• Inferring specific instances from general principles
o Categorical Syllogism
• An argument describing the relations between categories of
– Premise 1: All A are B All VWs are reliable.
– Premise 2: C is an A The Beetle is a VW.
– Conclusion: C is B The Beetle is reliable.
o Conditional Syllogism
• An argument describing the conditional relations between
– Premise 1: If P then Q If it is a VW, then it is
– Premise 2: P is true The Beetle is a VW.
– Conclusion: Q is true The Beetle is reliable.
Errors in Deductive Reasoning
• Social Contract Theory (Tooby & Cosmides)
o Evolutionary selection pressures have equipped us with a “cheater
detection mechanism”—an innate set of inferential rules that help us
to detect the violation of social contracts
o Evidence: Wason Selection Task performance improves when the task
is framed in terms of contract violation
• Inferring general principles from specific instances
o General Induction: known instances →*all* instances
o Specific Induction: some instances →other instances
o Hypothesis—a proposition that can be evaluated or tested by gathering
evidence to support or refute it
o No inductive process can ever be certain: we cannot know all the
instances that may exist, any one of which may disprove the
Errors in Inductive Reasoning
• Confirmation Bias
o The disinclination to seek evidence that would indicate whether a
hypothesis is false
o E.g., the Wason 2–4–6 Task
• Participant’s goal: Discover the rule
• “Even numbers increasing by two:” e.g., 8–10–12
• “Any set of numbers increasing by two:” e.g., 7–9–11
• Participants then