Critical Thinking: The Art of Reasoning
Lecture 22: Cognitive Biases
© Critical Thinking Skills BV
http://www.theinvisiblegorilla.com/videos.html
2
‘Attentional blindness’:

http://www.theinvisiblegorilla.com/index.html
Second time?


http://www.youtube.com/watch?gl=NL&v=IGQmdoK_ZfY
3
Do you see the dancer turning clockwise
or anti-clockwise?
4
See:



http://www.dailytelegraph.com.au/news/wacky/t
he-right-brain-vs-left-brain/story-e6frev201111114577583
http://www.youtube.com/watch?v=9CEr2GfGilw
5
Mad Gamble


You have $500, but you desperately need
$1000; nothing less will do. You go to the
casino, hoping to turn your $500 into $1000
in an “all or nothing” bid.
Question: should you bet all your money in
one go? Or should you split your $500 into,
say, ten lots of $50, and bet those one at a
time?
6
Ace in the hand?
1.
2.
3.
Only one of the following
statements about a
particular hand of cards is
true:
There is a king in the
hand, or an ace, or both.
There is a queen in the
hand, or an ace, or both.
There is a jack in the
hand, or a ten, or both.
Is it possible
there is an ace in
the hand?
Brooks, New Scientist, 9 December 2000
7
Visual Blind Spot
Close one eye.
Position the other eye
directly above this point,
about 8-12 inches away.
Focus on this writing.
Move your head gently up
and down until you find
black dot or the gap
disappears.
8
Visual Blind Spot




Universal
(everyone has
it)
Innate (from
birth)
Hard-wired
Invisible
Blind
Spot
9
It is NOT possible there is an ace…
1.
2.
3.
Only one of the
following statements
about a particular hand
of cards is true:
There is a king in the
hand, or an ace, or both.
There is a queen in the
hand, or an ace, or both.
There is a jack in the
hand, or a ten, or both.
If there is an ace,
1 and 2 must
both be true.
10
Mad Gamble


You have $500, but you
desperately need $1000;
nothing less will do. You go
to the casino, hoping to turn
your $500 into $1000 in an
“all or nothing” bid.
Question: should you bet all
your money in one go? Or
should you split your $500
into, say, ten lots of $50,
and bet those one at a time?
Answer: you
should gamble
everything in
one go.
11
Cognitive Bias

Cognitive biases
are universal,
innate tendencies
for humans to
think in certain
ways, ways which
often result in
poor judgments.
12
Cognitive Biases in..








Perception and Observation
Estimating quantities and
frequencies
Randomness, probabilities and
statistics
Identifying causal relations
Explanation and hypothesis
testing
Decision making
Reasoning and argument
Social cognition (e.g., thinking
about others)
13
Example: Hindsight Bias
14
Where do cognitive biases come from?
Our brains are the result of
an evolutionary process in
which we were adapting to
contexts very different from
those we find ourselves in
today. Hence there is an
occasional mismatch
between the cognitive
capacities we have, by
nature, and those we need
to make the good
judgments.
15
Cognitive Biases – Key Points
Cognitive Biases are







Universal
Innate
Hard-wired
Due to evolved nature of our brains
Can sometimes be overcome by
training
More typically, cannot be overcome;
can only be counteracted
16
Critical Thinking and Cognitive Biases
The critical thinker:





knows about cognitive biases
actively monitors her own thinking to detect
their operation
knows of, and practices, techniques for
counteracting cognitive biases
applies those techniques when relevant
17
More
18
What is a cognitive bias?
Cognitive biases are the human tendencies to make
systematic, predictable errors in certain cirumstances
that cause the human brain to draw incorrect
conclusions.
Such biases are thought to be a form of information
processing shortcuts (called heuristics), often based upon
rules of thumb, and include errors in statistical judgment,
social attribution, and memory.
These biases are a common outcome of human thought, and
often drastically skew the reliability of anecdotal and legal
evidence. The phenomenon is studied in cognitive science
and social psychology.
http://en.wikipedia.org/wiki/Cognitive_bias
S. Pinker: Our mind is made for fitness, not for truth
Our brains aren’t wired for objectivity.
They are wired for adaptation & survival
20