Perception
&
Sensation
Complementary Afterimage #1
Complementary AfterImage #2
Complementary AfterImage #3
Illusion Haze
Top-down vs. Bottom-up Processing
• So far, we have studied the flow of information
from the world into the perceptual system
(bottom-up processing). But there is an equally
important influence of pre-existing knowledge
on our eventual perception of things in the world
(top-down processing).
• That is, our prior experiences and expectations
have a very strong influence on the things we
see. As a result, our perceptions of the world
result from a combination of sensory
information (data-driven) and pre-existing
knowledge (concept-driven).
Prior knowledge guides vision
Prior knowledge guides vision
Face Perception: Which one is Vanna?
Face Perception: Which one is Vanna?
Gestalt Grouping Principles
• group nearby
figures together
Gestalt Grouping Principles:
Proximity
Objects near each other tend
to be seen as a unit
Gestalt Grouping Principles
• group figures
that are similar
Gestalt Grouping Principles:
Similarity
Objects similar to each
other tend to be seen as a
unit
Gestalt Grouping Principles:
Similarity
Objects similar to each
other tend to be seen as a
unit
Gestalt Grouping Principles
• Fill in gaps to
create a complete,
whole object
Gestalt Grouping Principles:
Closure
• Fill in gaps to
create a complete,
whole object
•But, doesn’t the
white triangle look
whiter than the
background?
Gestalt Grouping Principles:
Continuity
• Objects that are
connected by a
smooth curve tend to
be seen as a unit
Gestalt Grouping Principles:
Common Movement
• Objects moving in the same speed and at
the same direction tend to be grouped
•The Hidden Bird Illusion
•THIS IS THE APPLET
Gestalt Grouping Principles:
Common Movement
• Which direction are the triangles pointing?
Who do you see?
What do you see?
Depth Perception
How do we create a 3 dimensional world
from 2 dimensions?
Stereogram
•Cross eyes so that the left eye is looking at the right square
and the right looking at the left
•Try ‘fixating’ on an imaginary point in front of the viewing
screen at which point you will see three squares- left center
and right. The center one will be the stereo image
Relative Size
Perceived Size and Perceived Depth
• To perceive the size
of objects accurately
we must also perceive
their distance
accurately.
• Thus, many visual
illusions occur simply
because a particular
image lacks sufficient
depth cues.
Retina
Image
Image
Pupil
A
B
A
This figure shows that image size depends
upon both object size and distance
The Size-Distance Problem
• The Ames room is designed so that the
monocular depth cues give the illusion that the
two people are equally far away
Other Size-Distance Illusions
• In each of these
examples, the top
and bottom lines are
actually the same
length.
• In each case the top
line looks longer.
• Why?
(a) Müller-Lyer illusion
(b) Ponzo illusion
Muller-Lyer Illusion
• Perceptual psychologists
have hypothesized that the
top horizontal line looks
longer because it also looks
farther away.
• Specifically, the inward
pointing arrows signify that
the horizontal line is closest
to you, and the outward
pointing arrows signify the
opposite case.
Ponzo Illusion
• Converging lines indicate that top line is
farther away than bottom line
Another Size-Distance Illusion
Another Size-Distance Illusion
Linear Perspective
Texture Gradients
The elements of a texture become smaller and smaller as
they recede into the distance...another reliable depth cue.
Cues to Depth Perception
Texture Gradient
Cues to Depth Perception
Texture Gradient
Which Triangle is closer?
Relative Height
horizon line
Objects closer to the horizon appear to be farther away...
Cues to Depth Perception
Relative Height
Size Constancy
• Cylinders at
positions A and B
are the same size
even though their
image sizes differ
• The depth cues such
as linear perspective
and texture help the
visual system judge
the size accurately
Point B
Point A
Shape Constancy
• It is hard to tell if the
figure on the upper
right is a trapezoid or
a square slanted
backward.
• If we add texture, the
texture gradient helps
us see that it is
actually a square.
Attention Demos
The Stroop Effect, part 1
As fast as you can,
read the names
of the colors
The Stroop Effect, part 2
As fast as you can,
(don’t read the
word) but read the
name of the color
of the word.
The Stroop Effect, part 2
As fast as you can,
(don’t read the
word) but read the
name of the color
of the word.
The Stroop Effect, part 2
As fast as you can,
(don’t read the
word) but read the
name of the color
of the word.
Attention as a Selector: Find the
Green Scarf
Attention as a Selector: Find the
Bald Man
Selection Based on Color is Easy
Selection Based on upright vs
upside down is not easy
Treisman’s Feature Integration Theory
The following is a demonstration that (a) detecting features is
relatively automatic, and (b) that integrating multiple features
together and identifying the object is more attention-demanding.
Slap your thigh when you
see the blue line.
Detecting the blue line was pretty easy, right? Is
orientation also easy to detect?
Slap your thigh when you
see the horizontal line.
Identifying Integrated Features
Conjunction Search
When targets are defined by:
• Combination of features (e.g., red AND horizontal)
• Spatial arrangements of features (e.g. black above white)
Slap your thigh when you see the bar that
is both horizontal AND blue
So, the conjunction of color and orientation does not
pop out.
What about the spatial arrangement of a basic visual
feature?
Slap your thigh when you find the black
square above the white square:
Can you attend to
something without
moving your eyes?
Stare at the cross
+
X
L
H
Q
+
C
M
P
E
What were the letters that you saw?
+
Now, focus on the cross but pay
attention to the right side.
+
U
D
I
F
+
O
S
W
N
What were the letters?
+
Attending without moving eyes
• Focus of attention does NOT depend on where your
eyes are pointing. We can move our attention
independently of our eyes. You can look one way and
attend to something that is elsewhere. WHY?
• Attention amplifies our ability to sense information.
• Who has noticed that events seem to slow down when
you’re in an accident? Perhaps there’s an expansion of
time that occurs when you strongly attend to something?
Attention as a
“Selection Mechanism”
What happens to stuff we don’t attend to?
+
While looking at the center plus sign, attend to the
yellow cross and report whether its vertical or
horizontal bar is longer
Stare at the cross
+
Attend Here
+
Which was longer?
Stare at the cross
+
Attend Here
+
Which was longer?
Stare at the cross
+
Attend Here
stint
Which was longer?
Who noticed the word “stint”???
Visual Version of Experiment
Task: Is this a word you find
generally positive? YES/NO.
+
Fish
Mouse
Land
House
Rabbit
Lemon
Idea
• Subjects have virtually no memory of the
unattended objects in a visual version of the
dichotic listening task.
• Attention is a gateway to memory. You will
not consciously remember stuff that is not
attended to.
How Powerful is our ability to attend to
something?
How powerful of a selector mechanism
is attention?
Some Video Examples
Your Task
Count the number of
passes of the ball by the
members on the White
Team.
Attentional Deficits
Left Visual Neglect
• Inability or difficulty to attend to the left
side of visual space or of an object. Caused
by lesion in the right parietal lobe.
Line-bisection task
Memory Demos
Sensory Memory Demonstration
Focus on the cross
+
Sensory Memory Demonstration
X
M
D
N
I
F
B
Z
Sensory Memory Demonstration
What were all of the letters?
Sensory Memory Demonstration
Focus on the cross
+
Sensory Memory Demonstration
Q
U
C
L
T
J
R
M
Sensory Memory Demonstration
• Report the letter that was where the arrow points
--
--
--
--
--
--
--
--
Visuo-Spatial Sketchpad
Demonstration
• Examine this boat for a minute
Visuo-Spatial Sketchpad
Demonstration
Was the anchor closer to the front or to the
center of the boat?
Chunking: An Example
• Remember these 19 numbers
• Write them down when I’m finished
Chunking
• Chunk: a category of information that lets
you group/organize underlying items.
• Here were the numbers:
1776 2002 24/7 911 22904
Our short term memory capacity is 7 plus or
minus 2 chunks of information.
Amnesia
caused by damage
to hippocampus
and/or surrounding
areas
•
• See the Jeremy
video
• Remember the
Clive video
Hippocampus
Which is the real penny?
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(m)
(n)
(o)
(k)
(l)
Answer
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(m)
(n)
(o)
(k)
(l)
Class Demonstration
As fast as you can, unscramble the words on
the sheet of paper. Turn the page over when
you’re finished.
Class Demonstration
Raise your hand if you spelled the last word as
PETAL
Raise your hand if you spelled the last word as
PLATE
Priming Example #2
• There were two sets of scrambled words
preceding the last one. One set was related to
kitchen items.
All related
to
•
•
•
•
•
F I N E K --> KNIFE
K R O F --> FORK
P U C --> CUP
E C U S A R --> SAUCER
L T E P A --> PLATE
Priming Example #2
• The other set was related to flowers.
All related
to
•
•
•
•
•
NYPAS --> PANSY
FELA --> LEAF
KTALS --> STALK
LOBSOMS --> BLOSSOMS
L T E P A --> PETAL
Priming Example #2
• Whether you deciphered LTEPA as “Plate” or
as “Petal” was likely influenced by the
preceding words.
• These preceding words primed (i.e,.
activated) either Plate or Petal.
A 3 minute Task
Spend the next 3 minutes writing down as many
U.S. states as you can.
Face memory test
100
Face Memory Results
80
60
40
20
0
Don’t Describe Face
100
Face Memory Results
80
60
Why are people worse
after describing the face?
40
20
0
Don’t Describe Face Describe Face
Social Demos
The Attribution Scale Task
Each row contains a pair of adjectives and a
“Depends on the situation” response.
I want you to rate George Bush. Put a
CHECK (do not circle) next to the item that
is most characteristic of George Bush.
While driving through a rural area near your home you are
stopped by a county police officer who informs you that you
have been clocked (with radar) at 38 miles per hours in a 25mph zone. You believe this information to be accurate. After
the policeman leaves, you inspect the citation and find that the
details on the summons regarding weather, visibility, time, and
location of violation are highly inaccurate. The citation
informs you that you may either pay a $50 fine by mail
without appearing in court or you must appear in municipal
court within the next two weeks to contest the charge.
•
Which option would you choose?
(a)
•
pay fine
(b) contest charge
What % of the people in this class do you estimate would pay
the fine? _______
False Consensus:
Tendency to see one’s own choices and opinions as
more common than they are
Class results from last year
47% said they would pay fine
They estimated that: _38_% would contest
_62_% would pay
53% said they would contest the charge
They estimated that: _64_% would contest
_36_% would pay
A Judgment Task
• All subjects perform a boring task for 1 hour, and are
then asked to lie to the next subject and say that the
experiment was fun and exciting.
• Subjects are paid either $1 or $20 to lie.
• Finally, all subjects privately rate how much they
enjoyed the initial task.
• Question: Which subjects reported that they enjoyed
the initial task more? Will the subjects paid $1 or those
paid $20 rate the task as more enjoyable?
Measuring Implicit Stereotypes
The Implicit Association Test
for more information: www.yale.edu/implicit
Unpleasant
Pleasant
abuse
crash
filth
murder
sickness
accident
caress
freedom
health
love
peace
cheer
Old People
Young People
LEFT
for
Unpleasant
murder
love
crash
freedom
peace
filth
abuse
caress
cheer
accident
health
sickness
RIGHT
for
Pleasant
LEFT
for
Old
RIGHT
for
Young
cheer
sickness
LEFT
for
Unpleasant
or
Old
murder
peace
accident
RIGHT
for
Pleasant
or
Young
LEFT
for
Young
RIGHT
for
Old
love
crash
LEFT
for
Unpleasant
or
Young
filth
health
abuse
RIGHT
for
Pleasant
or
Old
Personality Demos
Social-Cognitive Perspective
• External Locus of Control
– the perception that chance or outside forces
beyond one’s personal control determine
one’s fate
• Internal Locus of Control
– the perception that one controls one’s own
fate
On a sheet of paper, write a series of numbers from 1 to 18.
For each of the following questions, imagine the situation
happening to you, even if it never has. Next, write down the
alternative (either A or B) that you prefer. Always record an
alternative, even if both are equally preferable.
1. You get very good grades in a course.
A. I am a hard worker.
B. School work is simple.
2. You feel stronger and more energetic.
A. This season of the year makes me feel better.
B. I feel better when I exercise.
3. A salesperson is very unpleasant to you.
A. I am always polite, even to unpleasant people.
B. I can be unpleasant at times.
4. You fail to get the promotion you want.
A. I didn’t work as hard as I could have.
B. The company suffered a loss and could not
promote anybody.
5. You get picked to represent your neighborhood
association at a dinner with the mayor.
A. It was my turn to go.
B. I showed great interest in going.
6. You read an article that contradicts your views.
A. I don’t mind when people disagree with me.
B. I never get angry. I always stay calm and collected.
7. A friend is avoiding you.
A. Once in a while I am mean to other people.
B. Once in a while people are mean to me.
8. Your doctor tells you that despite her recommendations,
you still eat too much salt.
A. Salt is in everything -- you can’t avoid it.
B. I don’t pay much attention to my diet.
9. A friend invites you to dinner.
A. My friend feels lonely and wants some company.
B. I make pleasant and interesting company.
10. You have a disagreement with a neighbor.
A. Once in a while I may lose my temper and get angry.
B. I never get angry. I always stay calm and collected.
11. Your spouse/friend says that you don’t share thoughts
with him/her.
A. I share with my spouse/friend even my most
personal and intimate thoughts.
B. I sometimes have ideas that I do not like other
people to know about.
12. Your boss criticizes you.
A. He is a critical person.
B. I am a poor worker.
13. You make a new friend.
A. I am a nice person.
B. The people that I meet are nice.
14. A friend who helped you when in need asks to borrow a
large sum of money.
A. I am always eager to return a favor.
B. Lending money to a friend can be a problem.
15. Your spouse/friend yells at you.
A. I must have done something wrong to upset him/her.
B. He/she has a quick temper.
16. Your friend is making a long argument that you want to
comment on.
A. I never interrupt others when they are talking.
B. I sometimes interrupt others when they are talking.
17. You’ve recovered very quickly from the flue.
A. I have a good resistance because I take care of my health
B. Fortunately, it was a minor flue.
18. You twist your shoulder in exercise class.
A. The instructor pushed us too hard.
B. I was not careful in exercise class.
For questions 1, 4, 7, 13, 15, and 17: give yourself a 1 if
you selected A and a 0 if you selected B.
[Alternative A corresponds to an internal locus of
control]
For questions 2, 5, 8, 9, 12, and 18: give yourself a 1 if you
selected B and 0 if you selected A.
[Alternative B corresponds to an internal locus of
control]
Now, add up your total number of points.
Raise your hand if your score is below 6
Raise your hand if your score is below 6
High scores --> associated with an internal locus of control
Low scores --> associated with an external locus of control
Mental Disorders Demos
Dissociative Amnesia
• Marian and her brother were recently
victims of a robbery. Marian was not
injured, but her brother was killed when
he resisted the robbers. Marian is unable
to recall any details from the time of the
accident until four days later.
Dissociative Amnesia
• Memory loss is the only symptom
– Often selective memory loss surrounding
traumatic events
• Key characteristic is that the person still
knows their identity.
Dissociative Fugue
• Jay, a high school teacher in New York,
disappeared three days after his wife
unexpectedly left him for another man. Six
months later, he was discovered tending bar in
Miami Beach. Calling himself Martin, he
claimed to have no recollection of his past life
and insisted that he had never been married.
Dissociative Fugue
• Global amnesia with identity replacement
– Person develops a new identity
– No recollection of former life
• If fugue wears off
– old identity recovers
– new identity is totally forgotten
Dissociative Identity Disorder
(DID)
• Norma has frequent memory gaps and cannot
account for her whereabouts during certain
periods of time. While being interviewed by a
psychologist, she began speaking in a childlike
voice. She claimed that her name was Donna
and that she was only six years old. Moments
later, she seemed to revert to her adult voice
and had no memory of speaking in a childlike
voice or claiming that her name was Donna.
Dissociative Identity Disorder
(DID)
• Originally known as “multiple personality
disorder”
• 2 or more distinct personalities manifested by
the same person at different times
• VERY rare
• Can vary in severity (see video)
Intelligence Demos
Are There Multiple Intelligences?
• Savant Syndrome
– condition in which a person, otherwise limited in
mental ability, has an amazing specific skill
• computation
• drawing
Savants
George and Charles
Could instantly compute
the day of week for any
given date over a span of
80,000 years
But, IQ between 40 -70
Modern intelligence tests
• The Stanford-Binet Scale
– intelligence quotient (IQ) = child’s mental age
divided by child’s chronological age and then
multiplied by 100
– IQ = MA/CA x 100 (CA = Chronological age)
» E.g., IQ = 13/10 x 100 = 130
– used widely in the US, not as much as previously
Stanford-Binet Scale
The Intelligence Quotient (i.e., MA/CA) is absurd
when applied to adults.
Hence, the following joke:
Thinking Demos
Some True/False Questions
1. We notice evidence that contradicts our beliefs more
readily than evidence that is consistent with them.
2. In general, people underestimate how much they
really know.
3. Only humans seem capable of insight (I.e., the sudden
realization of a problem’s solution).
Problem
Write down the names of 6 U.S. cities that
are WEST of San Diego.
Here’s the kicker: each city must be in a
different state (6 cities from 6 different
states.)
Problem
Write down the names of 6 U.S. cities that
are WEST of San Diego.
Reno is West of
San Diego
Falling Object Problem
Spiral Tube Problem
Confirmation Bias
Below are four cards. Each card has a letter on one side and a
digit on the other side. You are to verify whether or not the
following rule is true: If there is a vowel on one side, there is
an even number on the other side. You should verify this rule
by turning over 2 cards. Which cards do you choose?
A
2
X
3
Verify Rule: If there is a vowel on one side, there is an even
number on the other side.
A
2
X
3
Answer: A and 3
If there’s a vowel on the other side of
the 3 card then the rule is dead
Most people choose “A” and “2”. Why?
Because of a confirmation bias.
Confirmation Bias
People generally seek evidence that will confirm, not falsify, a
hypothesis
It would seem, then that we stink at logic.
But . . . .
IF A PERSON IS DRINKING BEER, THEN THE
PERSON MUST BE OVER 21 YEARS OF AGE. Select
the 2 cards that you definitely need to turn over to
determine whether or not they are violating the rule.
Beer
22
Coke
17
• Solve problems and syllogisms by applying
information to pre-existing schemas
• More relevant = easier to solve
• The Bottom Line: People are not logic machines
who can plug any problem into a logical formula
Representativeness Heuristic
Linda is 31 years old, single, outspoken and very
bright. As a student, she was deeply concerned
with issues of discrimination and social justice,
and also participated in anti-nuclear
demonstrations.
What is the probability that Linda is a….?
Representativeness Heuristic
Linda is 31 years old, single, outspoken and very
bright. As a student, she was deeply concerned
with issues of discrimination and social justice, and
also participated in anti-nuclear demonstrations.
What is the probability that Linda is a Bank Teller?
Write a number between 0 and 100
Representativeness Heuristic
Linda is 31 years old, single, outspoken and very
bright. As a student, she was deeply concerned
with issues of discrimination and social justice, and
also participated in anti-nuclear demonstrations.
Representativeness Heuristic
Linda is 31 years old, single, outspoken and very
bright. As a student, she was deeply concerned
with issues of discrimination and social justice, and
also participated in anti-nuclear demonstrations.
What is the probability that Linda is a Feminist
Bank Teller?
Write a number between 0 and 100
Representativeness Heuristic
Time after time, people say that there’s a higher
likelihood that Linda is a feminist bank teller
than that she’s a bank teller. But this is
impossible because:
Feminist Bank Tellers are a sub-group of Bank
Tellers.
• Representativeness Heuristic
– rule of thumb for judging the likelihood of
things in terms of how well they seem to
represent, or match, particular prototypes
– However, it can cause people to generalize too
broadly from single cases.
Availability Bias
• Is the letter “k” most likely to occur in the first
position of a word or the third position?
• Answer: “k” is 2-3 times more likely to be in
the third position
• Most people respond that “k” is more frequent
in the first position. Why does this occur?
Availability Heuristic
• Because it is easier to recall words starting
with “k” , people overestimate the number of
words starting with “k”
Which of the following are more frequent causes of death in
the U.S.?
Rate how confident you are in your choice on a scale from 0
(guessing) to 100 (absolutely certain that your choice is correct).
1. All accidents or strokes?
confidence rating?
2. Electrocution or asthma?
confidence rating?
3. Homicide or diabetes?
confidence rating?
4. Lightning or appendicitis?
confidence rating?
5. Drowning or Leukemia?
confidence rating?
Which of the following are more frequent causes of death in
the U.S.?
1. All accidents (55,000) or strokes (102,000)
2. Electrocution (500) or asthma (920)
3. Homicide (9200) or diabetes (19,000)
4. Lightning (52) or appendicitis (440)
5. Drowning (3600) or Leukemia (7100)
• Availability Heuristic
– estimating the likelihood of events based on
their availability in memory
– if instances come readily to mind (perhaps
because of their vividness), we presume such
events are common
– We tend to be overly influenced by events that
come easily to mind
Language and Development
Critical Stage & Language
Genie spent her first 14 years
confined to a small bedroom
and weighed just 59 pounds
when discovered. She never
learned to speak in complete
sentences.
Konrad Lorenz & Imprinting