PSYCHOLOGY
(8th Edition)
David Myers
PowerPoint Slides
Aneeq Ahmad
Henderson State University
Worth Publishers, © 2006
1
Perception
Chapter 6
2
Perception
Selective Attention
Perceptual Illusions
Perceptual Organization
 Form Perception
 Motion Perception
 Perceptual Constancy
3
Perception
Perceptual Interpretation
 Sensory Deprivation and
Restored Vision
 Perceptual Adaptation
 Perceptual Set
 Perception and Human Factor
4
Perception
Is there Extrasensory
Perception?
 Claims of ESP
 Premonitions or Pretensions
 Putting ESP to Experimental Test
5
Perception
The process of selecting, organizing, and
interpreting sensory information, which
enables us to recognize meaningful objects
and events
(Top down processing).
6
7
Selective Attention
Perceptions about objects change from moment to
moment. We can perceive different forms of the
Necker cube; however, we can only pay attention
to one aspect of the object at a time. Other
examples: the Stroop Task, dichotic listening)
Necker Cube
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Stroop Task
9
GREEN
YELLOW
BLUE
BLUE
YELLOW
GREEN
BLUE
RED
STROOP TASK
Green
Red
Blue
Purple
Blue
Purple
Blue
Purple
Red
Green
Purple
Green
11
SELECTIVE ATTENTION
• Stress narrows attention
• OTHER EXAMPLES:
– Cell phones in car
–?
12
Count the number of times the
ball is passed:
• http://www.youtube.com/watch?v=vJG6
98U2Mvo
13
Inattentional Blindness
Daniel Simons, University of Illinois
Inattentional blindness refers to the inability to
see an object or a person in our midst. Simmons
& Chabris (1999) showed that half of the
observers failed to see the gorilla-suited
assistant in a ball passing game..
14
Change Blindness
• http://www.youtube.com/watch?v=HVw9kWkPX0
15
Change Blindness
Change blindness is a form of inattentional blindness in which
two-thirds of individuals giving directions failed to notice a change
in the individual asking for directions.
© 1998 Psychonomic Society Inc. Image provided courtesy of Daniel J. Simmons.
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INATTENTIONAL
BLINDNESS
• CHANGE DEAFNESS
• CHOICE BLINDNESS
• CHOICE BLINDNESS BLINDNESS
17
POP-OUT, opposite of
inattentional blindness
• A STRIKINGLY
DISTINCT
STIMULUS
AUTOMATICALLY
DRAWS OUR EYE:
accomplished by
parallel processing
18
ATTENTION
•
•
•
•
•
Attentional resources are limited
Attention can be divided
Attention requires effort.
Attention improves mental processing
Control of attention can be voluntary or
involuntary
19
ATTENTION
• Overt vs covert orienting
– Overt: pointing sensory systems at a
particular stimulus Example?
– Covert: Shifting attention without the
appearance of shifting the sensory system
Example?
20
Perceptual Illusions
Illusions provide good examples in
understanding how perception is organized.
Studying faulty perception is as important as
studying other perceptual phenomena. MullerLyer Illusion:
Line AB is longer than line BC.
21
Tall Arch
Rick Friedman/ Black Star
In this picture, the
vertical dimension
of the arch looks
longer than the
horizontal
dimension.
However, both are
equal.
22
Illusion of a Worm
© 1981, by permission of Christoph Redies and
Lothar Spillmann and Pion Limited, London
The figure on the right gives the illusion of a blue hazy
“worm” when it is nothing else but blue lines identical
to the figure on the left.
23
Reprinted with kind permission of Elsevier Science-NL. Adapted from
Hoffman, D. & Richards, W. Parts of recognition. Cognition, 63, 29-78
3-D Illusion
It takes a great deal of effort to perceive this figure in
two dimensions.
24
Reprinted with kind permission of Elsevier Science-NL. Adapted from
Hoffman, D. & Richards, W. Parts of recognition. Cognition, 63, 29-78
3-D Illusion
It takes a great deal of effort to perceive this figure in
two dimensions.
25
Sidewalk Art
http://www.youtube.com/watch?v=fKJ0KY
nB5R8
26
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:
”the whole is greater than the sum of its parts”.
27
PERCEPTUAL
ORGANIZATION
• Sensation (bottom up processing) and
Perception (top down processing) blend into
one continuous process
• Fundamental point: We constantly filter
sensory information and infer perceptions in
ways that make sense to us. Mind matters.
28
Form Perception
Organization of the visual field into objects
(figures) that stand out from their surroundings
(ground). Another example: cocktail party
phenomena
Time Savings Suggestion, © 2003 Roger Sheperd.
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REVERSIBLE FIGURE
GROUND
• Reversible figureground illusions
demonstrate that the
same stimulus can
trigger more than
one perception.
33
REVERSIBLE FIGURE
GROUND
• Reversible figureground illusions
demonstrate that the
same stimulus can
trigger more than
one perception.
34
Grouping
After distinguishing the figure from the ground,
our perception needs to organize the figure into
a meaningful form using grouping rules.
35
GESTALT GROUPING
PRINCIPLES
graphicdesign.spokanefalls.edu/tutorials/p
rocess/gestaltprinciples/gestaltprinc.htm
36
GROUPING
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FIRST IMPRESSIONS
_____1. Sometimes interviewers focus on one trait to the
exclusion of others; this one trait, good or bad, is dominant
against the background of other traits.
_____2. “The purpose of this interview, “ Sarah was told, “is
to gather bits and pieces of information about you so that I
might form an overall, meaningful ‘picture’ of you.”
_____3. Sometimes applicants are compared to other
applicants who are the same age, gender, race, education, and so on.
Interviewers have to avoid this tendency because it prevents their
seeing the person as an individual.
_____4. John sees the whole interview process as one, long continuous
stream of asking questions and gathering information.
_____5. Mrs. Thatcher tends to group interviewees together into her
morning” applicants, afternoon” applicants, and “drop-in’s”,
depending on who comes in with whom during the course of a
day’s appointments.
A. gestalt
B. similarity
C. proximity
D. continuity
E figure-ground
37
Grouping & Reality
Although grouping principles usually help us
construct reality, they may occasionally lead us
astray.
Both photos by Walter Wick. Reprinted from GAMES
Magazine. .© 1983 PCS Games Limited Partnership
38
OTHER GROUPING
PRINCIPLES
• LIKLIHOOD PRINCIPLE: we tend to
perceive objects in the way that
experience tells us is the most likely
physical arrangement
• Auditory scene analysis
– Sound localization
– Visual capture
39
Depth Perception
Innervisions
Depth perception enables us to judge distances.
Gibson and Walk (1960) suggested that human
infants (crawling age) have depth perception.
Depth perception appears to be innate, amplified by
experience
Visual Cliff
40
DEPTH PERCEPTION
• Two dimensional images fall on our retina,
how do we see three dimensionally?
• Depth perception (seeing objects in three
dimensions) allows us to judge distance
41
RETINAL DISPARITY
• Note on the diagram how each eye
sees the object from a different angle
• Retinal disparity = binocular disparity
42
Binocular Cues
Retinal disparity: Images from the two eyes differ. Brain
compares these images, their differences provide cues to relative
distance of different objects 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.
43
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.
Accomodation – muscles surrounding the lens
tightening
44
45
BINOCULUAR CUES
• Hole in the Hand – roll a sheet of paper into a
tube and raise it to your right eye like a
telescope.
• Look through it, focusing on a blank wall in
front of you. Hold open left hand beside the
tube and continue to focus ahead
• The images received by the two eyes will fuse
and the hole in the tube will appear to be in
your hand!
46
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.
47
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.
48
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.
49
Monocular Cues
Texture Gradient: Indistinct (fine) texture
signals an increasing distance.
© Eric Lessing/ Art Resource, NY
50
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
51
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.
52
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.
53
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.
54
Motion Perception
Motion Perception: Objects traveling towards us
grow in size (looming) and those moving away
shrink in size. The same is true when the observer
moves to or from an object. Evolutionary importance
of detecting movement: wiggle your finger demo
55
Apparent Motion
Phi Phenomenon: When lights flash at a certain
speed they tend to present illusions of motion.
Neon signs use this principle to create motion
perception.
Two lights
one
after the Illusion
other. of motion.
One light jumping
from flashing
one point
to another:
56
Perceptual Constancy
Perceiving objects as unchanging even as
illumination and retinal images change. Brain needs
to recognize the object without being deceived by
changes. Perceptual constancies include
constancies of shape and size.
Shape Constancy
57
Perceptual Constancy
• Hold a hand in front of you at arm’s length and move
it toward your head, then away; there will be no
perceived change in size. However, retinal image
size is changing. How can we detect?
• Hold forefinger of left hand about 8 inches in front of
your face and focus on it
• Now position your right hand at arm’s length past
your left forefinger.
• While maintaining fixation on left fingertip, move your
right hand toward and away from your face.’
• Focus on finger, but also notice image of the hand as
it moves. It will change dramatically in size
58
Size Constancy
Stable size perception amid changing size of the
stimuli.
Size Constancy
59
Size-Distance Relationship
The distant monster (below, left) and the top red bar
(below, right) appear bigger because of distance cues.
Cultural experience also influences.
Alan Choisnet/ The Image Bank
From Shepard, 1990
60
Size-Distance Relationship
Both girls in the room are of similar height.
However, we perceive them to be of different
heights as they stand in the two corners of the
room.
Both photos from S. Schwartzenberg/ The Exploratorium
61
Ames Room
The Ames room is designed to demonstrate the size- 62
distance illusion.
Lightness Constancy
The color and brightness of square A and B are the
same. Depends on relative luminance - the amount of 63
light an object reflects relative to its surroundings.
Color Constancy
Perceiving familiar objects as having consistent
color even when changing illumination filters
the light reflected by the object.
Color Constancy
64
COLOR CONSTANCY
• http://www.cnn.com/2009/OPINION/10/
26/lotto.optical.illusions/index.html
65
Perceptual Interpretation
Immanuel Kant (1724-1804) maintained that
knowledge comes from our inborn ways of
organizing sensory experiences.
John Locke (1632-1704) argued that we learn to
perceive the world through our experiences.
How important is experience in shaping our
perceptual interpretation?
66
Restored Vision
After cataract surgery,
blind adults were able to
regain sight. These
individuals could
differentiate figure and
ground relationships, yet
they had difficulty
distinguishing a circle
and a triangle. (Von
Senden, 1932).
67
Facial Recognition
Courtesy of Richard LeGrand
After blind adults
regained sight, they were
able to recognize distinct
features, but were unable
to recognize faces.
Normal observers also
show difficulty in facial
recognition when the
lower half of the pictures
are changed.
68
Sensory Deprivation
Kittens raised without
exposure to horizontal
lines later had difficulty
perceiving horizontal
bars. Influence of
critical periods shown.
Blakemore & Cooper (1970)
69
Perceptual Adaptation
Courtesy of Hubert Dolezal
Visual ability to adjust to
an artificially displaced
visual field, e.g., prism
glasses. Stratton
experiment with optical
headgear.
70
PECEPTUAL ADAPTATION
• Form groups of four or five.
• Pick up a set of goggles and a ball.
• Assign roles: catcher, pitcher, subject
(rotate roles)
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Problems with Schemas
(Allport & Postman, 1947)
73
Allport and Postman
• LEVELING - perceiver drops certain
details because they don’t “fit”
• SHARPENING - details consistent with
values and interests are emphasized
• ASSIMILATION - padding and
organization used to make central
theme fit subject’s expectations
74
Perceptual Set
A mental predisposition to perceive one thing
and not another. What you see in the center
picture is influenced by flanking pictures.
Whisper Down the Lane example.
From Shepard, 1990.
75
PERCEPTUAL SET
• Our Whisper Down the Lane example
was based on Allport and Postman’s
1945 study
• Story was altered to fit the social
expectations and stereotypes of the
subjects.
• Three major perceptual distortions in
transmission of information:
76
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Perceptual Set
Other examples of perceptual set.
Dick Ruhl
Frank Searle, photo Adams/ Corbis-Sygma
(a) Loch ness monster or a tree trunk;
(b) Flying saucers or clouds?
78
Other Examples of Perceptual
Set
• Provide punctuation that will make the
words meaningful:
• “TIME FLIES I CANT THEYRE TOO
FAST!”
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EXPLANATION
• Apostrophes come easily, but the rest is
difficult.
• We’re too familiar with the slogan.
• Think of time as a verb rather than a
noun. Now it makes sense!
80
PERCEPTUAL SET
What determines perceptual set?
• Through experience we form concepts, or
schemas, that organize and interpret unfamiliar
information.
– Example: a child’s simplified drawing of people
• Our innate schemas for faces primes us, especially
attune to the eyes and mouth
81
Schemas
Schemas are concepts that organize and
interpret unfamiliar information.
Courtesy of Anna Elizabeth Voskuil
Children's schemas represent reality as well as their
abilities to represent what they see.
82
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.
83
Eye & Mouth
Eyes and mouth play a dominant role in face
recognition.
Courtesy of Christopher Tyler
84
Context Effects
Context can radically alter perception.
Is the “magician cabinet” on the floor or hanging from the
ceiling?
85
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.
86
Perception Revisited
Is perception innate or acquired?
87
Perception & Human Factors
Human Factor Psychologists design machines
that assist our natural perceptions.
Courtesy of General Electric
Photodisc/ Punchstock
The knobs for the stove burners on the right are easier to
understand than those on the left.
88
Human Factors &
Misperceptions
Understanding human factors enables us to
design equipment to prevent disasters.
Two-thirds of airline crashes caused by human error are
largely due to errors of perception.
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Human Factors in Space
To combat conditions of monotony, stress, and
weightlessness when traveling to Mars, NASA engages
Human Factor Psychologists.
Transit Habituation (Transhab), NASA
90
HUMAN FACTORS
PSYCHOLOGY
• Examples of poor design?
• Why do experts often come up with poor
solutions?
“Curse of knowledge” – the mistaken
assumption that others share our expertise and will
behave as we would
Fail to schedule user-testing to reveal
perception-based problems prior to production and
distribution
91
Is There Extrasensory
Perception?
Perception without sensory input is called extrasensory
perception (ESP). A large percentage of scientists do
not believe in ESP.
PARAPSYCHOLOGY: THE STUDY OF
PARANORMAL PHENOMENON.
92
Claims of ESP
Paranormal phenomena include astrological
predictions, psychic healing, communication with
the dead, and out-of-body experiences, but most
relevant are telepathy, clairvoyance, and
precognition.
93
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.
94
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.
95
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.
96
ESP CLAIMS
• To give ESP credibility, you would need:
A reproducible phenomenon and a theory to
explain it
97
EXPERIMENTAL DESIGN
Representative
Sample (larger
Apply methods of
control
Apply Methods of
control
Population
the better)
Experimental
Group
Independent
Variable
Measure
Dependent
Variable
Random
Assignment
Control
Group
=
Placebo
Is the difference
statistically
significant?
Measure
Dependent
Variable
98
PERCEPTION EXPERIMENT
• Step One: Brainstorm ideas for an
experiment.
• Remember: develop an idea based on a
perceptual concept.
• Develop a hypothesis, with an independent
variable and dependent variable. A good
format for hypothesis: If ________, then
_____.
• Operationally define variables.
99
INTRODUCTION – Why Am I
Doing This Study?
• You will need to research your topic for the
Introduction (review of past research, justify
the logic of the study, and presenting your
hypothesis)
• Check your textbook for background
information. You need to cite two additional
sources in your Introduction.
• Introduction: two pages; last sentence should
be the hypothesis, with iv,dv, op def
100
METHOD – What Did I Do?
• Based on your description of the
apparatus and procedures could
someone replicate your experiment?
• Have separate sections labeled:
Subjects (include description of
population and method of selection),
Procedures (you may number this),
Materials and Apparatus
101
CONSENT FORM
• ..\AP Notes\Perception\Consent Form
for Experiment.doc
102
RESULTS – What Did I Find?
• Graphs, charts, tables that present an
analysis of your findings.
• You do NOT interpret the results in this
section.
• You do not present the raw data here,
but you should include it in an Appendix
if required.
103
DISCUSSION - What is the
Significance of My Findings?
• You relate your findings to your hypothesis
and the theories you investigated. Did you
support your hypothesis? A null hypothesis is
one where no effect is expected.
• You may need to explain why you did not get
the results you expected. Were there
confounding variables, experimenter bias,
etc.?
• Identify new or additional questions raised by
your study.
104
REFERENCES – How Do I Give
Credit Where Credit Is Due?
• Requirement: two sources in addition to
textbook
• You need to use the APA style for your
citations and reference page
• Place appropriate citations in the paper
as well as including a reference page.
• It is better to overcite than to undercite.
105
APA STYLE
• CITATION EXAMPLES:
– the effects of unchecked infections
accumulate (Neese, 1991)
– Carrie Armel and Vilayanur Ramachandran
(2003) cleverly illustrated….
106
APA STYLE
•
Reference Page Examples:
Journal:
Murzynski, J. (1996). Body language of women. Journal of Applied Social
Psychology, 26, 1617 – 1626.
Book:
Paloutzian, R. F. (1996). Invitation to the psychology of religion. (2nd ed.).
Boston: Allyn and Bacon.
Online:
Nielsen, M.E. Notable people in psychology. Retrieved August 3, 2005,
from http://www. psywww.com
Encyclopedia
Shea, J.D. (2004) Depression and Adjustment. In J.F. Schumaker (Ed),
Encyclopedia of Mental Health (pp. 70-84). New York: Oxford /University
Press.
107
APPENDIX
• If necessary, this might include:
– Copies of surveys, pictures, etc used as
materials
– Raw data
108