Dynamic Probabilistic Entailment. Improving on Adams' Dynamic Entailment Relation

The inferences of contraposition (A ⇒ C ∴ ¬C ⇒ ¬A), the hypothetical syllogism (A ⇒ B, B ⇒ C ∴ A ⇒ C), and others are widely seen as unacceptable for counterfactual conditionals. Adams convincingly argued, however, that these inferences are unacceptable for indicative conditionals as well. He argued that an indicative conditional of form A ⇒ C has assertability conditions instead of truth conditions, and that their assertability ‘goes with’ the conditional probability p(C|A). To account for inferences, Adams developed the notion of probabilistic entailment as an extension of classical entailment. This combined approach (correctly) predicts that contraposition and the hypothetical syllogism are invalid inferences. Perhaps less well-known, however, is that the approach also predicts that the unconditional counterparts of these inferences, e.g., modus tollens (A ⇒ C, ¬C ∴ ¬A), and iterated modus ponens (A ⇒ B, B ⇒ C, A ∴ C) are predicted to be valid. We will argue both by example and by calling to the results from a behavioral experiment (N = 159) that these latter predictions are incorrect if the unconditional premises in these inferences are seen as new information. Then we will discuss Adams’ (1998) dynamic probabilistic entailment relation, and argue that it is problematic. Finally, it will be shown how his dynamic entailment relation can be improved such that the incongruence predicted by Adams’ original system concerning conditionals and their unconditional counterparts are overcome. Finally, it will be argued that the idea behind this new notion of entailment is of more general relevance

How we reason about explanations : philosophy and psychology of explanatory reasoning

Cette thèse porte sur le raisonnement explicatif : quel rôle les explications jouent-elles dans nos inférences, comment guident-elles nos stratégies d'exploration, et comment nous amènent-elles parfois à l'adoption de fausses croyances ? Ces questions théoriques sont motivées par la philosophie du raisonnement, de la connaissance et de la logique. Elles sont traitées avec les méthodes empiriques des sciences cognitives, au moyen d'expériences comportementales qui utilisent des matériaux concrets et réalistes. La thèse commence par analyser la portée descriptive de l'inférence à la meilleure explication, qui a été théorisée en philosophie comme permettant de justifier les croyances dans des contextes non déductifs. Elle examine ensuite l'inférentialisme, une récente sémantique des conditionnels selon laquelle le sens d'un énoncé conditionnel dépend de la relation entre antécédent et conséquent, relation qui peut être notamment de nature déductive, inductive ou abductive. Elle étudie aussi comment d'autres attitudes épistémiques, notamment les décisions de recherche, prennent en compte la qualité explicative des hypothèses examinées. Enfin, elle propose d'expliquer l'attrait des théories du complot par deux sources : la prédisposition de certaines personnes à un mode de pensée complotiste et l'impression de qualité explicative que ces théories sont capables de produire. Sa conclusion, que les considérations explicatives jouent un rôle important dans le raisonnement et la cognition, constitue une avancée pour les domaines de la philosophie et de la psychologie. Elle souligne aussi la fertilité d'une alliance de ces deux disciplines pour la recherche en sciences cognitives.This research investigates how people reason about explanations: what role do they play in people's inferences, how do they guide people's exploration strategies, and how do they sometimes lead them to endorse false beliefs? These theoretical questions are motivated by the philosophy of reasoning, knowledge and logic. They are pursued with the rigorous empirical methods of cognitive science, using behavioral experiments with realistic and concrete materials. The thesis starts with an examination of the empirical adequacy of inference to the best explanation, an explanatory inference rule that philosophers have theorized to provide grounds for warranted belief in non-deductive contexts. Next, it puts inferentialism to the test, a novel semantic of conditionals according to which the interpretation of a conditional depends on the strength of the relationship between antecedent and consequent, which can be deductive, inductive, or abductive in nature. Then, it considers how other epistemic attitudes, and in particular pursuit decisions, take into account the explanatory quality of the hypotheses being investigated. Finally, it develops an account of belief in conspiracy theories that proposes two types of sources for their appeal: people's predisposition to conspiracist ideation and the explanatory virtues that these theories appear to exhibit. The finding that explanatory considerations play an important role in reasoning and cognition contributes both to the philosophical and psychological literatures; it also emphasizes how fruitful an alliance between these two fields can prove for research in cognitive science

Best, Second-Best, and Good-Enough Explanations: How They Matter to Reasoning.

International audienceThere is a wealth of evidence that people’s reasoning is influenced by explanatory considerations. Little is known, however, about the exact form this influence takes, for instance about whether the influence is unsystematic or due to people’s following some rule. Three experiments investigate the descriptive adequacy of a precise proposal to be found in the philosophical literature, to wit, that we should infer to the best explanation, provided certain additional conditions are met. The first experiment studies the relation between the quality of an explanation and people’s willingness to infer that explanation when only one candidate explanation is given. The second experiment presents participants always with two explanations and investigates the effect of the presence of an alternative on the participants’ willingness to infer the target explanation. While Experiments 1 and 2 manipulate explanation quality and willingness to infer to the best explanation between participants, Experiment 3 manipulates those measures within participants, thereby allowing to study the influence of explanatory considerations on inference at the individual level. The third experiment also studies the connection between explanation quality, willingness to infer, and metacognitive confidence in the decision to infer. The main conclusions that can be drawn from these experiments are that (i) the quality of an explanation is a good predictor of people’s willingness to accept that explanation, and a better predictor than the prior probability of the explanation, and (ii) if more than one possible explanation is given, people are the less willing to infer the best explanation the better they deem the second-best explanation

Explanatory Virtues and Belief in Conspiracy Theories

Conspiracy theories are “alternative” explanations ofwell-understood events or phenomena. What makes themattractive explanations to so many people? We investigatewhether people ascribe characteristics typical of goodexplanations to conspiracy theories and whether they areperceived as more appealing explanations when they arearticulated as a refutation of the official version of events. Intwo experiments, participants read explanations of fourconspiracy theories and rated them along six dimensions ofexplanatory quality. We find that some explanatory virtues areascribed to conspiracy theories even by people who do notbelieve the conspiracy. Contrary to our predictions, we alsofind that framing a conspiracy as a refutation did not generallyelicit higher ascriptions of explanatory virtues. These resultssuggest that explanatory considerations may play a morecentral role in conspiracist beliefs than was previously thought

The Development of Reasoning About Abductive, Inductive and DeductiveConditionals

Conditionals are statements of the form ”If P, Then Q”. Reasoning about conditionals is a core component of humancognition. However, studies of how adults and children interpret and use conditionals have highlighted discrepancies be-tween human reasoning and logic inference rules. Recently, Douven and Verbrugge (2010) have found that a classificationof conditionals based on the type of inferential connection between the antecedent and the consequent (e.g., deductive,inductive and abductive conditionals) allowed for a finer analysis of adult conditional reasoning. Do these findings ex-tend to child conditional reasoning? We report a study (N=200, ages 4 to 11) that examines how performance in modusponens and modus tollens tasks depends on the type of conditional embedded in the argument. These results will shedlight on how the development of conditional reasoning in children is sensitive to the nature of the inferential relationshipof conditionals

Explanatory Considerations Guide Pursuit

Evidence is typically consistent with more than one hypothesis.How do we decide which hypothesis to pursue (e.g., to subjectto further consideration and testing)? Research has shown thatexplanatory considerations play an important role in learningand inference: we tend to seek and favor hypotheses thatoffer good explanations for the evidence we invoke them toexplain. Here we report three studies testing the proposal thatexplanatory considerations similarly inform decisions concern-ing pursuit. We find that ratings of explanatory goodness predictpursuit (though to a lesser extent than they predict belief), andthat these effects hold after adjusting for subjective probability.These findings contribute to a growing body of work suggestingan important role for explanatory considerations in shapinginquiry

Explanatory Virtues and Belief in Conspiracy Theories

Conspiracy theories are alternative explanations of well-understood events or phenomena. What makes them attractive explanations to so many people? We investigate whether people ascribe characteristics typical of good explanations to conspiracy theories and whether they are perceived as more appealing explanations when they are articulated as a refutation of the official version of events. In two experiments, participants read explanations of four conspiracy theories and rated them along six dimensions of explanatory quality. We find that some explanatory virtues are ascribed to conspiracy theories even by people who do not believe the conspiracy. Contrary to our predictions, we also find that framing a conspiracy as a refutation did not generally elicit higher ascriptions of explanatory virtues. These results suggest that explanatory considerations may play a more central role in conspiracist beliefs than was previously thought

Managing and aggregating group evidence under quality and quantity trade-offs

International audienc

Inference strength predicts the probability of conditionals better than conditional probability does

The file attached to this record is the author's final peer reviewed version.According to the philosophical theory of inferentialism and its psychological counterpart, Hypothetical Inferential Theory (HIT), the meaning of an indicative conditional centrally involves the strength of the inferential connection between its antecedent and its consequent. This paper states, for the first time, the implications of HIT for the probabilities of conditionals. We report two experiments comparing these implications with those of the suppositional account of conditionals, according to which the probability of a conditional equals the corresponding conditional probability. A total of 358 participants were presented with everyday conditionals across three different tasks: judging the probability of the conditionals; judging the corresponding conditional probabilities; and judging the strength of the inference from antecedent to consequent. In both experiments, we found inference strength to be a much stronger predictor of the probability of conditionals than conditional probability, thus supporting HIT