Language selection in bilingual speech: Evidence for inhibitory processes
Introduction
When bilinguals perform even the simplest production task, such as speaking the name of a familiar object in one of their two languages, there is evidence that both languages are active and influence performance (e.g., Colomé, 2001, Costa et al., 1999, Hermans et al., 1998, Kroll et al., 2006). Although there is abundant evidence for parallel activity of the bilingual’s two languages in comprehension tasks (e.g., Spivey and Marian, 1999, Van Heuven et al., 1998), finding that the unintended language is available during spoken production remains surprising. Unlike the bottom–up processing that characterizes word recognition (e.g., Dijkstra & Van Heuven, 2002), speaking is initiated by a conceptually-driven process that takes a thought and maps it on to available lexical information. In theory, the conceptual nature of spoken production should allow the language to be selected early in speech planning as one aspect of the thought to be expressed. Although some instances of early language selection may be possible, for example, when bilinguals who have a stronger first (L1) than second (L2) language speak in their L1 (e.g., Bloem and La Heij, 2003, La Heij, 2005), most recent studies of bilingual word production have shown that the intention to speak one language only does not suffice to limit activation to alternatives in that language alone.
A striking aspect of bilingual speech is that proficient bilinguals do not make random errors of language. At the same time, they are able to code switch with ease with others who are similarly bilingual (e.g., Muysken, 2000, Myers–Scotton, 2002). Although one might argue that fluency at the level of sentence or discourse production is supported by a range of mechanisms that might be unavailable in decontextualized word production, the fact remains that bilingual spoken production is better than what might be expected if we assume that both languages are available in parallel and potentially compete for selection. That observation has led some to propose that bilinguals possess an exquisite mechanism of cognitive control that develops as they gain skill in the L2 (e.g., Green, 1998) and that has consequences more generally for executive control processes (e.g., Bialystok, Craik, Klein, & Viswanathan, 2004) and for their neural representation (e.g., Abutalebi & Green, 2007).
Understanding the way in which spoken word production is accomplished in bilinguals when two or more alternatives are available requires that the nature of cross-language activity be characterized and that a mechanism of selection be specified. A number of previous studies have considered the first of these questions in detail (see Costa, 2005, and Kroll et al., 2006, for recent reviews). The available evidence provides support for a number of different loci of cross-language activation during the planning of a single word utterance. Fig. 1 is a representative model of bilingual word production adapted from previous work by Hermans, 2000, Poulisse and Bongaerts, 1994. The general assumption in models of lexical production (e.g., De Bot and Schreuder, 1993, Levelt, 1989) is that at least three component processes must be engaged prior to articulation. A concept and its closest lexical representation must be selected and the phonology that corresponds to that lexical representation must be specified. For bilinguals, because there are multiple alternatives in each language, there can be activation of abstract candidates at the lemma level or among phonological competitors.1 Note that the model illustrated in Fig. 1 assumes that a language cue represents the intention to name the object in one of the two languages. As we will discuss later, the representation of the intention to speak one language alone may be influenced by the relative dominance of the two languages for the bilingual, by the context in which spoken production occurs, and by features of the two languages themselves.
Kroll et al. (2006) argued that cross-language alternatives may be active at any of the loci shown in the model. The degree to which there is sustained activity of the nontarget language will depend on a variety of factors, including the language of production, proficiency in the L2, the task that initiates speech planning, and the degree to which specific lexical alternatives are primed. As noted above, when production occurs in L1, there may be little evidence of L2 influence because L1 is more skilled than L2 and the rapid time course of speech planning in L1 may not provide an opportunity for L2 to come into play (e.g., Bloem and La Heij, 2003, Kroll et al., in preparation).
In contrast, when bilinguals speak in the L2, particularly when they are more dominant in L1, there may be multiple influences of L1 on L2 (e.g., Costa et al., 2000, Costa et al., 2006, Hermans et al., 1998, Hoshino and Kroll, 2008). Notably, these cross-language interactions in production appear to function between lexical and sub-lexical levels (Costa, La Heij, & Navarrete, 2006), to extend to feed-back as well as feed-forward interactions (Kroll et al., in preparation), and to late specification of the phonetic properties of realized speech (e.g., Engstler and Goldrick, 2007, Gerfen et al., 2005).
Although there is not complete agreement about the extent to which each result in the past studies uniquely demonstrates the presence and the locus of cross-language activation in the planning of words in each of the bilingual’s two languages (see Costa et al., 2006), taken together, the evidence is quite compelling. If alternatives are active in the two languages, how is the correct word selected? Two types of selection mechanisms have been contrasted. According to a language-specific selection model (e.g., Costa et al., 1999), information about words in the unintended language may be activated but those words are not candidates themselves for selection. Note that the presence of cross-language activation itself rules out an extreme language-specific model in which one of the two languages is effectively switched off or inhibited in advance to enable the bilingual to function as a monolingual speaker (and see Wang, Xue, Chen, Xue, & Dong, 2007, for recent neuroimaging evidence suggesting that there is no brain area uniquely associated with a language switch). The proposed language-specific model is functionally a “mental firewall” such that the language cue effectively signals the activated alternatives that are on the right side of the wall. A threshold version of the language-specific model assumes that the language cue acts to set the activation level higher for candidates in the target language, thereby avoiding potential competition between them at the point when selection occurs. Finkbeiner, Gollan, and Caramazza (2006) proposed the threshold model to be a mechanism to avoid what they consider to be the “hard” problem of lexical competition. In contrast, the non-specific language model assumes that words in both languages are potential candidates for selection. The non-specific language model allows competition for selection such that candidates within and across languages actively compete with alternatives in the unintended language which are eventually inhibited to allow accurate production to proceed (e.g., Green, 1998). Costa and Santesteban (2004) recently proposed a reconciliation of these alternatives by arguing that more proficient bilinguals have acquired the skills to avoid the “hard” problem, whereas L2 learners and less proficient bilinguals may be more likely to face cross-language competition that requires subsequent inhibition. On this view, the models are both correct but describe different states of bilingualism.
In the remainder of this paper we consider the selection models in more detail, reviewing existing findings as well as new evidence that we believe provides a more compelling case for the need for an inhibitory mechanism for even proficient bilinguals. In the course of our review, we consider the role that the production tasks used may have contributed to this debate and the evidence that bilinguals can exploit language-specific cues when they are present. Most critically, we consider the emerging literature that examines the neural basis of language selection using event related potentials (ERPs) and functional magnetic resonance imaging (fMRI) to examine the time course and localization of bilingual speech planning processes.
Section snippets
Testing accounts of language selection using behavioral evidence
Three approaches have been adopted to test the language-specific vs. non-specific models of spoken word production. The first approach is to use a variant of the Stroop task (Stroop, 1935) in which pictures are named (e.g., Hermans et al., 1998) or words are translated (e.g., LaHeij et al., 1990). During speech planning, a distractor word, related to the name of the picture or word to be translated, is presented visually or auditorily. The general prediction is that at the point in planning
ERP and fMRI studies of bilingual word production
In the search for a locus of selection effects in bilingual word processing, we and others have turned to methods that can better elucidate the time course and locus of cognitive processes involved in selecting and producing words in both the languages. The different accounts of language selection that we have already discussed would seem to make contrasting hypotheses about the time at which these effects should reveal themselves. Accounts which claim that language cues, operating at a
Conclusions: interpreting the evidence on language selection
The behavioral and neuroimaging studies we have reviewed suggest that the problem of language selection is indeed a hard problem, contrary to the suggestion that it may be possible to bypass processes that negotiate competition and potential inhibition across the bilingual’s two languages (Finkbeiner et al., 2006). The available evidence is not conclusive, as this is a relatively young area of investigation and like other research on bilingualism, there are a host of factors whose influence is
Acknowledgements
The writing of this article was supported in part by NSF Grant BCS-0418071 and NIH Grant F33HD055003 to Judith F. Kroll, by NIH Grant R56-HD053146 to Judith F. Kroll, Maya Misra, Taomei Guo, and Chip Gerfen, and by the Open Project Grant at State Key Laboratory for Cognitive Neuroscience and Learning, Beijing Normal University to Judith F. Kroll, Maya Misra, and Taomei Guo, and by the National Natural Science Foundation of China (30600179) to Taomei Guo.
References (88)
- et al.
Bilingual language production: The neurocognition of language representation and control
Journal of Neurolinguistics
(2007) - et al.
Accessing word meaning in two languages: An event-related brain potential study of beginning bilinguals
Brain and Language
(2003) - et al.
Semantic facilitation and semantic interference in word translation: Implications for models of lexical access in language production
Journal of Memory and Language
(2003) - et al.
Memory and language skill in simultaneous interpreting: The role of expertise and language proficiency
Journal of Memory and Language
(2006) - et al.
Bilingual language control: An event-related brain potential study
Brain Research
(2007) Lexical activation in bilinguals’ speech production: Language-specific or language-independent?
Journal of Memory and Language
(2001)- et al.
Bilingualism aids conflict resolution: Evidence from the ANT task
Cognition
(2008) - et al.
Lexical selection in bilinguals: Do words in the bilingual’s two lexicons compete for selection?
Journal of Memory and Language
(1999) - et al.
Lexical access in bilingual speech production: Evidence from language switching in highly proficient bilinguals and L2 learners
Journal of Memory and Language
(2004) - et al.
Effects of orthography on speech production in a form-preparation paradigm
Journal of Memory and Language
(2003)
More use almost always means a smaller frequency effect: Aging, bilingualism, and the weaker links hypothesis
Journal of Memory and Language
Cognate effects in picture naming: Does cross-language activation survive a change of script?
Cognition
Does bilingualism hamper lexical access in speech production?
Acta Psychologica
The role of proficiency on processing categorical and associative information in the L2 as revealed by reaction times and event-related brain potentials
Journal of Neurolinguistics
Bilingual language switching in naming: Asymmetrical costs of language selection
Journal of Memory and Language
Switching languages, switching palabras (words): An electrophysiological study of code switching
Brain and Language
Electrophysiological estimates of semantic and syntactic information access during tacit picture naming and listening to words
Neuroscience Research
Bilingual lexical activation in sentence context
Journal of Memory and Language
Orthographic neighborhood effects in bilingual word recognition
Journal of Memory and Language
Neural bases of asymmetric language switching in second-language learners: An ER-fMRI study
NeuroImage
Neighborhood effects in auditory word recognition: Phonological competition and orthographic facilitation
Journal of Memory and Language
Shifting intentional set: Exploring the dynamic control of tasks
Remembering can cause forgetting: Retrieval dynamics in long-term memory
Journal of Experimental Psychology: Learning, Memory and Cognition
Bilingualism, aging, and cognitive control: Evidence from the Simon task
Psychology and Aging
Lexical access in bilingual production
The cognate facilitation effect: Implications for the model of lexical access
Journal of Experimental Psychology: Learning, Memory, and Cognition
The dynamics of bilingual lexical access
Bilingualism: Language and Cognition
The lexical bias effect in bilingual speech production: Evidence for feedback between lexical and sublexical levels across languages
Psychonomic Bulletin & Review
How do highly proficient bilinguals control their lexicalization process? Inhibitory and language-specific selection mechanisms are both functional
Journal of Experimental Psychology: Learning, Memory, and Cognition
Word production and the bilingual lexicon
Language context effects on interlingual homograph recognition: Evidence from event-related potentials and response times in semantic priming
Bilingualism: Language and Cognition
Determinants of word translation
Journal of Experimental Psychology: Learning, Memory, and Cognition
Bilingual word recognition and lexical access
The architecture of the bilingual word recognition system: From identification to decision
Bilingualism: Language and Cognition
Visual word recognitions by bilinguals in a sentence context: Evidence for nonselective access
Journal of Experimental Psychology: Learning, Memory, and Cognition
Bimodal bilingualism: Code-blending between spoken English and American sign language
Lexical selection in bilingual speech production does not involve language suppression
Journal of Experimental Psychology: Learning, Memory, and Cognition
Bilingual lexical access: What’s the (hard) problem?
Bilingualism: Language and Cognition
Bilingual semantic and conceptual representation
Repetition priming in picture naming and translation depends on shared processes and their difficulty
Journal of Experimental Psychology: Learning, Memory, and Cognition
What is a TOT? Cognate and translation effects on tip-of-the-tongue states in Spanish–English and Tagalog–English bilinguals
Journal of Experimental Psychology: Learning, Memory, and Cognition
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