2. Reasoning What is the difference between deductive and inductive reasoning? What are heuristics, and how do we use them? How do we reason about categories? How do we make decisions?

3. Deductive Reasoning Reasoning from general to specific Drawing conclusions from stated premises

4. Syllogism logical argument with two premises and a conclusion – All Wongas are rice farmers. – Smith is a Wonga. – Is Smith a rice farmer?

5. Logic of Syllogisms If both premises are true, then a conclusion that logically follows from the premises is true If the conclusion follows logically for every possible case, it is valid Validity depends on the logical form, not on the content

6. People from cultures that emphasize experience answer: “I don’t know Smith, so I can’t say.” (Cole & Scribner, 1974) People from cultures that emphasize logical structure answer: “Yes” Culture and Logic

7. Belief Bias Conclusions are more likely to be judged as valid if they are consistent with the person’s beliefs (Janis & Frick, 1943) –All poisons are bitter –Arsenic is not bitter –Therefore, arsenic is not a poison

8. Atmosphere Effect The use of particular words in the premises can set a mood that influences what conclusion is drawn (Chapman & Chapman, 1959) –“All” premises suggest an “All conclusion” –“Some” premises suggest a “Some” conclusion

9. Atmosphere Effect All A are B All C are B *Therefore, all A are C

10. Inductive Reasoning Reasoning from specific observations to general conclusions Scientific reasoning Use of heuristics in everyday life

11. Heuristics Shortcuts in reasoning based on knowledge May result in errors Fast

12. Availability Heuristic Probability judgments are based on how easy it is to remember events (Tversky & Kahneman, 1973) McKelvie’s (1997) famous name experiment

13. Representativeness Heuristic Probability judgments are based on the similarity of an event to a population The bank teller problem (Tversky & Kahneman, 1983)

14. The Bank Teller Problem Linda is 31 years old, majored in philosophy, and is outspoken about political issues. Which is more likely? Linda is – A. a bank teller – B. a feminist bank teller

16. Confirmation Bias Tendency to look for only for evidence that supports your belief Most participants guessing the rule for a number series did not try sequences that would disconfirm their hypotheses (Wason, 1960)

19. Learning Categories Conservative focusing: change one feature at a time Focus gambling: change multiple features at a time

20. Categorization Similarity Coverage Model (Osherson et al., 1990): knowledge of categories influences reasoning –More typical examples are more influential –More diverse examples are more influential –Specific knowledge can override these effects (Lopez et al., 1997)

21. Decision-Making Framing Effects (Tversky & Kahneman, 1981) –Risk aversion strategy for choices framed in terms of gains –Risk taking strategy for choices framed in terms of losses

22. Tversky and Kahneman (1981)

23. Decision-Making Focusing Illusion (Wilson et al., 2000) –One aspect of a situation is emphasized and other aspects are ignored –Life satisfaction ratings for others tend to focus on only the most obvious qualities (Schkade & Kahneman, 1998)

24. Examples of Irrational Reasoning ad hominem majority must be right straw man

25. Evolutionary Psychology How can biases in reasoning be adaptive?