In this paper, I present an exploratory study on cross-linguistic interference among Quechua-Spanish bilingual children living in a language contact situation. The study focuses on convergence in the tense, aspectual and evidentiality systems of the two languages. While in Quechua past tense features are strongly linked to evidentiality in the matrix of features associated with the functional category Tense, in Spanish, past tense features are linked to aspectual features. The study presents evidence that supports the Functional Convergence Hypothesis according to which syntactic convergence among bilingual speakers is favored when the matrix of features associated with a functional category is partially divergent, as is the case for Tense in Spanish and Quechua. The Spanish results indicate that among bilinguals past tense is associated with evidentiality features and contrast sharply with the results of the monolingual comparison group. Bilingual Quechua results exhibit an incipient emergence of discourse-oriented background and foreground distinctions, similar to those found in Spanish in association with aspectual morphology.

Liliana Sánchez' paper is a welcome contribution to the growing body of literature on Andean Spanish (cf. a recent survey in Muysken, 2004a), welcome both because a well-motivated and clearly described methodology is used and because it is embedded in an explicit theoretical framework. I do not have reservations about the overall conclusions of the study, but would like to draw attention to three issues: grammatical encoding versus pragmatic inference, the completeness of the analysis, and the issue of form learning versus meaning construction.

This essay by Truscott and Sharwood-Smith is a valiant attempt with a laudable goal. It seeks to show how different perspectives and disciplines can capture what is happening in acquisition and notably in L2 acquisition. Nonetheless, I think that the results are much closer to an elaborated grammatical theory than an elaborated processing theory (thus it seems less important to me than to the authors to choose one label over the other). Their essential, sensible idea is that where different grammars provide independent analyses of constructions, both are computed (even where the lexical items belong to only one grammar). Therefore conflict is experienced which produces computational demands. However this is pure grammar – just a more sophisticated situation where, as I like to argue, the L2 person has Multiple Grammars (Roeper, 1999), creating more computational work as well. In this respect, the situation is no different from L1 acquisition, where the course of acquisition involves generation and maintenance of multiple grammars, some of which are shed and some retained in the Final State.

The present article examines one property of bilingual speech – convergence – and strives towards explanatory depth by attending to the insights of the antecedent research in formal linguistics, psycholinguistics, and sociolinguistics. In particular, the paper adopts as a point of departure (and further substantiates) the argument that convergence will be evidenced in the syntax–pragmatic interface (Hulk and Müller, 2000) and the assertion that convergence is a ‘bilingual optimization strategy’ (Muysken, 2002), in advancing the claim that convergence (cum congruent lexicalization) in bilingual speech may be amplified or attenuated in tandem with the language mode (bilingual versus monolingual) of the bilingual (Grosjean, 1998). Specifically, it will be demonstrated through an analysis of two individual bilinguals' productions in both monolingual and bilingual modes that the convergence that is already manifested to some degree in these individuals' Spanish is enhanced in Spanish-English code-switching when their languages are simultaneously activated and deployed.

To begin with, we thank the commentators for their remarks, which both intrigued and challenged us in various ways. Time and space limits prevent us from doing justice to all the points they raised, so we will focus on those we consider most significant and are best prepared to deal with. One of these points, of course, is the overall character and status of our proposal. Pienemann terms Acquisition by Processing (APT) ‘an interesting point of departure’ (p. 38) for the development of a theory of acquisition and processing. Harrington and Carroll say in effect that it can't be done; others seem more open to the possibility. In any case, we quickly accept Roeper's suggestion that what we have presented is more a ‘prole-gomena’ (p. 21) to a theory than a full-fledged theory in itself.

We present a hypothesis for a specific kind of code-mixing in young bilingual children, during the development of their two first languages, one of which is considerably weaker than the other. Our hypothesis, which we label the Ivy Hypothesis, is that, in the interaction meant to be in the weaker language, the child uses portions of higher syntactic structure lexically instantiated in the stronger language combined with lower portions in the weaker language. Code-mixing patterns were studied in five Swedish-French/Italian children aged 2–4. The parts of the code-mixed utterances reflected as much syntactic structure of each language as was used in monolingual utterances in the same recording of each child. This uneven development, which is due to different amounts of input of the two languages, can be accounted for by assuming that syntactic structure is acquired by building each language from the bottom up through lexical learning.

In an important theoretical contribution to our understanding of language contact, Toribio elaborates on the familiar generalization, best known from the work of Silva-Corvalán, that contact varieties resemble monolingual lects of the same language in overall grammar, but differ with regard to (a) the selection of structures and (b) the semantic-pragmatic constraints on the use of structures. In Toribio's valuable elaboration of this basic idea, these peculiar patterns of selection and constraint in the contact variety are not the same in all contexts of use, but differ depending on whether the bilingual is in the single-language mode, or in the codeswitching mode where stretches of speech in the contact variety alternate, rapidly and relatively seamlessly, with stretches in the acrolect. The insight is that the same type of process that distinguishes the contact variety from its monolingual reference lects also distinguishes, within the contact variety, the codeswitching mode from its single-language reference mode.

This study examines the acquisition of the voicing contrast in German-Spanish bilingual children, on the basis of the acoustic measurement of Voice Onset Time (VOT). VOT in four bilingual children (aged 2;0–3;0) was measured and compared to VOT in three monolingual German children (aged 1;9–2;6), and to previous literature findings in Spanish. All measurements were based on word-initial stops extracted from naturalistic speech recordings. Results revealed that the bilingual children displayed three different patterns of VOT development: 1. Delay in the phonetic realization of voicing: two bilingual children did not acquire long lag stops in German during the testing period; 2. Transfer of voicing features: one child produced German voiced stops with lead voicing and Spanish voiceless stops with long lag voicing; and 3. No cross-language influence in the phonetic realization of voicing. The relevance of the findings for cross-linguistic interaction in bilingual phonetic/phonological development is discussed.

This issue of Bilingualism: Language and Cognition is about convergence, a type of language change that is contact-induced and results in greater similarity between two languages that are in contact with each other. In Backus (forthcoming), I have attempted an overview of contact-induced language change, focusing on causal factors, on mechanisms of change, and on the actual changes. In this conclusion, I will try to give convergence its rightful place in this general typology, referencing the contributions to this volume where appropriate.

This note points out an incorrect quotation of the theory of codeswitching outlined in various publications of Carol Myers-Scotton as cited by Boussofara-Omar (2003). In addition, the issue is raised whether the type of multi-lectal situation encountered in the varieties of Arabic spoken in Tunisia should be analyzed with a model designed to deal with ‘classic’ codeswitching.