Much developmental work has been devoted to scalar implicatures. These are implicitly communicated propositions linked to relatively weak terms (consider how Some pragmatically implies Not all) that are more likely to be carried out by adults than by children. Children tend to retain the linguistically encoded meaning of these terms (wherein Some is compatible with All). In three experiments, we gauge children's performance with scalars while investigating four factors that can have an effect on implicature production: (i) the role of (the presence or absence of) distractor items; (ii) the nature of the task (verbal judgments versus action-based judgments); (iii) the choice of scalar expression (the French quantifier quelques versus certains); and (iv) the type of scale that contextualizes the weak utterance (the affirmative All versus the negative None earlier findings showing that 9-year-olds are more likely than adults to consider as true statements such as Some turtles are in the boxes (uttered when all turtles are in the boxes) while employing the quantifier certains in a truth evaluation task containing multiple distractor items. The task in Experiment 2 increased implicature production across all ages (4-, 5-, and 7-year-olds as well as adults) but maintained the developmental effect while using quelques in an action-based task containing no distractor items. Experiment 3 showed that 9-year-olds are more likely to produce implicatures with quelques than they are with certains in the action task while adults are not affected by the choice of term. Overall, these results identify seemingly harmless task features that can prevent even older children (9-year-olds) from carrying out implicatures (e.g., through the inclusion of distractors) while also showing how implicature production among even young children (4-to 5-year-olds) can be facilitated by task features (e.g., the use of an action task) and without the introduction of special training.

International audienceThe new paradigm in the psychology of reasoning adopts a Bayesian, or prob-abilistic, model for studying human reasoning. Contrary to the traditional binary approach based on truth functional logic, with its binary values of truth and falsity, a third value that represents uncertainty can be introduced in the new paradigm. A variety of three-valued truth table systems are available in the formal literature, including one proposed by de Finetti. We examine the descriptive adequacy of these systems for natural language indicative condi-tionals and bets on conditionals. Within our framework the so-called " defective " truth table, in which participants choose a third value when the antecedent of the indicative conditional is false, becomes a coherent response. We show that only de Finetti's system has a good descriptive fit when uncertainty is the third value. The new Bayesian, or probabilistic, paradigm in the psychology of reasoning (Oaksford & Chater, 2007, 2009; Over, 2009; Pfeifer & Kleiter, 2010) implies a close parallel relationship between assertions of the indicative conditional of natural language, if A then C, and other uses of conditionals, particularly bets on conditionals, I bet that if A then B. Politzer, Over, and Baratgin (2010) explain how this predicted relation goes back to Ramsey (1926/1990, 1929/1990) and de Finetti (1936/1995, 1937/1964) and provide experimental evidence that this parallel relation exists (see also Baratgin, Over, & Politzer, in press). Financial support for this work was provided by the French ANR agency under grant ANR Chorus 2011 (project BTAFDOC). We would like to thank Paul Egr e, Jean-Louis Stilgenbauer, and Tatsuji Takahashi for much discussion and other help in our research. We also thank Shira Elqayam, Jean-François Bonnefon, and two anonymous reviewers

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It is proposed that reasoning about social contracts, such as conditional promises and warnings, is under the control of a compound schema made of two pragmatic schemas (Cheng & Holyoak, 1985), expressing an obligation and a permission. Two experiments were run using thematic versions of the Wason selection task in which the rule and the core of the scenario were kept constant and the point of view of the actor (e.g. promisor or promisee) was varied. The results supported the predictions (including the occurrence of a correct pattern of response that consists of all four cards) and falsified predictions derived from Cosmides' (1989) theory of social exchange. The mental models theory and Evans' two-stage theory of reasoning are also discussed in the light of the present results.

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This paper begins with a review of the literature on plausible reasoning with deductive arguments containing a conditional premise. There is concurring evidence that people presented with valid conditional arguments such as Modus Ponens and Modus Tollens generally do not endorse the conclusion, but rather find it uncertain, in case (i) the plausibility of the major conditional premise is debatable, (ii) the major conditional premise is formulated in frequentist or probabilistic terms, or (iii) an additional premise introduces uncertainty about the major conditional premise. This third situation gives rise to non monotonic effects by a mechanism that can be characterised as follows: the reasoner is invited to doubt the major conditional premise by doubting the satisfaction of a tacit condition which is necessary for the consequent to occur. Three experiments are presented. The first two aim to generalise the latter result using various types of conditionals and the last shows that performance in conditional reasoning is significantly affected by the representation of the task. This latter point is discussed along with various other issues: we propose a pragmatic account of how the tacit conditions mentioned earlier are treated in plausible reasoning; the relationship of this account with the conditional probability view on conditional sentences is examined; an application of the same account to the Suppression Effect (Byrne, 1989) is proposed and compared with the counterexample availability explanation; and finally some suggestions on how uncertainty could be implemented in a mental logic system are presented. Uncertain Conditionals 2People may have more or less confidence in the truth of the propositions that originate from their sources of information: communication, perception, memory, and inference. A person was told that P, saw that Q, recalls that R, infers that S; but was her informant dependable, her senses reliable, her memory faithful, her conclusion valid ? People face such questions constantly (this is made possible by their metacognitive skills): they are more or less confident in the truth of the propositions they entertain. We take this fact as a psychologically primitive phenomenon and call degree of belief the subjective degree of confidence that people experience in such situations.Belief comes by degrees: having full belief in a proposition is to consider it as true (hence full belief in not-P is to consider not-P as true, i. e. , P as false, which is full disbelief in P). One can have less than full belief in P, in which case one is uncertain (or doubts) about the truth of P; in particular, one can have slightly less than full belief, in which case one is slightly uncertain about P (and at the same time nearly certain about not-P): uncertainty about P is the extent to which one disbelieves P (within the limits where belief in P is greater than belief in not-P). When degree of belief decreases from full belief in P, a point of indeterminacy is reached where belief in P equals belief in not-P: ...