Conducting Cognitive Developmental Research in Museums: Theoretical Issues and Practical Considerations

Pragmatic differentiation in bilinguals is the ability to use two languages appropriately with different speakers. Although some sensitivity emerges by 2 years, the effects of context on these skills and their relation to other developing metacognitive capacities have not been examined. The current study compared the language use of 28 bilingual children (aged 2;7 to 3;10 and 4;1 to 4;11) across two tasks. All children were bilingual in English and Marathi, an Indian language. Theory of mind measures were included to assess whether developing cognitive capacities relate to pragmatic language ability. Results indicated that pragmatic differentiation is not an all-or-none ability but one which develops during the preschool years and varies based on the conversational context. This development is also related to metacognitive abilities which emerge during this time.     

Developmental Changes in the Consideration of Sample Diversity in Inductive Reasoning

Determining whether a sample provides a good basis for broader generalizations is a basic challenge of inductive reasoning. Adults apply a diversity-based strategy to this challenge, expecting diverse samples to be a better basis for generalization than homogeneous samples. For example, adults expect that a property shared by two diverse mammals (e.g., a lion and a mouse) is more likely to be shared by all mammals than a property that is shared by two more similar mammals (e.g., a lion and a tiger). Across four studies, we document a developmental progression in children's understanding that diverse samples provide a strong basis for generalizations, such that young children (grade 1) consistently failed to consider sample diversity within their inductive reasoning, but older children (grade 5) preferred to create diverse samples on which to base inferences about basic-level categories. These results suggest that recognizing the value of a diverse sample for inductive reasoning emerges slowly across the elementary school years.     

Visual nesting impacts approximate number system estimation

The approximate number system (ANS) allows people to quickly but inaccurately enumerate large sets without counting. One popular account of the ANS is known as the accumulator model. This model posits that the ANS acts analogously to a graduated cylinder to which one ??cup?? is added for each item in the set, with set numerosity read from the ??height?? of the cylinder. Under this model, one would predict that if all the to-be-enumerated items were not collected into the accumulator, either the sets would be underestimated, or the misses would need to be corrected by a subsequent process, leading to longer reaction times. In this experiment, we tested whether such miss effects occur. Fifty participants judged numerosities of briefly presented sets of circles. In some conditions, circles were arranged such that some were inside others. This circle nesting was expected to increase the miss rate, since previous research had indicated that items in nested configurations cannot be preattentively individuated in parallel. Logically, items in a set that cannot be simultaneously individuated cannot be simultaneously added to an accumulator. Participants?? response times were longer and their estimations were lower for sets whose configurations yielded greater levels of nesting. The level of nesting in a display influenced estimation independently of the total number of items present. This indicates that miss effects, predicted by the accumulator model, are indeed seen in ANS estimation. We speculate that ANS biases might, in turn, influence cognition and behavior, perhaps by influencing which kinds of sets are spontaneously counted.     

Language in the two-year old

Two stages in the vocabulary development of two-year-olds are reported. In the earlier Receptive stage, the child says many fewer nouns than he understands and says no verbs at all although he understands many. The child then begins to close the comprehension/production gap, entering a Productive stage in which he says virtually all the nouns he understands plus his first verbs. Frequency and length of word combinations correlate with these vocabulary stages.     

Children's Use of Different Information Types When Learning Homophones and Nonce Words

This study examines whether 3-year-olds are able to use ontological distinctions in homophone and nonce word acquisition. In the homophone (denotation-1 present) condition, children heard stories introducing second meanings of homophones; for example, a skate (i.e., fish). Stories contained perceptual information, information about theory-based properties, or filler material. Children identified the referent from 3 drawings depicting the familiar meaning, the secondary meaning, and a distractor. In the homophone (denotation-1 absent) condition, the picture of the familiar meaning was replaced with a distractor. The nonce word condition, a control condition, was identical to the homophone (denotation-1 present) condition except that a nonce word replaced the homophone. Children were rarely able to construct a second homophone interpretation when the familiar denotation was available. Interestingly, in the remaining conditions, children used information about the animate-inanimate distinction in choosing the referent. We discuss children's use of this ontological distinction when inducing word meaning.     

The role of preschoolers' social understanding in evaluating the informativeness of causal interventions

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.     

Bewitchment, biology, or both: the co-existence of natural and supernatural explanatory frameworks across development

Three studies examined the co-existence of natural and supernatural explanations for illness and disease transmission, from a developmental perspective. The participants (5-, 7-, 11-, and 15-year-olds and adults; N = 366) were drawn from 2 Sesotho-speaking South African communities, where Western biomedical and traditional healing frameworks were both available. Results indicated that, although biological explanations for illness were endorsed at high levels, witchcraft was also often endorsed. More important, bewitchment explanations were neither the result of ignorance nor replaced by biological explanations. Instead, both natural and supernatural explanations were used to explain the same phenomena, and bewitchment explanations were highest among adults. Taken together, these data provide insight into how diverse, culturally constructed belief systems about illness co-exist across development.     

Five-year-olds’ beliefs about the discreteness of category boundaries for animals and artifacts

Research on adult concepts indicates that category structure varies by domain; adults view membership in animal categories as absolute but membership in artifact categories as graded. In this study, we examined domain differences in beliefs about category boundaries among young children (5-year-olds). The results indicated that young children, like adults, were less likely to endorse graded category membership for animal than for artifact categories. These domain differences could not be attributed to domain differences in typicality. Implications for conceptual development and for models of domain specificity in adult cognition are discussed.