In the context of joint decision-making, we investigated whether preschoolers alter the informativeness of their justifications depending on the common ground that they share with their partner. Pairs of 3- and 5-year-olds (N = 146) were introduced to a novel animal with unique characteristics (e.g., eating rocks). In the common ground condition, the children learned about the animal together. In the one-expert condition, one learned about it, the other was naïve. In the two-experts condition, children learned about it separately. Later, the pairs had to decide together on 3 items that the novel animal might need. Both age groups referred to the unique characteristics of the animal in their justifications more in the 2 conditions without common ground than in the common ground condition. Thus, preschoolers begin to use common ground flexibly in their justifications and reason-giving in peer interactions.

Language and other forms of communication are inherently ambiguous and therefore require some form of common ground to specify the intended meanings of utterances. Theoretical accounts usually focus on interactions between adults and consider recursive mindreading a prerequisite to establishing common ground. Contrasting these accounts, in this article, we offer a developmental perspective on common ground. We propose that instead of using recursive mindreading, infants rely initially on the expectation that communicative partners act rationally in light of previous interactions, which serves as a starting point for common ground to develop. We describe the changing role of common ground across development. Initially, common ground constrains the meaning of ambiguous communicative acts and facilitates children's acquisition of language. Later in development, common ground makes communication efficient by helping speakers coordinate their actions and intentions, and eventually arrive at recursive mindreading.

We would like to thank Roger Mundry for statistical assistance; Isabelle de Gaillande-Mustoe and Nadine Kante for their help in recruiting the children and collecting data; Doreen Schrimpf; Christina Stockmann, and Irka Wetzig for their help in transcribing and coding the data; Petra Jahn for her help with the bibliography, and all daycare centers and children for their friendly cooperation.Correspondence concerning this article should be addressed to Bahar AbstractThis study investigates how children negotiate social norms with peers. In Study 1, 48 pairs of 3-and 5-year-olds (N = 96) and in Study 2 48 pairs of 5-and 7-year-olds (N = 96) were presented with sorting tasks with conflicting instructions (one child by color, the other by shape) or identical instructions. Three-year-olds differed from older children: They were less selective for the contexts in which they enforced norms, and they (as well as the older children to a lesser extent) used grammatical constructions objectifying the norms ("It works like this" rather than "You must do it like this").These results suggested that children's understanding of social norms becomes more flexible during the preschool years.

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Moral justifications work, when they do, by invoking values that are shared in the common ground of the interlocutors. We asked 3- and 5-year-old peer dyads (N = 144) to identify and punish norm transgressors. In the moral condition, the transgressor violated a moral norm (e.g., by stealing); in the social rules condition, she/he violated a context-specific rule (e.g., by placing a yellow toy in a green box, instead of a yellow box). Children in both age groups justified their punishment in the social rules condition mostly by referring to the rule (e.g., "He must put yellow toys in the yellow box"). In contrast, in the moral condition they mostly justified their punishment by simply referring to the observed fact (e.g., "He stole"), seeing no need to state the norm involved (e.g., "He must not steal"), presumably because they assumed this as part of their moral common ground with their partner. These results suggest that preschoolers assume certain common ground moral values with their peers and use these in formulating explicit moral judgments and justifications. (PsycINFO Database Record