Cognitive ProcessesPSY 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.