Scientists' Understanding of Propositional Logic: An Experimental Investigation

Seventy-two scientists (psychologists, biologists, and physicists) from a large US midwestern state university completed a questionnaire designed to assess understanding of the principles of formal logic believed by philosophers of science to be essential to theory and hypothesis testing. The questionnaire, in a multiple-choice format, required solutions to problems presented in either abstract (symbolic) or concrete (specific example) terms. Across academic disciplines the participants' performance reflected substantial deficits in the appreciation of straightforward logical propositions. For example, nearly half of the scientists failed to recognize the logical validity of modus tollens, an inferential rule of propositional logic which, from a strictly normative standpoint, has been depicted as the only form of valid conclusive inference in theory and hypothesis testing. The pivotal role of formal logic in philosophical analyses of scientific inference is questioned on empirical grounds.