Conceptual and Perceptual

1
Conceptual and Perceptual
Illusions

• SV Ch 5 Looking for Truth in Personal Experience

2
The Argument

• Perception, memory and reason are reliable but
  not infallible.
• There are errors of reasoning and sensory
  illusions to which all people are prone.
• But if we know about them we can avoid being
  fooled.

3
Concepts

• Veridical and non-veridical experience
• Perception and memory as constructive
• Judgment we can avoid being fooled!
• Conceptual Illusions Informal Fallacies and
  other errors of judgment
• Denying the evidence
• Confirmation bias
• Representativeness heuristic (stereotyping) and
  implicit bias
• Conjunction fallacy
• How conditionals are falsified
• Strength of a proposition

4
Some Errors of Judgment

• Denying the evidence
• Confirmation bias
• Representativeness heuristic (stereotyping) and
  implicit bias
• Conjunction fallacy

5
Angels of Mons
Denying the Evidence
6
Crop Circles
7
More crop circles
8
Confirmation Bias
We look for evidence that confirms a
hypothesis--and tend to ignore data that would
falsify it
A
D
4
7
Hypothesis If a card has a vowel on one side
then it has an even number on the other
9
How do you determine the most effective means for
deciding whether the hypothesis is correct or
incorrect?
A
D
4
7
Most subjects thought that only the A and 4 cards
needed to be turned over.
10
Hypothesis If a card has a vowel on one side
then it has an even number on the other.
A
D
4
7
2
11
Hypothesis If a card has a vowel on one side
then it has an even number on the other.
A
D
4
7
2
E
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Hypothesis If a card has a vowel on one side
then it has an even number on the other.
A
D
4
7
2
6
E
13
Hypothesis If a card has a vowel on one side
then it has an even number on the other.
A
D
4
7
2
6
E
I
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Hypothesis If a card has a vowel on one side
then it has an even number on the other.
A
D
4
7
An even number supports thehypothesis
Turning thiscard iscompletelypointless!
A vowelis consistent with thehypothesis
A vowelfalsifies thehypothesisconclusively
15
For future reference . . .
The hypothesis we were testing was a
CONDITIONAL--an if-then statement. In a
conditional the if clause is called the
antecedent and the then clause is called the
consequent, e.g.
If a card has a vowel on one side then it has an
even number on the other.
A conditional is conclusively shown to be false
if its antecedent is true and its consequent is
false!
16
Representativeness Heuristic (stereotyping)

• The Linda Problem Linda is 31, single, outspoken
  and very bright. She majored in philosophy. As a
  student she was deeply concerned with issues of
  discrimination and social justice and also
  participated in antinuclear demonstrations.
• Rank the following in order of likelihood
• Linda is an insurance salesperson
• Linda is a bank teller
• Linda is a bank teller and is active in the
  feminist movement

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Wheres Linda?
Bank tellers who are feminist activists
Bank Tellers
Feminist Activists
18
A and B cant be more likely
Things that are both A and B

• Predicting A leaves it open whether it is or
  isnt a B too.
• Predicting that its an A and B is riskier!

19
The Conjunction Fallacy

1. Linda is a bank teller and Linda is active in the
   feminist movement.
2. Linda is a bank teller

(1) cant be more probable than (2) because it is
stronger, i.e. conveys more information, than
(2)
A conjunction (and statement) can never be more
probable than one of its conjuncts!
Moral In weakness there is strength!
20
Implicit Bias

• Many cognitive processes that affect behavior are
  unconscious in nature and are inaccessible to
  observation by the actor.
• These implicit processes affect perception,
  influence behavior, and color interpretation of
  past events.

21
The Implicit Association Test

• The IAT requires the rapid categorization of
  various stimulus objects, such that easier
  pairings (and faster responses) are interpreted
  as being more strongly associated in memory than
  more difficult pairings (slower responses).

22
The Implicit Association Test

• The IAT measures the thumbprint of culture on
  our minds.
• 88 percent of white people had a pro-white or
  anti-black implicit bias
• Nearly 83 percent of heterosexuals showed
  implicit biases for straight people over gays and
  lesbians
• More than two-thirds of non-Arab, non-Muslim
  volunteers displayed implicit biases against Arab
  Muslims.

23
The Implicit Association Test

• We all have the thumbprint of culture on our
  minds
• 48 percent of blacks showed a pro-white or
  anti-black bias
• 36 percent of Arab Muslims showed an anti-Muslim
  bias.
• 38 percent of gays and lesbians showed a bias for
  straight people over homosexuals.

24
Real World Consequences

• The results of the IAT are confirmed by real
  world tests of biased behavior
• Economists at the Massachusetts Institute of
  Technology and the University of Chicago recently
  sent out 5,000 résumés to 1,250 employers who had
  help-wanted adsSome applicants were given
  stereotypically white-sounding names such as
  Greg others were given black-sounding names such
  as TyroneEvery employer got four résumés an
  average white applicant, an average black
  applicant, a highly skilled white applicant and a
  highly skilled black applicant.

25
Employers wanted minorities!

• Interviews beforehand with human resources
  managers at many companies in Boston and Chicago
  had led the economists to believe that black
  applicants would be more likely to get interview
  calls.
• Employers said they were hungry for qualified
  minorities and were aggressively seeking
  diversity.

26
Results of the Experiment

• Résumés with white-sounding names triggered 50
  percent more callbacks than résumés with
  black-sounding names.
• High-quality black résumés drew no more calls
  than the average black résumés.
• Highly skilled candidates with white names got
  more calls than average white candidates, but
  lower-skilled candidates with white names got
  many more callbacks than even highly skilled
  black applicants.

27

• "Mind bugs operate without us being conscious of
  them. They are not special things that happen in
  our heart because we are evil."

28
Philosophy kills mind-bugs!
Dont go with your gut!

• If we understand the pecularities of our minds
  at work we can factor them out and make correct
  judgments.

29
Perceptual Illusions
Trust me--Ima politician.
Should we trust the evidence of the senses?
Things are not always as they seem
30
The morals to be drawn from the discussion that
follows

• Perception (and memory) are reliable but not
  infallible.
• Knowledge doesnt require certainty--but we
  should know when to be careful.
• If we know whats going on we can avoid being
  fooled.

31
Perception is constructive

• What we perceive is determined not only by the
  senses but by
• What we know
• What we expect
• What we believe
• What our psychological state is

32
When we should be careful

• Our conclusions are at odds with all known past
  experience
• Our experience is uncorroborated
• Peculiarities of our minds could be at work

I never sawa purple cow
33
Theres is a first time for everything
34
Deceptive Illusions
35
Checks
and more scintillating grids
36
Parallel lines?
The Café Wall Illusion in motion
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Poggendorff Interactive
The Poggendorff Illusion
38
Whats the illusion here?
39
Heres some more of the same
Maybe you dont believe me so
40
Munker-White Illusion
Another color illusion
41
We see what we expect to see
42
We expect to see faces
Face on Mars,Face in beans,...and more faces
43
Ambiguity Illusions
44
What animal?
45
Figure-ground ambiguity
46
Rubin vase
47
Escher Face(s)
48
How old is she?
49
Young Woman/Old Woman
50
Another young/old woman
51
So bigsize and size constancy
52
Look familiar?
Müller-Lyer Illusion (interactive)
53
Im not paranoid
Someone really is out to get me
54
Autokinetic effectillusions of motion

• UFOs
• The Rotating Snake (nausea warning)
• Stepping Feet

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Totally mad illusions!
56
Close up
57
The Greek version
58
Impossible triangle
59
Another impossible triangle
60
Going nowhere fast
61
Escher stairs
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Simpson Stairs
63
Simpson Stairs
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TheEnd