In defense of reasoning: A reply to Greene (1992).
Philip Nicholas Johnson-Laird, Ruth M. J. Byrne, Patrizia Tabossi · Psychological Review · 1992
Greene (1992) argued that assertions of the form "None of the A are in the same place as some of the C " are difficult for subjects to generate and that this phenomenon explains the results of our study of multiply quantified reasoning without having to invoke mental models or deductive reasoning (see Johnson-Laird, Byrne, & Tabossi, 1989). The present article shows, first, that the phenomenon fails to explain most of our principal results; second, that, far from undermining the theory of mental models, it can actually be explained by the theory; and, third, that the best available account of our results is that subjects both reason and rely on mental models to do so. In a study of reasoning with quantifiers such as some, all, and none, we presented evidence that subjects make deductions, not by using formal rules of inference, but by imagining the relevant states of affairs, formulating a putative conclusion from such a mental model, and then searching for alternative models that might refute the conclusion (Johnson-Laird, Byrne, & Tabossi, 1989). We argued that, for example, premises of the form None of the A are in the same place as any of the B All of the B are in the same place as all of the C readily elicit a valid conclusion: "Therefore, None of the A are in the same place as any of the C, " because they yield only one model, in which the As are in one place and the Bs and Cs are all together in another place. For example, | aaa | bbbccc |, where the number of tokens for each set is arbitrary. In contrast, premises of the form None of the A are in the same place as any of the B All of the B are in the same place as some of the C only rarely elicit a valid conclusion: "Therefore, None of the A are in the same place as some of the C, " or equivalently, "Some of the C are not in the same place as any of the A, " because they support more than one qualitatively distinct model. For example, or