It has been claimed that children simultaneously acquiring two languages go through an initial stage when they are unable to differentiate between their two languages. Such claims have been based on the observation that at times virtually all bilingual children mix elements (e.g. lexical, morphological) from their two languages in the same utterance. That most, if not all, children acquiring two languages simultaneously mix linguistic elements in this way is widely documented. Although such code-mixing is not well understood or explained, there are a number of explanations unrelated to lack of language differentiation that may explain it. Moreover, while language differentiation is widely attested among bilingual children once functional categories emerge, usually during the third year, there is still some question as to how early in development differentiation is present. In this study, we examined language differentiation in five bilingual children prior to the emergence of functional categories (they ranged in age from 1;10 to 2;2 and in MLU from 1·23 to 2·08). They were observed with each parent separately and both together, on separate occasions. Our results indicate that while these children did code mix, they were clearly able to differentiate between their two languages. We also examine the possibility that the children's mixing is due to (a) their language dominance, and (b) their parents' rate of mixing. We could find no evidence that their mixing was due to parental input, but there was some evidence that language dominance played a role.

Recent research on pragmatic and syntactic development in bilingual 2-year-olds has shown that these children have differentiated language systems. However, it remains to be shown whether their grammars develop autonomously or interdependently from 2 years onward. The present study investigates the potential interference between the grammars of French-English bilingual children, aged 2–3 years. We examined their acquisition of functional categories, specifically the properties of INFL (finiteness and agreement) and negation, as these grammatical properties differ in both adult French and English and child French and English. Our results indicate that the bilingual children show no evidence of transfer, acceleration, or delay in acquisition, and support the hypothesis that their grammars are acquired autonomously. Some implications of these findings for the debate on continuity in the emergence of functional categories are discussed.

A number of studies have reported that there is a negative correlation between age of L2 acquisition and performance on a variety of measures of L2 ability, and that individuals who begin learning an L2 after approximately 15 years of age fail to attain native-like levels of competence. These results have been interpreted as support both for the hypothesis that there is a critical period for L2 acquisition and for the hypothesis that there is a maturational decline in access to Universal Grammar (UG). We argue that extant results are not an adequate test of the critical periods hypothesis because they are based on the performance of learners who have not necessarily achieved native-like proficiency in the L2. In this study, we develop criteria to establish whether an L2 speaker has achieved native-like proficiency. We compare the performance of three groups (near-native speakers of English, non-native speakers and controls) on two tasks designed to tap aspects of UG which have been claimed to be subject to critical period effects. We found no significant differences between our near-native group and native speakers on either of the tasks. We conclude that native-like competence in an L2 is achievable, even by older L2 learners.

The growing interest in Content and Language Integrated Learning (CLIL) has resulted in enthusiasm in and active pursuit of improved methods of foreign/ second-language (L2) teaching in Europe. However, the definition and scope of the term CLIL both internally, as used by CLIL advocates in Europe, and externally, as compared with immersion education in and outside Europe, indicate that the core characteristics of CLIL are understood in different ways with respect to: the balance between language and content instruction, the nature of the target languages involved, instructional goals, defining characteristics of student participants, and pedagogical approaches to integrating language and content instruction. We argue further that attempts to define CLIL by distinguishing it from immersion approaches to L2 education are often misguided. The aim of this article is to examine these ambiguities and to call for clarification of the definition of CLIL. Clarification is critical if CLIL is to evolve and improve systematically and if CLIL educators are to benefit from the experiences and knowledge acquired in other educational settings.

It is commonly thought that children learning two languages simultaneously during infancy go through a stage when they cannot differentiate their two languages. Virtually all studies of infant bilingual development have found that bilingual children mix elements from their two languages. These results have been interpreted as evidence for a unitary, undifferentiated language system (the unitary language system hypothesis). The empirical basis for these claims is re-examined and it is argued that, contrary to most extant interpretations, bilingual children develop differentiated language systems from the beginning and are able to use their developing languages in contextually sensitive ways. A call for more serious attention to the possible role of parental input in the form of mixed utterances is made.