Transcript Cognitive Biases 2 - Michael Johnson's Homepage

Cognitive Biases 2
Confirmation Bias
COURSE REVIEW
Course Instructor
Office: HSH (Ho Sin Hang) 213
Office Hours
Friday 14:00-16:00
My Email
michael.dracula.johnson@
gmail.com
Course Website
michaeljohnsonphilosophy.com
Course Meeting Times
Tuesday 15:00-16:30 LKK 103
Friday 9:30-11:00 LKK G05
ASSESSMENT
Reading
There is no required reading in this class.
There is lots of optional reading on the course
website. I may give bonus marks to students
who can answer questions in class about the
optional reading!
Assessment
10 short homework assignments, each 6 marks,
for a total of 60 marks.
Attendance: 10 marks
Participation: 10 marks
1 final exam, worth 20 marks
Short Homework Assignments
Every week we will have a homework
assignment where you apply what we’ve
learned that week.
Example…
Out of Context
In Context
HW1
Find an example, from your own life and
experiences, where a piece of information was
taken out of context in a misleading way.
Rubric
• Describe the information taken out of context:
1 mark
• Describe the claim the information was used
to support, and who was making the claim:
2 marks
• Describe the broader context and why the
information presented was misleading:
2 marks
• Students’ own experience: 1 mark
Late Assignments
I won’t accept late homework. Even 1 minute
late is late. Sorry.
Participation
Participation is just like HW1.
You cannot get an ‘A’ in this course if you do not
participate.
I will give you 1 mark for every (good) example
up to 10 marks.
Attendance
Attendance is required and accounts for 10% of
your final grade.
You cannot get an ‘A’ in this course if you do not
attend classes.
Every day you don’t attend, you lose 0.5 marks
off your final grade, up to a maximum of 10.
Late to Class
You will not be counted as present if you show
up after I have called attendance. Please be in
class on time.
Final Exam
The final exam will happen during the scheduled
exam period. Exact time/ date TBA.
It will consist of short answer questions and
involve application of critical thinking skills.
It is worth 20 marks.
Curve Based Grading
SUBJECT REVIEW
Critical Thinking
Is there any evidence to support the claim?
Is the evidence reliable and trustworthy? How
reliable is it? Should you accept it?
Does the evidence actually support the claim?
Is there other evidence you should consider?
Critical Thinking and Skepticism
“Skepticism [critical thinking]… is essentially a
form of basic intellectual hygiene, something
that everyone is capable of to varying degrees
and something that everyone should do.”
-- Chris Clarke
Critical Thinking as Mental Hygiene
“Skepticism is to the intellect as brushing is to
teeth. Sometimes we need expert assistance,
but the only way it really does us any long term
good is if we engage in the practice of mental
hygiene as a habit, preferably after each bout of
consuming something that might cause
problems down the road, whether it’s a bag of
chips or an article in the New York Toast.”
Difference
“There is one thing where skepticism differs
from toothbrushing.
There aren’t legions of non-toothbrushers who
pour support and money towards cranks that
tell them to keep their mouths dirty.” – vaiyt
(Comment #20)
WASON SELECTION TASK
Even vs. Odd
Even numbers: 2, 4, 6, 8, 10, 12…
Odd numbers: 1, 3, 5, 7, 9, 11, 13…
Wason Selection Task
Suppose that I present you with four cards. On each
card there is a number on one side and a color
(blue or red) on the other. I claim:
If a card has an even number on one side
then it is blue on the other side.
Which of the four cards do you need to turn over to
tell whether this claim is true or false?
A
B
C
D
Results!
Wason Selection Task
Card A doesn’t matter. First possibility:
1. The other side is blue. The claim says if it’s
even, then it’s blue. It does not say that if it’s not
even, then it is not blue.
Example
True claim: if a student makes an appointment,
she can see me in my office.
Does not mean false claim: if a student does not
make an appointment, she cannot see me in my
office.
Wason Selection Task
Card A doesn’t matter. Second possibility:
2. The other side is red. The claim says even
cards can’t be red. It does not say odd cards
can’t be red.
A
B
C
D
Wason Selection Task
Card D doesn’t matter. Two possibilities:
1. The other side is even (for example, it’s “4”).
The claim says if it’s even, then it’s blue. It does
not say that if it’s blue, then it’s even.
Example
True claim: If something is a dog, then it is an
animal.
Does not mean false claim: if something is an
animal, then it is a dog.
Wason Selection Task
Card D doesn’t matter. Two possibilities:
2. The other side is odd (for example, it’s “3”).
The claim says if it’s even, then it’s blue. It does
not say that if it’s not even, then it is not blue.
A
B
C
D
Wason Selection Task
Card B is important.
4 is an even number. If other side of card B is
red, then the claim is false, because B is a card
with an even number on one side but it is not
blue on the other side.
You must turn over B and make sure it is not red
on the other side.
A
B
C
D
Wason Selection Task
Card C is also important.
If the claim is true, this card must have an odd
number on the other side. If it has an even
number on the other side, then the claim is
false.
You must turn over #3 and make sure there is
not an odd number on the other side.
Statistical Results
Around ½ of people studied say “B: 4” and “D:
Blue”.
About 1/3 say just “B: 4”.
Only about 1/20 get the right answer: “B: 4” and
“C: Red”!
Analysis
People look for results that would agree with
the claim.
Turning over B and D, you could get agreement–
for example, [4, Blue] and [6, Blue].
You cannot get agreement by turning over C. But
you can get disagreement and that is why the
card is important!
CONFIRMATION BIAS
Confirmation Bias
People tend to look for evidence that agrees
with what they already believe.
This is called confirmation bias.
Bacon on Confirmation Bias
“The human understanding when it has once
adopted an opinion… draws all things else to
support and agree with it. And though there be
a greater number and weight of instances to be
found on the other side, yet these it either
neglects and despises, or else by some
distinction sets aside and rejects; in order that
by this great and pernicious predetermination
the authority of its former conclusions may
remain inviolate.” – Sir Francis Bacon
Confirmation Bias
“Confirmation bias is perhaps the best known
and most widely accepted notion of inferential
error to come out of the literature on human
reasoning.” (Evans, 1989, p. 41)
Confirmation Bias
“Many have written about this bias, and it
appears to be sufficiently strong and pervasive
that one is led to wonder whether the bias, by
itself, might account for a significant fraction of
the disputes, altercations, and
misunderstandings that occur among
individuals, groups, and nations.” – Nickerson
1998
It’s Ordinary
“Your day might start on a sour note: you wake
up late, the barista screws up your coffee (even
after you’ve waited forever in line), your car
won’t start again. If you mentally set yourself up
to say “This is a bad day,” you will look for
further evidence to support that notion
throughout your day, potentially ignoring
evidence that it’s a day like any other or maybe
even a good day overall.” -- Satya Putumbaka
Fish vs. Obama
“There’s no mistaking what’s going on in the
speech delivered last week. No preliminary
niceties; just a rehearsal of Obama’s actions and
expectations. Eight ‘I’’s right off the bat:”
-- Stanley Fish
“I”s
“Just over two months ago I spoke with you… “
“and I laid out what needed to be done.”
“From the beginning I made it clear that I would not
put any more tax dollars on the line.”
“I refused to let those companies become
permanent wards of the state.”
“I refused to kick the can down the road.”
“But I also recognized the importance of a viable
auto industry.”
“I decided then…”
Presidential Pronouns
US President
“I”
“me” “my”
Total
Obama
1st Press Conf.
Bush Jr.
1st 2 Press
Conf.
Clinton
1st 2 Press
Conf.
2.10%
0.55%
2.65%
3.58%
0.91%
4.49%
3.14%
0.73%
3.87%
Stereotypes
Stereotypes are another instance where our
expectations lead us into the wrong beliefs.
A Strange Example
Americans were asked:
Which of these pairs of countries are more
similar to one another?
1. West Germany, East Germany
2. Sri Lanka, Nepal
They said (1), West Germany and East Germany.
Others (Americans) were also asked:
Which of these pairs of countries are more
different from one another?
1. West Germany, East Germany
2. Sri Lanka, Nepal
They also said (1).
Americans thought that West Germany and East
Germany were both more similar to each other
than Sri Lanka and Nepal and less similar to each
other than Sri Lanka and Nepal.
How is that possible?
First, when considering the question ‘which are
more similar?’ the subjects looked for all the
positive evidence that West Germany and East
Germany were similar, and all the positive
evidence that Sri Lanka and Nepal were similar.
Since Americans know nothing about Asian
countries, they had no positive reason to think
Sri Lanka and Nepal were similar.
Similarly, when asked ‘which are more
different?’ the subjects considered the positive
evidence that West Germany and East Germany
were different and the positive evidence that Sri
Lanka and Nepal were different.
Again, having no knowledge of Sri Lanka or
Nepal, Americans chose (1), because of all the
positive evidence in its favor.
But it cannot be true that East Germany and
West Germany are both more similar and more
different than Sri Lanka and Nepal.
What the subjects did not do is consider the
relevant negative evidence that would
disconfirm their hypotheses.