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Lecture 11

LEC11 – Inference Insight and Relevance Nov 26 2009

5 Pages
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Department
Psychology
Course Code
PSY370H1
Professor
John Vervaeke

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PSY370: Thinking and Reasoning
LEC11 Inference Insight and Relevance
Nov, 26th, 2009
Inference
! use of evidence to alter belief so as to preserve truth
! looking for patterns that are truth preservative
! deduction: there are inference patterns that guarantee if the premises are true then the
conclusion must be true
! reasons cannot be valid, only arguments can be valid
! induction: if the premises are true this increase the probability that the conclusion will be true
! almost all evidence in science is inductive argument
! deduction is the paramount exemplar of how logic should operate: formal logic
! distinction b/w form and content in logic
Critical detachment
! A + B -> C
! are ppl able to see the invalid arguments which leads to a conclusion that agrees with their
personal conviction
! to do this they must be able to detach themselves from their personal view when assessing
validity
Rules of formal logic
! forms of argument that will always produce the forms of argument that are valid
! fallacies: a logical characterization and psychological characterization
! logical: it is a pattern of inference that is invalid
! psychological: it is mistaken for being a valid argument
! has to be both invalid and you have to mistake it for a valid argument
! logic is normative: try to produce the best patterns for truth preserve
! logic is prescriptive: help us identify when we are making mistakes
! conditional reasoning: make use of if then relationship
! if A then B
! allows you to link thinks together in reasoning
! 4 basic patterns of conditional
Names
Modus Ponens
Fallacy of
Affirming
Consequent
Fallacy of denying
antecedent
Modus Tollens
If P then Q
If P then Q
If P then Q
If P then Q
P
Q
not P
not Q
Therefore
Q
P
not Q
not P
! when ppl are reasoning do they use formal arguments of logic or are ppl. often taken in by
fallacious forms of argument
! if ppl's goal is to obtain/preserve truth and they are usually falling prey to fallacy, then prima
facie that would mean they are irrational
! this matters b/c if ppl were irrational then this would have lots of implication in psychology
! are humans rational in that they will reliably use logical form of argument and reliably avoid
www.notesolution.com
fallacies of argument?
! experimentally study
Wason Selection Task
! might overtake the stroop effect as the most studied effect
Front
E
K
4
7
Back
types of argument
(if you turned over
this card)
modus ponens
fallacy of affirming
the consequent
modus tollens
! you have to name the cards in order to test the following rule / truth of following statements:
! if there is a vowel on one side of the card then there is an even number on the other side of the
card
! ppl pick E and 4 to flip, falling to prey to the fallacy of affirming the consequent but they fail to
pick 7 which is a valid form of argument
! 10% of subjects get the correct answer (at best)
! why are ppl making these kinds of mistakes?
Griggs and Cox 1982
Front
Drinking a Beer
Drinking a Coke
22 yrs of age
16 yrs of age
Back
types of argument
modus ponens
fallacy of affirming
the consequent
modus tollens
! imagine you are a police officer on duty here is the rule
! if a person is drinking beer then he must be over 19yrs of age
! 72% correct response, ppl pick drinking a beer and 16yrs of age
! even though content does not determine validity, ppl are able to get better results when we
change content
! this is called CONTENT EFFECTS / THEMATIC EFFECTS
! ppl are paying attention to content
! what are content effects and how do they facilitates reasoning?
Availability Thesis
! try to explain content effect, includes 2 parts: familiarity and concreteness
! when we give ppl common day content, this eases their cognitive load which can be used for
argument facilitation
! familiarity
! ppl done this before and remember the correct way of doing this
! concreteness
! give concrete example as opposed to abstract
www.notesolution.com

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Description
PSY370: Thinking and Reasoning LEC11 – Inference Insight and Relevance Nov, 26th, 2009 Inference use of evidence to alter belief so as to preserve truth looking for patterns that are truth preservative deduction: there are inference patterns that guarantee if the premises are true then the conclusion must be true reasons cannot be valid, only arguments can be valid induction: if the premises are true this increase the probability that the conclusion will be true almost all evidence in science is inductive argument deduction is the paramount exemplar of how logic should operate: formal logic distinction b/w form and content in logic Critical detachment A + B -> C are ppl able to see the invalid arguments which leads to a conclusion that agrees with their personal conviction to do this they must be able to detach themselves from their personal view when assessing validity Rules of formal logic forms of argument that will always produce the forms of argument that are valid fallacies: a logical characterization and psychological characterization logical: it is a pattern of inference that is invalid psychological: it is mistaken for being a valid argument has to be both invalid and you have to mistake it for a valid argument logic is normative: try to produce the best patterns for truth preserve logic is prescriptive: help us identify when we are making mistakes conditional reasoning: make use of if then relationship if A then B allows you to link thinks together in reasoning 4 basic patterns of conditional Names Modus Ponens Fallacy of Fallacy of denying Modus Tollens Affirming antecedent Consequent If P then Q If P then Q If P then Q If P then Q P Q not P not Q Therefore Q P not Q not P when ppl are reasoning do they use formal arguments of logic or are ppl. often taken in by fallacious forms of argument if ppl's goal is to obtain/preserve truth and they are usually falling prey to fallacy, then prima facie that would mean they are irrational this matters b/c if ppl were irrational then this would have lots of implication in psychology are humans rational in that they will reliably use logical form of argument and reliably avoid www.notesolution.com fallacies of argument? experimentally study Wason Selection Task might overtake the stroop effect as the most studied effect Front E K 4 7 Back types of argument modus ponens fallacy of affirming modus tollens (if you turned over the consequent this card) you have to name the cards in order to test the following rule / truth of following statements: if there is a vowel on one side of the card then there is an even number on the other side of the card ppl pick E and 4 to flip, falling to prey to the fallacy of affirming the consequent but they fail to pick 7 which is a valid form of argument 10% of subjects get the correct answer (at best) why are ppl making these kinds of mistakes? Griggs and Cox 1982 Front Drinking a Beer Drinking a Coke 22 yrs of age 16 yrs of age Back types of argument modus ponens fallacy of affirming modus tollens the consequent imagine you are a police officer on duty here is the rule if a person is drinking beer then he must be over 19yrs of age 72% correct response, ppl pick drinking a beer and 16yrs of age even though content does not determine validity, ppl are able to get better results when we change content this is called CONTENT EFFECTS / THEMATIC EFFECTS ppl are paying attention to content what are content effects and how do they facilitates reasoning? Availability Thesis try to explain content effect, includes 2 parts: familiarity and concreteness when we give ppl common day content, this eases their cognitive load which can be used for argument facilitation familiarity ppl done this before and remember the correct way of doing this concreteness give concrete example as opposed to abstract www.notesolution.com most refuted thesis in psychology Manliterla and Evans 1979 replaced EK47 with haddock and gin but there was no facilitation simply using concrete things did not provide facilitation D'Andrde 1981 & Mandler 1981 no retail experience P's had to imagine sear manager replaced EK47 with purchase over $30 then manager's signature should be on back since familiarity is decreased there should be similar results to 10% correct but the answer is 70% Social Rules as source I use the social rules in order to facilitate the logical rules social rules are easier b/c we have to use them all the time and we are inherently social Pragmatic Reasoning Schema ppl are not using logical rules, they are using pragmatic rules they are not strict logical rules pragmatic rules and logic rules overlap on some areas when you do the reasoning when they overlap you do a valid assessment when we are thinking/communicating with each other we care more than truth preservation ie. explanatory and causal relationsh
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