Language production in bilinguals

Just as language comprehension has often been considered from the bottom up, from word recognition, to syntax, to semantics, so has language production often been

considered from the top down. Accounts of production assume that speakers first

conceptualise their utterance, then convert that concept into syntactic representations, and then construct sound-based representations before they articulate (e.g., Bock & Levelt, 1994). The conceptual level has traditionally been viewed as non-language specific, and non-automatic (Levelt, 1989). Once speakers decide on the message they wish to convey, they formulate the message by selecting words (lemmas) in their syntactic context, and activate their phonology (sound processing) before articulating. At these later stages the process is traditionally considered as taking place automatically (Levelt, 1989). Ferreira and Pashler (2002) demonstrated that lemma selection and word-form selection require

cognitive resources, and are thus affected by performance of a concurrent task, while phoneme selection is not. They conclude that lemma selection and word-form selection are subject to a processing bottleneck, meaning that they cannot occur simultaneously (see Boiteau, Malone, Peters, & Almor, 2014; Sjerps & Meyer, 2015 for further empirical evidence that speech planning is more cognitively demanding than articulating).

De Bot (1992) proposes an adapted version Levelt’s (1989) model of speech

production for bilingual production. The model assumes that production mechanisms are essentially the same for native and non-native languages, and that bilinguals make use of two essentially equivalent production systems, choosing the language of production after

conceptualising their utterance. By this account, production becomes language specific directly after the message is conceptualised. The idea of two separate lexicons is also central to Kroll and Stewart’s (1994) model, which assumes that L1 words are more strongly linked to the conceptual level than L2 words, suggesting that switching into L2 is more demanding in terms of lexical selection than switching into L1. However, as reviewed above (Section 1.2), there is now extensive evidence of cross-linguistic activation at almost every level of representation, and this is also the case for language production (for a review see Brysbaert & Duyck, 2010)

Recent empirical studies have shown that languages share the syntactic and lexical levels of processing. Hartsuiker et al. (2004) showed that, in dialogue, L1-Spanish-L2-English bilinguals tended to repeat syntactic structures used by a confederate when describing pictures, even although the confederate spoke Spanish and the participant spoke English. In a similar experiment, Loebell and Bock (2003) had L1-German-L2-English participants

describe a picture using a designated sentence in German, before freely describing another picture in English (or the reverse, starting with the designated sentence in English). They found that dative constructions were primed across the two languages. More recently, Hatzidaki, Branigan, and Pickering (2011) showed cross-linguistic syntactic number agreement in English-Greek and Greek-English bilinguals. Participants read aloud a noun phrase in either English or Greek, in which the noun had a different syntactic number across the two languages (e.g., The money; singular or Ta λεφτά; plural). They were asked to complete the phrase in either the same language, or in the other language. Participants sometimes produced a verb which agreed in number with the translation of the subject noun, and did so much more often when they produced the verb in the language of the

noun’s translation (i.e., when they switched languages). This suggests that they concurrently activated both languages’ syntax (on many occasions at least). In a corpus-based analysis of English-Spanish bilinguals, Fricke and Koostra (2016) showed that these findings extend to priming in spontaneous code-switching. These findings support accounts according to which syntax and grammatical encoding are shared across languages.

When it comes to word production, the top-down nature of speech production means it cannot simply be considered as speech comprehension in reverse. Unlike in speech

recognition, where a bilingual’s other language may be activated in a bottom-up manner (Dijkstra & van Heuven, 2002), speakers do exert some control over which language is activated for word production (Costa & Santesteban, 2004). This control is the focus of Green and Abutalebi’s (2013) adaptive control model for bilingual production. The model places an emphasis on communicative goals, such as speaking in one language rather than another, and supposes that bilingual speakers can maintain their goal even in the presence of activation of the other language, by suppressing lexical competition. This contrasts with monolingual models of speech production, which do not assume any inhibitory processes (Costa, 2005). Importantly, Green and Abutalebi (2013) thus assume that bilingual

production involves more cognitive control than monolingual production; that regularly exercising cognitive control for language selection leads to enhanced cognitive control in bilinguals; and that this enhanced cognitive control also manifests in nonverbal tasks.

This idea that lexical access is more difficult for bilinguals is supported by empirical evidence from Ivanova and Costa (2008), who compared picture naming speeds between a group of Spanish monolinguals and group of L1-Spanish-L2-Catalan bilinguals and found that the monolingual group was faster at picture naming. Similarly, Gollan, Montoya,

Fennema-Notestine, and Morris (2005) found that English-dominant bilinguals named pictures more slowly than English monolinguals (although they named the same pictures just as quickly as monolinguals once they had been shown multiple times). These findings could be the result of cross-language interference as bilinguals retrieve a lexical representation. However, other factors may be at play: in Gollan et al.’s (2005) study, participants’ dominant language and their first acquired language were not always the same, and they were tested in the dominant language; frequency effects may play a role, as bilingual speakers will use both lexicons correspondingly less than monolingual speakers, making each lexical entry less frequent; and the typical age-of-acquisition of a particular word may also affect lexical retrieval, and this is often, but not always, confounded with the frequency effect. These studies thus illustrate, on the one hand, that lexical access may be more difficult for bilinguals, and, on the other hand, that it is difficult to ascribe this additional difficulty to any one feature of bilingual production.