Kristien Dieussaert

The relative contribution of content and context factors on the interpretation of conditionals

Previous research showed that conditional reasoning is affected by the content and the context of the studied problems. In this study, we investigate in detail the relative effect of three factors, namely the number of alternative or disabling reasons, speaker control, and pragmatic type, on the interpretation of conditionals. These factors were subject to prior research, but mostly in a fragmented way. This study indicates that some important nuances must be added to earlier findings. The number of alternatives and disablers, the speaker control, and the pragmatic type of conditional statements all have a considerable effect on how we interpret these sentences and reason with them, but they do not have equal weight. Alternatives/disablers play a significant but very limited role on the interpretation of conditionals, while the influence of speaker control and of pragmatic type is far more imperative.

Strategies during complex conditional inferences

In certain contexts reasoners reject instances of the valid Modus Ponens and Modus Tollens inference form in conditional arguments. Byrne (1989) observed this suppression effect when a conditional premise is accompanied by a conditional containing an additional requirement. In an earlier study, Rumain, Connell, and Braine (1983) observed suppression of the invalid inferences “the denial of the antecedent” and “the affirmation of the consequent” when a conditional premise is accompanied by a conditional containing an alternative requirement. Here we present three experiments showing that the results of Byrne (1989) and Rumain et al. (1983) are influenced by the answer procedure. When reasoners have to evaluate answer alternatives that only deal with the inferences that can be made with respect to the first conditional, then suppression is observed (Experiment 1). However, when reasoners are also given answer alternatives about the second conditional (Experiment 2) no suppression is observed. Moreover, contrary to the hypothesis of Byrne (1989), at least some of the reasoners do not combine the information of the two conditionals and do not give a conclusion based on the combined premise. Instead, we hypothesise that some of the reasoners have reasoned in two stages. In the first stage, they form a putative conclusion on the basis of the first conditional and the categorical premise, and in the second stage, they amend the putative conclusion in the light of the information in the second premise. This hypothesis was confirmed in Experiment 3. Finally, the results are discussed with respect to the mental model theory and reasoning research in general.

Some effort for some: Further evidence that scalar implicatures are effortful

Under the assumption of the principle of cooperation (Grice, 1989), a statement such as “some eels are fish” is thought to be false since it contains less information than is considered sufficient. However, the statement is logically sound since the meaning of “some” is compatible with “all”. Currently, the primary interpretation of such underinformative statements remains subject to debate. According to Levinson (2000), the pragmatic “some but not all” interpretation is the default interpretation, while others (e.g., Sperber & Wilson, 1995) argue that this pragmatic interpretation only comes to the fore when relevant within the context and is thus considered secondary to the logical “some and perhaps all” interpretation. In this study, three factors that may influence the answer pattern are studied: task load, working memory capacity, and repetition of the statements. In Experiment 1, we used a secondary task paradigm to manipulate the cognitive load under which a number of underinformative statements had to be judged. We observed that for participants with a rather limited working memory span it is harder to reach a pragmatic interpretation under cognitive load. In Experiment 2, we manipulated the repetition of the statements. We observed that with a higher number of filler statements, participants produced fewer consistent answer patterns. This study provides further evidence against the automaticity of the pragmatic interpretation: It shows that the pragmatic interpretation requires more cognitive effort than the logical interpretation and that increasing the number of filler statements inhibits the development of a response strategy.

Truth table tasks: The relevance of irrelevant

Two types of truth table tasks are used investigating mental representations of conditionals: a possibilities-based and a truth-based one. In possibilities tasks, participants indicate whether a situation is possible or impossible according to the conditional rule. In truth tasks participants evaluate whether a situation makes the rule true or false, or is irrelevant with respect to the truth of the rule. Comparing the two-option version of the possibilities task with the truth task in Experiment 1, the possibilities task yields logical answer patterns whereas the truth task yields defective patterns. Adding the irrelevant option to the possibilities task in Experiment 2 leads to a considerable amount of defective patterns in the possibilities task, but still to more logical patterns in the possibilities task than in the truth task. Experiment 3 shows that directionality matters since rule-to-situation tasks yield more logical answer patterns than do situation-to-rule tasks. We conclude that both task types are not comparable as such since wording, number of options and directionality influence the results.

Pronounced inferences: A study on inferential conditionals

An experimental study is reported which investigates the differences in interpretation between content conditionals (of various pragmatic types) and inferential conditionals. In a content conditional, the antecedent represents a requirement for the consequent to become true. In an inferential conditional, the antecedent functions as a premise and the consequent as the inferred conclusion from that premise. The linguistic difference between content and inferential conditionals is often neglected in reasoning experiments. This turns out to be unjustified, since we adduced evidence on the basis of a quantitative and a qualitative analysis that this difference has a manifest psychological relevance. For the inferential conditionals, participants appear to retrieve the order of events of the original content conditional on which it was based, before they start reasoning with it. The implications of this finding for reasoning research and linguistics will be discussed.

Conditional assertions, tense, and explicit negatives

We report an experiment in which we test the possible influence of the tense of the verb and explicit negatives with indicative conditionals. We tested the effects of systematically negating the constituents of four fundamental inferences based on conditionals in three different tenses (present tense, past tense, future tense): Modus Ponens (i.e., inferences of the form: if p then q; p; therefore q), Modus Tollens (if p then q; not-q; therefore not-p), Affirmation of the Consequent (if p then q; q; therefore p), and Denial of the Antecedent (if p then q; not-p; therefore not-q). The latter two inferences are invalid for true conditionals, but are valid for bi-conditionals (if, and only if, p then q). The participants drew their own conclusions from premises about letters and numbers on cards. We discuss the results in relation to an affirmation premise bias, a negative conclusion bias, and a double negation effect. We outline the importance of our findings for theories about conditional and counterfactual...

Is the truth table task mistaken

There is ample evidence that in classical truth table task experiments false antecedents are judged as “irrelevant”. Instead of interpreting this in support of a suppositional representation of conditionals, Schroyens (2010a, 2010b) attributes it to the induction problem: the impossibility of establishing the truth of a universal claim on the basis of a single case. In the first experiment a truth table task with four options is administered and the correlation with intelligence is inspected. It is observed that “undetermined” is chosen in one third of the judgements and “irrelevant” in another third. A positive correlation is revealed between intelligence and the number of “irrelevant” and “undetermined” judgements. The data do not exclude that a part of the “irrelevant” judgements in classical truth table task experiments might be caused by the induction problem. In the second experiment participants are presented with a simplified four-option truth table task and asked for a justification of their judgements. These justifications show the induction problem is not the reason for choosing the “irrelevant” or “undetermined” option, which is supportive for a suppositional representation of conditionals.