Online research in philosophy

Two experiments examined the contribution of working memory (WM) to the retrieval and inhibition of background knowledge about counterexamples (alternatives and disablers, Cummins, 1995) during conditional reasoning. Experiment 1 presented a conditional reasoning task with everyday, causal conditionals to a group of people with high and low WM spans. High spans rejected the logically invalid AC and DA inferences to a greater extent than low spans, whereas low spans accepted the logically valid MP and MT inferences less frequently than high spans. In Experiment 2, an executive-attention-demanding secondary task was imposed during the reasoning task. Findings corroborate that WM resources are used for retrieval of stored counterexamples and that people with high WM spans will use WM resources to inhibit the counterexample activation when the type of counterexample conflicts with the logical validity of the reasoning problem.

Recent work on the interpretation of counterfactual conditionals has paid much attention to the role of causal independencies. One influential idea from the theory of Causal Bayesian Networks is that counterfactual assumptions are made by intervention on variables, leaving all of their causal non-descendants unaffected. But intervention is not applicable across the board. For instance, backtracking counterfactuals, which involve reasoning from effects to causes, cannot proceed by intervention in the strict sense, for otherwise they would be equivalent to their consequents. We discuss these and similar cases, focusing on two factors which play a role in determining whether and which causal parents of the manipulated variable are affected: Speakers' need for an explanation of the hypothesized state of affairs, and differences in the ‘resilience’ of beliefs that are independent of degrees of certainty. We describe the relevant theoretical notions in some detail and provide experimental evidence that these factors do indeed affect speakers' interpretation of counterfactuals.

Four experiments are reported which investigated the types of truth tables that people associate with conditional sentences and the kinds of inferences that they will draw from them. The present studies differed from most previous ones in using different types of content in the conditionals, for example promises and warnings. It was found that the type of content had a strong and consistent effect on both truth tables and inferences. It is suggested that this is because in real life conditionals make probabilistic assertions, and that the strength of the probabilistic link is determined by the situation in which the conditional occurs. The implications of these findings for current theories of reasoning are considered and it is concluded that none of them is entirely satisfactory. It is suggested that more linguistically based theories may prove more successful.

Cosmides, Wason, and Johnson-Laird, among others, have suggested evidence that reasoning abilities tend to be domain specific, insofar as humans do not appear to acquire capacities for logical reasoning that are applicable across different contexts. Unfortunately, the significance of these findings depends upon the specific variety of logical reasoning under consideration. Indeed, there seem to be at least three grounds for doubting such conclusions, since: (1) tests of reasoning involving the use of material conditionals may not be appropriate for representing ordinary thinking, especially when it concerns causal processes involving the use of causal conditionals instead; (2) tests of domain specificity may fail to acknowledge the crucial role fulfilled by rules of inference, such as modus ponens and modus tollens, which appear to be completely general across different contexts; and, (3) tests that focus exclusively upon deductive reasoning may misinterpret findings involving the use of inductive reasoning, which is of primary importance for human evolution.

Deontic reasoning is reasoning about permission and obligation: what one may do and what one must do, respectively. Conceivably, people could reason about deontic matters using a purely formal deontic calculus. I review evidence from a range of psychological experiments suggesting that this is not the case. Instead, I argue that deontic reasoning is supported by a collection of dissociable cognitive adaptations for solving adaptive problems that likely would have confronted ancestral humans.

Fairley and Manktelow (1997) have mistaken an error of presentation for an error of substance. My causal the- ory remains the same: Causal reasoning scenarios that require the reasoner to decide whether or not an effect will occur in the presence of a viable cause trigger considera- tion of disabling conditions—that is, factors that could prevent the effect from occurring in the presence of a vi- able cause. Scenarios that require the reasoner to decide whether or not a particular cause has produced an ob- served effect trigger consideration of possible alternative causes. The data reported by Cummins (1995) and Cum- mins, Lubart, Alksnis, and Rist (1991) are consistent with this theoretical analysis.

Power has been studied in various guises in both the social cognition and the reasoning literatures. In this paper, three experiments are reported in which this factor was investigated in the domain of deontic thinking. Power of source of deontic statements was varied within several scenarios, and participants judged the degree to which they thought an injunction would be carried out. In the first experiment, permission statements were used, and it was found that, as predicted, power was positively related to degree of endorsement of deontic conclusions across scenarios. In the second experiment, these findings were generalised across three further deontic domains (threat, warning, and promise) and two different syntactic forms (conjunctive and disjunctive). In the third experiment, the hypothesis that power effects were mediated by subjective judgements of conditional probability was investigated and confirmed. It is argued that these results favour theories that give a general role to probabilistic factors, rather than those based on domain-specific schemas.

We report two new phenomena of deontic reasoning: (1) For conditionals with deontic content such as, "If the nurse cleaned up the blood then she must have worn rubber gloves", reasoners make more modus tollens inferences (from "she did not wear rubber gloves" to "she did not clean up the blood") compared to conditionals with epistemic content. (2) For conditionals in the subjunctive mood with deontic content, such as, "If the nurse had cleaned up the blood then she must have had to wear rubber gloves", reasoners make the same frequency of all inferences as they do for conditionals in the indicative mood with deontic content. In this regard, subjunctive deontics are different from subjunctive epistemic conditionals: reasoners interpret subjunctive epistemic conditionals as counterfactual and they make more negative inferences such as modus tollens from them. The experiments show these two phenomena occur for deontic conditionals that contain the modal auxiliary "must" and ones that do not. We discuss the results in terms of the mental representations of deontic conditionals and of counterfactual conditionals.

Causal conditional reasoning means reasoning from a conditional statement that refers to causal content. We argue that data from causal conditional reasoning tasks tell us something not only about how people interpret conditionals, but also about how they interpret causal relations. In particular, three basic principles of people's causal understanding emerge from previous studies: the modal principle, the exhaustive principle, and the equivalence principle. Restricted to the four classic conditional inferences—Modus Ponens, Modus Tollens, Denial of the Antecedent, and Affirmation of the Consequent—causal conditional reasoning data are only partially able to support these principles. We present three experiments that use concrete and abstract causal scenarios and combine inference tasks with a new type of task in which people reformulate a given causal situation. The results provide evidence for the proposed representational principles. Implications for theories of the na ve understanding of causality are discussed.

Deontic reasoning is thinking about whether actions are forbidden or allowed, obligatory or not obligatory. It is proposed that social norms, imposing constraints on individual actions, constitute the fundamental concept for the system of these four deontic modalities, and that people reason from such norms flexibly according to deontic core principles. Two experiments are presented, one on deontic conditional reasoning, the other on “pure” deontic reasoning. Both experiments demonstrate people's high deontic competence and confirm the proposed representational and inferential principles. Experiment 1 additionally shows small effects of the conditional formulations. These findings support the dual source approach (Beller & Spada, 2003) that distinguishes between domain-specific and domain-general inferences. Implications for other theories of deontic reasoning are discussed.