Latest results: Orenes & Johnson-Laird 2012

Isabel Orenes and Phil Johnson-Laird have discovered that people do not tend to accept ‘paradoxical’ inferences. Their experiments examined the ‘paradoxes of material implication’ such as the inference ‘Lucia didn’t wear the shoes. Therefore, If Lucia wore jewelry then she didn’t wear the shoes’ (Not-B ∴ If A then not-B) and the inference ‘It won’t rain today. Therefore, if it rains today then the forecast is right’ (Not-A ∴ If A then B). Their results are published in their article,   Logic, models, and paradoxical inferences in Mind and Language (2012, 27, 4, 357-377) and they summarise them in their abstract there as follows:

Abstract: “People reject ‘paradoxical’ inferences, such as: Luisa didn´t play music; therefore, if Luisa played soccer, then she didn´t play music. For some theorists, they are invalid for everyday conditionals, but valid in logic. The theory of mental models implies that they are valid, but unacceptable because the conclusion refers to a possibility inconsistent with the premise. Hence, individuals should accept them if the conclusions refer only to possibilities consistent with the premises: Luisa didn´t play soccer; therefore, if Luisa played a game then she didn´t play soccer. Two experiments corroborated this prediction for three sorts of ‘paradox’, including a disjunctive one.”

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