Cog5 lecppt chapter11

© 2010 by W. W. Norton & Co., Inc.

Judgment and Reasoning

Chapter 11Lecture Outline

Chapter 12: Judgment and Reasoning

Lecture OutlineJudgment HeuristicsAnchoringDetecting CovariationAssessing the DamageConfirmation and DisconfirmationLogicDecision Making

Judgment Heuristics

Induction（歸納） is a pattern of reasoning in which one seeks to draw general claims from specific bits of evidenceBased on what you know about Allen, what is

likely to cheer him up today?Based on what you know about cars, what is

the best kind to buy?

Judgment Heuristics

Heuristic （捷思）Reasonably efficient and accurate Gain efficiency lose accuracy

Judgment heuristics includeAttribute substitutionAvailability heuristicRepresentativeness heuristic

Judgment Heuristics

Attribute substitution is a strategy used when we do not have easy access to a desired piece of information

Instead, we base our decision on readily available information (a proxy or index) that we believe is correlated with the desired information

Judgment Heuristics

Ease of reading = author intelligence

Judgment Heuristics

Availability heuristic Specific case of attribute substitution Ease with which examples come to mind is

an index of frequency or likelihood This class is easy—I know four people who got

A’s.

Judgment Heuristics

For instance, consider In the English language, are there more

words that start with the letter “R” or with the letter “R” in the third position?

Who washes the dishes more often, you or your roommates?

Are more deaths caused by crimes or by diseases?

Judgment Heuristics

The availability heuristic More words that begin with “R”

RealityMore words with “R” in the third position,But words that begin with “R” are easier to

bring to mind

Judgment Heuristics

The availability heuristic may lead us to believe that we always do the housework ourselves

Judgment Heuristics

The availability heuristic may lead us to think that more deaths are caused by crimes or accidents than by disease

In reality, far more deaths are caused by disease

Judgment Heuristics

Availability heuristicGroup of students asked to recall past

episodes in which they had been assertive (Schwarz et al., 1991)

One group gave 6 examples, and another, 12 examples

Which group then judged themselves to be more assertive in general?

Judgment Heuristics

Those that gave 6 examples judged themselves as more assertive

Easier to come up with 6 examples

Judgment Heuristics

The representativeness heuristic is another example of attribute substitution

Member Prototype Categoryresembles resembles

Judgment Heuristics

For instance, considerDo you assume anything about someone if

you discover that he or she is a lawyer or an engineer?

If a coin toss results in “heads” six times in a row, what are the odds of getting “tails” the seventh time?

If you hear an anecdote about a marathon runner who has smoked for decades and is perfectly healthy, does this mean that smoking is safe?

Judgment Heuristics

The representativeness heuristic All lawyers or all engineers are

homogeneous (a stereotype)We assume that each individual member of a

category has the traits we associate with the category overall.

Judgment Heuristics

The representativeness heuristic The seventh coin toss is more likely to be tails

(the gambler’s fallacy), but the odds are still 50-50

Judgment Heuristics

The representativeness heuristic Smoking must be okay for your health based

on one example (anecdotal evidence or “man who” stories)

This is an example of reasoning from one instance to the population.

Judgment Heuristics

Representativeness heuristic Watched “prison guard” discussing his job (Hamill et

al., 1980)

One variable of the study was whether the guard was compassionate or contemptuous. Another variable was whether the participants were told the guard was representative of all guards.

What did participants later conclude about prison guards in general?

Judgment Heuristics

Compassionate Contemptuous

Representative Compassionate Contemptuous

Not Representative Compassionate Contemptuous

Judgments were based on characteristics independent of whether participants were told the guard was representative or not

Detecting Covariation

Covariation Relationship between two variables

Negative or positive and can vary in strength. Does college education lead to a higher paying

job? Do you feel better when you have a good

breakfast?


An illusory covariation A perceived pattern such that

one variable predicts another A study of Rorschach inkblots

found that even when fictitious patients and fictitious responses were randomly paired, people believed they had found patterns.

Other studies have found that clinicians believed that homosexuals and heterosexuals interpreted these images differently even though the data did not show this.


Confirmation biasMore responsive to evidence that confirms

one’s beliefsSimilar to overregularization by schemataEssentially we ignore disconfirming data


Big dogs are viciousNotice examples that fit this pattern more

readily (biased attention)Will recall examples that fit the pattern more

readily (biased memory)


Another reason that estimates of covariation can be inaccurate is a neglect of base-rate information.

Base-rate information—information about the likelihood of an event

Diagnostic information—does an individual case belong to a category?


Consider this exampleTesting a new drug, in hopes that it will cure

hepatitis Does taking the drug covary with a better

medical outcome?


Results70% of the patients taking the drug do recover

from the illness Uninterpretable If it turns out that the overall recovery rate is

70%, then our new drug is having no effect whatsoever.


InterpretationWe need to know the base rate

How many are cured with no treatment How many more are cured with treatment


Kahneman and Tversky (1973) Base-rate information: 70 lawyers and 30

engineers Diagnostic information (engineering):

“likes carpentry, sailing, math puzzles; dislikes politics”


The base-rate with no diagnostic information = base rateThe base rate is not neglected!

Base-rate and diagnostic information = diagnostic information.The base rate is neglected!


Is Tom an engineer? Does Tom resemble an engineer?

Representativeness heuristicWhat percentage are engineers?

Attend to base rate Base-rate neglect

Assessing the Damage

Imagine your friend has a system for playing the lottery What if she tells you it only worked the last

time she played orShe tells you it worked the last ten times she

playedWhich do you believe?

Data set size and drawing conclusions about a new category: One time might be lucky; ten times is likely to be true.


Dual-process modelsSystem 1 refers to thinking that is fast,

automatic, and uses heuristicsSystem 2 refers to thinking that is slower,

effortful, and more likely to be correct


Whether System 1 or System 2 is used depends on the context of the decisionHow much time is available for the decision?How much attention and working memory are

available? And how the problem is presented

What format are the data in?Are statistical concepts primed?


Emphasizing chance cues statistical reasoningA story about a restaurant assessment based

on a single meal chosen by one person Informed assessment?

Now imagine that the person dropped his or her pencil on the menu to pick that meal

Informed assessment?


Background knowledge increases the likelihood that participants will pay attention to base ratesFor instance, when predicting whether a

particular student will pass an exam, participants do pay attention to the base-rate information that only 30% of students pass the exam


37


Training can influence the likelihood of reasoning with System 2For instance, participants can be trained that

large samples of data are more reliable than small samples

Taking a statistics class also improves reasoning when sample size is important

Confirmation and Disconfirmation

Deduction start with general premises and ask what follows If you believe that red wine gives you

headaches, what follows from this? If relationships based on physical attraction

never last, what follows from this?


Rooster wants to prove his crowing causes the sun to rise

Confirming evidence: every day the rooster crows, and the sun rises

Disconfirming evidence: one day he must not crow and see what happens


Confirmation bias—more responsive to evidence that confirms one’s beliefs and less responsive to evidence that challenges one’s beliefs


In a classic demonstration of confirmation bias, Wason (1966) presented sequences like “2-4-6” Several minutes to figure out rule (ascending

numbers two apart) They only sought confirming evidence Did not seek disconfirming evidence

A few did discover the rule Sought disconfirming evidence


Selective Memory.Gamblers betting on a football game

Wins are confirming evidence Losses are remembered as near-wins


Belief perseverance is a tendency to continue endorsing a belief even when evidence has completely undermined it


Assigned to good or bad groups Told about assignment

Bad judgers Good judgers

Ability to judge whether authentic

Bad Good

Self-ratings of social sensitivity

Low High

Logic

Categorical syllogisms logical arguments containing two premises and a conclusion

Syllogisms（三段論） can be valid or invalid

Logic

Is this syllogism valid? All P are M. All S are M. Therefore, all S are P.

In concrete terms: All plumbers 水電工

are mortal凡人 . All sadists 虐待狂 are

mortal. Therefore, all sadists

are plumbers.

Logic

The errors people make on syllogisms tend to fall into predictable categories

One pattern is belief bias—if the syllogism’s conclusion is something people already believe to be true, they are more likely to judge the conclusion as following from the premises

Logic

Low-level matching strategy between the words in the premises and those in the conclusions (the atmosphere effect)Some A are not X.Some B are not X.Therefore, some A are not B. (invalid)

Logic

A conditional statement If X, then Y. If antecedent, then consequent

Logic

modus ponens, affirming the antecedent If P is true, then Q is true.P is true.Therefore, Q must be true.

Easiest form of logic

Logic

modus tollens, denying the consequent If P is true, then Q is true.Q is false.Therefore, P must be false.

More difficult

Logic

Two common errors are affirming the consequent If P is true, then Q is true.Q is true.Therefore, P must be true. (invalid)

And denying the antecedent If P is true, then Q is true.P is false.Therefore, Q must be false. (invalid)

Logic

If P is true, then Q is true.

P true P no true

Q true Modus ponens Illogical

Q not true Illogical Denial of the consequent

Logic

If P is true, then Q is true.

Conditional statement Type of reasoning

P true, Q true Modus ponens

P not true, Q not true Denial of the antecedent

Q true, P true Affirmation of the consequent

Q not true, P not true Modus tollens

Logic

Logic

For both syllogisms and conditional statements, errors are more likely when Negatives are involved The terms are abstract

(e.g., letters) and not concrete

Logic

Wason’s four-card task “If a card has a vowel on one side, then it must

have an even number on the other side” Which cards must be turned over to test this

rule?

Logic

4% of people

Logic

A more concrete example

“If a person is drinking beer, then the person must be over 19 years of age.”

Logic

73% of participants

Logic

Why are some versions of the four-card problem difficult and others easy?

Evolutionary psychologists suggest people can “detect cheaters” who are not following rules of social interaction

Logic

Alternatively, a pragmatic reasoning schema may help explain the ease

These schemas involve “permission” or “cause and effect” relations

Logic

Problem: “If a form says ‘entering’ on one side, then the other side must include ‘cholera.’”

Logic

Permission schema “If a passenger wishes to enter the country, he

or she must first receive a cholera inoculation.”

Logic

Necessary condition “If Jacob passed his driver’s test, then it’s

legal for him to drive.” Sufficient condition

“If Solomon is eligible for jury duty, then he is over 21.”

Logic

Summary of logicPeople commonly rely on reasoning

strategies that are different from the principles of formal logic

Some of these principles are simple, such as the “matching strategy”

Others are more sophisticated, such as a “permission schema,” but may only be triggered under the right circumstances

Decision Making

UtilityTheory Expected value = (probability of a particular

outcome) x (utility of the outcome)

Decision Making

Many of our decisions follow the principle of utility maximization, or choosing the option with the greatest expected value

Decision Making

However, many decisions do not follow this principle

For instance, consider the following problem, as framed either in terms of lives saved or lives lost

Decision Making

Decision Making

Framing changes the choicesProgram A if the problem is “positively framed”

in terms of lives savedProgram B if the problem is “negatively

framed” in terms of lives lost Identical utility

Decision Making

Decision Making

Risk-seeking

Risk-averse

Decision Making

To which parent would you award full child custody?

Decision Making

To which parent would you deny full child custody?

Decision Making

An alternative view is known as reason-based choice, the idea that people make a decision only when they detect what they believe to be a persuasive reason for making that choice

Decision Making

Decision Making

Reason-based choiceScenario A—there is only one choice (the

Sony)Scenario B—there are two choices

Decision Making

80

Number of choices increases the sure choice

Decision Making

The orbitofrontal cortex is essential for evaluation of somatic markers

Patients with damage will make risky decisions

Decision Making

Emotions play a role in decision making, through what might be called affective heuristics

For instance, decisions that involve assessing risk may depend on the feeling of dread of an undesirable outcome, or anticipating the feeling of regret for having made the wrong choice

Note that the latter involves predictions about our future emotions, which are not necessarily accurate

Decision Making

People overestimate their future feelings

83

Decision Making

Decision making and happiness Unable to forecast our future feelings Would be better off having others make our choices We end up “stumbling on happiness” We end up stressed by the “paradox of choice”

Chapter 11 Questions

1. The fact that people report motor-vehicle deaths as more common than diabetes and homicides as more common than stomach cancer reflects which of the heuristics?

a) simulation heuristic

b) anchoring heuristic

c) availability heuristic

d) representativeness heuristic

2. Which of the following is TRUE of covariation?

a) A negative covariation indicates that there is no relationship between two variables.

b) People tend to underestimate covariation when they have theories about the relationship between two variables.

c) Covariations are “all-or-none” and cannot vary in strength.

d) Illusory covariations sometimes generate prejudice toward groups of people.

3. Which of the following is FALSE regarding confirmation bias?

a) It works to bring our recollections into line with our expectations.

b) It makes people more alert and responsive to evidence that confirms their beliefs than to challenging evidence.

c) Its effects are usually offset by our general ability to think about covariation.

d) It makes us unlikely to seek counterexamples.

4. Poor diagnostic reasoning and illusory correlations have been documented in all of the following cases EXCEPT

a) individuals with considerable experience in the domain being judged.

b) participants who have been offered cash bonuses for accurate performance.

c) individuals for whom the stakes are very high (e.g., doctors and financial advisors).

d) All of the above individuals demonstrate these errors.

5. According to the dual-process model of reasoning, one mode of thought is ___, while the other mode of thought is ___.

a) association driven; speedy

b) automatic; effortful

c) slower; effortful

d) automatic; effortless

6. In the study in which people were asked to judge their social sensitivity after being given false-positive or negative feedback (but then debriefed), participants were clearly influenced by

a) views they had of themselves before the experiment.

b) the feedback they had been given, even though they knew it was false.

c) the feedback they had been given, but only if they had forgotten the debriefing that undermined this feedback.

d) a memory search done after debriefing to help them disconfirm the false feedback.

7. In the context of a syllogism, what is a matching strategy?

a) If the two premises match each other, the conclusion is accepted.

b) If the conclusion matches the premises in wording and structure, it is accepted.

c) Statements with the same structure are all seen as identical.

d) People accept syllogisms when the conclusions match their beliefs.

Cog5 lecppt chapter11

Education

representativeness

matching strategy

judgment heuristics

detecting

availability

decision making

pay attention

ten times