Simultaneous bilingual children sometimes display crosslinguistic influence (CLI), widely attested in the domain of morphosyntax. It remains less clear whether CLI affects bilinguals’ event construal, what motivates its occurrence and directionality, and how developmentally persistent it is. The present study tested predictions generated by the structural overlap hypothesis and the co-activation account in the motion event domain. 96 English–French bilingual children of two age groups and 96 age-matched monolingual English and French controls were asked to describe animated videos displaying voluntary motion events. Semantic encoding in main verbs showed bidirectional CLI. Unidirectional CLI affected French path encoding in the verbal periphery and was predicted by the presence of boundary-crossing, despite the absence of structural overlap. Furthermore, CLI increased developmentally in the French data. It is argued that these findings reflect highly dynamic co-activation patterns sensitive to the requirements of the task and to language-specific challenges in the online production process.

Previous research in child language shows that many aspects of language acquisition are frequency-linked. This study tests whether input or usage frequency predicts the order of acquisition and accuracy of a bilingual Greek–English child's English possessives. The child was followed longitudinally from age 2;6 to 3;11. Order of acquisition was comparable to that of same-aged monolingual children. The child's usage frequency and order of acquisition were highly correlated with input frequency, while her accuracy was not. We argue that the child's already-acquired Greek possessives facilitated acquisition of English possessives, even though the child's English input and usage frequencies were lower than in monolingual English children.

This paper presents the results of two sentence production studies addressing the role of language exposure, prior linguistic modelling and discourse-pragmatic appropriateness on the phenomenon of cross-linguistic influence (CLI) in bilingual 5-year-olds. We investigated whether French–English bilingual children would be as likely as monolingual children to use a left-dislocation structure in the description of a target scene. We also examined whether input quantity played a role in the degree of accessibility of these syntactic constructions across languages. While the results indicate a significant effect of elicitation condition only in French, the relative amount of language exposure in each language predicted the likelihood of producing a left-dislocation in both French and English. These findings make a new contribution to the role of language exposure as a predictor of CLI. The data also support the recent proposal that CLI arises out of processing mechanisms.

Recent findings suggest some properties of input in dual-language environments that influence its value for bilingual development, but the extant data base is small and sometimes inconclusive. The present study sought additional evidence regarding three quality indicators: the percent of input provided by native speakers, the number of different speakers providing input, and the frequency of language mixing. Participants were 90 thirty-month-olds exposed to Spanish and English. Using the Language Diary method to assess input and using multiple measures of children's bilingual skills, results replicated previous findings that the percent of input provided by native speakers is a positive quality indicator and found suggestive evidence that the number of speakers is also a positive quality indicator. There was little evidence that the frequency of language mixing is a negative indicator. These findings advance understanding of sources of variability in bilingual outcomes and have implications for programs to support bilingual development.

Children acquiring their first languages are frequently regarded as the principal agents of diachronic change. The causes and the precise nature of the processes of change are, however, far from clear. The following discussion focuses on possible changes of core properties of grammars which, in terms of the theory of Universal Grammar, can be characterized as reflecting different settings of parameters. In such cases, learners develop grammatical competences differing from those of speakers of the previous generation who provided the primary data serving as input for the developmental processes. It has been argued that reanalyses of this type must be conceived of as instances of transmission failure. Yet acquisition research has demonstrated that the human Language Making Capacity is extraordinarily robust, thus leading to the question of what might cause unsuccessful acquisition. Changing frequencies in use or exposure to data containing ambiguous or even contradictory evidence are unlikely to suffice as causes for this to happen. Language acquisition in multilingual settings may be a more plausible source of grammatical reanalysis than monolingual first language development. The study of contemporary bilingualism can therefore contribute to an explanation of diachronic change. Yet one such insight is that simultaneous acquisition of two languages (2L1) typically leads to a kind of grammatical knowledge in each language which is qualitatively not different from that of the respective monolinguals, obliging us to look for other sources of transmission failure. 2L1 acquisition in settings where one language is “weaker” than the other has been claimed to qualify as such. But I will argue that even such problematic cases do not provide convincing evidence of reanalysis. If, on the other hand, children receive sustained input from second language learners, or if their onset of acquisition is delayed, this can indeed lead to incomplete acquisition. I conclude that successive acquisition of bilingualism plays a crucial role as a source of grammatical change. In order for such changes to happen, however, grammar-internal and language-external factors may have to concur.