Language as a mechanism for reasoning about possibilities.

The ability to entertain and reflect on possibilities is a crucial component of human reasoning. However, the origin of this reasoning-whether it is language-based or not-is highly debated. We contribute to this debate by investigating the relation between language and thought in the domain of possibility from a developmental perspective. Our investigation focuses on disjunctive syllogism, a specific type of possibility reasoning that has been explored extensively in the developmental literature and has clear linguistic correlates. Seeking links between conceptual and linguistic representations, we review evidence on how children reason by the disjunctive syllogism and how they acquire logical and modal language. We sketch a proposal for how language and thought interact during development. This article is part of the theme issue 'Thinking about possibilities: mechanisms, ontogeny, functions and phylogeny'.

Children's (and Adults') Production Adjustments to Generic and Particular Listener Needs.

Adults design utterances to match listeners' informational needs by making both "generic" adjustments (e.g., mentioning atypical more often than typical information) and "particular" adjustments tailored to their specific interlocutor (e.g., including things that their addressee cannot see). For children, however, relevant evidence is mixed. Three experiments investigated how generic and particular factors affect children's production. In Experiment 1, 4- to 5-year-old children and adults described typical and atypical instrument events to a silent listener who could either see or not see the events. In later extensions, participants described the same events to either a silent (Experiment 2) or an interactive (Experiment 3) addressee with a specific goal. Both adults and 4- to 5-year-olds performed generic adjustments but, unlike adults, children made listener-particular adjustments inconsistently. These and prior findings can be explained by assuming that particular adjustments can be costlier for children to implement compared to generic adjustments.

Toddlers' understanding and use of verbal negation in inferential reasoning search tasks.

Past research has demonstrated that young children and nonhuman animals are able to reason by elimination ("If not A, then B") by relying on visual cues such as seeing that one container is empty. Other research has shown that young children can solve similar, simple inferential reasoning tasks where "emptiness" is conveyed verbally through negation (e.g., "The toy is not in the box"). However, it is unclear whether these tasks involved reasoning through the disjunctive syllogism, which requires the representation of logical negation (NOT A) and disjunction (A OR B) or simpler, nondeductive strategies. In Study 1, we extended this work by investigating whether 2-year-olds can infer the location of a toy in typical two-location elimination trials, when given both affirmative and negative sentences, and more complex three-location trials, when information about emptiness was conveyed verbally and visually. Younger 2-year-olds performed significantly better on the search task when hearing affirmative than negative sentences, whereas older 2-year-olds were equally successful with both types of sentences. Study 2 examined children's ability to use verbal negation to solve a more complex deductive task involving disjunctive syllogism. Results showed that, in this linguistic version of the disjunctive reasoning task, both 2.5- and 3-year-olds made accurate inferences about the location of a reward, unlike prior (nonlinguistic) evidence that demonstrated this ability in 3-year-olds but not in younger children. We conclude that by the end of their second year of life, children have a robust understanding of negation which they can apply in abstract reasoning.

Interactive contexts increase informativeness in children's referential communication.

Adults adjust the informativeness of their utterances to the needs of their addressee. For children, however, relevant evidence is mixed. In this article we explore the communicative circumstances under which children offer informative descriptions. In Experiment 1, 4- and 5-year-old children and adults described a target event from a pair of almost identical events to a passive confederate listener who could either see or not see the referents. Adults provided disambiguating information that picked out the target event but children massively failed to do so (even though 5-year-olds were more informative than 4-year-olds). Furthermore, both children and adults were more likely to mention atypical than typical disambiguating event components. Because of the contrastive nature of the task, the listener's visual access had no effects on production. Experiment 2 was a more interactive version of Experiment 1 where participants played a guessing game with a "naïve" listener. In this context, children (and adults) became overall more informative, and the difference between child groups disappeared. We conclude that the informativeness of children's event descriptions is heavily context-dependent and is boosted when children engage in a collaborative interaction with a "true" interlocutor. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Pragmatics and spatial language: The acquisition of front and back.

Across languages, children produce locative back earlier and more frequently than front, but the reasons for this asymmetry are unclear. On a semantic misanalysis explanation, early meanings for front and back are nonadult (nongeometric), and rely on notions of visibility and occlusion respectively. On an alternative, pragmatic inference explanation, visibility and occlusion are simply pragmatic aspects of the meaning of front and back; the profile of back can be explained by the fact that occlusion is more noteworthy compared with visibility. We used cross-linguistic data to test these two hypotheses. In Experiment 1, we examined the production and comprehension of front/back by 3- and 4-year-old children and adults speaking two different languages (English and Greek). Children, unlike adults, used back more frequently than front in both languages; however, no such asymmetry surfaced in the comprehension of the two prepositions. In Experiment 2, both adults and children from the same language groups showed the front/back asymmetry when describing a more variable battery of spatial stimuli. Our results support the pragmatic inference hypothesis. We conclude that the emergence of spatial terms does not solely index semantic development but may be linked to pragmatic factors that also shape adults' production of spatial language cross-linguistically. (PsycINFO Database Record (c) 2019 APA, all rights reserved).