Memory and Cognition PSY 324 Topic: Reasoning Dr. Ellen Campana Arizona State University

Memory and Memory and CognitionCognition

PSY 324PSY 324

Topic: ReasoningTopic: Reasoning

Dr. Ellen CampanaDr. Ellen Campana

Arizona State UniversityArizona State University

ReasoningReasoning

ReasoningReasoning is is Process of drawing conclusions Process of drawing conclusions Cognitive process by which people start Cognitive process by which people start

with information and come to with information and come to conclusions that go beyond that conclusions that go beyond that informationinformation

Using those definitions we’ve Using those definitions we’ve already seen many examples of already seen many examples of reasoning – can you think of some?reasoning – can you think of some?

ReasoningReasoning Focus today on two specific types of Focus today on two specific types of

reasoningreasoning Deductive reasoningDeductive reasoning (Aristotle) (Aristotle)

Sequences of statements (Sequences of statements (syllogismssyllogisms)) What can logically be concluded?What can logically be concluded? DefiniteDefinite conclusions conclusions

Inductive reasoningInductive reasoning Based on evidenceBased on evidence What is What is probablyprobably true in the world? true in the world? ProbableProbable conclusions conclusions

Both types tell us about cognition in Both types tell us about cognition in generalgeneral

Deductive Deductive ReasoningReasoning

Deductive ReasoningDeductive Reasoning Deductive reasoningDeductive reasoning is all about logic is all about logic

This is logic as mathematicians, This is logic as mathematicians, philosophers and computer scientists define philosophers and computer scientists define itit

As we’ll see, it doesn’t always match up As we’ll see, it doesn’t always match up with common sensewith common sense

Note for tests: When you encounter a Note for tests: When you encounter a logic problem, be careful. It’s asking for logic problem, be careful. It’s asking for very specific things. I’ll give you a very specific things. I’ll give you a strategy later.strategy later.

Deductive ReasoningDeductive Reasoning

Basic form of deductive reasoning is Basic form of deductive reasoning is syllogismsyllogism Includes 2 or more statements Includes 2 or more statements

((premisespremises), followed by a ), followed by a conclusionconclusion Categorical syllogisms are a type of Categorical syllogisms are a type of

syllogismsyllogism Premises and conclusion describe the Premises and conclusion describe the

relationship between categoriesrelationship between categories Words like Words like allall, , nono, and , and somesome are used are used

Categorical SyllogismsCategorical Syllogisms

This is an example of a categorical This is an example of a categorical syllogism:syllogism:Premise 1: All birds are animalsPremise 1: All birds are animals

Premise 2: All animals eat foodPremise 2: All animals eat food

Conclusion: (Therefore) all birds eat foodConclusion: (Therefore) all birds eat food In “perfect form” this can be written asIn “perfect form” this can be written as

Premise 1: All A are BPremise 1: All A are B

Premise 2: All B do CPremise 2: All B do C

Conclusion: (Therefore) all A do CConclusion: (Therefore) all A do C

Validity and Deductive Validity and Deductive ReasoningReasoning

Syllogisms can be Syllogisms can be validvalid or or not validnot valid Here Here validvalid means something means something very specific very specific – be – be

careful!careful! ValidValid syllogisms syllogisms

The conclusions The conclusions follow logically follow logically from the from the premisespremises

If all premises are true, then the conclusion is If all premises are true, then the conclusion is truetrue

What if one premise is not true?What if one premise is not true? Syllogism can still be valid if the Syllogism can still be valid if the formform is valid is valid

Truth and validity are NOT the sameTruth and validity are NOT the same This is difficult for people!This is difficult for people!


Let’s practice…. Valid or not?Let’s practice…. Valid or not?Premise 1: All red cars are sports carsPremise 1: All red cars are sports cars

Premise 2: All sports cars are fastPremise 2: All sports cars are fast

Conclusion: All red cars are fastConclusion: All red cars are fast

VALID!


Let’s practice…. Valid or not?Let’s practice…. Valid or not?Premise 1: All red cars are sports carsPremise 1: All red cars are sports cars

Premise 2: All red cars are fastPremise 2: All red cars are fast

Conclusion: All sports cars are fastConclusion: All sports cars are fast

NOT VALID!


Let’s practice…. Valid or not?Let’s practice…. Valid or not?Premise 1: All of the students are tiredPremise 1: All of the students are tired

Premise 2: Some tired people are Premise 2: Some tired people are irritableirritable

Conclusion: Some of the students are Conclusion: Some of the students are irritableirritable

NOT VALID!


Let’s practice…. Valid or not?Let’s practice…. Valid or not?Premise 1: All of the men are tiredPremise 1: All of the men are tired

Premise 2: Some tired people are womenPremise 2: Some tired people are women

Conclusion: Some men are womenConclusion: Some men are women

NOT VALID!


Let’s practice…. Valid or not?Let’s practice…. Valid or not?Premise 1: All lava lamps are lampsPremise 1: All lava lamps are lamps

Premise 2: All lamps are furniturePremise 2: All lamps are furniture

Conclusion: All lava lamps are furnitureConclusion: All lava lamps are furniture

VALID!


This practice was intended to illustrate This practice was intended to illustrate that that truthtruth and and validityvalidity are not the same are not the same TruthTruth depends on consistency with the world depends on consistency with the world ValidityValidity depends on the form of the depends on the form of the

statementsstatements Does it follow a Does it follow a logical progressionlogical progression??

Do people think logically?Do people think logically? Philosophers say yes, errors are due to Philosophers say yes, errors are due to

carelessnesscarelessness Cognitive Psychologists say no, errors tell us Cognitive Psychologists say no, errors tell us

how people really think in everyday situationshow people really think in everyday situations

Studying Deductive Studying Deductive ReasoningReasoning

Two methods have been usedTwo methods have been used Evaluation method:Evaluation method: present premises and present premises and

conclusion, ask people to judge validityconclusion, ask people to judge validity Production method:Production method: present premises, ask present premises, ask

what can logically be concluded, if anythingwhat can logically be concluded, if anything Most research has used the evaluation Most research has used the evaluation

methodmethod People make lots of errors (70-80%)People make lots of errors (70-80%) Error rate determined by many factors, Error rate determined by many factors,

including whether problem is including whether problem is abstractabstract or or concreteconcrete

Problem StatementProblem Statement A categorical syllogism that’s A categorical syllogism that’s concreteconcrete::

Premise 1: All robins are birdsPremise 1: All robins are birdsPremise 2: All birds are animalsPremise 2: All birds are animalsConclusion: (Therefore) all robins are animalsConclusion: (Therefore) all robins are animals

A categorical syllogism that’s A categorical syllogism that’s abstractabstract::Premise 1: All A are BPremise 1: All A are BPremise 2: All B are CPremise 2: All B are CConclusion: (Therefore) all A are CConclusion: (Therefore) all A are C

Lower error rates for abstract Lower error rates for abstract statementsstatements

Here’s my tip: convert to abstract for Here’s my tip: convert to abstract for the test the test

Errors and Concrete Errors and Concrete ProblemsProblems

When logic problems are stated in When logic problems are stated in concrete terms, error rate goes upconcrete terms, error rate goes up

Part of this effect is due to Part of this effect is due to biasesbiases that that people bring to the task of reasoningpeople bring to the task of reasoning Atmosphere effectAtmosphere effect Belief biasBelief bias

Biases are another example of Biases are another example of heuristicsheuristics Much faster, often right Much faster, often right Sometimes cause errorsSometimes cause errors

Atmosphere EffectAtmosphere Effect

Atmosphere effect: the words Atmosphere effect: the words allall, , somesome, , nono in the premises create an overall “mood” in the premises create an overall “mood” or “atmosphere” that can influence or “atmosphere” that can influence judgementjudgement AllAlls in premise suggest s in premise suggest allall in conclusion in conclusion NoNos in premise suggest s in premise suggest nono in conclusion in conclusion SomeSomes in premise suggest s in premise suggest some some in conclusionin conclusion

This is sometimes, but not always, correctThis is sometimes, but not always, correct Be careful of this bias in the test!Be careful of this bias in the test!

Belief BiasBelief Bias

If a conclusion is true (meaning it If a conclusion is true (meaning it matches the world) or consistent matches the world) or consistent with a person’s belief, the whole with a person’s belief, the whole syllogism will often be judged validsyllogism will often be judged valid It’s as if people skip the logic and move It’s as if people skip the logic and move

right to evaluating the conclusionright to evaluating the conclusion


Let’s practice…. Valid or not?Let’s practice…. Valid or not?Premise 1: No police dogs are viciousPremise 1: No police dogs are vicious

Premise 2: Some highly trained dogs are Premise 2: Some highly trained dogs are viciousvicious

Conclusion: Some police dogs are not Conclusion: Some police dogs are not highly trainedhighly trained

NOT VALID!


Let’s practice…. Valid or not?Let’s practice…. Valid or not?Premise 1: No addictive drugs are Premise 1: No addictive drugs are

inexpensiveinexpensive

Premise 2: Some cigarettes are Premise 2: Some cigarettes are inexpensiveinexpensive

Conclusion: Some addictive drugs are not Conclusion: Some addictive drugs are not cigarettescigarettes

NOT VALID!

Thinking ConditionallyThinking Conditionally Much of the research on deductive Much of the research on deductive

reasoning has focused on reasoning has focused on conditional conditional syllogismssyllogisms Conditional syllogismsConditional syllogisms are like are like categorical categorical

syllogismssyllogisms, except the first premise is , except the first premise is if… if… then..then..

Common in everyday lifeCommon in everyday life

Let’s say you lent your friend Steve $20, but Let’s say you lent your friend Steve $20, but he has never paid you back. Knowing Steve, he has never paid you back. Knowing Steve, you might say to yourself that you knew this you might say to yourself that you knew this would happen.would happen.

Thinking ConditionallyThinking Conditionally Much of the research on deductive Much of the research on deductive

reasoning has focused on reasoning has focused on conditional conditional syllogismssyllogisms Conditional syllogismsConditional syllogisms are like are like categorical categorical

syllogismssyllogisms, except the first premise is , except the first premise is if… if… then..then..

Common in everyday lifeCommon in everyday life

Premise 1: If I lend Steve $20, then I won’t get Premise 1: If I lend Steve $20, then I won’t get it backit back

Premise 2: I lent Steve $20Premise 2: I lent Steve $20Conclusion: I won’t get my $20 backConclusion: I won’t get my $20 back

Thinking ConditionallyThinking Conditionally

The second premise can either The second premise can either affirmaffirm or or denydeny either the either the antecedentantecedent or the or the consequentconsequent This relationship is what determines This relationship is what determines validityvalidity

As before, validity is NOT the same as truth in the worldAs before, validity is NOT the same as truth in the world

If then…… ……p q

antecedent consequent

Valid Conditional Valid Conditional SyllogismsSyllogisms

Affirming the antecedentAffirming the antecedent is is validvalid Affirming the antecedentAffirming the antecedent is when the is when the

second premise asserts that the second premise asserts that the antecedentantecedent of the first premise is of the first premise is truetrue

Premise 1: If Premise 1: If pp, then , then qq..

Premise 2: Premise 2: pp..

Conclusion: (Therefore), Conclusion: (Therefore), qq..


Affirming the antecedentAffirming the antecedent is is validvalid Affirming the antecedentAffirming the antecedent is when the is when the

second premise asserts that the second premise asserts that the antecedentantecedent of the first premise is of the first premise is truetrue

Premise 1: If Premise 1: If I studyI study, then , then I’ll get a good I’ll get a good gradegrade..

Premise 2: Premise 2: I studiedI studied..

Conclusion: (Therefore), Conclusion: (Therefore), I’ll get a good I’ll get a good gradegrade..


Denying the consequentDenying the consequent is is validvalid Denying the consequentDenying the consequent is when the is when the

second premise asserts that the second premise asserts that the consequentconsequent of the first premise is of the first premise is NOT NOT truetrue


Premise 2: Premise 2: not qnot q..

Conclusion: (Therefore), Conclusion: (Therefore), not pnot p..


Denying the consequentDenying the consequent is is validvalid Denying the consequentDenying the consequent is when the is when the

second premise asserts that the second premise asserts that the consequentconsequent of the first premise is of the first premise is NOT NOT truetrue


Premise 2: Premise 2: I didn’t get a good gradeI didn’t get a good grade..

Conclusion: (Therefore), Conclusion: (Therefore), I didn’t studyI didn’t study..

Invalid Conditional Invalid Conditional SyllogismsSyllogisms

Affirming the consequentAffirming the consequent is is not not validvalid Affirming the consequentAffirming the consequent is when the is when the

second premise asserts that the second premise asserts that the consequentconsequent of the first premise is of the first premise is truetrue


Premise 2: Premise 2: qq..

Conclusion: (Therefore), Conclusion: (Therefore), pp..


Affirming the consequentAffirming the consequent is is not not validvalid Affirming the consequentAffirming the consequent is when the is when the

second premise asserts that the second premise asserts that the consequentconsequent of the first premise is of the first premise is truetrue


Premise 2: Premise 2: I got a good gradeI got a good grade..

Conclusion: (Therefore), Conclusion: (Therefore), I studiedI studied..


Denying the antecedentDenying the antecedent is is not validnot valid Denying the antecedentDenying the antecedent is when the is when the

second premise asserts that the second premise asserts that the antecedentantecedent of the first premise is of the first premise is NOT NOT truetrue


Premise 2: Premise 2: not pnot p..

Conclusion: (Therefore), Conclusion: (Therefore), not qnot q..


Denying the antecedentDenying the antecedent is is not validnot valid Denying the antecedentDenying the antecedent is when the is when the

second premise asserts that the second premise asserts that the antecedentantecedent of the first premise is of the first premise is NOT trueNOT true


Premise 2: Premise 2: I didn’t studyI didn’t study..

Conclusion: (Therefore), Conclusion: (Therefore), I didn’t get a good I didn’t get a good gradegrade..

Conditional SyllogismsConditional Syllogisms

Let’s practice…. Type? Valid or not? Let’s practice…. Type? Valid or not? Premise 1: If it’s a robin, then it’s a birdPremise 1: If it’s a robin, then it’s a bird

Premise 2: It’s not a robin.Premise 2: It’s not a robin.

Conclusion: (Therefore) it’s not a bird.Conclusion: (Therefore) it’s not a bird.

Denyingthe

Antecedent

NOT VALID!



Premise 2: It’s not a bird.Premise 2: It’s not a bird.

Conclusion: (Therefore) it’s not a robin.Conclusion: (Therefore) it’s not a robin.

Denying the

Consequent

VALID!



Premise 2: It’s a bird.Premise 2: It’s a bird.

Conclusion: (Therefore) it’s a robin.Conclusion: (Therefore) it’s a robin.

Affirming the

Consequent

NOT VALID!



Premise 2: It’s a robin.Premise 2: It’s a robin.

Conclusion: (Therefore) it’s a bird.Conclusion: (Therefore) it’s a bird.

Affirming the

Antecedent

VALID!

Errors in ReasoningErrors in Reasoning

If people used logical rules in reasoning If people used logical rules in reasoning there would be no effect of the problem there would be no effect of the problem statementstatement As we’ll see, there is an effect of problem As we’ll see, there is an effect of problem

statementstatement Errors can tell us how people represent the Errors can tell us how people represent the

problem and reason about itproblem and reason about it One task that has been used to study errors One task that has been used to study errors

in reasoning is the in reasoning is the Wason four-card Wason four-card problemproblem Different versions lead to different patterns Different versions lead to different patterns

Coglab NoteCoglab Note

If you have not done this week’s If you have not done this week’s Coglab, the Wason Selection Task, Coglab, the Wason Selection Task, do it now!do it now!

The Wason Four-Card The Wason Four-Card ProblemProblem

Four cardsFour cards Number on one sideNumber on one side Letter on the other sideLetter on the other side

Test the following ruleTest the following rule If there’s a If there’s a vowelvowel on one side, then on one side, then

there’s an there’s an even numbereven number on the other on the other sideside

The cache: Flip the The cache: Flip the minimumminimum number of cardsnumber of cards


Rule: If vowel, then even numberRule: If vowel, then even number Which card would you flip first?Which card would you flip first? Are there any other cards you would Are there any other cards you would

need to flip in order to be completely need to flip in order to be completely sure?sure?

E K 4 7


Rule: If vowel, then even number Rule: If vowel, then even number Flipping the E directly tests the ruleFlipping the E directly tests the rule

Even number consistent with the ruleEven number consistent with the rule Odd number Odd number violatesviolates the rule the rule

In this version 53% picked E (correct)In this version 53% picked E (correct)

E K 4 7


Rule: If vowel, then even number Rule: If vowel, then even number What about flipping the 4? What about flipping the 4?

Vowel consistent with the ruleVowel consistent with the rule Consonant Consonant does not violatedoes not violate the rule the rule

In this version 46% picked 4 In this version 46% picked 4 (incorrect/suboptimal)(incorrect/suboptimal)

E K 4 7


Rule: If vowel, then even number Rule: If vowel, then even number What about flipping the 7? What about flipping the 7?

Consonant consistent with the ruleConsonant consistent with the rule Vowel Vowel violatesviolates the rule the rule

In this version 4% picked 4 (correct)In this version 4% picked 4 (correct)

E K 4 7


The correct answer to the problem is that in The correct answer to the problem is that in order to be 100% certain that the rule is order to be 100% certain that the rule is correct you would need to flip a minimum of correct you would need to flip a minimum of 2 cards2 cards E (affirmation of antecedent) E (affirmation of antecedent) 7 (denial of the consequent)7 (denial of the consequent)

Key to solution is the Key to solution is the falsification principlefalsification principle Falsification principle:Falsification principle: to test a rule it is to test a rule it is

necessary to look for situations that falsify necessary to look for situations that falsify (violate) that rule(violate) that rule

This version is called the This version is called the abstract versionabstract version


FlipFlip……

Result Result is…is…

Then this __ the ruleThen this __ the rule

EE EvenEven ConfirmsConfirms

EE OddOdd FalsifiesFalsifies

KK EvenEven Is irrelevant toIs irrelevant to

KK OddOdd Is irrelevant toIs irrelevant to

44 VowelVowel ConfirmsConfirms

44 ConsonanConsonantt

Is irrelevant toIs irrelevant to

77 VowelVowel FalsifiesFalsifies

77 ConsonanConsonantt

Is irrelevant toIs irrelevant to

Real-world Four-card Real-world Four-card ProblemsProblems

If we change the way the problem is If we change the way the problem is stated, people change their behaviorstated, people change their behavior

Griggs and Cox did a version with Griggs and Cox did a version with drinking agedrinking age Imagine you are a police officer applying Imagine you are a police officer applying

the following rule: the following rule: if a person is drinking if a person is drinking beer, then he or she must be over 19 beer, then he or she must be over 19 years oldyears old

Each card has an age on one side and a Each card has an age on one side and a drink on the otherdrink on the other

Griggs and Cox (1982)Griggs and Cox (1982)

Rule: If drinking beer, must be over 19 Rule: If drinking beer, must be over 19 years oldyears old Which card would you flip first?Which card would you flip first? Are there any other cards you would need Are there any other cards you would need

to flip in order to be completely sure?to flip in order to be completely sure?

Beer Soda 24 16

Griggs and Cox (1982)Griggs and Cox (1982)

Rule: If drinking beer, must be over 19 years Rule: If drinking beer, must be over 19 years oldold Correct answers are Correct answers are BeerBeer and and 1616 (no others) (no others) This is much easier for people than the abstract This is much easier for people than the abstract

version of the task (73% correct vs. 0% correct)version of the task (73% correct vs. 0% correct)

Beer Soda 24 16

Real-world Four-card Real-world Four-card ProblemsProblems

The beer version of the problem was easier The beer version of the problem was easier for people because it was more concrete for people because it was more concrete Or could it have been experience with the Or could it have been experience with the

situation described by the problem?situation described by the problem? There’s another version of the problem that There’s another version of the problem that

was used to investigate this possibilitywas used to investigate this possibility Problem described in terms of postal regulationsProblem described in terms of postal regulations Great Britain has different regulations than the Great Britain has different regulations than the

USUS

Johnson-Laird and Johnson-Laird and Coworkers (1972)Coworkers (1972)

Rule: If a letter is sealed, must have 5d Rule: If a letter is sealed, must have 5d stampstamp This rule was familiar to people in Great BritainThis rule was familiar to people in Great Britain Original experiment done in Great BritainOriginal experiment done in Great Britain Easier for British people than the abstract Easier for British people than the abstract

version of the task (81% correct vs. 15% correct)version of the task (81% correct vs. 15% correct) Griggs and Cox (1982) tested Americans, Griggs and Cox (1982) tested Americans,

found that this was just as difficult as found that this was just as difficult as abstract abstract

5d 4d

Postal Four-Card Postal Four-Card ProblemProblem

What’s the point of the postal version of the What’s the point of the postal version of the four-card problem?four-card problem? Demonstrates that problem statement affects Demonstrates that problem statement affects

accuracyaccuracy Effect goes beyond Effect goes beyond concreteconcrete vs. vs. abstractabstract

wordingwording Related to experience with the situation, tooRelated to experience with the situation, too

Next, two more aspects that affect Next, two more aspects that affect performanceperformance Permission schemasPermission schemas Social-exchange theorySocial-exchange theory

Permission SchemasPermission Schemas

Cheng & Holyoak (1985) proposed that Cheng & Holyoak (1985) proposed that people solve the real-world versions of people solve the real-world versions of the task using the task using pragmatic reasoning pragmatic reasoning schemasschemas Pragmatic reasoning schemasPragmatic reasoning schemas: ways of : ways of

thinking about cause & effect that we learn thinking about cause & effect that we learn in daily lifein daily life

Permission schemasPermission schemas are one type are one type If a person satisfies condition A, they have If a person satisfies condition A, they have

permission to carry out action Bpermission to carry out action B

Activating a Activating a permission schemapermission schema can can improve performance in a four-card taskimprove performance in a four-card task

Permission SchemasPermission Schemas In the abstract problem, participants were In the abstract problem, participants were

not encouraged to activate permission not encouraged to activate permission schemasschemas indicated whether an abstract statement was indicated whether an abstract statement was

truetrue In the drinking problem, people were In the drinking problem, people were

encouraged to activate permission schemasencouraged to activate permission schemas Indicated whether people drinking beer had Indicated whether people drinking beer had

permission to do sopermission to do so In the postal problem, British people but not In the postal problem, British people but not

Americans were encouraged to activate Americans were encouraged to activate permission schemas (based on experience)permission schemas (based on experience)

Cheng and Holyoak Cheng and Holyoak (1985)(1985)

Previous results were consistent with Previous results were consistent with the hypothesis, but it needed a direct the hypothesis, but it needed a direct testtest

Another version of the problem, related Another version of the problem, related to immigrationto immigration

Two descriptions, same cards, same Two descriptions, same cards, same solutionsolution Some participants were encouraged to Some participants were encouraged to

activate permission schemasactivate permission schemas Other participants were not encouraged to Other participants were not encouraged to

activate permission schemasactivate permission schemas


You are an immigration officer at the International You are an immigration officer at the International Airport in Manila, capital of the Philippines. Among Airport in Manila, capital of the Philippines. Among the documents you have to check is a sheet called the documents you have to check is a sheet called

Form H. One side of the form indicates the whether Form H. One side of the form indicates the whether the passenger is entering the country or in transit the passenger is entering the country or in transit

and the other side of the form lists names of tropical and the other side of the form lists names of tropical diseases. You have to make sure that if the form diseases. You have to make sure that if the form says “entering” on one side, that the other side says “entering” on one side, that the other side

includes cholera among the list of diseases. Which of includes cholera among the list of diseases. Which of the following forms would you have to turn over to the following forms would you have to turn over to

check? Indicate only those that you need to check to check? Indicate only those that you need to check to be sure.be sure.

Entering TransientCholeraTyphoidHepatitis

TyphoidHepatitis


You are an immigration officer at the International You are an immigration officer at the International Airport in Manila, capital of the Philippines. Among Airport in Manila, capital of the Philippines. Among the documents you have to check is a sheet called the documents you have to check is a sheet called

Form H. One side of the form indicates the whether Form H. One side of the form indicates the whether the passenger is entering the country or in transit the passenger is entering the country or in transit

and the other side of the form lists and the other side of the form lists inoculations the inoculations the travelers had received in the past 6 monthstravelers had received in the past 6 months. You . You have to make sure that if the form says “entering” on have to make sure that if the form says “entering” on one side, that the other side includes cholera among one side, that the other side includes cholera among

the list of diseases. the list of diseases. This is to ensure that the This is to ensure that the entering passengers are protected against the entering passengers are protected against the disease.disease. Which of the following forms would you Which of the following forms would you

have to turn over to check? Indicate only those that have to turn over to check? Indicate only those that you need to check to be sure.you need to check to be sure.


TyphoidHepatitis


first version = abstract taskfirst version = abstract task second version = checking to see if the second version = checking to see if the

travelers had the correct inoculations travelers had the correct inoculations to gain to gain permissionpermission to enter the country to enter the country

This difference had an important effectThis difference had an important effect No permission / abstract: 56% correctNo permission / abstract: 56% correct Permission: 91% correctPermission: 91% correct


TyphoidHepatitis


It seems likely that people use permission It seems likely that people use permission schemas to reason in four-card problemsschemas to reason in four-card problems Analogy may play a role, because Analogy may play a role, because

participants had never been immigration participants had never been immigration officers in the Philippinesofficers in the Philippines

More on this point a little laterMore on this point a little later There is another explanation (as always)There is another explanation (as always)

This one comes from the This one comes from the evolutionary evolutionary approachapproach

It is based on It is based on social-exchange theorysocial-exchange theory and and the idea of the idea of cheatingcheating

The Evolutionary The Evolutionary ApproachApproach

The The evolutionary perspective on evolutionary perspective on cognitioncognition: we can trace many properties of : we can trace many properties of our minds to the evolutionary principles of our minds to the evolutionary principles of natural selectionnatural selection Characteristics that help an individual survive Characteristics that help an individual survive

will, over time, become basic characteristics of will, over time, become basic characteristics of humanshumans

This is applied to cognition as well as physical This is applied to cognition as well as physical traitstraits

One such adaptive characteristic relates to One such adaptive characteristic relates to social-exchange theorysocial-exchange theory

Social-Exchange TheorySocial-Exchange Theory An important aspect of human behavior is the An important aspect of human behavior is the

ability for two people to cooperate in a way ability for two people to cooperate in a way that is beneficial to both peoplethat is beneficial to both people Morg lends Eng a carving tool in exchange for foodMorg lends Eng a carving tool in exchange for food

Works well when each person receives Works well when each person receives benefits, but problems arise when someone benefits, but problems arise when someone cheatscheats Morg lends Eng a carving too but gets no foodMorg lends Eng a carving too but gets no food

According to According to Evolutionary ApproachEvolutionary Approach, , detecting cheating is adaptive due to detecting cheating is adaptive due to Social-Social-ExchangeExchange Those who can Those who can detect and avoid cheatingdetect and avoid cheating have have

had a better chance of survival, so it has become had a better chance of survival, so it has become part of uspart of us

Card Task: Evolutionary Card Task: Evolutionary Explanation Explanation

In the abstract task, no reference to In the abstract task, no reference to cheatingcheating

In the beer task, people detect cheatingIn the beer task, people detect cheating Find underage drinkersFind underage drinkers

In the postage task, British people but not In the postage task, British people but not Americans, detect cheatingAmericans, detect cheating Find letters without proper postageFind letters without proper postage

In the immigration task, people detect In the immigration task, people detect cheating in the permission versioncheating in the permission version Find people entering without proper Find people entering without proper

vaccinationsvaccinations

Cosmides and Tooby Cosmides and Tooby (1992)(1992)

Goal: separate permission and cheatingGoal: separate permission and cheating Used unfamiliar situations to do thisUsed unfamiliar situations to do this

Story involved a fake culture called the Story involved a fake culture called the KulwaneKulwane If a man eats cassava root, then he must have a If a man eats cassava root, then he must have a

tatoo on his face (violators would be cheating)tatoo on his face (violators would be cheating) People performed well in this task, compared to People performed well in this task, compared to

similar unfamiliar stories that didn’t involve similar unfamiliar stories that didn’t involve cheatingcheating

Interpretation: observed effects are due to Interpretation: observed effects are due to ability to detect cheating (not permissions)ability to detect cheating (not permissions)

Permission vs. CheatingPermission vs. Cheating

Others have gone on to investigate the Others have gone on to investigate the permissions account with unfamiliar permissions account with unfamiliar situationssituations ““If you clean up spilt blood you must wear gloves”If you clean up spilt blood you must wear gloves” Permissions improve accuracyPermissions improve accuracy

Evidence for and against both accountsEvidence for and against both accounts Situations where improvements are not observedSituations where improvements are not observed

Others have proposed other explanationsOthers have proposed other explanations Evidence to support and refute these, tooEvidence to support and refute these, too

Take-home MessageTake-home Message We still don’t know exactly how people do We still don’t know exactly how people do

conditional reasoning in the four-card conditional reasoning in the four-card problemproblem Familiarity sometimes (not always) affects itFamiliarity sometimes (not always) affects it Permissions and Cheating sometimes (not Permissions and Cheating sometimes (not

always) may affect italways) may affect it Example of how different researchers come Example of how different researchers come

to different conclusions about the same to different conclusions about the same datadata The workings of the mind must be observed The workings of the mind must be observed

from behavioral observationsfrom behavioral observations Just like Donders’ experiment in the first Just like Donders’ experiment in the first

chapterchapter

Inductive Inductive ReasoningReasoning

Deductive vs. Inductive Deductive vs. Inductive ReasoningReasoning

Deductive reasoningDeductive reasoning Premises are facts (general)Premises are facts (general) Reason about specificsReason about specifics Definite conclusionsDefinite conclusions Validity is importantValidity is important

Inductive reasoningInductive reasoning Based on observation of specificsBased on observation of specifics Reason about general conclusionReason about general conclusion Conclusions are suggestive (not Conclusions are suggestive (not

definite)definite) Strength of argument is importantStrength of argument is important

Inductive ReasoningInductive Reasoning

Observation: All the crows I’ve seen in Observation: All the crows I’ve seen in Pittsburgh are black. When I visited Pittsburgh are black. When I visited my brother in Washington D.C. the my brother in Washington D.C. the crows I saw there were black, too.crows I saw there were black, too.

Conclusion: I think it’s a pretty good Conclusion: I think it’s a pretty good bet that all crows are black.bet that all crows are black.

Inductive ReasoningInductive Reasoning

Observation: Here in Nashville, the sun Observation: Here in Nashville, the sun has risen every morning.has risen every morning.

Conclusion: The sun is going to rise in Conclusion: The sun is going to rise in Nashville tomorrow morning.Nashville tomorrow morning.

The second argument is more The second argument is more convincingconvincing We say it is a “stronger argument”We say it is a “stronger argument”

Strength of Inductive Strength of Inductive ArgumentArgument

Strong arguments are more likely to Strong arguments are more likely to result in conclusions that are true result in conclusions that are true than weak onesthan weak ones

Many factors contribute to argument Many factors contribute to argument strengthstrength Representativeness of observationsRepresentativeness of observations Number of observationsNumber of observations Quality of evidenceQuality of evidence

Scientific evidence contributes to qualityScientific evidence contributes to quality

Inductive Reasoning in Inductive Reasoning in ScienceScience

Inductive reasoning is the basic Inductive reasoning is the basic procedure used for scientific discoveriesprocedure used for scientific discoveries Goal: discover something newGoal: discover something new Method: collect specific observationsMethod: collect specific observations

Representative sampleRepresentative sample As many observations as possibleAs many observations as possible High quality through experimental designHigh quality through experimental design

Inductive Reasoning: use this data to make Inductive Reasoning: use this data to make inferences about the general case with inferences about the general case with theorytheory


Example: determining attitudes by pollingExample: determining attitudes by polling If you poll only a few people, it’s less strongIf you poll only a few people, it’s less strong If you poll only this class, results may not If you poll only this class, results may not

generalize to the whole U.S. population (less generalize to the whole U.S. population (less strong)strong)

The postal version of the 4-card problem was first The postal version of the 4-card problem was first tested with British people, did not generalize to tested with British people, did not generalize to Americans)Americans)

If the poll is not well-designed it will be difficult If the poll is not well-designed it will be difficult to see how the results relate to other findings to see how the results relate to other findings or predict behavior in the general case (less or predict behavior in the general case (less strong)strong)


Inductive reasoning can be used to reach Inductive reasoning can be used to reach conclusions about the dataconclusions about the data These conclusions can also be seen as general These conclusions can also be seen as general

predictions about future experimentspredictions about future experiments Can then be combined with Can then be combined with deductive deductive

reasoningreasoning to set forth the rationale for the to set forth the rationale for the next experimentnext experiment

If the rationale is logically valid, then if the If the rationale is logically valid, then if the conclusion is not true it tells us something conclusion is not true it tells us something about the truth of the individual premisesabout the truth of the individual premises

Reasoning in ScienceReasoning in Science Reasoning in action: Immigration 4-card Reasoning in action: Immigration 4-card

problem problem Inductive inference Inductive inference

Wason, Griggs & Cox, and Johnson-Laird collected Wason, Griggs & Cox, and Johnson-Laird collected observations and wrote about themobservations and wrote about them

Cheng and Holyoak looked at those observations and Cheng and Holyoak looked at those observations and made an inductive inference based on theorymade an inductive inference based on theory

Observation: Performance on the 4-card task Observation: Performance on the 4-card task improves when the problem is stated in improves when the problem is stated in terms of permissionterms of permission

Conclusion: In general, people use permission Conclusion: In general, people use permission schemas to reason about problemsschemas to reason about problems


problem problem Inductive inference Inductive inference

Cheng and Holyoak could have stopped there, but Cheng and Holyoak could have stopped there, but they wanted/needed to strengthen the argumentthey wanted/needed to strengthen the argument

To strengthen argument there are 3 things you To strengthen argument there are 3 things you can docan do

Increase representativeness of sample of observationsIncrease representativeness of sample of observations Increase number of observationsIncrease number of observations Increase quality of evidenceIncrease quality of evidence

Adding another experiment accomplished all threeAdding another experiment accomplished all three Deductive Inference was used to lay out the Deductive Inference was used to lay out the

rationale for their next experimentrationale for their next experiment


problem problem Deductive (Conditional) InferenceDeductive (Conditional) Inference

Premise 1: If a permission schema is activated, then Premise 1: If a permission schema is activated, then performance on the Wason task should improveperformance on the Wason task should improve

Premise 2: In this experiment, one of the groups Premise 2: In this experiment, one of the groups will read a sentence that will activate a will read a sentence that will activate a permissions schemapermissions schema

Conclusion: Therefore, performance of this group Conclusion: Therefore, performance of this group will improvewill improve This is a valid conditional syllogismThis is a valid conditional syllogism If the conclusion is not true in the experiment, then we If the conclusion is not true in the experiment, then we

know that at least one of the premises is untrueknow that at least one of the premises is untrue

Inductive Reasoning in Inductive Reasoning in Daily LifeDaily Life

We use inductive reasoning for We use inductive reasoning for determining choices we make in daily lifedetermining choices we make in daily life Based on observations about previous tests in Based on observations about previous tests in

this class you predict what the next test will be this class you predict what the next test will be likelike

You use this prediction to make choices about You use this prediction to make choices about how to study and what notes to preparehow to study and what notes to prepare

Often not even aware that we’re Often not even aware that we’re reasoningreasoning Predict that a chair will be stable, so just sit on Predict that a chair will be stable, so just sit on

it (without testing it to see if it’s sturdy)it (without testing it to see if it’s sturdy)


Every time we make a prediction about Every time we make a prediction about what what will happenwill happen based on based on what has happened in what has happened in the pastthe past, we are using inductive reasoning, we are using inductive reasoning

It would be very time-consuming if every It would be very time-consuming if every situation was experienced as if it was the situation was experienced as if it was the firstfirst Every time you chose your route to schoolEvery time you chose your route to school Every problem-solving situationEvery problem-solving situation

It would be especially time-consuming if you It would be especially time-consuming if you also had to reach definite (100%) also had to reach definite (100%) conclusionsconclusions


When people use past experience to When people use past experience to guide current behavior they often use guide current behavior they often use short-cuts to help them reach a decision short-cuts to help them reach a decision quicklyquickly These short-cuts are called These short-cuts are called heuristics heuristics

We’ve seen heuristics before (vision, language, We’ve seen heuristics before (vision, language, etc.)etc.)

Rapid and often correct, but sometimes cause Rapid and often correct, but sometimes cause errorserrors

We’ll talk about two of these heuristicsWe’ll talk about two of these heuristics Availability heuristicAvailability heuristic Representativeness heuristicRepresentativeness heuristic

Availability HeuristicAvailability Heuristic

Availability heuristic:Availability heuristic: Events that Events that are more easily remembered are are more easily remembered are judged as being more probablejudged as being more probable Which is more probable? Words that begin Which is more probable? Words that begin

with with rr or words that have or words that have rr in the third in the third position?position?

It’s actually those that have It’s actually those that have r r in the third in the third position, but people guess the other optionposition, but people guess the other option

rr at the start is easier to remember (coded at the start is easier to remember (coded phonologically)phonologically)

Lichtenstein and Lichtenstein and Coworkers, 1978Coworkers, 1978

Which cause of death is more likely?Which cause of death is more likely? Homicide or AppendicitisHomicide or Appendicitis Auto-train Collision or DrowningAuto-train Collision or Drowning Measles or SmallpoxMeasles or Smallpox Botulism or AsthmaBotulism or Asthma Asthma or TornadoAsthma or Tornado Appendicitis or PregnancyAppendicitis or Pregnancy


Which cause of death is more likely?Which cause of death is more likely? HomicideHomicide or Appendicitis (20x) or Appendicitis (20x) Auto-train Collision or Auto-train Collision or Drowning Drowning (5x)(5x) MeaslesMeasles or Smallpox (infinite) or Smallpox (infinite) Botulism or Botulism or Asthma Asthma (920x)(920x) AsthmaAsthma or Tornado (20x) or Tornado (20x) AppendicitisAppendicitis or Pregnancy (2x) or Pregnancy (2x)



Does not match actual probabilitiesDoes not match actual probabilities

9% error30% error40% error41% error58% error80% error



Does not match actual probabilitiesDoes not match actual probabilities

9% error30% error40% error41% error58% error80% error


What does account for the error What does account for the error patterns?patterns? Those causes of death that are talked Those causes of death that are talked

about most (in media, etc) are more about most (in media, etc) are more available in memoryavailable in memory

Because they’re more available, they’re Because they’re more available, they’re assumed to be more probableassumed to be more probable

This is the This is the availability heuristicavailability heuristic at at workwork

McKelvie (1997)McKelvie (1997) Direct test of the availability heuristic Direct test of the availability heuristic

hypothesishypothesis People saw lists of names and had to estimate People saw lists of names and had to estimate

whether there were more males or females whether there were more males or females Some saw famous women, non-famous menSome saw famous women, non-famous men Some saw famous men, non-famous womenSome saw famous men, non-famous women Whichever was famous actually had fewer namesWhichever was famous actually had fewer names

ResultsResults Famous women condition: 77% error (“more Famous women condition: 77% error (“more

women”)women”) Famous men condition: 81% error (“more men”)Famous men condition: 81% error (“more men”)

Famous = more available Famous = more available

Availability Heuristic Availability Heuristic

911 Example911 Example After 911 there were many images of planes After 911 there were many images of planes

smashing into buildings in the mediasmashing into buildings in the media Air travel dropped – people drove insteadAir travel dropped – people drove instead Fatality rate of driving is 500x greater than air Fatality rate of driving is 500x greater than air

travel on commercial planes, even after 911travel on commercial planes, even after 911 Correlations between eventsCorrelations between events

When it smells a certain way in the morning it When it smells a certain way in the morning it rains later that day – I should bring my rains later that day – I should bring my umbrella umbrella

Illusory CorrelationsIllusory Correlations

Being able to detect correlations is useful, Being able to detect correlations is useful, but because of the availability heuristic we but because of the availability heuristic we can observe correlations where they don’t can observe correlations where they don’t really existreally exist

StereotypesStereotypes: oversimplified generalizations : oversimplified generalizations about a group of people that often focuses on about a group of people that often focuses on negativesnegatives Examples that are consistent are more available Examples that are consistent are more available

because we focus attention on aspects that are because we focus attention on aspects that are consistent with stereotypesconsistent with stereotypes

Related to Related to confirmation biasconfirmation bias (later) (later)

Representativeness Representativeness HeuristicHeuristic

Representativeness HeuristicRepresentativeness Heuristic: : probability that event A comes from class probability that event A comes from class B can be determined by how well A B can be determined by how well A resembles properties of class Bresembles properties of class B

We randomly pick one male from the We randomly pick one male from the population of the US. That male, Robert, population of the US. That male, Robert,

wears glasses, speaks quietly, and reads a wears glasses, speaks quietly, and reads a lot. Is it more likely that Robert is a lot. Is it more likely that Robert is a

librarian or a farmer?librarian or a farmer?


We randomly pick one male from the We randomly pick one male from the population of the US. That male, Robert, population of the US. That male, Robert,

wears glasses, speaks quietly, and reads a wears glasses, speaks quietly, and reads a lot. Is it more likely that Robert is a lot. Is it more likely that Robert is a

librarian or a farmer?librarian or a farmer?

Most people think he’s a librarian because Most people think he’s a librarian because the facts about him are more consistent the facts about him are more consistent with stereotypes of typical librarianswith stereotypes of typical librarians Ignore the Ignore the base ratebase rate – there are more – there are more

farmers in USfarmers in US


In a group of 100 people, there are 70 In a group of 100 people, there are 70 lawyers and 30 engineers. What is lawyers and 30 engineers. What is

the chance that if we pick on person the chance that if we pick on person from the group at random that from the group at random that

person will be an engineer?person will be an engineer?

People get this problem right – 30% People get this problem right – 30% chances (more likely it’s a lawyer)chances (more likely it’s a lawyer)


In a group of 100 people, there are 70 In a group of 100 people, there are 70 lawyers and 30 engineers. Say we pick a lawyers and 30 engineers. Say we pick a person from that group at random. The person from that group at random. The

person is Jack. Jack is a 45-year-old man. person is Jack. Jack is a 45-year-old man. He is married and has 4 children. He He is married and has 4 children. He

shows no interest in political and social shows no interest in political and social issues and spends most of his free time on issues and spends most of his free time on

his many hobbies, which include home his many hobbies, which include home carpentry, sailing, and mathematical carpentry, sailing, and mathematical

problems. What is the chance that Jack is problems. What is the chance that Jack is an engineer?an engineer?

Still 30% but people get it wrong Still 30% but people get it wrong (disregard base rate)(disregard base rate)


Perhaps a stronger demonstration of Perhaps a stronger demonstration of the heuristic comes from cases the heuristic comes from cases where people ignore the where people ignore the conjuction conjuction rulerule Conjunction rule:Conjunction rule: the probability of the probability of

the conjunction of two events (A and B) the conjunction of two events (A and B) cannot be higher than the probability of cannot be higher than the probability of the single constituents (A alone or B the single constituents (A alone or B alone)alone)

When A is a subset of B it is easy to see When A is a subset of B it is easy to see why this is the casewhy this is the case

ConjunctionsConjunctions

Probability of femist bank tellers Probability of femist bank tellers cannot be higher than probability of cannot be higher than probability of bank tellersbank tellers

Bank TellersFeministBank Tellers


Linda is 31 years old, single, outspoken, and Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As very bright. She majored in philosophy. As a student, she was deeply concerned with a student, she was deeply concerned with issues of discrimination and social justice, issues of discrimination and social justice,

and also participated in antinuclear and also participated in antinuclear demonstrations. Which of the following demonstrations. Which of the following

alternatives is more probable?alternatives is more probable?

1. Linda is a bank teller1. Linda is a bank teller2. Linda is a bank teller and is active in the 2. Linda is a bank teller and is active in the

feminist movementfeminist movement


Correct answer to the bank teller problem Correct answer to the bank teller problem is that it’s more probable that Linda is a is that it’s more probable that Linda is a bank tellerbank teller This is due to the This is due to the conjunction ruleconjunction rule

When Tversky and Kaneman (1983) asked When Tversky and Kaneman (1983) asked people to do this rating, 85% got it wrongpeople to do this rating, 85% got it wrong The details about Linda were more The details about Linda were more

representative of bank tellers who are active in representative of bank tellers who are active in the feminist movementthe feminist movement

Representativeness guided choice, instead of Representativeness guided choice, instead of relationships between probabilitiesrelationships between probabilities


Another demonstration of the heuristic is Another demonstration of the heuristic is when people ignore the when people ignore the law of large law of large numbersnumbers Law of large numbers:Law of large numbers: the larger the the larger the

number of individuals that are randomly number of individuals that are randomly drawn from a population, the more drawn from a population, the more representative the resulting group will be of representative the resulting group will be of the populationthe population

Male and Female births example is a good Male and Female births example is a good demonstration of how people ignore this demonstration of how people ignore this rulerule

Ignoring Sample SizeIgnoring Sample Size

A certain town is served by two hospitals. In the A certain town is served by two hospitals. In the larger hospital about 45 babies are born each larger hospital about 45 babies are born each

day and in the smaller hospital about 15 day and in the smaller hospital about 15 babies are born each day. As you know, about babies are born each day. As you know, about 50% of babies are boys. However, the exact 50% of babies are boys. However, the exact

percentage varies from day to day. percentage varies from day to day. Sometimes it may be higher than 50% and Sometimes it may be higher than 50% and

sometimes it may be lower. For a period of 1 sometimes it may be lower. For a period of 1 year, each hospital recorded the number of year, each hospital recorded the number of days in which more than 50% were boys. days in which more than 50% were boys. Which hospital recorded more such days?Which hospital recorded more such days?

The larger hospitalThe larger hospitalThe smaller hospitalThe smaller hospital

About the same (within 5%)About the same (within 5%)

Ignoring Sample SizeIgnoring Sample Size

Correct answer is Correct answer is the smaller hospitalthe smaller hospital Because of the law of large numbers the Because of the law of large numbers the

larger hospital is more representative of the larger hospital is more representative of the population probabilitypopulation probability

It’s easy to see this if we pretend that the It’s easy to see this if we pretend that the smaller hospital only had 1 birth a day smaller hospital only had 1 birth a day Probabilities would always be 100% or 0%Probabilities would always be 100% or 0%

In the study (Tversky & Kahneman, 1974)In the study (Tversky & Kahneman, 1974) 22% smaller, 22% larger, 56% said no diff22% smaller, 22% larger, 56% said no diff 56% demonstrated representativeness 56% demonstrated representativeness

heuristicheuristic

Errors in ReasoningErrors in Reasoning

We’ve talked about 2 heuristics that We’ve talked about 2 heuristics that people use in reasoningpeople use in reasoning Availability heuristicAvailability heuristic Representativeness heuristicRepresentativeness heuristic

I also promised we’d come back to I also promised we’d come back to confirmation biasconfirmation bias Confirmation bias:Confirmation bias: our tendency to our tendency to

selectively look for information that selectively look for information that conforms to our hypotheses and to conforms to our hypotheses and to overlook information that argues against overlook information that argues against itit

Confirmation BiasConfirmation Bias

Wason (1960)Wason (1960) Asked people to try and guess a rule he was Asked people to try and guess a rule he was

using to generate lists of numbersusing to generate lists of numbers At each step, they produced a set of numbers At each step, they produced a set of numbers

and their rationale for choosing themand their rationale for choosing them Feedback on whether numbers fit experimentor’s Feedback on whether numbers fit experimentor’s

rulerule No feedback on rationaleNo feedback on rationale

Very few participants found Wason’s rule Very few participants found Wason’s rule because they focused only on finding support because they focused only on finding support for theirsfor theirs

Confirmation BiasConfirmation Bias

The key to finding Wason’s solution was The key to finding Wason’s solution was to create sequences that to create sequences that disconfirmed disconfirmed their own current hypotheses their own current hypotheses Like in the 4-card task, key is Like in the 4-card task, key is falsificationfalsification

Not only do people seek out Not only do people seek out confirmingconfirming information, rather than information, rather than disconfirming disconfirming information, they also information, they also disregard falsifying information when it disregard falsifying information when it is presented to themis presented to them Lord and Coworkers (1979) – Capital Lord and Coworkers (1979) – Capital

punishment punishment

Lord and Coworkers Lord and Coworkers (1979)(1979)

Questionairre used to separate people into Questionairre used to separate people into groups in favor of or against capital groups in favor of or against capital punishmentpunishment

Groups were presented with articles about Groups were presented with articles about research on capital punishmentresearch on capital punishment Evidence that CP deters murderEvidence that CP deters murder Evidence that CP has no effect on murderEvidence that CP has no effect on murder

Results – reactions consistent with Results – reactions consistent with questionairre ratings (no main effect of questionairre ratings (no main effect of article)article)

Confirmation bias is like blinders that we Confirmation bias is like blinders that we wear!wear!

Decision-MakingDecision-Making


Decision-making:Decision-making: choosing among choosing among alternativesalternatives What college to attendWhat college to attend Who to marryWho to marry What job to chooseWhat job to choose What to eat or wearWhat to eat or wear

Decision-making uses both inductive and Decision-making uses both inductive and deductive reasoningdeductive reasoning Affected by biases and heuristics we’ve Affected by biases and heuristics we’ve

discusseddiscussed


In discussing reasoning, the focus In discussing reasoning, the focus was on how people make judgments was on how people make judgments of probability or validityof probability or validity

In discussing decision-making we’ll In discussing decision-making we’ll focus on how people make focus on how people make judgments that involve different judgments that involve different courses of actioncourses of action Decisions involve Decisions involve costscosts and and benefitsbenefits

Utility Approach to Utility Approach to DecisionsDecisions

Early theory on decision-making was Early theory on decision-making was influenced by influenced by economic utility theoryeconomic utility theory People are basically rationalPeople are basically rational If they have all relevant information, they If they have all relevant information, they

will decide based on maximum expected will decide based on maximum expected utilityutility

Utility:Utility: outcomes are in the person’s outcomes are in the person’s best interestbest interest Maximum monetary payoff in economicsMaximum monetary payoff in economics

Utility Approach to Utility Approach to DecisionsDecisions

Advantage of Utility Approach is that it Advantage of Utility Approach is that it clearly specifies procedures that will clearly specifies procedures that will allow people to determine which allow people to determine which choice will result in highest payoffchoice will result in highest payoff Given the odds of winning at slots over Given the odds of winning at slots over

time it is possible to determine that time it is possible to determine that playing slots has low utilityplaying slots has low utility

It is unwise to play the slotsIt is unwise to play the slots But people do play the slots, even But people do play the slots, even

though they know thisthough they know this

Limits of Utility TheoryLimits of Utility Theory

It could be that people play slots (and do It could be that people play slots (and do other things that don’t maximize payoff) other things that don’t maximize payoff) because they’re irrationalbecause they’re irrational Not likely to be the caseNot likely to be the case

Maybe they just value other things Maybe they just value other things besides moneybesides money Benefit of winning may outweigh monetary Benefit of winning may outweigh monetary

costcost Maybe they represent the decision Maybe they represent the decision

differentlydifferently

Limits of Utility TheoryLimits of Utility Theory

Tickets to the ball game, $60. Hot Tickets to the ball game, $60. Hot dogs, $10. Your team’s baseball cap, dogs, $10. Your team’s baseball cap, $20. Seeing the game with your son $20. Seeing the game with your son or daughter, “priceless.”or daughter, “priceless.”

Costs and benefits cannot always be Costs and benefits cannot always be determined or compared objectivelydetermined or compared objectively Often in the mind of the person making Often in the mind of the person making

the decisionthe decision

Mental Simulations Mental Simulations People create People create mental simulationsmental simulations and and

use them to make decisionsuse them to make decisions To decide between college A and college B, To decide between college A and college B,

one could imagine what it might be like to be one could imagine what it might be like to be at each oneat each one

Simulations used to estimate costs and Simulations used to estimate costs and benefitsbenefits

Sometimes simulations can be inaccurateSometimes simulations can be inaccurate People only imagine positive outcomes of People only imagine positive outcomes of

winning the lotterywinning the lottery There are negative outcomes tooThere are negative outcomes too

Decisions and EmotionsDecisions and Emotions

Many decisions involve estimating Many decisions involve estimating the emotions you will have with each the emotions you will have with each possible outcomepossible outcome Having a baby will make me happyHaving a baby will make me happy

People are bad at estimating how People are bad at estimating how things will make them feelthings will make them feel One factor responsible is the One factor responsible is the focusing focusing

illusionillusion, in which focusing attention , in which focusing attention changes estimates of emotionchanges estimates of emotion

Strack and Coworkers Strack and Coworkers (1988)(1988)

Students were asked two questions:Students were asked two questions: How happy are you?How happy are you? How many dates did you have last month?How many dates did you have last month?

The order of the questions affected the The order of the questions affected the answersanswers Happy first, correlation 0.12Happy first, correlation 0.12 Happy second, correlation 0.66Happy second, correlation 0.66

Dating question first caused people to Dating question first caused people to focus on dating as a determinant of focus on dating as a determinant of happinesshappiness

Schkade and Kahneman Schkade and Kahneman (1998)(1998)

Asked students two questionsAsked students two questions How would you rate your life satisfaction?How would you rate your life satisfaction? Are people who live in California or the Are people who live in California or the

Midwest more satisfied?Midwest more satisfied? ResultsResults

For self ratings, no difference between For self ratings, no difference between locationslocations

For other ratings, everyone said CaliforniaFor other ratings, everyone said California For other vs. self, people focused on For other vs. self, people focused on

different determinants of satisfactiondifferent determinants of satisfaction

Presentation FormPresentation Form

Decisions can also depend on how Decisions can also depend on how the decision is presentedthe decision is presented Just like for reasoningJust like for reasoning

Different problem statementsDifferent problem statements Opt-inOpt-in vs. vs. opt-outopt-out

85% of people support organ donation, but 85% of people support organ donation, but only 28% of Americans opt-in to the only 28% of Americans opt-in to the programprogram

In countries with the opt-out version, 99% In countries with the opt-out version, 99% stay in (support rate is about the same)stay in (support rate is about the same)

Justification In Decision Justification In Decision MakingMaking

Participants heard a story about taking an Participants heard a story about taking an exam and then being offered a vacation exam and then being offered a vacation packagepackage Some knew they’d passed in the storySome knew they’d passed in the story Some knew they’d failed in the storySome knew they’d failed in the story Some knew results were not yet availableSome knew results were not yet available

People who “knew” about a pass OR fail People who “knew” about a pass OR fail were more likely to say they’d buy the were more likely to say they’d buy the packagepackage Like to attach a “reason” to a risky decisionLike to attach a “reason” to a risky decision

Physiology of Physiology of ThinkingThinking

Prefrontal Cortex (PFC)Prefrontal Cortex (PFC)

NeuropsychologyNeuropsychology PFC damage impaired meal planningPFC damage impaired meal planning PFC damage leads to PFC damage leads to perseverationperseveration, less , less

flexibilityflexibility PFC damage leads to poor problem solvingPFC damage leads to poor problem solving Patients with PFC damage have difficulty Patients with PFC damage have difficulty

arranging people by height when given arranging people by height when given statements like “Paul is taller than Sarah”. statements like “Paul is taller than Sarah”.

Imaging Imaging PFC activation during problem-solvingPFC activation during problem-solving

Final Example: Personal Final Example: Personal HealthHealth

Imagine that there will be a deadly flu going around Imagine that there will be a deadly flu going around your area next winter. Your doctor says that you have a your area next winter. Your doctor says that you have a 10 percent chance (10 in 100) of dying from this flu. A 10 percent chance (10 in 100) of dying from this flu. A new flu vaccine has been developed and tested. If new flu vaccine has been developed and tested. If administered, the vaccine will prevent you from administered, the vaccine will prevent you from catching the deadly flu. However, there is one serious catching the deadly flu. However, there is one serious risk involved: The vaccine is made from a somewhat risk involved: The vaccine is made from a somewhat weaker type of the flu virus, so there is a 5 percent risk weaker type of the flu virus, so there is a 5 percent risk (5 out of 100) that the vaccine could kill you. (5 out of 100) that the vaccine could kill you. Considering this information, what would you do?Considering this information, what would you do? I will not take the vaccine and I accept the 10 percent chance of I will not take the vaccine and I accept the 10 percent chance of

dying from this fludying from this flu I will take the vaccine and I accept the 5 percent chance of I will take the vaccine and I accept the 5 percent chance of

dying from the weaker flu in the vaccinedying from the weaker flu in the vaccine

Flu Vaccine ExampleFlu Vaccine Example

People choose the higher risk People choose the higher risk because of the because of the omission biasomission bias Do nothing to avoid making a decision Do nothing to avoid making a decision

that could be seen as causing harmthat could be seen as causing harm If deciding for others, more likely to If deciding for others, more likely to

go with the lower risk option go with the lower risk option (getting the shot)(getting the shot) If anything bad happens (either way) If anything bad happens (either way)

they may be held responsiblethey may be held responsibleREMINDER: Get your flu shot this year (with H1N1). And in case you are wondering I actually did get mine….

The EndThe End

This is the end of the last This is the end of the last chapter! Good luck on exams!chapter! Good luck on exams!

Judging ValidityJudging Validity

Some syllogisms are easier to judge than Some syllogisms are easier to judge than othersothers ValidValid syllogisms syllogisms

Affirming the antecedentAffirming the antecedent – easiest (97% correct) – easiest (97% correct) Denying the consequentDenying the consequent – medium (60% correct) – medium (60% correct)

InvalidInvalid syllogisms syllogisms Affirming the consequentAffirming the consequent – difficult (40% correct) – difficult (40% correct) Denying the antecedentDenying the antecedent – difficult (40% correct) – difficult (40% correct)

As before, error rate depends on problem As before, error rate depends on problem statement (example: statement (example: concreteconcrete vs. vs. abstractabstract)) Which one is easier, again?Which one is easier, again?

Evans and Coworkers Evans and Coworkers (1983)(1983)

Presented syllogisms Presented syllogisms Valid – believable conclusionValid – believable conclusion Valid – less believable conclusionValid – less believable conclusion Not valid – believable conclusionNot valid – believable conclusion Not valid – less believable conclusionNot valid – less believable conclusion

People judged validity (evaluation People judged validity (evaluation method)method) Believability bias for both valid and not validBelievability bias for both valid and not valid Stronger bias for syllogisms that were not Stronger bias for syllogisms that were not

validvalid

Memory and Memory and CognitionCognition

PSY 324PSY 324

Topic 12: ReasoningTopic 12: Reasoning

Dr. Ellen CampanaDr. Ellen Campana

Arizona State UniversityArizona State University

Deductive ReasoningDeductive Reasoning

Last time we were talking about Last time we were talking about deductive reasoningdeductive reasoning This is difficult for peopleThis is difficult for people Errors depend on surface formErrors depend on surface form

Atmosphere EffectAtmosphere Effect Belief biasBelief bias

Today we’ll start by talking about Today we’ll start by talking about how people might go about solving how people might go about solving these problemsthese problems


Let’s practice…. Valid or not?Let’s practice…. Valid or not?Premise 1: None of the artists are Premise 1: None of the artists are

beekeepersbeekeepers

Premise 2: All of the beekeepers are Premise 2: All of the beekeepers are chemistschemists

Conclusion: Some of the chemists are not Conclusion: Some of the chemists are not artistsartists

VALID!

Solving Deductive Solving Deductive Reasoning ProblemsReasoning Problems

One approach is to learn and use logical One approach is to learn and use logical rulesrules Computers usually do thisComputers usually do this Doesn’t account for belief bias, atmosphere Doesn’t account for belief bias, atmosphere

effectseffects Another is to learn and use graphical toolsAnother is to learn and use graphical tools

Venn diagramsVenn diagrams Euler circlesEuler circles

A third approach is to use a A third approach is to use a Mental ModelMental Model Proposed by Johnson-Laird (1995)Proposed by Johnson-Laird (1995)

Mental Models Mental Models An example problem: An example problem:

On a pool table there is a black ball directly On a pool table there is a black ball directly above the cue ball. The green ball is on the above the cue ball. The green ball is on the right side of the cue ball and there is a red right side of the cue ball and there is a red ball between them. If I move so the red ball between them. If I move so the red ball is between me and the black ball the ball is between me and the black ball the cue ball is on the __________ side of my line cue ball is on the __________ side of my line of sight.of sight.

How did you solve it?How did you solve it?

Mental ModelsMental Models

This problem could be solved by writing This problem could be solved by writing out logical rules and using them in out logical rules and using them in deductive reasoningdeductive reasoning Seems unlikely, doesn’t it?Seems unlikely, doesn’t it?

General point: people don’t use logical General point: people don’t use logical rules without being trained how to do rules without being trained how to do soso Instead they develop a Instead they develop a mental modelmental model of of

the specific situation and use it to find the the specific situation and use it to find the answeranswer

Mental Models and Mental Models and SyllogismsSyllogisms

Johnson-Liard’s proposalJohnson-Liard’s proposal Develop a mental model of the situation Develop a mental model of the situation Use the model to produce a tentative Use the model to produce a tentative

conclusion conclusion Look for exceptions to disprove the Look for exceptions to disprove the

conclusionconclusion If no exceptions found, accept conclusionIf no exceptions found, accept conclusion

We can see how this works using the We can see how this works using the artists, beekeepers, chemists syllogismartists, beekeepers, chemists syllogism


Premise 1: None of the artists are beekeepersPremise 1: None of the artists are beekeepers

Premise 2: All of the beekeepers are chemistsPremise 2: All of the beekeepers are chemists

Conclusion: Some of the chemists are not artistsConclusion: Some of the chemists are not artists

Imagine we are visiting a meeting of the Imagine we are visiting a meeting of the Artists, Beekeepers and Chemists society Artists, Beekeepers and Chemists society (ABC). (ABC). Everyone there is an artist, beekeeper, or chemistEveryone there is an artist, beekeeper, or chemist Two premises = rules determining membershipTwo premises = rules determining membership





Now imagine that each person has hats Now imagine that each person has hats on, telling what they do on, telling what they do Artists wear berets, beekeepers wear veils, Artists wear berets, beekeepers wear veils,

and chemists wear moleculesand chemists wear molecules





People can wear several hats, limited by People can wear several hats, limited by rulesrules Artists cannot wear veilsArtists cannot wear veils All those wearing veils must also wear All those wearing veils must also wear

moleculesmolecules Now imagine walking around at the Now imagine walking around at the

meeting – who do you see?meeting – who do you see?





Let’s say you meet two peopleLet’s say you meet two people Alice: wearing a beret, but no veil or moleculeAlice: wearing a beret, but no veil or molecule Beechem: wearing veil and molecule, no beretBeechem: wearing veil and molecule, no beret

Tentative conclusion: Tentative conclusion: No artists are chemistsNo artists are chemists





You continue wandering, looking for You continue wandering, looking for exceptionsexceptions Cyart: wearing a beret and moleculeCyart: wearing a beret and molecule

Revised conclusion: Revised conclusion: Some of the chemists Some of the chemists are not artistsare not artists





You continue wandering, looking for You continue wandering, looking for exceptionsexceptions Clara: wearing a molecule but no beret or veilClara: wearing a molecule but no beret or veil

No revision necessaryNo revision necessary Doesn’t refute Doesn’t refute some of the chemists are not some of the chemists are not

artistsartists





You continue wandering, looking for You continue wandering, looking for exceptionsexceptions You don’t encounter anyone else, though you You don’t encounter anyone else, though you

meet everyone at the meetingmeet everyone at the meeting Accept conclusion: Accept conclusion: some of the chemists some of the chemists

are not artistsare not artists


What’s the point of this example?What’s the point of this example? Illustrates how mental models work in Illustrates how mental models work in

deductive reasoning (according to Johnson-deductive reasoning (according to Johnson-Laird)Laird)

A conclusion is valid only if it cannot be A conclusion is valid only if it cannot be refuted by any model of the premisesrefuted by any model of the premises

The Mental Models Theory is appealingThe Mental Models Theory is appealing Doesn’t require training on rules of logicDoesn’t require training on rules of logic Makes testable predictionsMakes testable predictions

Problems with more / more complicated models Problems with more / more complicated models are more difficult to solve are more difficult to solve


The Mental Model Theory isn’t the only The Mental Model Theory isn’t the only one out there, and there is still one out there, and there is still disagreement about how people solve disagreement about how people solve syllogismssyllogisms

Challenging area of studyChallenging area of study People seem to be able to use a variety of People seem to be able to use a variety of

strategies for reasoningstrategies for reasoning Some people are much better at solving Some people are much better at solving

syllogisms than otherssyllogisms than others Related to next topic: Conditional Related to next topic: Conditional

ReasoningReasoning

Inductive Inductive ReasoningReasoning

Documents

Memory and Cognition PSY 324 Topic: Reasoning Dr. Ellen Campana Arizona State University