.com/watch?v=ORoTCBrCKIQ
Perceptual set: a mental predisposition to perceive one thing and not
another.
Stare at the black dot in the middle. You should see the outer edges of the circle fade away!
Troxler’s fading
It occurs because even if our eyes move a little when we are fixating a point,
away from that point, in the perception field, the movements aren’t large
enough to observe other elements; in conclusion the neurons remain focused
on the main object and our visual system doesn’t involve new ones for the
other elements.
Big Idea
• Although it seems the brain
interacts directly with the outside
world, it does not.
• The brain senses the world
indirectly because the sense
organs convert stimulation into
the language of the nervous
system: neural messages.
– In short, the brain never receives
stimulation directly from the outside
world.
http://www.michaelbach.de/ot/
Chapter 8
Are the red lines parallel?
http://www.thedesignwork.com/65-amazing-optical-illusion-pictures/
http://www.michaelbach.de/ot/col_lilacChaser/index.html
Afterimages
following bright lights
or adapting stimuli of
excessively longer
alternating patterns
(contingent
perceptual
aftereffect, CAE), are
the effects on the
eyes or brain of
excessive stimulation
of a specific type brightness, tilt,
colour, movement,
and so on. The
theory is that stimuli
have individual
dedicated neural
paths in the visual
outer wall of an
organism for the
early stages of visual
processing; repetitive
stimulation of only a
few channels
misleads the visual
system.
Our experiences shape how we
perceive things:
Let us try something out:
You are about to witness the perpetrator of a crime!
Describe what you saw. Keep in mind, that this
is a police investigation and that your
testimony can be used in a court of law.
Young lady or Old lady?
1.
P a s t e x p e rie n c e s
“ S ta r s p a n g le d _ _ _ _ _ _ _ _ _ _ _ _ _ _ ”
2.
M o o d s , A t t it u d e s , a n d V a lu e s
H a v in g a b a d d a y a n d “ th in g s ” s e e m to s n o w b a ll
3. Needs
If y o u ’re h u n g ry , y o u th in k a b o u t…
4. What the group believes
W e h a v e a te n d e n c y to , “ g o a lo n g w ith th e c ro w d .”
S E E IN G – H E A R IN G – T O U C H IN G – T A S T IN G – S M E L L I N G
'lateral inhibition' - the term used to describe the complex way in which the cells on
the back of the retina respond to areas of black and white. There is, however, little
point in explaining the theory. Why? Because a few years ago it was shown to be
completely untrue, and thus the explanation for the illusion remains a mystery...
Context Effects
Context effect is the influence that our environment plays on us
intellectually, emotionally, and sometimes even physically.
• For example, if a constant noise was made and it was disrupted
by the phrase, “ill is on the duck” your brain would most likely
make “ill”, “bill.” All this change is meant to satisfy the
perceptual set element of our brains. I myself have had stuff
like this happen to me. Walking in on conversation or being
distracted usually ends up with me hearing something different.
"Context" is close in meaning to "environment,"
•
Brain Games 1
http://www.youtube.com/watch?v=PN1NAiM55hU&feature=related
Auditory Illusions
If the sounds do not work click here for link.
Amazingly
the "blue"
spirals
actually have
the same
color as the
green. In
other words
no blue exists
in the
illusion; it
only exists in
your mind.
Perceptual Interpretation
 Perceptual Adaptation
 (vision) ability to adjust to an
artificially displaced visual field
prism glasses
 Perceptual Set
 a mental predisposition to perceive
one thing and not another
Perceptual Set:
Schemas
 What you see in the
center is influenced
by perceptual set
Perceptual Organization
When vision competes with our other senses,
vision usually wins – a phenomena called visual
capture.
How do we form meaningful perceptions from
sensory information?
We organize it. Gestalt psychologists showed that
a figure formed a “whole” different than its
surroundings.
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Perceptual Organization
Gestalt Laws of Grouping
• Proximity
– Seeing 3 pair of lines in A
• Similarity
– Seeing columns of orange
and red dots in B
• Continuity
– Seeing lines that connect
1 to 2 and 3 to 4 in C
• Closure
– Seeing a horse in D
Psychology, 4/e by Saul Kassin ©2004
Prentice Hall
Continuity
• Continuation – Leads the eye along a path. The
principles of continuation is used to lead the
viewers attention to a certain area or to connect
an object to a specific action
• Closure – The eyes fill in the missing gaps
to make the image/object whole.
Proximity
• Continuation – Leads the eye along a path. The
principles of continuation is used to lead the
viewers attention to a certain area or to connect
an object to a specific action
Depth Perception is the ability to judge the distances
of objects, which also allows us to see them in three
dimensions
Innervisions
Later research has demonstrated,
however, that children as young as
three-months are able to perceive
the visual cliff.
Depth perception enables
us to judge distances.
Visual Cliff:
E.J. Gibson and R.D. Walk This
tool was originally developed to
determine if infants had
developed depth perception. A
visual cliff is created by
connecting a transparent glass
surface to an opaque patterned
surface. The floor below has the
same pattern as the opaque
surface. This apparatus creates
the visual illusion of a cliff, while
protecting the subject from
injury.
Visual Cliff
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• How do we see depth?
MONOCULAR CUE—HOW IT WORKS
Aerial Perspective
Objects that are near seem crisper and clearer; far
away objects appear fuzzier.
MONOCULAR CUE—HOW IT WORKS
Aerial Perspective
Height in Plane
Objects that are near seem
crisper and clearer; far away
objects appear fuzzier.
Height in Plane
Objects that are farther away
appear higher in the visual
scene.
Interposition
Objects that are nearer block
objects that are farther away.
Interposition
Linear Perspective
Objects that are nearer block objects that are
farther away.
Lines that are parallel (e.g., railroad tracks) look
like they come to a point in the distance. The
farther the lines, the closer they are.
Linear Perspective
Lines that are parallel (e.g.,
railroad tracks) look like they
come to a point in the
distance. The farther the
lines, the closer they are.
Motion Parallax
When you are moving and
you fixate on a spot, objects
closer to you than that spot
appear to move in the
direction opposite to your
motion; objects farther than
that spot appear to move in
the same direction as you are
moving.
Relative Size
If two objects are of the same
size, the closer one is bigger.
Motion Parallax
Relative Size
Objects that are farther away appear higher in the
visual scene.
When you are moving and you fixate on a spot,
objects closer to you than that spot appear to
move in the direction opposite to your motion;
objects farther than that spot appear to move in
the same direction as you are moving.
If two objects are of the same size, the closer one
is bigger.
Binocular Cues: Depth cues such as retinal
disparity that depends on the use of two eyes.
Retinal disparity: Images from the two eyes differ. Try
looking at your two index fingers when pointing them
towards each other half an inch apart and about 5 inches
directly in front of your eyes. You will see a “finger
sausage” as shown in the inset.
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Binocular Cues
Convergence: Neuromuscular cues. When two
eyes move inward (towards the nose) to see near
objects and outward (away from the nose) to see
faraway objects.
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Monocular Cues
Relative Size: If two objects are similar in size, we
perceive the one that casts a smaller retinal image
to be farther away.
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Monocular Cues
Interposition: Objects that occlude (block) other
objects tend to be perceived as closer.
Rene Magritte, The Blank Signature, oil on canvas,
National Gallery of Art, Washington. Collection of
Mr. and Mrs. Paul Mellon. Photo by Richard Carafelli.
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Monocular Cues
Relative Clarity: Because light from distant objects
passes through more light than closer objects, we
perceive hazy objects to be farther away than
those objects that appear sharp and clear.
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Monocular Cues
Texture Gradient: Indistinct (fine) texture signals
an increasing distance.
© Eric Lessing/ Art Resource, NY
45
Monocular Cues
Relative Height: We perceive objects that are higher in our
field of vision to be farther away than those that are lower.
Image courtesy of Shaun P. Vecera, Ph. D.,
adapted from stimuli that appered in Vecrera et al., 2002
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Monocular Cues
Relative motion: Objects closer to a fixation point
move faster and in opposing direction to those
objects that are farther away from a fixation point,
moving slower and in the same direction.
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Monocular Cues
Linear Perspective: Parallel lines, such as railroad
tracks, appear to converge in the distance. The
more the lines converge, the greater their
perceived distance.
© The New Yorker Collection, 2002, Jack Ziegler
from cartoonbank.com. All rights reserved.
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Monocular Cues
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.
From “Perceiving Shape From Shading” by Vilayaur
S. Ramachandran. © 1988 by Scientific American, Inc.
All rights reserved.
49
Motion perception
• Phi Phenomenon: with a succession of lights
that creates the impression of, say, a moving
arrow.
Perceptual Constancy
Perceiving objects as unchanging even as
illumination and retinal images change. Perceptual
constancies include constancies of shape and size.
Shape Constancy
52
Size-Distance Relationship
Size Constancy:
From Shepard, 1990
Alan Choisnet/ The Image Bank
The distant monster
(below, left) and the
top red bar (below,
right) appear bigger
because of distance
cues.
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Perceptual Constancies
Size Constancy:
Alan Choisnet/ The Image Bank
From Shepard, 1990
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Perceptual Constancies
Shape Constancy Have you ever
noticed, for example, when you approach the
dinner table that the shapes of the plates do
not change? When you look at them from
some distance away from the table, the
shapes of the round plates are elliptical on
your retina. The only time that the image of a
round plate is approximately round on your
retina is when you look at it straight on. If you
are not sure what I mean, look at the dinner
plate demo.
Psychology, 4/e by Saul Kassin ©2004
Prentice Hall
Perceptual Adaptation
Courtesy of Hubert Dolezal
Visual ability to adjust
to an artificially
displaced visual field,
e.g., prism glasses.
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Features on a Face
Face schemas are accentuated by specific
features on the face.
Kieran Lee/ FaceLab, Department of Psychology,
University of Western Australia
Students recognized a caricature of Arnold
Schwarzenegger faster than his actual photo.
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Eye & Mouth
Eyes and mouth play a dominant role in face
recognition.
Courtesy of Christopher Tyler
Portrait artists understood the importance of this recognition and
therefore centered an eye in their paintings.
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Cultural Context
Context instilled by culture also alters
perception.
To an East African, the woman sitting is balancing a metal
box on her head, while the family is sitting under a tree.
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Is There
Extrasensory
Perception?
 Extrasensory Perception
 controversial claim that perception can occur apart from sensory input
 telepathy
 clairvoyance
 precognition
 Parapsychology
 the study of paranormal phenomena
 ESP
 psychokinesis
Claims of ESP
1. Telepathy: Mind-to-mind communication. One
person sending thoughts and the other
receiving them.
2. Clairvoyance: Perception of remote events,
such as sensing a friend’s house on fire.
3. Precognition: Perceiving future events, such as
a political leader’s death.
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Premonitions or Pretensions?
Can psychics see the future? Can psychics aid
police in identifying locations of dead bodies?
What about psychic predictions of the famous
Nostradamus?
The answers to these questions are NO!
Nostradamus’ predictions are “retrofitted” to
events that took place after his predictions.
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Putting ESP to Experimental Test
In an experiment with 28,000 individuals,
Wiseman attempted to prove whether or not one
can psychically influence or predict a coin toss.
People were able to correctly influence or predict a
coin toss 49.8% of the time.
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Subliminal Stimulation
• Below one’s absolute threshold for conscious
awareness.
•
Show clip
Does this work?
Yes and No
•Slide studies showed some emotional reactivi
(called priming a response).
•The effects are subtle and fleeting.