Reading focus
Syllabus: How Do We Reason and Solve Problems?
Follow how considering another possible situation changes a conclusion, and how the model account differs from applying an inference rule.
Why you're reading it. Establish a representational explanation that makes predictions about error and difficulty.
A question to consider. If a conclusion fits one interpretation of the premises but not another, what would an added counterexample reveal about the reasoner's first response?
Why this reading
A conclusion can feel inevitable because we have imagined one possible situation and overlooked another. Johnson-Laird turns that observation into an account of reasoning: people represent possibilities and inspect what follows from them. The paper connects a proposed representation to predictions about difficulty and error.
Before you read
A premise is a starting statement. A deductively valid conclusion must be true whenever all its premises are true. A counterexample is a possible situation in which the premises hold but the conclusion fails. A mental model need not be a visual picture; it can represent abstract relationships. Mental logic proposes inference rules, while model theory proposes reasoning over represented possibilities.
Read for
- Work through an example with more than one possibility. Identify the extra possibility needed to test the first conclusion.
- Follow the proposed links between working-memory demands, the number of models, and systematic errors. Separate a prediction from an illustration that merely fits the theory.
- Examine the evidence used to distinguish mental models from rule-based explanations. Ask which specific rival assumptions are tested and which remain open.
Consider afterwards
- All members of a club play chess, and some chess players swim. Must some club members swim? Construct both a situation where they do and one where they do not, then explain what a reasoner's first answer would and would not reveal.
Editorial context
This is an advocate's theoretical synthesis, not a neutral verdict on every account of reasoning. Its compact examples make representation and counterexamples unusually concrete. A successful model-based explanation does not show that people never use rules or probabilities. Claims about brain implementation, everyday reasoning, and differences among people require evidence beyond whether one example can be represented as a model.