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- An explanation of or-deletions and other paradoxical disjunctive inferencesPublication . Rasga, Célia; Quelhas, Ana Cristina; Johnson-Laird, P. N.Some inferences of the sort: A or B; therefore A, which are invalid in standard logics, are sensible in life: You can enter now or later; therefore, you can enter now. That these "or-deletions" follow necessarily or only possibly is a by-product of a theory of mental models. Its semantics for "or" refers to conjunctions of possibilities holding in default of knowledge to the contrary. It predicts new sorts of or-deletion, such as: He likes to drink red wine or white wine. So, he likes to drink red wine. and: You are permitted to do only one of the following: You can enter now. You can enter later. Therefore, you are permitted to enter now. They are invalid in standard logics, and neither previous pragmatic nor semantic theories predicted them. Four experiments corroborated their occurrence.
- The relation between factual and counterfactual conditionalsPublication . Quelhas, Ana Cristina; Rasga, Célia; Johnson-Laird, P. N.What is the relation between factual conditionals: If A happened then B happened, and counterfactual conditionals: If A had happened then B would have happened? Some theorists propose quite different semantics for the two. In contrast, the theory of mental models and its computer implementation interrelates them. It postulates that both can have a priori truth values, and that the semantic bases of both are possibilities: states that are possible for factual conditionals, and that were once possible but that did not happen for counterfactual conditionals. Two experiments supported these relations. Experiment 1 showed that, like factual conditionals, certain counterfactuals are true a priori, and others are false a priori. Experiment 2 replicated this result and showed that participants selected appropriate paraphrases, referring, respectively, to real and to counterfactual possibilities, for the two sorts of conditional. These results are contrary to alternative accounts of conditionals.
- 40th Anniversary of Mental Models TheoryPublication . Quelhas, Ana CristinaIn 2023, on July 21 and 22, a meeting was organised in honour of Phil Johnson-Laird, celebrating the 40th anniversary of the mental model theory, at the University College London. This book collects the testimonies of many fellow colleagues who wanted to celebrate these dates, and it shows that Phil Johnson-Laird is a unique personality.
- The mental model theory of free choice permissions and paradoxical disjunctive inferencesPublication . Laird, Jennifer Ann; Quelhas, Ana Cristina; Rasga, CéliaInferences of the sort: A or B; therefore A, are invalid. Yet, the paradoxes of free choice are acceptable: You can have sole or lobster; so, you can have sole. Pragmatic theories attempt to save logic. A semantic theory of human reasoning is founded on mental models of possibilities. “Or” refers to a conjunction of possibilities that each hold in default of knowledge to the contrary. A disjunction: it is permissible to do A or to do B, yields a deontic interpretation of the possibilities, and elicits mental models of a conjunction of default permissions. They yield or-deletions, such as: therefore, it’s permissible to do A. The theory predicts the paradoxes and new phenomena, which four experiments corroborated. For example, exclusive disjunctions such as: Few of the artists are brutalists or else cubists, have an intuitive model that yields or-deletions, but deliberation can construct models that refute them.
- Conditional content, explicit information and generating cases: Sources for suppressing inferencesPublication . Gómez-Sánchez, Jesica; Moreno, Sergio Moreno; Couto, Marta; Quelhas, Ana CristinaIn the present study, we evaluate the suppression effect by asking participants to make inferences with everyday conditionals ("if A, then B"; "if Ana finds a friend, then she will go to the theatre"), choosing between three possible conclusions ("she went to the theatre"; "she did not go to the theatre"; "it cannot be concluded"). We test how these inferences can be influenced by three factors: a) when the content of the conditional induces us to think about disabling conditions that prevent us from accepting the consequent (A and ¬B) or alternative conditions that induce us to think about other antecedents that could also lead to the consequent (¬A and B), b) when explicit information is given about what really happened (e.g. Ana found a friend but they did not go to the theatre; or Ana did not find a friend but she went to the theatre) and c) when participants have to look for concrete disabling (e.g. Ana's friend had to work) and alternative cases (e.g. Ana's sister wanted to go to the theatre) before making the inferences. Previous studies have shown what were called "suppression effects": disabling conditions reduced valid inferences while considering alternatives led to a reduction in fallacies. These two "suppression effects" were shown in Experiment 1: a) in an Implicit condition that included just the content factor of the conditional and b) with a greater magnitude in a second Explicit condition that included the three factors (content, explicit information and search for counterexamples). Experiment 2 compared the same Explicit condition with another in which participants, instead of looking for counterexamples, completed a control task of looking for synonyms. In addition, half the participants looked for a few items (2 cases) and the other half for many items (5 cases). Results again showed the suppressing effect in all the conditions, but the magnitude was greater in the counterexample condition. No relevant differences were obtained according to the number of cases generated; the most relevant result was that the factors provided an additive effect on the suppression.