Reasoning from an incompatibility: False dilemma fallacies and content effects

Find extra options or reason badly: An investigation of children's reasoning with incompatibility statements

The false dilemma or dichotomy is a logical fallacy that occurs when interlocuters accept the premises in an incompatibility statement as being jointly exhaustive (i.e., leaving no third option), whereas that is in fact not the case. Brisson et al. [Memory & Cognition (2018), Vol. 46, pp. 657-670] investigated this fallacy in an adult sample and discovered a content effect that influenced participants' performance. The current study aimed to elaborate on these findings by establishing whether similar patterns could be observed with children. A number of age-appropriate incompatibility premises were constructed. For every item, four different inferential problems were presented (Affirm First, Affirm Second, Deny First, and Deny Second) with three potential answers to choose from (X, not X, or uncertainty regarding X). A sample of 192 volunteer children, with ages ranging from 8 to 13 years, was collected. Statistical analysis showed no significant effect for participants' age but did reveal main effects for premise validity and the amount of available "third options" (possibilities outside of the presented dichotomy). These results are a clear replication of the general effects on adults found by Brisson et al. Affirm inferences were also easy for children, Deny inferences were difficult (even more so than for adults), and content had a profound effect on participants' performance. Whenever more third options could be generated, children were less likely to fall into the false dilemma fallacy. Our findings thus further support the idea that reasoning with incompatibilities is influenced by the same semantic retrieval processes that have been previously related to human conditional reasoning.

Conditional content, explicit information and generating cases: Sources for suppressing inferences

In 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.

Reasoning strategies and semantic memory effects in deductive reasoning

Growing evidence supports the dual-strategy model, which suggests that reasoners have access to both a statistical and a counterexample reasoning strategy. In this paper, we explore further the processes underlying strategy use. We report three studies, the aim of which was to clarify the relation between this model and two forms of everyday reasoning. One of the most robust effects found with conditional reasoning with meaningful premises is the effect of alternative antecedents on the endorsement of AC and DA inferences. In a first study, we presented participants with conditional reasoning problems having more or fewer accessible alternatives as well as our dual-strategy diagnostic questionnaire. As hypothesized, results showed that strategy use had an independent effect on the inferences made with the AC and DA forms, over and above the effect of the number of antecedents, but was not related to responding to the MP and the MT forms. In a second study, we found that this relation extended to reasoning from an incompatibility statement. Finally, a third study showed that this relationship did not hold with probabilistic rather than logical response instructions, suggesting that the way reasoners transform a probabilistic evaluation into a dichotomous judgment is a key determinant of strategy use.