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.

Speech comprehension and production are governed by control processes. We explore their nature and dynamics in bilingual speakers with a focus on speech production. Prior research indicates that individuals increase cognitive control in order to achieve a desired goal. In the adaptive control hypothesis we propose a stronger hypothesis: Language control processes themselves adapt to the recurrent demands placed on them by the interactional context. Adapting a control process means changing a parameter or parameters about the way it works (its neural capacity or efficiency) or the way it works in concert, or in cascade, with other control processes (e.g., its connectedness). We distinguish eight control processes (goal maintenance, conflict monitoring, interference suppression, salient cue detection, selective response inhibition, task disengagement, task engagement, opportunistic planning). We consider the demands on these processes imposed by three interactional contexts (single language, dual language, and dense code-switching). We predict adaptive changes in the neural regions and circuits associated with specific control processes. A dual-language context, for example, is predicted to lead to the adaptation of a circuit mediating a cascade of control processes that circumvents a control dilemma. Effective test of the adaptive control hypothesis requires behavioural and neuroimaging work that assesses language control in a range of tasks within the same individual.

Code-switching (CS) is central to many bilingual communities and, though linguistic and sociolinguistic research has characterised different types of code-switches (alternations, insertions, dense CS), the cognitive control processes (CPs) that mediate them are not well understood. A key issue is how during CS speakers produce the right words in the right order. In speech, serial order emerges from a speech plan in which items are represented in parallel. We propose that entry into the mechanism for speech planning (a competitive queuing mechanism) is governed by CPs best suited to the particular types of code-switches. Language task schemas external to the language network govern access. In CS, they are coordinated cooperatively and operate in a coupled or in an open control mode. The former permits alternations and insertions whereas the latter is required for dense CS. We explore predictions of this CP model and its implications for CS research.

This paper proposes that different experimental contexts (single or dual language contexts) permit different neural loci at which words in the target language can be selected. However, in order to develop a fuller understanding of the neural circuit mediating language control we need to consider the community context in which bilingual speakers typically use their two languages (the behavioral ecology of bilingual speakers). The contrast between speakers from code-switching and non-code-switching communities offers a way to increase our understanding of the cortical, subcortical and, in particular, cerebellar structures involved in language control. It will also help us identify the non-verbal behavioral correlates associated with these control processes

We used a visual lexical decision task to explore control processes in proficient German–English bilinguals. Participants pressed a “yes” button if the letter string was a word in English and a “no” button if it was not. Our critical stimuli were interlingual homographs such as the low-frequency English word TAG. In German, TAG means “day” and is a relatively high frequency word. Overall, our participants responded more slowly to an interlingual homograph than to a control word matched to its English frequency. As we expected, the size of this interference effect depended on various factors. First, including “pure” German words in the stimulus list increased interference. However, participants were able to reduce the degree of interference over time even in the presence of such words. Second, in the absence of pure German words, informing participants about the presence of interlingual homographs from the start of the experimental trials allowed them to reduce interference. We examined the locus of these control effects by analysing carry-over, i.e., reaction times on word trials immediately following an interlingual homograph or its matched control. We inferred from the patterns of interference and carry-over that the primary locus for reducing interference is external to the bilingual lexico-semantic system. We consider the implications of these data for theories of control.