When Time Shifts the Boundaries: Isolating the Role of Forgetting in Children's Changing Category Representations.

In studies of children's categorization, researchers have typically studied how encoding characteristics of exemplars contribute to children's generalization. However, it is unclear whether children's internal cognitive processes alone, independent of new information, may also influence their generalization. Thus, we examined the role that one cognitive process, forgetting, plays in shaping children's category representations by conducting three experiments. In the first two experiments, participants (NExp1=37, Mage=4.02 years; NExp2=32, Mage=4.48 years) saw a novel object labeled by the experimenter and then saw five new objects with between one and five features changed from the learned exemplar. The experimenter asked whether each object was a member of the same category as the exemplar; children saw the five new objects either immediately or after a five-minute delay. Children endorsed category membership at higher rates at immediate test than at delayed test, suggesting that children's category representations became narrower over time. In Experiment 3, we investigated forgetting as a key mechanism underlying the narrowing found in Experiments 1 and 2. We showed participants (NExp3=34, Mage=4.20 years) the same exemplars used in Experiments 1 and 2; then, either immediately or after a five-minute delay, we showed children seven individual object features and asked if each one had been part of the exemplar. Children's accuracy was lower after the delay, showing that they did indeed forget individual features. Taken together, these results show that forgetting plays an important role in changing children's newly-learned categories over time.

Does the public know what researchers know? Perceived task difficulty impacts adults' intuitions about children's early word learning.

The present study examined adults' understanding of children's early word learning. Undergraduates, non-parents, parents, and Speech-Language Pathologists (N = 535, 74% female, 56% White) completed a survey with 11 word learning principles from the perspective of a preschooler. Questions tested key principles from early word learning research. For each question, participants were prompted to select an answer based on the perspective of a preschooler. Adults demonstrated aligned intuitions for all principles except those derived from domain-general theories, regardless of experience with language development (Experiment 1). Experiment 2 revealed that perceived difficulty of a task for a preschooler impacted adults' reasoning about word learning processes. Experiment 3 ruled out level of confidence and interest as mechanisms to explain the results. These results highlight disconnects in knowledge between the cognitive development research community and the general public. Therefore, efforts must be made to communicate scientific findings to the broader non-academic community, emphasizing children's ability to excel at word learning in the face of task difficulty.

Effects of past language experience and present language context on the shape bias in Spanish-English bilingual children.

English-monolingual children develop a shape bias early in language acquisition, such that they more often generalize a novel label based on shape than other features. Spanish-monolingual children, however, do not show this bias to the same extent (Hahn & Cantrell, 2012). Studying children who are simultaneously learning both Spanish and English presents a unique opportunity to further investigate how this word-learning bias develops. Thus, we asked how Spanish-English bilingual children (Mage  = 21.31 months) perform in a novel-noun generalization (NNG) task, specifically examining how past language experience (i.e. language exposure and vocabulary size) and present language context (i.e. whether the NNG task was conducted in Spanish or English) influence the strength of the shape bias. Participants completed the NNG task either entirely in English (N = 16) or entirely in Spanish (N = 16), as well as language understanding tasks in both English and Spanish to ensure that they understood what the experimenter was asking them to do. Parents completed a language exposure survey and vocabulary checklists in Spanish and English. There was a significant interaction between condition and choice type: Bilingual children in the English condition showed a shape bias in the NNG task, but bilingual children in the Spanish condition showed no reliable biases. No measures of past language experience were related to NNG task performance. These results suggest that when learning new words, bilingual children are attuned to the regularities of the present language context, and prior language experiences may play a more secondary role.

Two-year-olds' executive functioning: The influence of task-specific vocabulary knowledge.

Although many executive function (EF) tasks require only nonverbal responses, the language used by experimenters to explain the task may be important for young children's EF task performance. This study investigated how the vocabulary used in explaining an EF task affects 2-year-olds' performance. Experiment 1 used the standard instructions for the Reverse Categorization Task, in which children are asked to sort different-sized blocks into different-sized buckets according to one rule and then switch to a new rule. In Experiment 2, the task remained the same, but different instructions requiring less knowledge of size words were used. Children's productive vocabulary was assessed in both experiments but was only correlated with task performance in Experiment 1. These results suggest that task-specific vocabulary knowledge may play a role in children's performance on tasks designed to measure nonverbal cognitive ability.