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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?

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?

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Page 1: 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?

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?

Page 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?

Deductive Reasoning

Reasoning from general to specific

Drawing conclusions from stated premises

Page 3: 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?

Syllogism

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

Page 4: 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?

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

Page 5: 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?

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

Page 6: 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?

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

Page 7: 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?

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

Page 8: 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?

Atmosphere Effect

All A are B

All C are B

*Therefore, all A are C

Page 9: 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?

Inductive Reasoning

Reasoning from specific observations to general conclusions

Scientific reasoning

Use of heuristics in everyday life

Page 10: 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?

Heuristics

Shortcuts in reasoning based on knowledge

May result in errors

Fast

Page 11: 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?

Availability Heuristic

Probability judgments are based on how easy it is to remember events (Tversky & Kahneman, 1973)

McKelvie’s (1997) famous name experiment

Page 12: 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?

Representativeness Heuristic

Probability judgments are based on the similarity of an event to a population

The bank teller problem (Tversky & Kahneman, 1983)

Page 13: 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?

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

Page 14: 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?
Page 15: 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?

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)

Page 16: 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?
Page 17: 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?
Page 18: 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?

Learning Categories

Conservative focusing: change one feature at a time

Focus gambling: change multiple features at a time

Page 19: 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?

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)

Page 20: 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?

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

Page 21: 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?

Tversky and Kahneman (1981)

Page 22: 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?

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)

Page 23: 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?

Examples of Irrational Reasoning

ad hominem

majority must be right

straw man

Page 24: 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?

Evolutionary Psychology

How can biases in reasoning be adaptive?