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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