Online research in philosophy

It has recently been reported that forward inferences from if p then q sentences (i.e., from antecedent to consequent) were faster than backward inferences from consequent to antecedent (Barrouillet, Grosset, & Lecas, 2000). The standard mental model theory assumes that this directionality effect is a figural effect due to the order the information enters working memory, whereas we claim that it results from the nature of the mental models that represent oriented relations from hypothetical values introduced by the word If . We tested these hypotheses in an experiment in which adult participants evaluated conditional syllogisms from either if p then q , p only if q , or p if q statements. Contrary to the predictions resulting from the standard theory, the three forms of the conditional provoked a reversed directionality effect and denial inferences took longer to endorse than affirmative inferences for all the forms of conditionals. We argue from these results that mental models of the conditional represent oriented relations instead of mere co-occurrences between events.

We examine the role of working memory's central executive in the mental model explanation of propositional reasoning by using two working memory measures: the classical “reading span” test by Daneman and Carpenter (1980) and a new measure. This new “reasoning span” measure requires individuals to solve very simple anaphora problems, and store and remember the word solution in a growing series of inferential problems. We present one experiment in which we check the involvement of the central executive in conditional and disjunctive inference tasks and compare predictions of the new reasoning span test with those of the classical reading span test. The results of the experiment confirm that reasoning responses, which according to mental model theory require high cognitive work, are predicted by working memory measures. Results also show that some reasoning responses are probably obtained by means of superficial biases or strategies that do not load working memory. The reasoning span test, which involves the central executive to a greater degree, predicts reasoning performance better than the reading span test. The significance and possibilities of the new measure in studying reasoning are discussed.

A number of single- and dual-process theories provide competing explanations as to how reasoners evaluate conditional arguments. Some of these theories are typically linked to different instructions?namely deductive and inductive instructions. To assess whether responses under both instructions can be explained by a single process, or if they reflect two modes of conditional reasoning, we re-analysed four experiments that used both deductive and inductive instructions for conditional inference tasks. Our re-analysis provided evidence consistent with a single process. In two new experiments we established a double dissociation of deductive and inductive instructions when validity and plausibility of conditional problems were pitted against each other. This indicates that at least two processes contribute to conditional reasoning. We conclude that single-process theories of conditional reasoning cannot explain the observed results. Theories that postulate at least two processes are needed to account for our findings.

A total of 152 students were asked to respond to a series of causal conditional (“If P then Q”) inferences with major premises for which there was variable access to information contradicting the premises. Half the students were given 12.5 s for each inference, the other half were given 8.5 s. The percentage of accepted inferences was significantly lower when the time was shorter for the MP and MT inferences, but no effect was observed for the AC and DA inferences. Results are interpreted as supporting the idea that inhibition of retrieved information contradicting the premise is necessary to explain reasoning with the MP and MT inferences under logical instructions (Markovits & Barrouillet, 2002).

A total of 152 students were asked to respond to a series of causal conditional (“If P then Q”) inferences with major premises for which there was variable access to information contradicting the premises. Half the students were given 12.5 s for each inference, the other half were given 8.5 s. The percentage of accepted inferences was significantly lower when the time was shorter for the MP and MT inferences, but no effect was observed for the AC and DA inferences. Results are interpreted as supporting the idea that inhibition of retrieved information contradicting the premise is necessary to explain reasoning with the MP and MT inferences under logical instructions (Markovits & Barrouillet, 2002).

This study examined the hypothesis that conditional reasoning involves visual short-term memory resources (Johnson-Laird, 1985). A total of 147 university students were given measures of verbal and visual short-term memory capacity and a series of concrete and abstract conditional reasoning problems. Results indicate that there is a positive correlation between verbal working memory capacity and reasoning with both concrete and abstract premises. A positive correlation was also obtained between visual working memory capacity and reasoning with concrete premises.

In most developmental studies the only error children could make on counterfactual tasks was to answer with the current state of affairs. It was concluded that children who did not show this error are able to reason counterfactually. However, children might have avoided this error by using basic conditional reasoning (Rafetseder, Cristi-Vargas, & Perner, 2010). Basic conditional reasoning takes background assumptions represented as conditionals about how the world works. If an antecedent of one of these conditionals is provided by the task, then a likely conclusion can be inferred based only on background assumptions. A critical feature of counterfactual reasoning is that the selection of these additional assumptions is constrained by actual events to which the counterfactual is taken to be counterfactual. In contrast, in basic conditional reasoning one enriches the given antecedent with any plausible assumptions, unconstrained by actual events. In our tasks basic conditional reasoning leads to different answers from counterfactual reasoning. For instance, a doctor, sitting in the park with the intention of reading a paper, is called to an emergency at the swimming pool. The question, “If there had been no emergency, where would the doctor be?” should counterfactually be answered “in the park”. But by ignoring the doctor's intentions, and just reasoning from premises about the default location of a hospital doctor who has not been called out to an emergency, one might answer: “in the hospital”. Only by 6 years of age did children mostly give correct answers.

This paper reviews the psychological investigation of reasoning with conditionals, putting an emphasis on recent work. In the first part, a few methodological remarks are presented. In the second part, the main theories of deductive reasoning (mental rules, mental models, and the probabilistic approach) are considered in turn; their content is summarised and the semantics they assume for if and the way they explain formal conditional reasoning are discussed, in particular in the light of experimental work on the probability of conditionals. The last part presents the recent shift of interest towards the study of conditional reasoning in context, that is, with large knowledge bases and uncertain premises.

This study examined the hypothesis that a key process in conditional reasoning with concrete premises involves on-line retrieval of information about potential alternate antecedents. Participants were asked to solve reasoning problems with causal conditional premises (If cause P then effect Q). These premises were inserted into short contexts. The availability of potential alternatives was varied from one context to another by adding statements that explicitly invalidated one or more of these alternatives (i.e., other causes that lead to the effect Q). The invalidated alternatives differed in the degree of their semantic association to the consequent term (Q). The results show that the effect of invalidating one or more potential alternatives on the two uncertain logical forms, AC and DA, was largely determined by their relative associative strength. These results strongly support a model for conditional reasoning with causal premises that supposes that a key element in responding to the uncertain logical forms is on-line retrieval of at least one potential alternative antecedent.

Johnson-Laird's mental models theory claims that reasoning is a semantic process of construction and manipulation of models in working memory of limited capacity. Accordingly, both a deduction and a given interpretation of a premise would be all the harder the higher the number of models they require. The purpose of the present experiment was twofold. First, it aimed to demonstrate that the interpretation of if...then conditional sentences in children (third, sixth, and ninth graders) evolves as a function of the number of models the children can produce. We proposed a theory of conditional reasoning development that hypothesises a developmental trend of three successive levels of interpretations underlain by one, two, and then three models, i.e. conjunctive, biconditional, and conditional respectively. Second, we aimed to show that these different levels correlate with working memory capacities: the higher the working memory span, the higher the number of models underlying the conditional interpretation. These two hypotheses were verified, supporting the mental models theory. The results are compared with the rival theory of mental logic.