Much research on bilingual first language acquisition has stressed the role of the dominant or preferred language when the two languages have some influence on one another. The present paper tries to look at transfer or interference from the perspective of the input the child is exposed to. Transfer will be argued to occur in those domains of the grammar where the language learner is confronted with ambiguous input. The bilingual child may, as a relief strategy, use parts of the analysis of one language in order to cope with ambiguous properties of the other. Ambiguity of input is crucial and will be evaluated through a comparison with monolingual language acquisition: if monolingual children have problems with the language material in question, it may be suggested that the input contains evidence for more than only one grammatical analysis. A quantitative difference between monolingual and bilingual language acquisition will be interpreted as evidence in favor of cross-linguistic influence in bilingual language development. The paper reviews longitudinal studies on the acquisition of word order in German subordinate clauses.

This paper aims to foster discussion of the means by which bilinguals control their two language systems. It proposes an inhibitory control (IC) model that embodies the principle that there are multiple levels of control. In the model a language task schema (modulated by a higher level of control) “reactively” inhibits potential competitors for production at the lemma level by virtue of their language tags. The IC model is used to expand the explanation of the effect of category blocking in translation proposed by Kroll and Stewart (1994), and predictions of the model are tested against other data. Its relationship to other proposals and models is considered and future directions proposed.

This paper has two major objectives: (1) to summarise Processability Theory, a processing-oriented approach to explaining language development and (2) to utilise this theory in the comparison of development in LI and L2 acquisition. Proponents of the Fundamental Difference Hypothesis (between L1 and L2) assume that L1 development can be explained with reference to Universal Grammar (UG) which, in their view, is inaccessible to L2 learners. Instead, they claim that a second language develops on the basis of language processing strategies.

I will show that the fundamentally different developmental paths inherent in first and second language acquisition can both be explained on the basis of the same language processing mechanics (as specified in Processability Theory). I will demonstrate that the developmental differences between L1 and L2 are caused by the qualitatively different early structural hypotheses which propagate through the acquisition process. The concept of “propagation of structural features” will be viewed as “generative entrenchment,” a logical-mathematical concept, which has proved to be highly productive in examining other kinds of developmental processes.

David Green's excellent paper “Mental control of the bilingual lexico-semantic system” raises three fundamental questions. My goal is to suggest elaborations on his answers that might make the arguments stronger and more comprehensive.

The tension between considering language acquisition to be a process of learning or a process of development is the visible surface of a theoretical iceberg. The difference between learning and development is neither simple nor self-evident, yet the implications that follow from a commitment to one or the other are considerable. Development is usually construed as an unfolding, the impassive evolution of “being.” Children develop physically, cognitively, emotionally almost in spite of themselves; they may not develop to their full potential, and they may require massive environmental support, but even in cases of benign neglect, children will normally become taller, smarter, and more stable. Learning implies a measure of control and responsibility. It depends on experience and on the availability of resources: conceptual, social, intellectual, and so on.

Natascha Müller's article concerns the acquisition of word order in German subclauses by young bilingual children. Müller's basic argument as I understand it runs as follows:

(1) In the acquisition of word order in German subclauses some children make errors and others do not;

(2) there are some monolingual and some bilingual children who do not make errors;

(3) there are some monolingual and some bilingual children who do make errors, and the errors are qualitatively similar for monolingual and bilingual children;

(4) when children do make errors, they occur more frequently in bilingual than in monolingual children;

(5) the errors in both monolingual and bilingual children are due to the misprojection of a separate functional category;

(6) in addition, the errors in bilingual children (but not in monolingual children) are due to influence from the other language they are simultaneously acquiring. The reason for positing this is that bilingual children's errors are more frequent than monolingual children's errors.

The schema concept has had a long and varied history in psychology. It was introduced by Bartlett (1932), who observed that subjects' reproductions of a story showed systematic deviations from the original. Elements in the original story that were uncommon or strange were lost or changed and elaborated such that they became more common and made more sense to the subjects, and infrequent words and concepts were replaced by more common ones. Bartlett explained this normalization behavior by assuming that humans adapt incoming information to existing knowledge structures in long-term memory and that they understand new information in terms of these structures. These knowledge structures were called schemas. Schemas may represent our knowledge of stereotypical events such as doing the laundry or cooking a meal (these schema structures are usually called scripts, Schank & Abelson, 1977), of objects and natural categories (see Anderson, 1985, for a discussion), and the knowledge underlying routine behavior (Norman, 1981). They provide a basis for explaining many different phenomena of information processing and memory functioning, such as inferencing, elaborating, stereotyping, reconstruction, false memorization, and the occurrence of slips in task performance. When, for instance, a reader encounters the word forest in a text, he is not surprised to see the noun phrase the trees, with the definite article, in the next sentence even though no trees were explicitly introduced before.

Natascha Müller's proposal to view transfer as a relief strategy used by bilingual learners to cope with problematic input is very interesting and has far-reaching consequences for theories of bilingual language acquisition. The author makes a strong case for the fact that bilingual children transfer parameter values from the language presenting unambiguous input to the other “puzzling language”. In what follows, I will not question the main thrust of her argument. Rather I will return to the definitions that have been proposed for transfer in the literature and show that they are usually too broad. I will then propose that anyone interested in studying transfer must take into account the language mode the language learner or bilingual subject is in when being studied, and I will end by showing the consequences that this may have if it is not done. Natascha Müller's main argument is not affected by the language mode factor but the quantitative difference she finds between monolingual and bilingual children could be.

Responding to an invitation to comment on Pienemann's paper leaves me on the horns of a dilemma: I think the approach is novel and shows how future second language acquisition (SLA) research can be done. However, it is difficult to judge from the paper what the exact contribution of the theory is to be.

The paper by Natascha Müller follows the new way of studying bilingual first language acquisition which has been advocated in the last few years by several researchers (Döpke, 1996, 1997; Gawlitzek-Maiwald & Tracy, 1996; Hulk & Van der Linden, 1996; Hulk, 1997). In this new approach, while it is taken as an established fact that bilingual children are capable of early language differentiation, at the same time a lot of attention is given to cross-linguistic influence as an important characteristic of bilingual first language acquisition. We will discuss the nature of differentiation and transfer here as presented by Müller's paper and the way we see it ourselves. We will illustrate our position with examples from the French-Dutch bilingual child we have been studying for some time.

A problem when reacting to a contribution as rich and as highly interesting as Pienemann's paper, is that it is much easier to react to what's not in it than to what is. An example is the relation between the theory proposed and the way linguistic knowledge is acquired: “[Processability theory] … is not designed to contribute anything to the question of the innate or learnt origin of linguistic knowledge or the inferential processes by which linguistic input is converted into linguistic knowledge.” It is not easy to interpret the full consequences of the model if we are not to take into account the inferential processes by which the learner adds new information to his/her system. Maybe here the dividing lines are drawn too strictly: if the hypothesis space of the learner is restricted by the procedures that can be applied, one wonders at what level in the cognitive system these restrictions are located. Does the conceptualizer already know what the system is capable of doing, or is it uninformed (as follows from a strict interpretation of Levelt's proposal of an incremental system without feedforward)? In the latter case, this would mean that the learners/speakers would still try to express their communicative intentions and only later on in the process would things go wrong, for example, because the S-procedure cannot be carried out.

The recent trend in psycholinguistics from autonomous, rule-oriented models with symbolic representations towards more interactive, regularity oriented, and subsymbolic models reflects an increasing awareness that the finer aspects of cognitive processing may be sensitive to “contextual factors.” Apparently, there is systematic variability in the data that depends on task demands and stimulus list composition, and their effect on the strategies and decision criteria maintained by the experimental subject. However, most current (computational) models at best embody a task-independent stimulus identification process with a simple decision process operating in the same rigid manner across different tasks (Dijkstra & de Smedt, 1996).

Green makes the critical observation that models of lexical and semantic representation in bilingual memory fail to specify a mechanism that would enable the bilingual speaker to act. Under the conditions typical of most experimental research, bilinguals are asked to perform a well-defined task, such as word or picture naming, lexical decision, or translation. The question Green raises is how is it that the bilingual effectively performs one of these tasks rather than another? And within a given task such as word translation, how does the individual manage to produce words in one language and suppress the other? The goal of Green's proposal is to provide a preliminary account of the control apparatus that a bilingual would need to possess in order to perform effectively in this environment. An adequate model of these control mechanisms will presumably allow us to understand not only how bilinguals perform simple laboratory tasks, but also how they manage to engage the appropriate language during normal discourse, including code-switching with other bilingual speakers.

Let me begin my comments on Pienemann's keynote paper by expressing my admiration for the scholar who has developed Processability Theory (PT) over a period of some fifteen years with great determination and perseverance. What in earlier publications (e.g. Pienemann, 1985, 1987) appeared to me to be a rather disparate set of principles aiming to account for a limited set of empirical data (the well known sequence of five word orders of the ZISA study), has now evolved into a coherent theory which meets the demands of falsifiability, as PT's claims are formulated in sufficient detail to allow SLA researchers to put them to empirical test. PT comprises a number of principles of great generality, accounting, in principle, for the acquisition of any structure in any language, thereby exceeding the limits of the ZISA data of natural German L2 acquisition. As such, it is to be hoped that PT will have a healthy influence on the field of SLA research, as this field, in the last few years, has perhaps been dominated too much by the issue of whether L2 learners have access to Universal Grammar.

The field of bilingual first language acquisition has focused on several important and interrelated issues: whether or not the young child acquiring two languages simultaneously differentiates his or her two languages from the onset of acquisition, what role the input plays in the acquisition of two languages, and whether the path of acquisition is similar to that of monolingual peers (see De Houwer, 1990). As a member of the DUFDE team, Natascha Müller has in previous work argued forcefully and convincingly for the bilingual child's separate development of his or her two languages, and hence how language-acquiring bilinguals behave like monolinguals. In her keynote article, Müller invokes the notion of transfer, a well-known term from research into second language acquisition, and proposes to consider transfer from the perspective of the input to which the young bilingual child is exposed. When this input is ambiguous, so that is there is variation in the input regarding one of the languages, the child will resort to transfer from the other language as a so-called relief strategy. In the following, I address the issue of cross-linguistic influence in language development and highlight the implications Müller's proposals may have for the field of bilingual first language acquisition. In conclusion I will relate these issues to the complexity of the notion of input in early bilingualism.

In this paper Green proposes an inhibitory control (IC) model of bilingual lexical processing. At the core of Green's arguments is the notion of “mental control,” formulated in terms of inhibition, control schemas, and a supervisory attentional system. The very notion of control, it seems, suggests some sort of intentional, exogenous force at work (e.g., the supervisory attentional system). Presumably mental control differs from automatic processes (Schneider & Shiffrin, 1977), yet in the IC model there is no precise computational specification of how the various parameters of the control system actually interact to determine automatic bilingual processes. In a computational view, the IC model has quite some symbolic AI flavor (e.g., with goal-oriented decision boxes and control schemas), but it also attempts to integrate activation-based accounts (e.g., interactive activation mechanisms). Again, because the model remains at a rather conceptual level as presented, it is difficult to determine how successful it will be in combining symbolic and connectionist approaches in understanding bilingual processing.

When you compare the behavior of two different age groups which are trying to master the same sensori-motor or cognitive skill, you are likely to discover varying learning routes: different stages, different intervals between stages, or even different orderings of stages. Such heterogeneous learning trajectories may be caused by at least six different types of factors:

(1) Initial state: the kinds and levels of skills the learners have available at the onset of the learning episode.

(2) Learning mechanisms: rule-based, inductive, connectionist, parameter setting, and so on.

(3) Input and feedback characteristics: learning stimuli, information about success and failure.

(4) Information processing mechanisms: capacity limitations, attentional biases, response preferences.

(5) Energetic variables: motivation, emotional reactions.

(6) Final state: the fine-structure of kinds and levels of subskills at the end of the learning episode.

This applies to language acquisition as well. First and second language learners probably differ on all six factors. Nevertheless, the debate between advocates and opponents of the Fundamental Difference Hypothesis concerning L1 and L2 acquisition have looked almost exclusively at the first two factors. Those who believe that L1 learners have access to Universal Grammar whereas L2 learners rely on language processing strategies, postulate different learning mechanisms (UG parameter setting in L1, more general inductive strategies in L2 learning). Pienemann opposes this view and, based on his Processability Theory, argues that L1 and L2 learners start out from different initial states: they come to the grammar learning task with different structural hypotheses (SOV versus SVO as basic word order of German).

Natascha Müller discusses a question which in recent years – after a period of focus on cross-linguistic principles of language acquisition – has regained its position as a current topic, namely transfer, and here in bilingual children. One of her points is that for transfer to take place, the transferred construction must have some correspondence in the target language, a position similar to the “transfer to somewhere” principle often advocated in the L2 acquisition literature (cf. Gass & Selinker, 1983). The specific structure studied is the lack of Verb-End in the German of a bilingual German-French child.

Compared with the wealth of investigations on monolingual language acquisition, research on early bilingualism still has some catching up to do. Papers such as the one by Natascha Müller show us what may be gained if results from both areas are integrated within one theoretical framework, in this case current generative theory.

The planning of speech involves making successive choices in a hierarchy of options. In the case of bilingualism, these options are provided by two lexicons and grammars rather than one internalized by a speaker. Conceptualization processes map a communicative intention onto a message indicating the conceptual information to be verbalized to reach a speaker's communicative goal. In bilinguals, the illocutionary intention may be to express oneself in one language rather than the other, or to mix languages. Formulation processes activate and select lemmas and forms for the message concepts, and plan a syntactic and a morphophonological structure. Lemmas specify the syntactic properties of words, crucial for their use in sentences. The result of formulation is an articulatory program, which, when executed by articulation processes, yields overt speech. A central theoretical problem is how bilingual speakers manage to keep the options provided by the two languages apart in monolingual conversation, and how speakers are able to integrate the options in bilingual conversation where language mixing (i.e., code-switching or borrowing) may take place.