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ABSTRACT: This paper examines what children believe about unmapped number words—those number words whose exact meanings children have not yet learned. In the Study 1, 31 children (ages 2-10 to 4-2) judged that the application of five and six changes when numerosity changes, although they did not know that equal sets must have the same number word. In Study 2, 15 children (ages 2-5 to 3-6) judged that six plus more is no longer six, but that a lot plus more is still a lot. Findings support the hypothesis that children treat number words as referring to specific, unique numerosities even before know exactly which numerosity each word refers to.

Children and adults commonly produce more generic noun phrases (e.g., birds fly) about animals than artifacts. This may reflect differences in participants' generic knowledge about specific animals/artifacts (e.g., dogs/chairs), or it may reflect a more general distinction. To test this, the current experiments asked adults and preschoolers to generate properties about novel animals and artifacts (Experiment 1: real animals/artifacts; Experiments 2 and 3: matched pairs of maximally similar, novel animals/artifacts). Data demonstrate that even without prior knowledge about these items, the likelihood of producing a generic is significantly greater for animals than artifacts. These results leave open the question of whether this pattern is the product of experience and learned associations or instead a set of early-developing theories about animals and artifacts. (Contains 3 figures and 2 tables.)

Evaluating whether a limited sample of evidence provides a good basis for induction is a critical cognitive task. We hypothesized that whereas adults evaluate the inductive strength of samples containing multiple pieces of evidence by attending to the relations among the exemplars (e.g., sample diversity), six-year-olds would attend to the degree to which each individual exemplar in a sample independently appears informative (e.g., premise typicality). To test these hypotheses, participants were asked to select between diverse and non-diverse samples to help them learn about basic-level animal categories. Across various between-subject conditions (N = 133), we varied the typicality present in the diverse and non-diverse samples. We found that adults reliably selected to examine diverse over non-diverse samples, regardless of exemplar typicality, six-year-olds preferred to examine samples containing typical exemplars, regardless of sample diversity, and nine-year-olds were somewhat in the midst of this developmental transition. (Contains 4 tables and 1 figure.)

Preschoolers use information from interventions, namely intentional actions, to make causal inferences. We asked whether children consider some interventions to be more informative than others based on two components of an actor's knowledge state: whether an actor "possesses" causal knowledge, and whether an actor is allowed to "use" their knowledge in a given situation. Three- and four-year-olds saw a novel toy that activated in the presence of certain objects. Two actors, one knowledgeable about the toy and one ignorant, each tried to activate the toy with an object. In Experiment 1, either the actors chose objects or the child chose for them. In Experiment 2, the actors chose objects blindfolded. Objects were always placed on the toy simultaneously, and thus were equally associated with the effect. Preschoolers' causal inferences favored the knowledgeable actor's object "only" when he was allowed to choose it (Experiment 1). Thus, children consider both personal and situational constraints on knowledge when evaluating the informativeness of causal interventions.

Humans construe their environment as composed largely of discrete individuals, which are also members of kinds (e.g., trees, cars, and people). On what basis do young children determine individual identity? How important are featural properties (e.g., physical appearance, name) relative to spatiotemporal history? Two studies examined the relative importance of these factors in preschoolers' and adults' identity judgments. Participants were shown pairs of individuals who looked identical but differed in their spatiotemporal history (e.g., two physically distinct but identical Winnie-the-Pooh dolls), and were asked whether both members in the pair would have access to knowledge that had been supplied to only one of the pairs. The results provide clear support for spatiotemporal history as the primary basis of identity judgments in both preschoolers and adults, and further place issues of identity within the broader cognitive framework of psychological essentialism.

Generic sentences (such as "Birds lay eggs") are important in that they refer to kinds (e.g., birds as a group) rather than individuals (e.g., the birds in the henhouse). The present set of studies examined aspects of how generic nouns are understood by English speakers. Adults and children (4- and 5-year-olds) were presented with scenarios about novel animals and questioned about their properties, using generic and non-generic questions. Three primary findings emerged. First, both children and adults distinguished generic from non-generic reference, interpreting generics as referring to kinds. Thus, under certain contexts children and adults accepted that "Dobles have claws" even when all the dobles in the available context were clawless. Second, adults further distinguished properties that are inborn from those that are acquired. Inborn properties were judged to be predicated of a generic kind, even when all available instances have lost the property, but this was not the case for acquired properties. Third, children did not distinguish inborn from acquired properties. These data suggest the existence of developmental changes in conceptual or semantic understanding, and are interpreted in light of recent theories of psychological essentialism.

Utterances expressing generic kinds (''birds fly'') highlight qualities of a category that are stable and enduring, and thus provide insight into conceptual organization. To explore the role that linguistic input plays in children's production of generic nouns, we observed American and Chinese deaf children whose hearing losses prevented them from learning speech and whose hearing parents had not exposed them to sign. These children develop gesture systems that have language-like structure at many different levels. The specific question we addressed in this study was whether the gesture systems, developed without input from a conventional language model, would contain generics. We found that the deaf children used generics in the gestures they invented, and did so at about the same rate as hearing children growing up in the same cultures and learning English or Mandarin. Moreover, the deaf children produced more generics for animals than for artifacts, a bias found previously in adult English- and Mandarin-speakers and also found in both groups of hearing children in our current study. This bias has been hypothesized to reflect the different conceptual organizations underlying animal and artifact categories. Our results suggest that not only is a language model not necessary for young children to produce generic utterances, but the bias to produce more generics for animals than artifacts also does not require linguistic input to develop.

Examined reasoning about physics principles within and across ontological kinds among 5- and 7-year-olds and adults. Found that all age groups tended to appropriately generalize what they learned across ontological kinds. Children assumed that principles learned with reference to one ontological kind were more likely to apply within that kind than to another kind. Five-year-olds projected concepts learned about people to a greater extent than principles learned about objects. (Author/KB)

Examined how 3- and 5-year-olds and adults extend names for human-made artifacts. Found that even 3-year-olds were more likely to provide artifact names (e.g., "knife") when they believed objects were intentionally created and to provide material-based descriptions (e.g., "plastic") when they believed objects were accidentally created. Results support a theory of artifact naming whereby intuitions about intention play an important role. (Author/KB)

Examined causal status effect (weighing cause features more than effect features in categorization). Presented adults and 7- to 9-year-olds animal descriptions wherein one feature caused two others. Asked which transfer item was more likely an example of novel animal. Found that both groups preferred an animal with a cause and an effect feature over one with two effect features. (Author/KB)

Three studies examined adults' generic noun phrases in English and Mandarin Chinese from child-directed speech of caregivers interacting with their toddlers. Found that generic noun phrases were reliably identified in both languages. Generic noun phrases most frequently referred to animals. Non-generic noun phrases were used most frequently for artifacts in both languages. (Author/KB)

Two studies examined the hypothesis that children rely on name representations, often indexed by shape, in their semantic representations. Results suggest that, although shape plays an important role in children's early naming, other factors are also important, including the mental state of the picture's creator (whether intentional or not). Children's picture naming incorporates their theory of mind. (Author)