In the last decade there has been a significant surge of interest in the psycholinguistics of bilingual memory which has resulted in a number of models of the relationship between words and concepts in the bilingual lexicon. Recently, authors such as Paradis (1997) and Grosjean (1998) have pointed out that many of these models do not distinguish between the semantic and the conceptual level, and that they suffer from confusion between processing and representation.

It has been suggested that the structural composition of mixed languages and the linguistic processes through which they emerge are to some extent predictable, and that they therefore constitute a language “type” (e.g. Bakker and Mous, 1994b; Bakker and Muysken, 1995). This view is challenged here. Instead, it is argued that the compartmentalisation of structures observed in mixed languages (i.e. the fact that certain structural categories are derived from one “parent” language, others from another) is the result of the cumulative effect of different contact mechanisms. These mechanisms are defined in terms of the cognitive and communicative motivations that lead speakers to model certain functions of language on an alternative linguistic system; each mechanism will typically affect particular functional categories. Four relevant processes are identified: lexical re-orientation, selective replication, convergence, and categorial fusion. Different combinations of processes will render different outcomes, hence the diversity of mixed languages as regards their structure, function, and development.

This special issue of Bilingualism: Language and Cognition is devoted to syntactic aspects of bilingual acquisition. For the purposes of this issue, bilingual acquisition is defined as the acquisition of two languages during the period of primary language development, extending from birth onward. Bilingual acquisition can entail the acquisition of more than two languages (see Cenoz and Jessner, 2000) as well as the acquisition of a spoken and signed language (e.g., Richmond-Welty and Siple, 1999) or of two spoken languages; only studies of the simultaneous acquisition of two spoken languages are reported in this volume. An ideal definition of bilingual acquisition would include not only reference to the age of first exposure to two languages, but also reference to the regularity and extent of exposure to each language. While such stipulations are not necessary in defining the context for monolingual acquisition since virtually all children receive sufficient language exposure to fully acquire one language, they are important considerations in cases of bilingual acquisition since some children have insufficient exposure to two languages, either in terms of amount or continuity, to attain full bilingual proficiency.

The present article reports on the findings of a case study of bilingual first language acquisition in Catalan and English. It first presents a general overview of a child's syntactic development from the age of 1;3 to 4;2 and then focuses on the question of subject realization in the two contrasting languages he is acquiring simultaneously. In this case, Catalan is a null subject language in opposition to the overt subject properties of English. Such data allow us to provide evidence on a key issue in bilingual acquisition research: the question of language separation in the early stages of acquisition. The data available suggest the absence of any major influence of one language on the other. In other words, our subject seems to be acquiring word order patterns which are different in the two adult systems in a language-dependent manner from the beginning of his production in both languages.

Research on early bilingual development has suggested that syntactic transfer in bilingual acquisition is dependent on patterns of dominance and properties of the dual input the child is exposed to. In a case study of a Hong Kong bilingual child we present evidence of transfer from Cantonese to English in three areas where the two languages contrast typologically: wh-in-situ interrogatives, null objects and prenominal relatives are observed at a period when Cantonese is dominant as measured by MLUw. Comparisons with monolingual development show both qualitative and quantitative differences attributable to transfer. Language dominance is seen as the major determinant of transfer, with input ambiguity playing a role in the domain of null objects. While two distinct and separate linguistic systems are simultaneously developing in the bilingual mind, the pervasiveness of transfer implies a high degree of interaction between them. The findings show that the bilingual subject in our case study has taken a different path from monolinguals toward the target.

The focus of this paper is on unusual developmental structures during the simultaneous acquisition of German and English in early childhood, which were evident parallel to a majority of target structures. The aim is to explain the cognitive motivation for unusual acquisition structures as well as the eventual retraction from them. I will show that they support the contentions of the Competition Model that language acquisition proceeds through orientation to surface structures and that cue competition across languages changes the weighting of cues within the language. The retreat from non-target structures was made possible through the children's attention to contrasts between the languages and the need to resolve structural incompatibilities within the language.

This paper has as its starting point the assumption that in acquiring two languages from birth, bilingual children separate their grammars from very early on. This does not, however, exclude cross-linguistic influence – the possible influence of one language on the other. The main focus of the paper is on the acquisition of syntax in a generative framework. We argue that cross-linguistic influence can occur if (1) an interface level between two modules of grammar is involved, and (2) the two languages overlap at the surface level. We show that both conditions hold for object drop, but not for root infinitives. Root infinitives satisfy the first condition: they involve the interface between syntax and pragmatics. However, they do not satisfy the second condition. Therefore, we expect cross-linguistic influence to occur only in the domain of object drop and not in the domain of root infinitives. Comparing the development of the two phenomena in a bilingual Dutch–French and a German–Italian child to the development in monolingual children, we show that this prediction is borne out by our data. Moreover, this confirms the hypothesis that cross-linguistic influence is due to language internal factors and not to language external factors such as language dominance: the periods during which we observe influence in the domain of object drop and non-influence in the domain of root infinitives are identical.

Does young bilingual children's code-mixing obey the same structural constraints as bilingual adults' code-mixing? The present study addresses this question using code-mixing data from 15 French–English bilingual children filmed in conversation with both parents at six-month intervals from the age of 2;0 to 3;6. The children's code-mixed utterances were examined for violations of the principles set out in the Matrix-Language Frame model (e.g. Myers-Scotton, 1993, 1997). The results show that the children obeyed all the constraints set out in the Matrix Language Frame model the majority of the time. With respect to the Morpheme Order Principle and to the interaction of Congruence and Matrix Language Blocking, they demonstrated consistent adherence with only marginal violations from the outset. In contrast, the children produced comparatively more frequent violations of the System Morpheme Principle and showed increasing adherence to this principle over time. We discuss possible explanations for the contrast between the children's performance on the System Morpheme Principle and the other constraints, which include the unequal emergence of INFL in the acquisition of French and English.

This study deals with the acquisition of Functional Categories in the French Determiner Phrase. The development of determiners and prenominal adjectives in three bilingual Swedish–French children is compared with that of four Swedish second language learners of French. It is argued that acquisition is crucially different in these two cases. The bilingual children initially have restrictions on phrase structure, resulting at one stage in a complementary distribution of determiners and adjectives. These results support a structure building view of L1 acquisition. For L2 acquisition of the same structure, there is no evidence for an initially reduced phrase structure. This finding is explained in terms of a transfer effect. A preliminary comparison with the acquisition of finiteness suggests that, whereas there is some correlation over time in the L1B subjects, no such correlation is found in the L2 learners.