This study investigated the role of domain-general inhibitory control in trilingual speech production. Taking an individual differences approach, we examined the relationship between performance on a non-linguistic measure of inhibitory control (the Simon task) and a multilingual language switching task for a group of fifty-six native English (L1) speakers learning French (L2) and Spanish (L3). Better inhibitory control was related to reduced switch costs, but only when switching into or out of the more dominant L1, where inhibitory control has been theorized to be most important (Green, 1998). The results provide evidence of a direct link between inhibitory control abilities and language switching capabilities, and suggest constraints on the conditions under which a domain-general inhibitory control mechanism supports language switching.

Recent research on language production suggests that bilinguals shift from using inhibitory control mechanisms to a language-specific selective mechanism during development (Costa, Santesteban, & Ivanova, 2006). Costa et al. argue that the robustness of the L2 lexical representations may be critical to the functionality of a language-specific selective mechanism. Accordingly, in the present study we measured the lexical robustness of a group of 54 English dominant learners of Spanish using a verbal fluency task and investigated its effect on their performance in a picture-naming task with language switches. The results suggest that L2 lexical robustness predicts the shift to a language-specific selective mechanism during speech production. Moreover, we demonstrate a specific threshold of lexical robustness necessary to engage the mechanism.

The present study investigates the locus of language selection in less and more proficient language learners, specifically testing differential predictions of La Heij's (2005) concept selection model (CSM) and Kroll and Stewart's (1994) revised hierarchical model (RHM). Less and more proficient English dominant learners of Spanish participated in a Stroop translation task that included semantically related and unrelated word or picture distracters. The results for the more proficient learners provide support for the CSM as well as the RHM. The results for the less proficient learners provide support for the RHM and demonstrate the continued reliance on lexical level links and the difficulty in accessing the conceptual store during second language production. The selection by proficiency model of bilingual speech production is discussed.

In the present study, we use a training design in two experiments to examine whether bilingual language switching facilitates two components of cognitive control, namely monitoring and inhibitory control. The results of Experiment 1 showed that training in language switching reduced mixing costs and the anti-saccade effect among bilinguals. In Experiment 2, the findings revealed a greater decrease of mixing costs and a smaller decrease of the anti-saccade effect from pre- to post-training for the language switching training group compared to the second language training group. Overall, the results suggest that extensive exercise in monitoring and inhibitory control in an experimental setting may enhance the corresponding components of cognitive control. We discuss these findings in the context of the relationship between bilingual language control and executive control.

In the present study, Vygotsky's (1978Vygotsky's ( , 1986 sociocultural framework of the zone of proximal development (ZPD) and scaffolding writing (Bodrova & Leong, 1995Ross, 1976)