It is well established in the masked translation priming literature that the priming effect is sensitive to language direction with noncognates—namely, the priming effect is consistently observed from first language (L1) to second language (L2), but not always from L2 to L1. Several recent reports demonstrated both L1–L2 and L2–L1 priming and attributed the restoration of L2–L1 priming to high proficiency in L2. Here, the current study tested two groups of highly proficient Chinese–English bilinguals, with one group more dominant in English and the other more balanced in both languages. The L2–L1 priming effect was only observed with the balanced bilinguals, but not the English-dominant ones. Based on these results, I argue that the language proficiency account is not sufficient to explain the priming asymmetry and that the relative bilingual balance is a more accurate account. Theoretically, the cross-language balance is determined by the representational difference between L1 and L2 at the semantic level. I discuss the results in relation to various bilingual models, in particular, the sense model and the distributional representational model (DRM), which capture the semantic representations of bilinguals.

Four experiments are reported which were designed to test hypotheses concerning the asymmetry of masked translation priming. Experiment 1 confirmed the presence of L2–L1 priming with a semantic categorization task and demonstrated that this effect was restricted to exemplars. Experiment 2 showed that the translation priming effect was not due to response congruence. Experiment 3 replicated this finding, and demonstrated that the 150 ms backward mask that had been used in earlier translation priming experiments was not essential. Finally, it was demonstrated in Experiment 4 that L2–L1 priming was not obtained for an ad hoc category, indicating that priming was not obtained merely because the task required semantic interpretation. These results provide further support for the Sense Model proposed by Finkbeiner et al. (2004).

Most empirical evidence on switch costs is based on bilingual production and interpreted as a result of inhibitory control. It is unclear whether such a top-down control process exists in language switching during comprehension. This study investigates whether a non-lexical switch cost is involved in reading code-switched sentences and its relation to language dominance with cross-script bilingual readers. A maze task is adopted in order to separate top-down inhibitory effects, from lexical effects driven by input. The key findings are: 1) switch costs were observed in both L1-L2 and L2-L1 directions; 2) these effects were driven by two mechanisms: lexical activation and inhibitory control; 3) language dominance modulated the lexical effects, but did not affect the inhibitory effects. These results suggest that a language control mechanism is involved in bilingual reading, even though the control process is not driven by selection as in production. At the theoretical level, these results lend support for the Inhibitory Control model during language switching in comprehension; while the BIA/BIA+ model needs to incorporate a top-down control mechanism to be able to explain the current findings.

Bilinguals need control mechanisms in order to switch between languages in different communication contexts (Green, 1998, Bilingualism: Language and Cognition, 1; Price, Green, & von Studnitz, 1999, Brain, 122). There has been neural evidence showing competition to control output in L2 vs. L1 in both cortical and sub-cortical areas, when language selection is carried out (Abutalebi & Green, 2007, Journal of Neurolinguistics, 20). Here we use intra-operative direct electrical stimulation to demonstrate that the head of the left caudate is critical not only in language switching tasks but other control tasks. A bilingual Chinese-English patient was instructed to perform both language switching and switching in color-shape naming tasks during awake glioma surgery. When stimulation was applied on the left caudate, failures or difficulties in both language switching and color-shape naming were observed, with the effects greater on language switching. Stimulation to neighboring brain regions either did not affect performance or generated mild problems specific to language switching. The results provide direct evidence of the necessary role of the left caudate in language control.