Bilinguals are susceptible to interaction between their two phonetic systems during speech processing. Using a language-switching paradigm, this study investigated differences in phonetic transfer of Cantonese–English bilingual adults with various language dominance profiles (Cantonese-dominant, English-dominant, and balanced bilinguals). Measurements of voice onset time revealed that unbalanced bilinguals and balanced bilinguals responded differently to language switching. Among unbalanced bilinguals, production of the dominant language shifted toward the nondominant language, with no effect in the opposite direction. However, balanced bilinguals’ speech production was unaffected by language switching. These results are analogous to the inhibitory control model, suggesting an asymmetrical switch cost of language switching at the phonetic level of speech production in unbalanced bilinguals. In contrast, the absence of switch cost in balanced bilinguals implies differences in the mechanism underlying balanced bilinguals’ and unbalanced bilinguals’ speech production.

Determining the meanings of words requires language learners to attend to what other people say. However, it behooves a young language learner to simultaneously encode relevant non‐verbal cues, for example, by following the direction of their eye gaze. Sensitivity to cues such as eye gaze might be particularly important for bilingual infants, as they encounter less consistency between words and objects than monolingual infants, and do not always have access to the same word‐learning heuristics (e.g., mutual exclusivity). In a preregistered study, we tested the hypothesis that bilingual experience would lead to a more pronounced ability to follow another's gaze. We used a gaze‐following paradigm developed by Senju and Csibra (Current Biology, 18, 2008, 668) to test a total of 93 6‐ to 9‐month‐old and 229 12‐ to 15‐month‐old monolingual and bilingual infants, in 11 laboratories located in 8 countries. Monolingual and bilingual infants showed similar gaze‐following abilities, and both groups showed age‐related improvements in speed, accuracy, frequency, and duration of fixations to congruent objects. Unexpectedly, bilinguals tended to make more frequent fixations to on‐screen objects, whether or not they were cued by the actor. These results suggest that gaze sensitivity is a fundamental aspect of development that is robust to variation in language exposure.

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Bilingual infants grow up with the unique experience of needing to learn two words for most concepts. These words are called translation equivalents, and translation equivalents that also sound similar (e.g., banana—banane) are called cognates. Research has consistently shown that children and adults process and name cognates more easily than non-cognates. The present study explored if there is such an advantage for cognate production in bilinguals’ early vocabulary development. Using longitudinal expressive vocabulary data collected from 47 English–French bilingual infants and toddlers starting at the ages of 16–20 months up to 27 months (a total of 219 monthly administrations in both English and French), results showed that overall children produced a greater proportion of cognate words than non-cognate words on the MacArthur-Bates Communicative Development Inventories. The findings suggest that cognate learning is facilitated in early bilingual vocabulary development. Just as in monolingual infants, these results suggest that phonological overlap supports bilingual language acquisition.