Bilingual experience may enhance attentional control, but little work has addressed whether monolinguals and bilinguals differ in allocating attentional resources. Focusing on speech processing, we examined listening effort via pupillometry in English monolinguals and simultaneous bilinguals, while they listened to passages in a familiar or unfamiliar language. Results demonstrated similar pupil responses across conditions in bilinguals, yet monolinguals showed significantly larger pupil size when listening to the unfamiliar language than the familiar one. Further, more English exposure (especially a longer stay in an English-speaking family) correlated with smaller pupil size in the familiar language condition. Overall, our findings suggest that bilinguals tend to exhibit greater listening effort than monolinguals, and a more cognitively demanding situation (i.e., listening to an unknown language) requires more effort in monolinguals. With this, we broadened the scope of research on bilingual cognition and demonstrated that bilingualism affects attentional resource allocation in spoken language processing.

Studies measuring inhibitory control in the visual modality have shown a bilingual advantage in both children and adults. However, there is a lack of developmental research on inhibitory control in the auditory modality. This study compared the comprehension of active and passive English sentences in 7–10 years old bilingual and monolingual children. The task was to identify the agent of a sentence in the presence of verbal interference. The target sentence was cued by the gender of the speaker. Children were instructed to focus on the sentence in the target voice and ignore the distractor sentence. Results indicate that bilinguals are more accurate than monolinguals in comprehending syntactically complex sentences in the presence of linguistic noise. This supports previous findings with adult participants (Filippi, Leech, Thomas, Green & Dick, 2012). We therefore conclude that the bilingual advantage in interference control begins early in life and is maintained throughout development.