Lecture27

Lecture27 - Lecture 27 Reasoning part 2 Review of...

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Lecture 27 – Reasoning, part 2 April 16, 2008

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Review of conditional reasoning Modus ponens: (short for modus ponendo ponens, mode that affirms by affirming) ‘If P, then Q. P. Therefore, Q.’ Modus tollens: (short for modus tollendo tollens , mode that denies by denying) ‘If P, then Q. Not Q. Therefore, not P. Most can easily understand and apply the modus ponens argument. Many have difficulty with the modus tollens argument, however.
Test your deductive reasoning You are told the following statement: ‘If a card has a consonant on one side, it has a even number on the other side.’ Four cards are laid down on the table in front of you. What is the minimum number of cards that you must turn over to determine if the statement is true or Laird, 1970) modus ponens modus tollens

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Why are we bad at this? Perhaps because everyday situations encourage this sort of thinking Example: If you by a Panasonic TV, then the manufacturer will give you a \$100 rebate. You didn’t buy the TV. Therefore, you will not receive a rebate. This logic is fallacious but likely to lead to the correct
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This note was uploaded on 05/01/2008 for the course PSY 340 taught by Professor Macdonald during the Spring '08 term at NMSU.

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Lecture27 - Lecture 27 Reasoning part 2 Review of...

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