Cognitive Biases 3
PARTICIPATION
Dear Michael,
My family lives in Tai Wai,
in Sha Tin district. Nearby
is a rock that everyone
calls “Lion Rock” because
it looks like a lion.
The other day I was
listening to music and I
heard the song 獅子山下,
“Under the Lion Rock.” It’s
a popular song in HK that
makes reference to Lion
Rock.
The rock is an example of
how our minds see
patterns everywhere, like
you talked about in class.
Sincerely,
Eason Chan
Dear Michael,
When I was a kid, I used to love to stand on the
harbor at Tsim Sha Tsui and look at the skyline of
Hong Kong Island. Now, every time I go down
there, there is so much smog that I can’t see
anything!
The government claims that pollution has been
falling since 2004, but I think this is just
regression to the mean. 2004 was an extremely
bad year, so we expect levels to go down. But if
you look at the long-term trend, pollution has
been increasing since the 1980’s.
Sincerely,
Gigi Lai
Participation
• Total of 5 examples throughout the semester.
• Turn them in any time– you can turn in a
regression fallacy example on the last week of
class.
• You cannot lose marks by turning in an
example that doesn’t work. No penalty for
“wrong answers”!
• “Your own experience” includes movies,
books, comics, commercials, etc.
SEEING WHAT WE EXPECT TO SEE
Representative Samples
From the SCMP, 29 August 2013:
“The Post poll, carried out by the Centre for
Communication and Public Opinion Survey at
Chinese University found that 49.9 per cent of
the 509 respondents were "against" or "strongly
against" the government surrendering Snowden
to the US if Washington were to ask the city to
do so. Only 17.6 per cent said he should be
handed over. “
Out of Context?
There are 7.155 million people in Hong Kong.
How can you say that 49.9% of people don’t
want Snowden handed over when you only
asked 509 people?
Let’s Find Out!
http://www.nss.gov.au/nss/home.nsf/pages/Sa
mple+size+calculator
BIAS
Bias
Our expectations often influence how we
evaluate claims and evidence.
We easily accept as true those things that we
expect to be true, but are much more skeptical
about things that are unexpected.
Bias
Bias can be a good thing. If someone tells you
they saw a construction worker, it makes sense
to believe them– construction workers are
numerous, and we expect there to be numerous
sightings of them.
But if someone tells you they saw an
extraterrestrial, things are different. You’ll be
right to be skeptical: that is very unexpected.
Bias
Bias can also be a bad thing. If you’re biased
against people of other races you might
• notice them behaving badly more often than
you notice other bad behavior and
• Be more skeptical of believing positive things
about them– even if they’re totally innocent,
wonderful human beings.
Racism in Hong Kong
Confirmation Bias
Last time we talked about confirmation bias:
people are inclined to look for evidence that
supports a hypothesis, and to ignore evidence
that goes against it.
This is important because the negative evidence
(the evidence against a claim, the red card) is
just as important as the positive evidence in
evaluating the claim’s truth.
Loftus & Palmer 1974
How things are described to us can affect how we
see them.
In one study, subjects were shown pictures of a car
accident involving multiple cars. They were asked:
“About how fast were the cars going when they
(hit/smashed/collided/bumped/contacted ) each
other?”
Loftus & Palmer 1974
Loftus & Palmer 1974
Additionally, the subjects were asked one week
later whether they remembered seeing broken
glass (from the cars) in the photographs.
There was no glass, but subjects who had been
asked “smash” or “collided” questions were
more likely to remember some than subjects
asked “contacted” or “hit” questions.
Context Affects Expectation
This study shows that context (how a picture is
described to us) can affect how we see a thing
(the picture itself), and what we remember
about it.
Bias against Black
Studies have shown that people in many
cultures have negative associations with the
color black. They are biased against blackcolored things.
Frank & Gilovich 1988
One study asked professional referees (for
American football) to watch a video clip of a play
and decide whether the players deserved a
penalty.
In one version of the clip, the players wore
white; in another, their uniforms were changed
to black.
Frank & Gilovich 1988
The referees were more likely to say that the
players deserved a penalty if they were wearing
black.
Frank & Gilovich also found that teams with
black uniforms actually did get penalized more
often than teams with other colored uniforms!
THE COMMITMENT EFFECT
The Endowment Effect
The amount of money people think something is
worth depends on whether or not they own it.
This is the endowment effect.
Endowment Effect
For example, suppose I
show you a mug. I ask
you:
“How much would you be
willing to pay me for this
mug?”
Endowment Effect
Now suppose I instead
give you the mug. It’s
yours. I ask you:
“How much would I have
to pay you for you to give
me the mug back?”
Kahneman, Knetsch and Thaler (1990)
Kahneman et al. found that people would be
willing to pay on average $24 HKD for the mug.
But if you gave it to them, they wanted $54 HKD
to give it back.
Other studies have shown that hypothetical
selling price is about 2.5x buying price.
Choice Supportive Bias
People think their decisions are better after
they’ve made them. If you don’t own a
smartphone and you’re deciding between a
Samsung and an Apple phone, you might think
that Apple is a little bit better.
But after you buy an Apple phone, you will think
it is a lot better.
People have a tendency to believe whatever
makes them look good: good decision makers
and even good critical thinkers.
Subliminal Persuasion
In 1957, market researcher James Vicary
announced that he had discovered a way to
revolutionize advertising.
By flashing subliminal messages during a movie,
he claimed that Coca-Cola sales increased 18.1%
and popcorn sales increased 57.7%.
Subliminal Persuasion
Subliminal Persuasion
Subliminal advertising doesn’t actually work,
and Vicary just made up the study to save his
advertising business.
But lots of people in the US still believe in
subliminal persuasion, and some even think the
government uses it to control people’s behavior.
Experiment
In one critical thinking class, a professor tested
how much students believed in subliminal
persuasion at the beginning of class and after:
• Summarizing the arguments from class against
it.
• Writing whatever arguments they thought
were best against it.
• Writing an unrelated essay.
Results
DISCONFIRMATION BIAS
Disconfirmation Bias
Our biases can lead us to accept evidence that
agrees with our views and reject evidence
against our views, even when the “for” and
“against” evidence is of the same quality.
Lord, Ross & Lepper 1979
One study looked at how people who were in
favor of the death penalty evaluated arguments
for and against it, and how people who were
against the death penalty evaluated those same
arguments.
There were four types of arguments:
Lord, Ross & Lepper 1979
AGAINST-SAME. A study that showed that
murder rates in a state increased after that state
instituted the death penalty.
AGAINST-DIFF. A study that showed that murder
rates were higher in states that had the death
penalty than in states that didn’t.
Lord, Ross & Lepper 1979
FOR-SAME. A study that showed that murder
rates in a state decreased after that state
instituted the death penalty.
FOR-DIFF. A study that showed that murder
rates were lower in states that had the death
penalty than in states that didn’t.
Lord, Ross & Lepper 1979
All the subjects got one study AGAINST the
death penalty and one study FOR it. If the study
they got AGAINST it was the SAME condition,
then they got FOR-DIFF; if the study they got
AGAINST it was DIFF, then they got FOR-SAME.
Lord, Ross & Lepper 1979
People who liked the death penalty and received
AGAINST-SAME and FOR-DIFF argued that SAME
studies were bad, and DIFF ones were good.
They liked the study that supported them.
If they got AGAINST-DIFF and FOR-SAME, they
argued the opposite: that DIFF studies were bad,
and that SAME studies were good.
Lord, Ross & Lepper 1979
The same was true for people who opposed the
death penalty: they liked SAME studies when
they got AGAINST-SAME, but not when they got
FOR-SAME; they liked DIFF studies when they
got AGAINST-DIFF, but not when they got FORDIFF.
Everyone liked the studies that agreed with
them!
Lord, Ross & Lepper 1979
What’s interesting is that the arguments given
by the subjects about why DIFF studies are bad
(or why SAME studies are bad) were good
arguments.
No one was arguing in bad faith. But their biases
made them see the flaws in studies that
disagreed with them, and made them ignore the
flaws in the studies that agreed with them.
Disconfirmation Bias
This is sometimes called disconfirmation bias.
It is the tendency to subject evidence against
your views to a greater degree of scrutiny than
evidence in favor of your views.
It is a double-standard for evidence evaluation.
Gamblers
A similar study was seen in a study of gamblers
(in particular, ones who bet on sports matches).
Why do gamblers keep gambling when they lose
money so often? Don’t they ever learn from
their mistakes? Are they just forgetting about all
those times they lost?
Gamblers
The study showed that gamblers didn’t forget
their losses– they were more likely to remember
them.
What they did was explain away the times they
lost. Losses were counted as accidents, bad luck,
“near wins”, etc. They weren’t counted as bad
gambles or mistakes.
Gamblers
Wins however were never attributed to accident
or luck. They were the result of skill.
So wins and losses were treated differently. A
win was taken as evidence that the gambler was
good at choosing bets. But losses were not taken
as evidence that the gambler was bad at
choosing bets, just that he was “unlucky”.
Evidential Double-Standards
Disconfirmation bias and evidential doublestandards can play a big (negative) role in
political disputes.
As a recent example, Harvard Law Professor Alan
Dershowitz has criticized Brooklyn College in
New York for hosting an event with speakers
critical of Israel, but no opposing voices.
Double-Standard
That might be a good reason to object to an
event, that it only presents one side.
But Dershowitz is applying a double-standard.
Dershowitz himself has spoken several times at
Brooklyn College, and never once had anyone
else speaking against his views at those times,
and never requested anyone to!
MULTIPLE ENDPOINTS
Multiple Endpoints
One way that our expectations can influence our
beliefs is called “the problem of multiple
endpoints.”
Multiple Endpoints
For example, suppose someone claims that
spending time on Facebook is bad for your social
life.
Well what does that mean? There are lots of
effects of Facebook that might be counted as
bad for your social life (spending less time faceto-face with friends) and lots of ways that might
be counted as good (talking more often with a
larger range of friends).
Multiple Endpoints
Here, if I’m biased because I dislike Facebook, I
can interpret “bad for your social life” in a way
that Facebook is bad; if I like Facebook, I can
interpret it in a way that is good.
There are multiple different events
(“endpoints”) that I can focus on when
evaluating the claim.
Multiple Endpoints
People often say to parents, “your child looks so
much like you!” even if (unknown to them) the
child is adopted.
There are lots of ways that any two people can
look alike (hair, eyes, mouth, nose…). Most
people will be similar in some ways. If you
expect that two people will look similar (you
think they’re biologically related), you will focus
on those “endpoints”.
John Edward
http://www.youtube.com/watch?v=EKSFi9dtg5
M
So-called “psychics” often use multiple
endpoints to their advantage to convince people
they have supernatural powers.
Lots of People with Relations
In this clip, Edward asks if there’s a son, younger
son, grandson, or younger brother who
“passed.”
Surely in a large audience some person is related
to some one other male who died at some point
in the past. It could be a long time ago, or
recent. It could be a son, brother, grandson…
Vague Guess Sometimes Wrong
Edward guesses that this person died in “an
event.” Can you think of someone who died
young whose death wouldn’t be an “event.” It
can’t be natural!
He insists that something is related to June. And
statistically it’s a good guess: something usually
happens every month. But here he’s wrong.
Last-Ditch Effort
Finally, not looking too good, Edward quickly
guesses two very likely things: that someone in
her family had “brain cancer or something brainrelated.” How many old people have not had
something brain related?
Second, he guesses her dog died. Lots of
Americans have dogs, many have many dogs,
and dogs don’t live all that long.
Main Point
The main point is this: very strange claims like
“dead people can speak to John Edward and
pass on messages to him for the living” can
seem to be supported by the evidence.
But this is only because very vague claims that
can be made true by multiple endpoints are
almost always true. They don’t support
anything.
ONE AND TWO SIDED EVENTS
Two-Sided Events
Some events are “one-sided” and some events
are “two-sided”.
A “two-sided” event is an event that can turn
out one of two ways. For example, if I bet on a
football match, I can either win or I can lose.
Winning is one “side” of the event and losing is
the other “side”.
One-Sided Events
“One-sided” events are different. They can
either (i) turn out in exactly one way or (ii) not
exist.
One-Sided Events
For example, suppose I believe that the phone
always rings when I’m in the shower.
If I’m in the shower and the phone rings, that
seems like an event– something happened: I
was in the shower, and the phone rang.
One-Sided Events
For example, suppose I believe that the phone
always rings when I’m in the shower.
But if I’m in the shower and the phone doesn’t
ring, it seems like nothing happened. I don’t say
“look what happened when I was in the
shower– the phone didn’t ring!”
Two-Sided Events & Memory
For two-sided events, we notice both outcomes
equally. So when evaluating claims about them,
like “I always win when I bet on a match,” we
will be confronted with the negative evidence
(all those times I bet on a match and lost).
For one-sided events, we only notice when they
happen, not when they don’t happen. So it may
seem to me that my phone rings frequently
when I’m in the shower, because I never notice
the many, many times it does not ring when I’m
in the shower.
Confirmations and Non-confirmations
Sometimes events are “one-sided” because we
are never inclined to notice the other side.
Only when the event confirms a certain belief do
we notice its relevance to the belief; if it doesn’t
confirm the belief, then we’re uninclined to
notice its relevance.
Confirmations and Non-confirmations
Suppose a fortune teller predicts that I will have
twins. If many years later, I have twins, I may
remember the prediction. I have evidence that
fortune tellers are accurate. If instead I have
only one child, I’m less likely to remember the
prophecy. One child doesn’t remind me of a
prophecy about two children.
Open-Ended Claims
Sometimes events are “one-sided” because the
claims they are relevant to are open-ended.
For example, suppose I predict that you will
someday break a bone. If you break a bone
tomorrow, next week, next month, next year, 30
years from now, etc. then the relevant event
happened. I was right.
But if you don’t break a bone tomorrow, nothing
happened. If you don’t break it next week,
nothing happened. If you don’t break it next
month, nothing happened.
None of this shows that I’m wrong. Only if you
died without breaking a bone would I be wrong.
And you wouldn’t be around to notice that.