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Neural Tracking of Auditory and Lexical Processing in Bilingual Children and Adult L2 Learners under Simulated Cochlear Implant Listening Conditions
Poster Session B, Friday, September 12, 4:30 - 6:00 pm, Field House
Magda Rojas-Mora1, Paul Iverson1; 1University College London
This study investigates auditory and lexical processing in Spanish–English bilingual children and adult second language (L2) English learners by applying multivariate temporal response function (mTRF) to analyse the electroencephalography (EEG) recordings. Participants listened to audiobooks in both languages, presented either in their original form or processed through a cochlear implant (CI) simulation, to compare their auditory encoding and lexical processing mechanisms. This work is of special interest because applying EEG/mtrf at the lexical level remains relatively novel, particularly in children. Furthermore, developmental differences in early versus late stage lexical measures have rarely been explored under CI simulation, making this study well placed to shed light on how maturation shapes semantic processing in challenging auditory conditions. The sample included 23 early bilingual children (ages 7–12) and 40 adult L2 learners (ages 18–50). Participants listened to the same narrative materials across both languages. During the listening tasks, EEG equipment recorded neural activity, and mTRFs tools were applied to model auditory and lexical tracking. Lexical properties, such as frequency, predictability, concreteness, arousal, and neighbourhood density, were estimated using a large pre-trained language model (GPT-4) based on the narrative content. Results revealed developmental differences in how degraded speech was processed. While both groups demonstrated cortical sensitivity to acoustic and lexical features, children exhibited greater difficulty with lexical prediction under vocoder conditions compared to adults. Adults’ lexical tracking remained stable across degradation, indicating a more mature and adaptable prediction mechanism. In contrast, children significantly declined the lexical predictability measure when the signal was vocoded, suggesting underdeveloped strategies for semantic prediction in acoustically compromised environments. Theta-band activity, associated with fast temporal modulations and lexical access, was significantly enhanced in children under vocoder conditions, possibly reflecting a compensatory cognitive effort. However, this enhanced activity did not correspond to improving lexical tracking, pointing to inefficiencies in integrating lexical content under perceptually demanding conditions. Adults demonstrated stronger lexical frequency and neighbourhood density tracking across conditions, consistent with more mature and interconnected lexical networks. Likewise, adults exhibit a significant 'language effect' when processing lexical frequency, with some evidence supporting better Spanish tracking than English. This suggests that adults can leverage their broader exposure and experience with language when recognising words. Nevertheless, children’s responses to these variables were weaker, showing a noticeable gap in lexical tracking capabilities. This suggests that their vocabulary and experiential basis for word frequency are less developed, which limits predictive processing during speech comprehension. The study concludes that while children’s auditory tracking is largely comparable to that of adults, significant differences remain in higher-order lexical processing, particularly under vocoded conditions. Spectral degradation impacts children and adults differently, with children demonstrating less mature and less efficient lexical prediction. These developmental differences highlight the need for age-appropriate auditory training and language instruction strategies. These findings contribute to our understanding of lexical development in bilingual populations and stress the need for tailored training approaches that address linguistic and perceptual challenges, especially for children with hearing impairments. Future research should explore how lexical processing develops across ages in challenging auditory contexts.
Topic Areas: Speech Perception, Multilingualism