Mathieu Declerck

A review of control processes and their locus in language switching

Language switching has been one of the main tasks to investigate language control, a process that restricts bilingual language processing to the target language. In the current review, we discuss the How (i.e., mechanisms) and Where (i.e., locus of these mechanisms) of language control in language switching. As regards the mechanisms of language control, we describe several empirical markers of language switching and their relation to inhibition, as a potentially important mechanism of language control. From this overview it becomes apparent that some, but not all, markers indicate the occurrence of inhibition during language switching and, thus, language control. In a second part, we turn to the potential locus of language control and the role of different processing stages (concept level, lemma level, phonology, orthography, and outside language processing). Previous studies provide evidence for the employment of several of these processing stages during language control so that either a complex control mechanism involving different processing stages and/or multiple loci of language control have to be assumed. Based on the discussed results, several established and new theoretical avenues are considered.

The Minimum Requirements of Language Control: Evidence from Sequential Predictability Effects in Language Switching.

The current study systematically examined the influence of sequential predictability of languages and concepts on language switching. To this end, 2 language switching paradigms were combined. To measure language switching with a random sequence of languages and/or concepts, we used a language switching paradigm that implements visual cues and stimuli. The other paradigm implements a fixed sequence of languages and/or concepts to measure predictable language switching. Four experiments that used these 2 paradigms showed that switch costs were smaller when both the language and concept were predictably known, whereas no overall switch cost reduction was found when just the language or concept was predictable. These results indicate that knowing both language and concept (i.e., response) can resolve language interference. However, interference resolution does not start solely based on the knowledge of which concept or language one has to produce. We discuss how existent models should be revised to accommodate these results.

Digits vs. pictures: The influence of stimulus type on language switching *

Stimuli used in cued language switching studies typically consist of digits or pictures. However, the comparability between both stimulus types remains unclear. In the present study, we directly compared digit and picture naming in a German–English language switching experiment. Because digits represent a semantic group and contain many cognates, the experiment consisted of four conditions with different stimulus sets in each condition: digits, standard language switching pictures, pictures depicting cognates, and semantically-related pictures. Digit naming caused smaller switch costs than picture naming. The data suggest that this difference can be attributed to phonology. Both methodological and theoretical implications are discussed.

Bilingual Control: Sequential Memory in Language Switching.

To investigate bilingual language control, prior language switching studies presented visual objects, which had to be named in different languages, typically indicated by a visual cue. The present study examined language switching of predictable responses by introducing a novel sequence-based language switching paradigm. In 4 experiments, sequential responses (i.e., weekdays, numbers or new sequences) and an alternating language sequence (e.g., L1-L1-L2-L2) were implemented, both of which were memory based. Our data revealed switch costs, showing that a language switch is associated with worse performance compared with a language repetition, and mixing costs, which constitutes the performance difference between pure and mixed language blocks, even while producing entirely predictable responses (i.e., language and concept). Additionally, we found these switch costs with overlearned and new sequences and found that switch costs were reduced with longer preparation time. The obtained data are consistent with a proactive interference account, such as the inhibitory control model.

Highly Proficient Bilinguals Implement Inhibition : Evidence From n-2 Language Repetition Costs

Several, but not all, models of language control assume that highly proficient bilinguals implement little to no inhibition during bilingual language production. In the current study, we tested this assumption with a less equivocal marker of inhibition (i.e., n-2 language repetition costs) than previous language switching studies have. N-2 language repetition costs denote worse performance when switching back to a recently abandoned language (i.e., worse performance in ABA language sequences than CBA sequences, where A, B, and C refer to different languages). Whereas this marker has solely been used to investigate second-language learners in prior studies, we examined highly proficient bilinguals. The results showed that substantial n-2 language repetition costs can be observed with highly proficient bilinguals. Moreover, this inhibition effect was substantial for all 3 languages, but larger for the 2 dominant languages (Turkish and German) relative to the less proficient language (English). These findings indicate that even highly proficient bilinguals implement inhibition to restrict language production to the target language.

A sentence to remember: Instructed language switching in sentence production

In the current study, we set out to investigate the influence of a sentence context on language switching. The task required German-English bilinguals to produce responses based on an alternating language sequence (L1-L1-L2-L2- …) and concepts in a specific sequential order. The concept sequence was either a sentence which was syntactically correct in both languages (language-unspecific sentence), a sentence which was correct in just one language (language-specific sentence) or a sentence which was syntactically incorrect in both languages (scrambled sentence). No switch costs were observed in language-unspecific sentences. Consequently, switch costs were smaller in those sentences than in the language-specific or scrambled sentences. The language-specific and scrambled sentence did not differ with respect to switch costs. These results demonstrate an important role of sentence context for language switch costs and were interpreted in terms of language interference and preparation processes.

The unusual suspect: Influence of phonological overlap on language control

The present study examined the influence of phonology on language switching. Unlike previous studies that investigated this influence by comparing words that are phonologically similar vs. dissimilar in two languages, the current language switching study focused on the role of phonological characteristics across words. Specifically, words with the first two phonemes being identical to those of the word in the previous trial were contrasted against words without such phonological overlap. The results revealed that the switch cost asymmetry was influenced by phonological overlap. Further investigation revealed that this influence was mainly due to persisting after-effects of phonological overlap, which caused a reversal of the asymmetrical switch cost pattern in the following trial. These results clearly indicate that manipulations on the level of phonology can have an effect on language switching. Therefore, we propose that, in contrast with the claims of most models, phonological characteristics of words play an important role in language control.

Dissociating language-switch costs from cue-switch costs in bilingual language switching

Cued language switching is used to examine language-control processes by comparing performance in language-switch trials with performance in repetition trials. In 1:1 cue-to-language mappings, language repetitions involve cue repetitions and language switches involve cue switches. Hence, the observed switch costs might reflect cue-switch costs rather than language-related control processes. By introducing a 2:1 cue-to-language mapping, we dissociated language switches (cue and language switched vs. cue switched, but language repeated) and cue switches (repeated language, with vs. without switched cue). We found cue-switch costs, but language-related switch costs were substantial, too, presumably reflecting language-control processes in cued language switching.

Is there lemma-based language control? The influence of language practice and language-specific item practice on asymmetrical switch costs

ABSTRACT Several models have proposed that language control occurs between language representations, such as language tags, and between lemmas. Yet, most research has solely focused on language-control processes between language representations. In the present study, we investigated whether language control can also occur between lemmas by allowing bilinguals to practice a language or language-specific items prior to a language-switching task, and thus change the relative activation of the language representations and/or lemmas. By changing the activation levels, relatively more language control should occur for this language representation and/or lemma relative to their translation-equivalent due to the reactive nature of language control. The results showed that this was all the more so when language-specific items were practiced than when merely a language was practiced. Hence, the current study provides evidence that language control is not restricted to language representations, but could also occur between lemmas.

Age-related differences in task switching and task preparation: Exploring the role of task-set competition

The present study focused on the role of task preparation in age-related task-switching deficits. In Experiment 1, we assessed the preparatory reduction of alternation costs (i.e., alternating-task conditions vs. single-task conditions) in twenty-two older adults (65-78years) and 22 young adults (20-28years) by varying the response-stimulus interval (RSI) in a task-switching paradigm with a predictable task sequence and univalent stimuli. In Experiment 2, in which new groups of 22 older adults (65-78years) and 22 young adults (18-24years) took part, we replicated Experiment 1 with bivalent stimuli, which were associated with both tasks and thus increased task-set competition. Whereas in Experiment 1, in which we used univalent stimuli, there were no age-related differences in the preparatory reduction of alternation costs, the data showed impaired task preparation in old age with bivalent stimuli in Experiment 2. These data support the notion that task-preparation deficits in old age occur particularly in situations of increased task-set competition.