PSY 341 Judgement, Decisions, Reasoning Notes Abyana

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Chapter 12 Judgement, Decisions and Reasoning
Reasoning
Cognitive processes by which people start with information and come to conclusions
that go beyond that information
Basic Processes
Reasoning
o Deduction (Deductive Reasoning)
Reasoning when facts are known
Broad principles to make logical predictions about specific
cases.
E.g. Formal Logic
Judgment
o Induction
Reasoning under uncertainty, must go beyond facts
Drawing general conclusions based on specific observations
and evidence.
o Conclusions we reach are probably, but not definitely
true.
E.g. statistical
Deductive Reasoning
Basic form is = Syllogism
o Syllogism includes:
2 Broad statements: Premises
Third Statement: Conclusion
Syllogism is valid if conclusions follows logically from its two
premises
o Categorical Syllogism
Premises and conclusion describe the relation between two
categories by using all, no or some.
o E.g.
Syllogism 1 (Example of categorical syllogism) --- VALID
Premise 1: All birds are animals
Premise 2: All animals eat food.
Conclusion: Therefore, all birds eat food.
Syllogism 2 ----VALID even if conclusion is not true.
Premise 1: All birds are animals
Premise 2: All animals have 4 legs
Conclusion: Therefore, all birds have 4 legs
o Validity depends on the form of the syllogism
o Truth refers to the content of the premises
DO NOT CONFUSE VALIDITY WITH TRUTH
How well can people judge validity?
Evaluation
o Ask people if conclusion follows logically from premises

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Production
o Ask people to indicate what logically follows from premises
E.g.
o Syllogism 3---NOT VALID
Premise 1: All of the students are tired
Premise 2: Some tired people are irritable
Conclusion: Some of the students are irritable
The conclusion DOES NOT follow from the two premises
o Syllogism not valid.
o Syllogism 4---NOT VALID
Illustrates the conclusion does not logically follow from the two
premises
Premise 1: All of the students live in Buffalo
Premise 2: Some people who live in Buffalo are millionaires
Conclusion: Therefore, some of the students are millionaires
Many errors in evaluation
o Belief Bias
be judged as valid.
Conditional Syllogisms
Have 2 premises and a conclusion ( as in categorical syllogisms)
But the first premise has the form
o
Common in everyday life
o Antecedent: If I
o Consequent: then I will get a good grade.
Example
Syllogism (Abstract version)
o Premise 1: If p, then q.
o Premise 2: p
o Conclusion: Therefore, q.
Syllogism 1(Affirming the antecedent) ---VALID,
97% judged correctly
o Premise 1: If I study, then I will get a good grade.
o Premise 2: I studied.
o Conclusion: Therefore, I will get a good grade.
Syllogism 2 (Denying the consequent) --- VALID
60% Judged correctly
o Premise 1: If I study, then I will get a good grade.
o Premise 2: I did not get a good grade
o Conclusion: Therefore, I did not study.
Syllogism 3 (Affirming the consequent) --- NOT VALID
40% Judged correctly
o Premise 1: If I study, then I will get a good grade.
o Premise 2: I got a good grade
o Conclusion: Therefore, I studied

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Syllogism 4 (Denying the antecedent) --- NOT VALID
40% Judged correctly
o Premise 1: If I study, then I will get a good grade.
o Premise 2: I did not study
o Conclusion: Therefore, I did not get a good grade.
Conditional Reasoning
o The Wason Four-Card Problem (Wason, 1966)
Indicate which cards you need to turn over to test the following rule
If there is a vowel on one side, then there is an even number
on the other side.
o E
o K
o 4
o 7
o How should we test a hypothesis?
Confirmatory Evidence
Evidence that is consistent with a hypothesis
Not informative because it is ambiguous
o There exist alternative explanations
Disconfirmatory Evidence (Falsification Principle)
Evidence that is inconsistent with a hypothesis
o Informative because it leads to tests that rule out
alternative explanations
o Crucial in scientific reasoning.
Falsification Principle
To test a rule, it is necessary to look for situations that would
falsify the rule.
o Most participants fail to do this
Wason Four card Problem (In real world
context)
Imagine you are a police officer who is
applying the rule:
o If a person is drinking beer, then
he or she must be over 19 years
old.
Beer
Soda
16 years old
24 years old
When problem is stated in concrete
everyday terms, correct responses
greatly increased.
T
Task
o Pragmatic reasoning schema
A way of thinking about
cause and effect in the

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world that is learned as
part of experiencing
everyday life
o Permission schema
If A is satisfied, B can be
carried out
People are familiar with
rules
If a person is drinking
beer, then they must be
over 19 years old.
Evolutionary Perspective on Cognition
Evolutionary principles of natural selection
o Wason task governed by a built-in cognitive program
for detecting cheating
The ability for 2 people to cooperate in a way
that is beneficial to both people
One proposed alternative to a
permission schema
o Conditional Reasoning Summary
Context is important
Familiarity is not always necessary for conditional reasoning
The controversy continues
Permission schema vs Detecting Cheating
Inductive Reasoning
Process of making general conclusions based on specific observations and evidences.
o Premises are based on observation of one or more specific cases
We generalize from these cases to more general conclusions with
varying degrees of certainty.
o A number of factors can contribute to the strength of an inductive argument
Representativeness of Observations
How well do the observations about a particular category
represent all of the members of that category?
o Observation:
All the crows I have seen in Pittsburgh are black.
When I visited my brother in Washington, DC,
the crows I saw there were black too.
o Conclusion:
I think it is a pretty good bet that all crows are
black
Number of Observations
o Adding more observations strengthen an inductive
argument
The argument about the crows is made stronger
by adding the Washington, DC observations to
the Pittsburgh observations

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others in the world are gray.
Quality of the Evidence
o Stronger evidence Stronger conclusions
Observation:
Here in New York, the sun has risen
every morning
Conclusion:
The sun is going to rise in New York
tomorrow.
The argument will become even stronger when
we consider scientific descriptions of how the
earth rotates on its axis and revolves around
the sun.
Inductive Reasoning
o Used to make scientific discoveries
Form hypotheses, test the hypotheses, and draw general conclusions
o We often use inductive reasoning in everyday life.
Make a prediction about what will happen based on observation
about what has happened in the past.
Heuristics
o Provide us with shortcuts to draw general conclusions based on specific
observations and evidence
Availability heuristic
Events that are more easily remembered are judged as being
more probable than events that are less easily remembered.
o Some possible causes of death are listed in the next
slide in pairs.
o Within each pair, which cause of death do you consider
to be more likely for people in the U.S.?
Homicide vs Appendicitis
Auto train collision vs Drowning
Asthma vs Tornado (58% thought tornado)
Appendicitis vs Pregnancy (83% thought
pregnancy)
Participants were more likely to pick
causes that had been publicized by the
media
Illusory correlations
A correlation between two events appears to exist, but in
reality, there is no correlation or it is much weaker than it is
assumed to be.
o People in big city are rude
Image from media or personal experiences
Illusory correlation reinforces stereotypes.
Representativeness Heuristic

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The probability that A is a member of Class B can be
determined by how well the properties of A resembles the
properties we usually associate with Class B
o Use base rate information if it is all that is available.
Base rate
Relative proportion of different classes
in a population.
o In a group of 100 ppl, 70 lawyers
and 30 engineers. What is the
chance that if we pick one
person at random, the person
will be an engineer?
30% CHANCE
o Use descriptive information if available and disregard
base rate information
Jack is a 45-year-old man. He is married and has
4 children. He is generally conservative, careful
and ambitious. He shows no interest in political
and social issues and spends most of his free
time on his many hobbies, which include home
carpentry, sailing and mathematical puzzles.
What is the chance that Jack will be an
engineer?
o 70% lawyer
o 30% engineer
Adding this description caused
participants to greatly increase their
estimate of the chances that the
randomly picked person was an
engineer.
Conjunction Rule:
The probability of a conjunction of 2 events (A and B) cannot
be higher than the probability of the single constituents (A
alone or B alone)
o Linda bank teller instead of bank teller and is active in
the feminist movement. (85% picked 2nd
)
Feminist bank tellers are a subset of bank
tellers, it is always more likely that someone is a
bank teller than a feminist bank teller.
Law of large numbers
The larger the number of individuals that are randomly drawn
from a population, the more representative the resulting
group will be of the entire population
o Samples of a small numbers of individuals will be less
representative of the population.
Which hospital recorded days on which more
than 60% of the babies born were boys?

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Smaller hospital
o 56% said about the same
Failed to consider the law
of large numbers
Confirmation Bias
Our tendency to selectively look for information that conforms
to our hypothesis and to overlook information that argues
against it.
o Wason (1966,1968)
Told participants that series was generated by
using a rule
Try to discover the rule by proposing
number trios of your own
2,4,6
o Get feedback on whether series
follows rule.
Announce rule when you
think you have figured it
out.
Most people
Ask: Does 8,10,12 follow
the rule?
Confirmation Bias
o Few ask
Does 1,2,3 or 6,4,2 or
10,10,10 follow the rule?
Myside bias
Type of confirmation bias in which people generate and test
hypotheses in a way that is biased toward their own opinions
and attitudes.
o Lord and coworkers (1979)
Identified one group of participants in favor of capital punishment and
another group against it.
Had both of the groups read the same article
o Those in favor found the article convincing
o Those against found the article unconvincing.
Decision Making
Expected Utility Theory
o People are basically rational
o So if they have all the relevant information, they will make a decision that
results in the maximum expected utility.
Utility
o
Economists The goal of good decision making is to make choices
that result in the maximum monetary payoff.
Advantages for the utility approach
o Specific

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o
Problems for utility approach
o People do not always make decisions that result in the desired outcome
Example.
Denes-Raj and Epstein (1994)
o Receive $1 when you draw a red jelly bean from a bowl
consisting red and white jelly beans.
Bowl containing 1 red and 9 white
10% probability of choosing red
Bowl containing 7 red and 93 white
7% Probability of choosing red
o But many chose this bowl with
less favorable probability.
Emotions after decisions
o Expected emotions
Emotions that people predict they will feel for a particular outcome.
Heads/Tails $10 example.
o Decline bc chances are 50/50
o Immediate emotions
Emotions that are experienced at the time a decision is being made
Two types:
o Integral immediate emotions
Emotions associated with the act of making a
decision.
o Incidental immediate emotions
Emotions that are unrelated to the decision
E.g.
o
o Something that happened earlier
in the day
Context can affect decisions
o Two camera models on display (Simonson & Tversky, 1992)
$170 model
$240 model
Decisions were split about equally between the $170 and $240
model
o But if a third camera for $470 was also on display,
Participants were more likely to choose the
$240 option than the $170 option
Decisions can depend on how choices are presented
o E.g.
Take a decision about whether to become a potential organ donor.
Only 28% have actually granted permission by signing a donor
card.
o This signing of the card = Opt-in procedure
Opt-in procedure
It requires the person to take an active step.

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Opt-out procedure
E.g.
o Everyone is a potential organ donor unless they
request not to be.
France and Belgium use an opt-out procedure
Consent rate is more than 99%
Framing effect
o Decisions are influenced by how the choices are stated, or framed
Can highlight one aspect of situation
Saved: 72% chose Program A
Die: 78% chose Program D
Taking risks
Justification in Decision Making
o Decision making process often includes looking for justification so the person
can state a rationale for his or her decision
I studied hard and performed well in the final exams, So I will treat
myself with Haagen-Dazs ice cream
The Physiology of Thinking
Prefrontal Cortex (PFC)
o The PFC plays a central role in determining complex behaviors that are
involved in thinking
Interferes with ability to act in a flexible manner
Important for problem solving
o One symptom of PFC damage is a behavior called perseveration
o Perseveration
Patients have difficulty switching from one pattern of behavior to
another
o Important for reasoning, planning and making connections among different
parts of a problem/story
As reasoning problems become more complex
Larger areas of the PFC are activated.
o Experiment

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Patients with prefrontal cortex damage
Deductive reasoning task (Waltz et al 1999)
o Participants were presented with relationships such as
Sam is taller than Nate
Nate is taller than Roger
o Participants asked to arrange the name in order of the
o Participants (3 groups)
Patients with PFC damage
Patients with temporal lobe damage
Participants without brain damage.
All groups did well when the task was
easy
However, when the task was made more
difficult by scrambling the order of the
presentation
o The patients with PFC damage
performed poorly.
Neuro economics
o Combines research from the fields of psychology, neuroscience, and
economics
One outcome of this approach
Has identified areas of the brain that are activated as people
make decisions while playing economic games
o Sanfey et al. (2003)
Ultimatum game
Two people play
o One is designated as the proposer
o Other designated as the responder
Proposer
o Given a sum of money ($10) and makes an offer to the
responder as to how this money should be split
between them
Responder
o If responder accepts the offer, then money is split
according to proposal
o If responder denies the offer, neither player receives
anything
Either way, game is over once responder makes
any decision
Results:
o Responders often rejected low offers
o Responders were angry because they felt the offers
were unfair
o They were less angry with an unfair computer
$5 accept
$3 most accept

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$1/$2 reject
Sanfey et al (2003) measured brain activity in the responders as they
were making their decisions
The right anterior insula, an area located deep within the brain
between parietal and temporal lobes,
o Was activated for about 3 times more strongly when
responders rejected an offer than when they accepted
it.
This area of the brain is connected with negative emotional
states
o Pain
o Distress
o Hunger
o Anger
o Disgust
Also found that the Prefrontal cortex (PFC) was also activated
by the decision task
o But this activation was the same for offers that are
rejected and offers that are accepted.
The same activation level in the PFC for offers
that were rejected and offers that were
accepted.
Omission Bias
o The tendency to do nothing to avoid having to make a decision that could be
interpreted as causing harm
o
I will not take the vaccine, and I accept the 10% chance of dying from
this flu
I will take the vaccine, and I accept the 5% chance of dying from the
weaker flu in the vaccine.
Zikmund-Fisher et al (2006)
o 52% of the participants decided to do nothing
Even though statistically this doubled their
chances of dying.
The end!!!!