Cognitive Processes PSY 334 Chapter 10 – Reasoning & Decision-Making August 19, 2003

Incubation Effects  Some kinds of problems tend to benefit from interruption (incubation). 55% without break, 64% 1 hr, 85% 4 hr. Delay may disrupt set effects.  Problems depending on a set of steps or procedures do not benefit from interruption. Subjects forget their plan and must review what was previously done.

Insight  There is no magical “aha” moment where everything falls into place, even though it feels that way. People let go of poor ways of solving the problem during incubation.  Subjects do not know when they are close to a solution, so it seems like insight – but they were working all along.

Research on Logic  Logic – a subdiscipline of philosophy and mathematics that formally specifies what it means for an argument to be correct.  Human deviations from logic were thought to be malfunctions of the mind.  Recent comparisons of human thinking show that logic is not an appropriate prescriptive norm.

Two Kinds of Reasoning  Reasoning – the process of inferring new knowledge from what we already know.  Deductive reasoning – conclusions follow with certainty from their premises. Reasoning from the general to the specific.  Inductive reasoning – conclusions are probable rather than certain. Reasoning from the specific to the general. Probabilistic – based on likelihoods.

Conditionals  If-then statements. Antecedent – the “if” part. Consequent – the “then” part.  Rules of inferences using conditionals: Modus ponens -- If A then B, A, conclude B Modus tollens – If A then B, not-B, conclude not-A Notation: negation, implication, therefore.

Logical Fallacies  Denial of the antecedent: If P then Q, not-P, conclude not-Q If P then Q, not-P, conclude Q  Affirmation of the consequent: If P then Q, Q, conclude P If P then Q, Q, conclude not-P  Subjects seem to interpret the conditional as a biconditional – if means “if and only if”

How People Reason  People may be reasoning in terms of conditional probabilities. Conditional probabilities can be found that correspond to acceptance rates for fallacies.  Wason selection task – can be explained in terms of probabilities. Also explained by a permission schema

Quantifiers  Categorical syllogism – analyzes propositions with quantifiers “all,” “no,” and “some.”  Fallacies: Some A’s are B’s Some B’s are C’s Conclude: Some A’s are C’s Substitute women for A, lawyers for B, men for C to see what is wrong.

Atmosphere Hypothesis  People commit fallacies because they tend to accept conclusions with the same quantifiers as the premises. No A’s are B’s All B’s are C’s Conclude No A’s are C’s.  The logical terms (some, all, no, not) create an atmosphere that predisposes acceptance of the same terms.

Two Forms  People tend to accept a positive conclusion to positive premises, negative conclusion to negative premises. Mixed premises lead to negative conclusions.  People tend to accept universal conclusions from universal premises (all, no), particular conclusions from particular premises (some, some not).

Limitations  Atmosphere hypothesis describes what people do, but doesn’t explain why.  People violate predictions of the atmosphere hypothesis. More likely to accept a syllogism if it contains a chain leading from A to C. People should accept a syllogism with two negative premises, but correctly reject it.

Process Explanations  People construct a mental model to think concretely about the situation.  Correct conclusions depend upon choosing the correct mental model.  Errors occur because people overlook possible explanations of the premises: All the squares are striped Some striped objects have bold borders. Some of the squares have bold borders.