Publications

Abstract

A long-standing question in language development concerns the nature of the relationship between early lexical and grammatical knowledge. The very strong correlation between the two has led some to argue that lexical and grammatical knowledge may be inseparable, consistent with psycholinguistic theories that eschew a distinction between the two systems. However, little research has explicitly examined whether early lexical and grammatical knowledge are statistically separable. Moreover, there are two under-appreciated methodological challenges in such research. First, the relationship between lexical and grammatical knowledge may change during development. Second, non-linear mappings between true and observed scores on scales of lexical and grammatical knowledge could lead to spurious multidimensionality. In the present study, we overcome these challenges by using vocabulary and grammar data from several developmental time points and a statistical method robust to such non-linear mappings. In Study 1, we examined item-level vocabulary and grammar data from two American English samples from a large online repository of data from studies employing a commonly used language development scale. We found clear evidence that vocabulary and grammar were separable by two years of age. In Study 2, we combined data from two longitudinal studies of language acquisition that used the same scale (at 18/19, 21, 24 and 30 months) and found evidence that vocabulary and grammar were, under some conditions, separable by 18 months. Results indicate that, while there is clearly a very strong relationship between vocabulary and grammar knowledge in early language development, the two are separable. Implications for the mechanisms underlying language development are discussed.

Abstract

We investigated whether learning an artificial language at 17 months was predictive of children’s natural language vocabulary and grammar skills at 54 months. Children at 17 months listened to an artificial language containing non-adjacent dependencies, and were then tested on their learning to segment and to generalise the structure of the language. At 54 months, children were then tested on a range of standardised natural language tasks that assessed receptive and expressive vocabulary and grammar. A structural equation model demonstrated that learning the artificial language generalisation at 17 months predicted language abilities – a composite of vocabulary and grammar skills – at 54 months, whereas artificial language segmentation at 17 months did not predict language abilities at this age. Artificial language learning tasks – especially those that probe grammar learning – provide a valuable tool for uncovering the mechanisms driving children’s early language development.

Abstract

There is consensus that the adult lexicon exhibits lexical competition. In particular, substantial evidence demonstrates that words with more phonologically similar neighbors are recognized less efficiently than words with fewer neighbors. How and when these effects emerge in the child's lexicon is less clear. In the current paper, we build on previous research by testing whether phonological onset density slows lexical access in a large sample of 100 English-acquiring 30-month-olds. The children participated in a visual world looking-while-listening task, in which their attention was directed to one of two objects on a computer screen while their eye movements were recorded. We found moderate evidence of inhibitory effects of onset neighborhood density on lexical access and clear evidence for an interaction between onset neighborhood density and vocabulary, with larger effects of onset neighborhood density for children with larger vocabularies. Results suggest the lexicons of 30-month-olds exhibit lexical-level competition, with competition increasing with vocabulary size.

Abstract

How children learn grammar is one of the most fundamental questions in cognitive science. Two theoretical accounts, namely, the Early Abstraction and Usage-Based accounts, propose competing answers to this question. To compare the predictions of these accounts, we tested the comprehension of 92 24-month old children of transitive sentences with novel verbs (e.g., “The boy is gorping the girl!”) with the Intermodal Preferential Looking (IMPL) task. We found very little evidence that children looked to the target video at above-chance levels. Using mixed and mixture models, we tested the predictions the two accounts make about: (i) the structure of individual differences in the IMPL task and (ii) the relationship between vocabulary knowledge, lexical processing, and performance in the IMPL task. However, the results did not strongly support either of the two accounts. The implications for theories on language acquisition and for tasks developed for examining individual differences are discussed.

Abstract

Children acquire language embedded within the rich social context of interaction. This paper reports on a longitudinal study investigating the developmental relationship between conversational turn‐taking and vocabulary growth in English‐acquiring children (N = 122) followed between 9 and 24 months. Daylong audio recordings obtained every 3 months provided several indices of the language environment, including the number of adult words children heard in their environment and their number of conversational turns. Vocabulary was measured independently via parental report. Growth curve analyses revealed a bidirectional relationship between conversational turns and vocabulary growth, controlling for the amount of words in children’s environments. The results are consistent with theoretical approaches that identify social interaction as a core component of early language acquisition.