Children's and adults' models for predicting teleological action: the development of a biology-based model.

Understanding that only living things must act to gain self-beneficial goals is important for developing a theory-like understanding of the living world. This research studied the models that preschoolers, fifth graders, and adults use to guide their predictions of self-beneficial, goal-directed (i.e., teleological) action. Four possible models have been suggested: finalist, complexity based, biology based, and animal based. In Study 1, participants (N = 104) were assigned to one of two conditions that differed in whether a beneficial or neutral object was pictured; they were asked to predict whether animals, plants, machines, and simple artifacts would modify their movement in the direction of that object. Preschoolers' predictions were consistent with an animal-based model, fifth graders' predictions were consistent with biology-based and complexity-based models, and adults' predictions were consistent with a biology-based model. Analysis of both individual response patterns and explanations supported these findings, but also showed that a significant number of preschoolers and fifth graders were finalist, and that very few individual fifth graders followed a complexity-based teleology. In Study 2, participants (N = 84) reported whether the animals, plants, machines, and simple artifacts in Study 1 had psychological capacities. All age groups attributed psychological capacities to animals at levels higher than other domains and at above-chance levels. The evidence from these two studies suggests that preschoolers, unlike fifth graders and adults, predict teleological action for plants and animals on the basis of these entities' inferred psychological capacities.

Children's understanding of psychogenic bodily reactions.

One hundred twenty-eight children in preschool through fifth grade (range = 4,3-11,4) and 76 adults serving as a comparison group participated in two studies that examined how children reason about psychogenic bodily reactions, that is, ailments or nonconscious physiological responses with origins in the mind (e.g., stress-induced headache). Psychogenic bodily reactions provide an opportunity to study how children integrate knowledge between the domains of bodily response and psychology. In Study 1, participants were asked whether various familiar psychogenic bodily reactions were possible (e.g., can someone get a tummyache from worrying?). In Study 2, participants were presented with a novel domain (hypothetical "aliens" from outer space) and were asked whether various unfamiliar bodily conditions (e.g., toes swelling) could arise from various physical or psychological causes. As predicted, adults typically reported that psychogenic bodily reactions were possible, and that unfamiliar bodily conditions could result from either psychological or physical causes. In contrast, young children typically denied that psychogenic bodily reactions could occur and predicted that unfamiliar bodily conditions resulted from physical causes only. The results support a developmental path: younger children view psychogenic bodily responses as wholly physical, but with age, view them as both physical and psychological phenomena.

The role of animacy in children's understanding of 'move'.

Animals are distinctive in that they are the causal agents of their own actions (e.g. a dog moves itself), whereas artifacts generally are not (e.g. a marble doesn't move itself). We examined whether children make use of this conceptual link between animacy and agency when interpreting the verb 'move' in English. Specifically, we hypothesized that the semantic interpretation of 'move' would differ, depending on whether the subject noun refers to an animal or to an inanimate object. We hypothesized that, for in animates, children would allow 'move' to have a patient subject (e.g. 'the marble moved' could mean 'the marble was moved by someone else') but not so for animates (e.g. 'the dog moved' could not mean 'the dog was moved by someone else'). In two studies, 65 three-year-olds, 57 five-year-olds, and 74 adults viewed video clips of animals or inanimate objects being transported by a person. For each clip, the child was asked whether the animal or object was moving. A 'yes' response would indicate acceptance of a patient subject (e.g. 'the dog/marble moved' means 'the dog/marble was moved by someone else'). Both five-year-old children and adults more often reported that the toys were moving, than that the animals were moving. However, three-year-olds showed no animacy effects. Thus, between the ages of three and five, children begin to link animacy and agency in language. These findings suggest that children's language use is guided by similar conceptual constraints as those of adults, and/or that children are sensitive to distributional information linking form and meaning in the input language.

Preschool children's use of trait labels to make inductive inferences.

One hundred one preschool children (ages 3 years 5 months to 4 years 10 months) participated in 3 studies examining the tendency to use verbal labels versus appearance information in making novel inductive inferences. A triad task analogous to that of S. A. Gelman and E. M. Markman (1986) was devised. Participants learned a different property for each of 2 children, and were asked which of the properties was true of a third child. One of the first 2 children was identified with the same label as the third child (e.g., both were labeled as shy) but looked different, and the other was identified with a different label than the third child but looked very similar. Results of Study 1 revealed that participants tended to use the trait labels, rather than superficial resemblance, in making psychological inferences. Studies 2 and 3 suggest that these results cannot be attributed to biases on the task. Study 4 provided a replication of the results of Study 1 in a context in which appearance information was explicitly pointed out and in which different trait labels were used.

Young children are sensitive to how an object was created when deciding what to name it.

How do young children extend names for human-made artifacts, such as knife, toy, and painting? We addressed this issue by showing 3-year-olds, 5-year-olds, and adults a series of simple objects and asking them for each, 'What is this?' In one condition, the objects were described as purposefully created; in another, the objects were described as being created by accident. This manipulation had a significant effect on the participants' responses: even 3-year-olds were more likely to provide artifact names (e.g. 'a knife') when they believed the objects were intentionally created and material-based descriptions (e.g. 'plastic') when they believed the objects were accidentally created. This result supports a theory of artifact naming in which intuitions about intention play an important role.

Causal status effect in children's categorization.

The current study examined the causal status effect (weighing cause features more than effect features in categorization) in children. Adults (Study 1) and 7-9-year-old children (Study 2) learned descriptions of novel animals, in which one feature caused two other features. When asked to determine which transfer item was more likely to be an example of the animal they had learned, both adults and children preferred an animal with a cause feature and an effect feature rather than an animal with two effect features. This study is the first direct demonstration of the causal status effect in children.

The use of trait labels in making psychological inferences.

Three studies investigated children's capacity to use trait labels as tools for making inferences about mental states. For example, knowledge that a story character is "nice" as opposed to "mean" could lead to predictions that the character would respond with greater negative affect upon discovering that his or her action had made someone upset. Study 1 (N = 48) examined whether participants (kindergartners, second graders, fifth graders, and adults) would make different psychological inferences based on whether a character was labeled as "nice" versus "mean." Study 2 (N = 30) examined the same issue with 4-year-olds using a simpler methodology. Study 3 (N = 30) extended the results of Study 2, by examining whether describing characters as "shy" versus "not shy" would lead 4-year-olds to make different mental state inferences. Taken together, these findings suggest that even for young children, trait labels can serve as a basis for making nonobvious inferences. Developmental differences are discussed.

Domain differences in absolute judgments of category membership: evidence for an essentialist account of categorization.

There has been some debate about the correspondence between typicality gradients and category membership. The present study investigates the relationship between these two measures in the domains of animals and artifacts. Forty-two adults judged the degree of typicality or category membership of 293 animals and artifacts. The subjects' tendency for animals, but not for artifacts, was to make more absolute ratings on category membership (i.e., judging exemplars as definitely members or definitely not members of their respective category) than on typicality. More importantly, at almost every level of typicality, subjects were more likely to make absolute judgments of category membership for animals than for artifacts. These results indicate that people treat category membership of animals as relatively absolute (which best fits an essentialist model of categorization) and treat category membership of artifacts as relatively graded (which best fits a prototype model of categorization). These domain differences add crucial supporting evidence for claims about the domain-specificity of essentialism.

Beyond labeling: the role of maternal input in the acquisition of richly structured categories.

Recent research shows that preschool children are skilled classifiers, using categories both to organize information efficiently and to extend knowledge beyond what is already known. Moreover, by 2 1/2 years of age, children are sensitive to nonobvious properties of categories and assume that category members share underlying similarities. Why do children expect categories to have this rich structure, and how do children appropriately limit this expectation to certain domains (i.e., animals vs. artifacts)? The present studies explore the role of maternal input, providing one of the first detailed looks at how mothers convey information about category structure during naturalistic interactions. Forty-six mothers and their 20- or 35-month-old children read picture books together. Sessions were videotaped, and the resulting transcripts were coded for explicit and implicit discussion of animal and artifact categories. Sequences of gestures toward pictures were also examined in order to reveal the focus of attention and implicit links. drawn between items. Results indicate that mothers provided a rich array of information beyond simple labeling routines. Taxonomic categories were stressed in subtle and indirect ways, in both speech and gesture, especially for animals. Statements and gestures that linked two pictures were more frequent for taxonomically related animal pictures than for other picture pairs. Mothers also generalized category information using generic noun phrases, again more for animals than for artifacts. However, mothers provided little explicit discussion of nonobvious similarities, underlying properties, or inductive potential among category members. These data suggest possible mechanisms by which a notion of kind is conveyed in the absence of detailed information about category essences.

Why is a pomegranate an apple? The role of shape, taxonomic relatedness, and prior lexical knowledge in children's overextensions of apple and dog.

Children's overextensions (e.g. referring to a pomegranate as apple) raise intriguing questions regarding early word meanings. Specifically, how do object shape, taxonomic relatedness, and prior lexical knowledge influence children's overextensions? The present study sheds new light on this issue by presenting items that disentangle the three factors of shape, taxonomic category, and prior lexical knowledge, and by using a novel comprehension task (the screened-alternative task) in which children can indicate negative exemplars (e.g. which items are NOT apples). 49 subjects in three age groups participated (Ms = 2;0, 2;6, and 4;5). Findings indicate: (1) Error patterns differed by task. In production, errors were overwhelmingly due to selecting items that matched the target word in BOTH shape and taxonomic relatedness. In comprehension, more errors were based on either shape alone or taxonomic relatedness alone, and the nature and frequency of the overextensions interacted with prior lexical knowledge. (2) Error patterns also differed markedly based on the word being tested (apple vs. dog), in both comprehension and production (3) As predicted, errors were more frequent in production than comprehension, though only for children in the two younger age groups. Altogether, the study indicates that overextensions are not simply production errors, and that both taxonomic relatedness and object shape play a powerful role in early naming errors.

Conceptual and linguistic biases in children's word learning.

Four studies examined the influence of essentialist information and perceptual similarity on preschoolers' interpretations of labels. In Study 1, 3-, 4-, and 5-year-olds were less likely to interpret 2 labels for animals as referring to mutually exclusive categories: when the animals were said to share internal, rather than superficial, properties and when the animals were perceptually similar rather than dissimilar. In Study 2, neither internal nor functional property information influenced 4-year-olds' interpretations of labels for artifacts. Studies 3 and 4 provide baseline data, demonstrating that the domain differences were not due to prior differences in children's lexical knowledge in the 2 domains. These results suggest that children have essentialist beliefs about animals, but not about artifacts, and that these beliefs interact with children's assumptions about word meaning in determining their interpretations of labels.

A cross-linguistic comparison of generic noun phrases in English and Mandarin.

Generic noun phrases (e.g. 'bats live in caves') provide a window onto human concepts. They refer to categories as 'kinds rather than as sets of individuals. Although kind concepts are often assumed to be universal, generic expression varies considerably across languages. For example, marking of generics is less obligatory and overt in Mandarin than in English. How do universal conceptual biases interact with language-specific differences in how generics are conveyed? In three studies, we examined adults' generics in English and Mandarin Chinese. The data include child-directed speech from caregivers interacting with their 19-23-month-old children. Examples of generics include: 'baby birds eat worms' (English) and da4 lao3shu3 yao3 bu4 yao3 ren2 ('do big rats bite people or not?') (Mandarin). Generic noun phrases were reliably identified in both languages, although they occurred more than twice as frequently in English as in Mandarin. In both languages, generic usage was domain-specific, with generic noun phrases used most frequently to refer to animals. This domain effect was specific to generics, as non-generic noun phrases were used most frequently for artifacts in both languages. In sum, we argue for universal properties of 'kind' concepts that are expressed with linguistically different constructions. However, the frequency of expression may be influenced by the manner in which generics are expressed in the language.

Shape and representational status in children's early naming.

Why are ontological distinctions commonly ignored in ordinary language use? For example, why is a toy bear called a 'bear'? Jones and Smith argue that shape is central to the semantic representations of both children and adults (Jones, S.S., Smith, L.B., 1993. The place of perception in children's concepts. Cognitive Development 8, 113-139). In contrast, Soja et al. suggest that children do not rely on shape per se, but rather name representations, which are often indexed by shape (Soja, N.N., Carey, S., Spelke, E.S. 1992. Perception, ontology, and word meaning. Cognition 45, 101-107). Two studies were designed to test the latter hypothesis. Forty-seven children (2 years 5 months-3 years 11 months) and 32 adults participated. Each saw a series of line-drawings roughly shaped like various namable objects (e.g. a man). For half the participants, each line-drawing was described as depicting a shape that was created intentionally (e.g. someone painted a picture). For the remaining participants, each drawing was described as depicting a shape that was created accidentally (e.g. someone spilled some paint). Participants were simply asked to name each picture. We hypothesized that subjects would use shape as the basis of naming primarily when the shapes were intentional (and thus plausibly representations). The findings supported the predictions, for both children and adults. These results suggest that, although shape does play an important role in children's early naming, other factors are also important, including the mental state of the picture's creator (intentional vs. not). Thus, the data suggest that from an early age, children's picture naming incorporates their theory of mind.

Generic noun phrases in mother-child conversations.

Generic noun phrases (e.g. Tigers are fierce) are of interest for their semantic properties: they capture 'essential' properties, are timeless, and are context-free. The present study examines use of generic noun phrases by preschool children and their mothers. Mother-child pairs were videotaped while looking through a book of animal pictures. Each page depicted either a single instance of a particular category (e.g. one crab) or multiple instances of a particular category (e.g. many crabs). The results indicated a striking difference in how generics vs. non-generics were distributed, both in the speech of mothers and in the speech of preschool children. Whereas the form of non-generic noun phrases was closely linked to the structure of the page (i.e. singular noun phrases were used more often when a single instance was presented; plural noun phrases were used more often when multiple instances were presented), the form of generic noun phrases was independent of the information depicted (e.g. plural noun phrases were as frequent when only one instance was presented as when multiple instances were presented). We interpret the data as providing evidence that generic noun phrases differ in their semantics and conceptual organization from non-generic noun phrases, both in the input to young children and in children's own speech. Thus, this simple linguistic device may provide input to, and a reflection of, children's early developing notion of 'kinds'.

Young children use motive information to make trait inferences.

The present study investigates children's capacity to understand traits in a psychologically meaningful way. Participants included 18 individuals in each of 4 age groups: kindergarten (ages 5-6), 2nd grade (ages 7-8), 5th grade (ages 10-11), and adult. They heard a series of 6 short stories in which a main character performs an action based on a particular motive (positive, negative, or incidental) that results in either a positive or a negative emotional consequence for another character. Participants evaluated each main character and predicted the character's behavior and mental states in different social contexts. Participants in all age groups, even the 5- to 6-year-olds, made trait inferences that were influenced by motive information. These results provide evidence that young children are capable of more sophisticated reasoning about traits than has been suggested previously.

Children's use of sample size and diversity information within basic-level categories.

Category-based induction involves making decisions about some member(s) of a category based on information concerning other category members. Recent studies indicate that although adults make use of information concerning sample size (larger samples are a stronger basis of inference than smaller samples) and sample diversity (more diverse samples are better than more homogeneous samples) when making category-based inductive judgments, children do not do so until age 8 or 9 and even then to only a limited degree. This research however, was conducted at the superordinate level of categorization, and it is unclear if general difficulty with this category level may have masked children's ability to use size and diversity, or if these results represent a more entrenched conceptual difficulty in using this information. We therefore conducted three studies that investigate both 8- and 9-year-olds' and adults' ability to use sample size and diversity within basic level categories. Our results indicate that children's difficulty with this information is independent of category level, and may be based on preferences for other strategies concerning category membership and perceptual similarity.