Lecture 11 Flashcards
What is induction?
Provides probabilistic evidence
What is deduction?
If the premises are valid then conclusion must be true
What is syllogistic reasoning?
Syllogism consists of two premises followed by a conclusion
Inference is valid if conclusion follows necessarily from the premises given
What is the modus ponens rule
If p then q, therefore q.
All bananas are yellow. This is a banana. Therefore it is yellow
What is affirming the consequent (errors)
If p then q, therefore p.
All bananas are yellow
This is yellow
Therefore it is a banana
What is the modus tollens rule?
If p then q
Not q
Therefore not p
All bananas are yellow
This is not yellow
Therefore it is not a banana
What is denying the antecedent? (error)
If p then q
Not p
Therefore not q
All bananas are yellow
This is not a banana
Therefore it is not yellow
How good are people at deductive reasoning?
- Modus ponens 97%
- Modus tollens 73%
- Affirming the consequent 63%
- Denying the antecedent 55%
What is the reason for failure of reasoning?
Because people know and use logistical rules. Failure of reasoning occurs because people have difficulty combining these rules
What was the results in Watson’s selection tasks?
People were able to comprehend the beer example better than the vowels example because the content of the prepositions effects our reasoning process
What are pragmatic rules?
Rules we use that are domain specific i.e rules that apply to certain situations
They are activated by the content of the reasoning process
What is the permission rule?
That if an action is to be taken, then a precondition is to be satisfied.
What is the evidence for pragmatic rules
Envelope problem
– If the letter is sealed, then it has a 5-‐d stamp on it
– Hong Kong Ss are familiar with the “sealed envelope” scenario
• Cholera problem
– If the form says “Entering” then the other side lists cholera among the list of diseases.
What are the characteristics of deductive reasoning?
It is slow and effortful. People make lots of errors, particularly if the scenario is unfamiliar.
What are the two systems involved in deductive reasoning?
System 1-
operates quickly and automatically, with little or no effort and no sense of voluntary control.
System 2-
allocates attention to the effortful, mental activities that demand it…and is associated with the subjective experience of agency, choice and control.
What is inductive reasoning?
Probabilistic reasoning; e.g.
John majored in accountancy
John now works in an accounting firm
John is an accountant.
Is not deductively valid but inductively strong
What is Heuristics?
Rules of thumb; asking an easier question
Tversky & Kahneman-
In inductive reasoning, heuristics is applied and probability rules are ignored.
What is availability heuristics?
Estimating the probability on the basis of how easy it is to generate instances
Leads to errors because factors other than frequency affect availability
e.g.
Are there more words in English beginning with K or with K in third position?
Are politicians more likely to be unfaithful?
Are film stars more likely to divorce?
What is Representativeness heuristic
Estimating the probability on the basis of similarity
e. g. Jane is medium height, wears nice but comfortable clothes, is single and likes the read 18th century English poetry and plays. Is she more likely to be a shop assistant or an english lecturer
answer: shop assistant because there are more of them.
What is a mood heuristic?
No correlation between answers to these questions
- How happy are you these days?
-How many dates did you have in the last month?
High correlation when the question order reversed.
Dating question provides ready answer to more complex question.
Examples of target questions vs heuristic questions
Target:
How much would you contribute to save an endangered species.
Heuristic (people might think):
How much emotion do i feel when i think about dying dolphins
Target:
How happy are you with your life these days
Heuristic: What is my mood right now
How does availability heuristics affect marriages?
Worsens them-
e. g. How large was your personal contribution to keeping the house tidy in percentages?
- What was your personal contribution to taking the garbage out?
Sum of both partners typically should add up to 100%- but always ends up much higher
How is judgement affected in Availability heuristics?
by the number of instances retrieved and by the ease of retrieval.
What is the base rate rules?
The probability of something being a member of a class is greater the more class members there are.
