5/4/18. PSYC315: Chapter 10. Reasoning. Reasoning and the Brain

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1 PSYC315: Chapter 10 Dr. Elizabeth Schwaiger Reasoning How do people reason about situations described in conditional language (e.g., if then )? How do people reason about situations described with quantifiers like all, some, and none? How do people reason from specific examples and pieces of evidence to general conclusions? (Inductive Reasoning) Reasoning and the Brain Content Free Reasoning vs Meaningful Content (Language) 1

2 Some Terms: Deductive Reasoning Syllogisms Conditional Statement Antecedent Consequent Modus Ponens Modus Tollens If you read this chapter, Then you will be wiser You read the chapter Therefore, you will be wiser Affirmation of the Consequent Denial of the Antecedent Modus Ponens If Joan understands this book, Then she will get a good Joan understands this book. Therefore, Joan will get a good Modus Tollens If Joan understands this book, Then she will get a good Joan will not get a good Therefore, Joan does not understand this book. 2

3 Fallacy: Affirmation of the Consequent If Joan understands this book, Then she will get a good Joan will get a good Therefore, Joan understands this book. Fallacy: Denial of the Antecedent If Joan understands this book, Then she will get a good Joan does not understand this book. Therefore, Joan will not get a good The Importance of Context Byrne (1989) 71% commit fallacy of ffirmation of the consequent Only 13% commit fallacy of affirmation of the consequent If she has an essay to write, She will study late in the library. (If she has textbooks to read, she will study late in the library.) She will study late in the library. Therefore, she has an essay to write. 3

4 The Importance of Context Byrne (1989) 96% accept modus ponens 36% accept modus ponens If she has an essay to write, She will study late in the library. (If the library stays open, then she will study in the library.) She has an essay to write. Therefore, she will study late in the library. Conditional Reasoning What is the valid conclusion? Cognitive psychology students are brilliant You are cognitive psychology students Therefore. Conditional Reasoning What is the valid conclusion? Students who study score high on exams You study Therefore. 4

5 Conditional Reasoning Not all valid conclusions are also necessarily the truth about life Students who eat biryani score high on exams You eat biryani Therefore The Wason Selection Task In Lab Deductive Reasoning: Reasoning About Quantifiers The Categorical Syllogism 5

6 Categorical Syllogisms Universal Statements: ALL cognitive psychologists are pianists. NO cognitive psychologists are flutists. Categorical Syllogisms: All doctors are rich. OR All A s are B s. Some lawyers are dishonest. OR Some C s are D s. No politician is trustworthy. OR No E s are F s. Some actors are not handsome. OR Some G s are not H s. Categorical Syllogisms All A s are B s. All B s are C s. All A s are C s. Categorical Syllogisms Some A s are B s. Some B s are C s. Some A s are C s. 6

7 Categorical Syllogisms Some A s are B s. Some B s are C s. No A s are C s. Categorical Syllogisms Atmosphere Hypothesis Woodworth and Sells (1935) Logical terms set the mood. People tend to accept: Positive conclusions to positive premises Negative conclusions to negative premises Negative conclusions to mixed premises Particular conclusions to particular premises Universal conclusions to universal premises Mental Model Theory Johnson-Laird (1983) People create mental models to solve these kinds of problems People stick with the first model that comes to mind rather than considering all possible options Inductive Reasoning and Hypothesis Testing What conclusion follows? The first number in the series is 1. The second number in the series is 2. The third number in the series is 4. 7

8 Hypothesis Formation Bruner, Goodnow, and Austin (1956) Hypothesis Formation Bruner, Goodnow, and Austin (1956) Wason (1960) Task This triad is consistent with a secret rule. Find out what the rule is by asking whether other triplets of numbers are instances of the rule. 8

9 Scientific Discovery In studies of scientific discovery, participants tend to focus on experiments consistent with their favorite hypothesis and show a reluctance to search for alternative hypotheses. 9

10 Dual-Process Theories Type 1 Processes Rapid Automatic Associative Type 2 Processes Slow Deliberate Working Memory Load 10