LECTURE 1
Predictably irrational
1. What is critical thinking?
critical thinking is:
1) rational – assessing the reliability of our beliefs by reflecting on how these
beliefs were formed
- not intuitive
- not emotionally tainted
- it is logical
2) autonomous – not relying on tradition or authority
goal of critical thinking: come to reliable beliefs and distinguish reliable from
unreliable beliefs
- this has to be learned (does not come spontaneously)
* learn how our minds work and what leads to irrational thinking
- no one is immune to irrationality
ex. author Conan Doyle – argued for the existed of a “spirited reality” (only
accessible to children, who have not lost their innocence) because young girls
were pretending to be playing with fairies and he believed their story
- spontaneous/ intuitive thinking leads to uncritical thinking and irrational
beliefs
critical thinking is not:
1) negative thinking – does not try to undermine any belief/ claim
2) skeptical thinking – does not assume that we cannot know anything and
therefore suspend the belief in any claim
3) intelligent thinking – intelligent people can come up with irrational
misguided beliefs
4) well-informed thinking – being well-informed is a necessary condition for
critical thinking, but it is not sufficient
1.1 usefulness of critical thinking
we take decisions based on information daily -> we have never been so
dependent on information as we are in this day and age
there is no shortage of misinformation, either
nonsense breeds more nonsense -> due to a coherent worldview
- our beliefs link up with one another
ex. belief in the predictive value of horoscopes could lead to belief in the
existence of mediums/ energy healing
1.2 why nonsense is hard to detect
, if we look at irrational beliefs of another culture/ from another historical era, we
might find it baffling how those people hold such strange beliefs
- it becomes more difficult to detect irrational beliefs in one’s own cultural
context/ day and time (the beliefs are a part of a coherent worldview)
* beliefs only seem irrational/ strange from the outside
ex. belief in the existence of witches (Mary Tuft was believed to have given
birth to rabbits and not human children)
ex. alchemy – recipes to make gold
ex. recipes to make living organisms (scorpions could be made if crushed basil
leaves between stones were left in the sun)
our intuition and commonsense do not guard us against illusions: they are often
the source of reasoning errors -> reasoning errors
three rules of thumb to think critically:
1. demand external (not psychological) support for beliefs
- extraordinary beliefs require extraordinarily compelling evidence
- a claim that simply sounds plausible is not justified/ reliable
- external support = facts
- it is for when beliefs confront other beliefs for which there is support
ex. cryptozoology – a belief in a singular weird kind of creature – goes against
scientific beliefs for which there is a lot of support
2. Occam’s razor: the most economical/ parsimonious explanation is the most
likely explanation
ex. crop circles explanations
- at first it was thought that aliens were responsible (conspiracy theory) -> it
requires multiple other questions to be answered (i.e. how did the aliens manage
to do that without being observed?/ why do they only leave these circles and do
not try to communicate otherwise?), and therefore the overall explanation loses
its credibility
- better explanations: the circles are made by Americans who like to spread
hoax
3. we should be aware of a number of cognitive pitfalls/ illusions
- they are systematic – everyone sees the lower bar as longer
permanent – even if you know that the lines are equal, one always
appears longer (knowledge does not change the visual
impression)
universal – all humans are susceptible to the illusions
ex. Muller-Lyer perceptual illusion
,2. Riddles to portray cognitive illusions
2.1 two can never be greater than one
correct answer: 1
most people would answer 2 due to the description
logically, two can never > one -> having a combination of two characteristics is
less probable
2.2 base-rate fallacy
correct answer: B
there are many more salesmen in the world than librarians -> it is more
probable for someone to be a salesman despite the description
base-rate – prior probability in the population
the actual probability is 2%
- base-rate = 1/10 000
- false positive = 50 times larger than true positive
most people would say around 99%
2.3 statistical thinking
, correct answer: 23 people
most people would think 365 divided by 2
2.4 exponential thinking
correct answer: 42 folds
most people would say millions
our brains are not equipped to think about exponential growth – only about
linear growth
- we underestimate how fast exponents grow
2.5 availability bias
correct answer 1: dislodged plane parts
- 30x > sharks
- sharks are more often portrayed in media
correct answer 2: third letter R
correct answer 3: 10%
availability bias – we misestimate the likelihood of something happening
because it is very easy for us to recall/ imagine some events
availability bias at work -> playing the lottery
- real chance of winning: 1 in 7-8 million
- obtaining a random security number and asking strangers if that is their
number: the chance of this happening is much greater than winning the lottery
2.6 anchoring
study with psychology students using that riddle:
Predictably irrational
1. What is critical thinking?
critical thinking is:
1) rational – assessing the reliability of our beliefs by reflecting on how these
beliefs were formed
- not intuitive
- not emotionally tainted
- it is logical
2) autonomous – not relying on tradition or authority
goal of critical thinking: come to reliable beliefs and distinguish reliable from
unreliable beliefs
- this has to be learned (does not come spontaneously)
* learn how our minds work and what leads to irrational thinking
- no one is immune to irrationality
ex. author Conan Doyle – argued for the existed of a “spirited reality” (only
accessible to children, who have not lost their innocence) because young girls
were pretending to be playing with fairies and he believed their story
- spontaneous/ intuitive thinking leads to uncritical thinking and irrational
beliefs
critical thinking is not:
1) negative thinking – does not try to undermine any belief/ claim
2) skeptical thinking – does not assume that we cannot know anything and
therefore suspend the belief in any claim
3) intelligent thinking – intelligent people can come up with irrational
misguided beliefs
4) well-informed thinking – being well-informed is a necessary condition for
critical thinking, but it is not sufficient
1.1 usefulness of critical thinking
we take decisions based on information daily -> we have never been so
dependent on information as we are in this day and age
there is no shortage of misinformation, either
nonsense breeds more nonsense -> due to a coherent worldview
- our beliefs link up with one another
ex. belief in the predictive value of horoscopes could lead to belief in the
existence of mediums/ energy healing
1.2 why nonsense is hard to detect
, if we look at irrational beliefs of another culture/ from another historical era, we
might find it baffling how those people hold such strange beliefs
- it becomes more difficult to detect irrational beliefs in one’s own cultural
context/ day and time (the beliefs are a part of a coherent worldview)
* beliefs only seem irrational/ strange from the outside
ex. belief in the existence of witches (Mary Tuft was believed to have given
birth to rabbits and not human children)
ex. alchemy – recipes to make gold
ex. recipes to make living organisms (scorpions could be made if crushed basil
leaves between stones were left in the sun)
our intuition and commonsense do not guard us against illusions: they are often
the source of reasoning errors -> reasoning errors
three rules of thumb to think critically:
1. demand external (not psychological) support for beliefs
- extraordinary beliefs require extraordinarily compelling evidence
- a claim that simply sounds plausible is not justified/ reliable
- external support = facts
- it is for when beliefs confront other beliefs for which there is support
ex. cryptozoology – a belief in a singular weird kind of creature – goes against
scientific beliefs for which there is a lot of support
2. Occam’s razor: the most economical/ parsimonious explanation is the most
likely explanation
ex. crop circles explanations
- at first it was thought that aliens were responsible (conspiracy theory) -> it
requires multiple other questions to be answered (i.e. how did the aliens manage
to do that without being observed?/ why do they only leave these circles and do
not try to communicate otherwise?), and therefore the overall explanation loses
its credibility
- better explanations: the circles are made by Americans who like to spread
hoax
3. we should be aware of a number of cognitive pitfalls/ illusions
- they are systematic – everyone sees the lower bar as longer
permanent – even if you know that the lines are equal, one always
appears longer (knowledge does not change the visual
impression)
universal – all humans are susceptible to the illusions
ex. Muller-Lyer perceptual illusion
,2. Riddles to portray cognitive illusions
2.1 two can never be greater than one
correct answer: 1
most people would answer 2 due to the description
logically, two can never > one -> having a combination of two characteristics is
less probable
2.2 base-rate fallacy
correct answer: B
there are many more salesmen in the world than librarians -> it is more
probable for someone to be a salesman despite the description
base-rate – prior probability in the population
the actual probability is 2%
- base-rate = 1/10 000
- false positive = 50 times larger than true positive
most people would say around 99%
2.3 statistical thinking
, correct answer: 23 people
most people would think 365 divided by 2
2.4 exponential thinking
correct answer: 42 folds
most people would say millions
our brains are not equipped to think about exponential growth – only about
linear growth
- we underestimate how fast exponents grow
2.5 availability bias
correct answer 1: dislodged plane parts
- 30x > sharks
- sharks are more often portrayed in media
correct answer 2: third letter R
correct answer 3: 10%
availability bias – we misestimate the likelihood of something happening
because it is very easy for us to recall/ imagine some events
availability bias at work -> playing the lottery
- real chance of winning: 1 in 7-8 million
- obtaining a random security number and asking strangers if that is their
number: the chance of this happening is much greater than winning the lottery
2.6 anchoring
study with psychology students using that riddle:
