Previous studies indicate that English-learning children acquire the distinction between singular and plural nouns between 22 and 24 months of age. Also, their use of the distinction is correlated with the capacity to distinguish nonlinguistically between singular and plural sets in a manual search paradigm (D. Barner, D. Thalwitz, J. Wood, S. Yang, & S. Carey, 2007). The authors used 3 experiments to explore the causal relation between these 2 capacities. Relative to English, Japanese and Mandarin had impoverished singular–plural marking. Using the manual search task, in Experiment 1 the authors found that by around 22 months of age, Japanese children also distinguished between singular and plural sets. Experiments 2 and 3 extended this finding to Mandarin-learning toddlers. Mandarin learners who were 20–24 months of age did not yet comprehend Mandarin singular–plural marking (i.e., yige vs. yixie, or –men), yet they did distinguish between singular and plural sets in manual search. These experiments suggest that knowledge of singular–plural morphology is not necessary for deploying the nonlinguistic distinction between singular and plural sets.

Early language development is characterized by predictable changes in the words children produce and the complexity of their utterances. In infants these changes could reflect increasing linguistic expertise or cognitive maturation and development. To disentangle these factors, we compared the acquisition of English in internationallyadopted preschoolers and internationally-adopted infants. Parental reports and speech samples were collected for one year. Both groups showed the qualitative shifts that characterize first-language acquisition. Initially, they produced single-word utterances consisting mostly of nouns and social words. The appearance of verbs, adjectives and multi-word utterances was predicted by vocabulary size in both groups. Preschoolers did learn some words at an earlier stage than infants, specifically words referring to the past or future and adjectives describing behavior and internal states. These findings suggest that cognitive development plays little role in the shift from referential terms to predicates but may constrain children’s ability to learn some abstract words.

Early language development is characterized by predictable changes in the words children produce and the complexity of their utterances. In infants these changes could reflect increasing linguistic expertise or cognitive maturation and development. To disentangle these factors, we compared the acquisition of English in internationally-adopted preschoolers and internationallyadopted infants. Parental reports and speech samples were collected for one year. Both groups showed the qualitative shifts that characterize first-language acquisition. Initially, they produced single-word utterances consisting mostly of nouns and social words. The appearance of verbs, adjectives and multiword utterances was predicted by vocabulary size in both groups. Preschoolers did learn some words at an earlier stage than infants, specifically words referring to the past or future and adjectives describing behavior and internal states. These findings suggest that cognitive development plays little role in the shift from referential terms to predicates but may constrain children’s ability to learn some abstract words.

These studies explore the effects of cognitive maturation on language development by examining the acquisition of English in internationally-adopted preschoolers. Parental reports (CDI) were collected from 48 preschoolers, within the first year after they were adopted from China or Eastern Europe. Children who were adopted at two or three years of age showed the same developmental patterns in language production as monolingual infants (matched for vocabulary size). Early on, their vocabularies were dominated by nouns and social words and the proportion of predicates and closed-class words increased with age. Thus shifts in lexical composition appear in older learners and are unlikely to reflect the development of new conceptual resources. Children who were adopted at four or five deviated from this pattern, acquiring fewer nouns and more predicates in the early stages of acquisition. Effects of the child’s birth language on the acquisition of English were limited to the older preschoolers, suggesting that they employ different strategies in word learning. In both groups, grammatical development and lexical development were synchronized in precisely the same way that they are in infancy, raising the possibility that word production and grammatical production are causally connected.

Early language development is characterized by predictable changes in the words children produce and the complexity of their utterances. In infants these changes could reflect increasing linguistic expertise or cognitive maturation and development. To disentangle these factors, we compared the acquisition of English in internationallyadopted preschoolers and internationally-adopted infants. Parental reports and speech samples were collected for one year. Both groups showed the qualitative shifts that characterize first-language acquisition. Initially, they produced single-word utterances consisting mostly of nouns and social words. The appearance of verbs, adjectives and multi-word utterances was predicted by vocabulary size in both groups. Preschoolers did learn some words at an earlier stage than infants, specifically words referring to the past or future and adjectives describing behavior and internal states. These findings suggest that cognitive development plays little role in the shift from referential terms to predicates but may constrain children’s ability to learn some abstract words.

There is ample evidence for a connection between linguistic abilities and performance in theory of mind tasks (ToM), however there is considerable dispute about precisely how these domains are linked. Disentangling the causal relations between domains in typically developing children is tricky because many skills are developing in synchrony. If ToM performance depends upon children’s current linguistic abilities, then the relation should be present even when language acquisition is delayed. We explored these issues in a group of late English learners, 45 internationally adopted children who came to the US at 2.5 years or older, and a control group of language matched preschoolers who were learning English as a first language. The children were tested on general English language abilities, sentence complement comprehension, English vocabulary and ToM. The two groups performed similarly on standard verbal ToM tasks, even though the adopted group was on average nearly 3 years older. However, the adopted children outperformed the controls in ToM tasks with reduced linguistic demands. General language skills predicted ToM ability in both groups and complement comprehension did not account for any additional variance. The data suggests that executive functioning along with general language skills may be the critical components in ToM success. 3