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Unit 4 Sensation and Perception pt. 2
http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/index.html
Perception a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events
Stare at the black dot in the middle. You should see the outer edges of the circle fade away!
http://www.thedesignwork.com/65-amazing-optical-illusion-pictures/
Selective Attention
• Focusing conscious awareness on a particular stimulus to the exclusion of others
• The ability to focus on one stimulus at a time
• Allows a person to function in a world filled with many stimuli
• People with ADD have trouble doing this.
What Does This Say? Now Read It Again!
Selective Attention Test
http://www.youtube.com/watch?v=vJG698U2Mvo
Inattentional blindness refers to the inability to see an object or a person in our midst. Simmons & Chabris (1999)
An example of selective attention is:
Cocktail Part Effect: ability to listen to one voice among many.
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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.
Dateline: Did you see that? July 16, 2010 http://www.msnbc.msn.com/id/38154937/ns/dateline_nbc-the_hansen_files_with_chris_hansen/
Color Vision
Two Major Theories
Trichromatic Theory
Three types of cones:
• Red
• Blue
• Green
• These three types of cones can make millions of combinations of colors.
• Does not explain afterimages or color blindness well.
Opponent-Process theory
The sensory receptors come in pairs.
• Red/Green
• Yellow/Blue
• Black/white
• If one color is stimulated, the other is inhibited.
Opponent Processing Theory
Does this make your eyes all
weird out??
Opponent processing theory: we see in pairs
Psychology, 4/e by Saul Kassin ©2004 Prentice Hall
Afterimage is where you see the image afterwards.
Opponent Process- Afterimage Effect They are caused by fatigued cells in the retina
responding to light.
• Stare at the eye of the red parrot while you count slowly to 20, then look immediately at one spot in the
empty bird cage. The faint, ghostly image of a blue green bird will appear in the cage.
• Try the same thing with the green cardinal. A faint magenta bird will appear in the cage.
• The ghostly birds you see here are called afterimages. An afterimage is an image that stays with you even
after you have stopped looking at an object. The back of your eye is lined with light sensitive cells, called
cones, which are sensitive to certain colors of light. When you stare at the red bird, your red-sensitive cones
adapt to the light and lose their sensitivity. When you shift your gaze to the white background of the bird
cage, you see white (minus red) where the red-sensitive cells have become adapted. White light minus red
light is blue-green light. That's why the afterimage you see is blue-green and in the shape of a parrot. The
same thing happens when you stare at the green bird, but this time it's the green-sensitive cones that adapt.
White minus green light is magenta light, so you see the afterimage as a magenta cardinal.
http://www.michaelbach.de/ot/col_lilacChaser/index.html
Sensation and Perception • Perception is essentially an interpretation and
elaboration of sensation. Therefore, sensation refers to the initial steps in the processing of a stimulus.
These pictures should look similar
The True Picture
The Famous Mona Lisa…Frown or Smile
The Famous Mona Lisa…Frown or Smile
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 r i e n c e s
“ S t a r s p a n g l e d _ _ _ _ _ _ _ _ _ _ _ _ _ _ ”
2 . M o o d s , A t t i t u d e s , a n d V a l u e s
H a v i n g a b a d d a y a n d “ t h i n g s ” s e e m t o s n o w b a l l
3 . N e e d s
I f y o u ’ r e h u n g r y , y o u t h i n k a b o u t …
4. What the group believes
W e h a v e a t e n d e n c y t o , “ g o a l o n g w i t h t h e c r o w d . ”
S E E I N G – H E A R I N G – T O U C H I N G – T A S T I N G – S M E L L I N G
• What is seen in the center figures depends on the order in which one looks at the figures:
– If scanned from the left, a man’s face is seen.
– If scanned from the right, a woman’s figure is seen.
Psychology, 4/e by Saul Kassin ©2004 Prentice Hall
Perceptual Set is a tendency to perceive or notice some aspects of the available sensory data and ignore others.
Perceptual Set is a tendency to perceive or notice some aspects of the available sensory data and ignore others.
Perceptual Set is a tendency to perceive or notice some aspects of the available sensory data and ignore others.
Bruner & Minturn, 1955 illustrated how expectation could influence set by showing participants an ambiguous figure '13' set in the context of letters or numbers e.g.
The physical stimulus '13' is the same in each case but is perceived differently because of the influence of the context in which it appears. We EXPECT to see a letter in the context of other letters of the alphabet, whereas we EXPECT to see numbers in the context of other numbers.
Auditory Illusions
If the sounds do not work click here for link.
38
Perceptual Illusions
Illusions provide good examples in understanding how perception is organized. Studying faulty perception is as important as
studying other perceptual phenomena.
Line AB is longer than line BC.
39
The images are exactly the same except for the thick black area in the right image (an example of the Poggendorff illusion (1860)). In the figure on the right, there appear to be two continuous diagonal lines: a red and a blue line. What occurs in your visual system that could account for the appearance of the continuous diagonal lines?
40
3-D Illusion
It takes a great deal of effort to perceive this figure in two dimensions.
Rep
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Impossible Triangle
44
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.
Perceptual Illusions
Perceptual Constancies 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.
Psychology, 4/e by Saul Kassin ©2004 Prentice Hall
The image above is constructed from about 7,000 randomly placed dots. In a sequence of frames, the dots in a square were randomized again, such that each of the subsequent frames has a different randomization pattern in a selected square area. The squares selected for randomization were constructed from 1/10 of the X and Y values progressively from the lower left to the upper right along the diagonal of the matrix. Dots change randomly within the succession of squares, but no dots move along the diagonal, despite the appearance that they do.
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
What if we could sense everything?
Life would hurt.
So we can only take in a window of what is out there.
This is the study of psychophysics: relationship between physical stimuli and our psychological experiences to them.
Flying Saucers or Clouds?
Binocular Cues
• We need both of our eyes to use these cues.
• Retinal Disparity (as an object comes closer to us, the differences in images between our eyes becomes greater.
• Convergence (as an object comes closer our eyes have to come together to keep focused on the object).
68
Organization of the visual field into objects (figures) that stand out from their surroundings
(ground).
Form Perception
Tim
e Sav
ings S
uggestio
n, ©
2003 R
oger S
hep
erd.
Grouping Principles Gestalt
• 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
Perceptual Organization Gestalt Laws of Grouping
71
1. Closure
2. Proximity
3. Continuity
4. similarity
Proximity
Perceptual Organization: Closure
Gestalt grouping principles are at work here.
Do you see triangles?
Perceptual Organization: Grouping Principles
Gestalt grouping principles are at work here.
78
Grouping & Reality
Although grouping principles usually help us construct reality, they may occasionally lead us astray.
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The General's Family There are 9 people in this picture, called The Generals Family, which is a work by the Mexican artist Octavio Ocampo. There are nine different faces in this picture combining to make up the face of the General and to tell the story and the secrets of his life. Although perceived as a distinguished gentleman of solid stock, the images of his past betray his emergence from a peasant family and his impoverished beginnings. We see his mother and father, his wife and other members of his family, even his dog (masquerading as his hand) and as you study the painting you see behind the facade and read the story of a remarkable life...
A Man With Ivy Leaves Around Him, but Do You See a Couple Kissing?
83
Depth Perception
Visual Cliff
Depth perception enables us to judge distances. Gibson and Walk (1960) suggested that human
infants (crawling age) have depth perception. Even newborn animals show depth perception.
Inner
vis
ions
85
Binocular Cues
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.
86
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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88
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.
89
Monocular Cues Interposition: Objects that occlude (block) other
objects tend to be perceived as closer. R
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Carafelli.
90
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.
91
Monocular Cues Texture Gradient: Indistinct (fine) texture signals
an increasing distance.
© E
ric Lessin
g/ A
rt Reso
urce, N
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Monocular Cues
Relative Height: We perceive objects that are higher in our field of vision to be farther away than those that are lower.
Imag
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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.
94
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.
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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.
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This illusion has been around for a while, and we were recently reminded of it again by Chris Stevenson, from London.
Hard as it may be to believe, the two squares A and B are actually the same color. There are different ways of proving this, and we have seen some elegant solutions.
http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/shadow___ball.html
http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/shadow.html Shadow one
• Brain Games 1
http://www.youtube.com/watch?v=PN1NAiM55hU&feature=related
100
Size-Distance Relationship
The distant monster (below, left) and the top red bar (below, right) appear bigger because of
distance cues.
Fro
m S
hep
ard, 1
99
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Alan
Cho
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Psychology, 4/e by Saul Kassin ©2004 Prentice Hall
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.
102
Perceptual Constancy
Perceiving objects as unchanging even as illumination and retinal images change. Perceptual constancies include constancies of shape and size.
Shape Constancy
104
Kittens raised without exposure to horizontal lines later
had difficulty perceiving horizontal
bars.
Blakemore & Cooper (1970)
Sensory Deprivation
105
Perceptual Adaptation
Visual ability to adjust to an artificially
displaced visual field, e.g., prism glasses.
Courtesy
of H
ubert D
olezal
106
Students recognized a caricature of Arnold Schwarzenegger faster than his actual photo.
Features on a Face
Face schemas are accentuated by specific features on the face.
Kieran
Lee/ F
aceLab
, Dep
artmen
t of P
sych
olo
gy,
Un
iversity
of W
estern A
ustralia
107
Eye & Mouth Eyes and mouth play a dominant role in face
recognition.
Co
urtesy
of C
hristo
pher T
yler
Portrait artists understood the importance of this recognition and therefore centered an eye in their paintings.
108
To an East African, the woman sitting is balancing a metal box on her head, while the family is sitting under a tree.
Cultural Context
Context instilled by culture also alters perception.
109
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.
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
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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.
112
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.
113
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.
Subliminal Stimulation
• Below one’s absolute threshold for conscious awareness.
• Show clip
Does this work?
Yes and No
•Slide studies showed some emotional reactivity (called priming a response).
•The effects are subtle and fleeting.
Subliminal Messages
Stimuli below our absolute threshold. Backmasking 25th frame Do Subliminal Messages work? Probably a placebo effect
1) The Pepsi Cool Can
In 1990, Pepsi actually withdrew one of its “Cool Can” designs after someone protested that Pepsi
was subliminally manipulating people by designing the cans such that when six-packs were stacked
at grocery stores, the word SEX would emerge from the seemingly random design. Critics alleged
that the red and blue lines on the “Cool Can” design were far from random <27>.
Backmasking
• http://jeffmilner.com/backmasking/index.html
