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Immersion affects attentional processing in bilinguals
Poster Session E, Friday, October 2, 11:00 am - 1:00 pm, Wangari Maathai
Jingkang Wang1, Taomei Guo2, Mirjana Bozic1; 1University of Cambridge, 2Beijing Normal University
Introduction: Bilingualism modulates neural mechanisms of auditory selective attention: bilinguals often organize mental resources more flexibly under challenging speech-processing scenarios while maintaining optimal comprehension (Olguin et al., 2019; Phelps et al., 2022). This reflects neuroplastic adaptation to an environment where target-language selection and non-target inhibition create competition and increased cognitive demands (Kroll & Bialystok, 2013). However, bilingualism is not a binary concept, but a complex spectrum of various facets (Yow & Li, 2015). Factors such as immersion in an L2-dominant environment may further fine-tune bilinguals’ cognitive processing (e.g., Nicolay & Poncelet, 2013), yet such influence remains under-explored. This study aimed to investigate how immersion in an L2 context impacts attentional processing of speech. Methods: Participants were native Mandarin Chinese speakers who learned English by the age of six: 31 in Beijing (without English immersion) and 27 in Cambridge, UK (with English immersion), matched for age, L2-acquisition age and proficiency. In a dichotic listening task simulating real-life scenarios, participants attended to a naturalistic, continuous Chinese narrative in one ear while simultaneously ignoring a competing stream in the other. The type of interference was manipulated to create four conditions featuring distractors of varying intelligibility: (1). Single Talker (ST; no interference), (2). Native-Musical Rain (MuR, non-linguistic interference), (3). Native-Unknown (unintelligible linguistic interference – narratives in Serbian), and (4). Native-Native (intelligible linguistic interference – narratives in Chinese). EEG was recorded, pre-processed and band-filtered to 1-12Hz. Neural tracking of stimuli was analyzed by mapping between speech envelopes and neural responses using backward temporal-response-function (mTRF). Linear mixed-effects models assessed effects of immersion group, conditions, attention and L2-immersion years on neural tracking of stimuli. Results: Behavioral comprehension was uniformly high and neural decoding patterns were similar in two groups. Analysis however revealed significantly more robust encoding of the attended streams in the immersed (Cambridge) group. Frequency decomposition indicated effects were primarily driven by the delta band (1–4 Hz), consistent with the role of delta oscillations in top-down control over language comprehension (Etard & Reichenbach, 2019). Importantly, within the Cambridge group (immersion group), there was also an interaction between L2-immersion time and attention, such that longer immersion was linked to weaker encoding of the attended streams. Additional spectral power analysis showed no group difference in task-related attentional allocation in alpha, theta and delta frequency bands. Conclusion: L2 immersion was shown to increase the strength of speech-brain mapping, without changing the overall power in underlying oscillatory brain systems. Compared with bilinguals in an L1-dominant environment, those immersed in L2 contexts show stronger differentiation between the tracking of attended speech and interference, regardless of interference type. Such boost in attentional tracking seems to decrease following longer L2-immersion, reflecting the dynamic neurocognitive adaptation of executive mechanisms as bilinguals shift from the early, effortful accommodation stage to a more stable, efficient functioning mode in L2 environment. These findings suggest that L2 immersion may generally help amplify top-down gain for task-relevant speech selectively, reflecting an enhanced “alertness” to target stimuli in background noise.
Topic Areas: Control, Selection, and Executive Processes, Multilingualism