Accent type modulates frequency-specific neural tracking of speech.

In the real world, listeners often find speech in a non-native (L2) accent harder to understand than speech in their own native (L1) accent. In ideal laboratory listening settings, these struggles can become smaller. For this reason, most research on L2 accent processing uses speech-in-noise paradigms to avoid ceiling effects. Here, we explore whether neural tracking provides a sensitive measure of L2-processing difficulties, even in ideal listening conditions. In our electroencephalography (EEG) study, Canadian English-speaking adults were presented with Canadian (L1) and Mandarin-accented (L2) English. We assessed neural tracking of speech by analyzing coherence between the speech envelope and EEG. We found significantly stronger tracking for L1-accented speech, in canonical delta-theta frequencies, as well as higher-frequency bands associated with fine-grained phonemic encoding. Exploratory analyses illustrated that transcription errors correlated with neural tracking and that neural tracking was greater for L1- than L2-accented speech at the word and phoneme rate. These findings indicate that accent type modulates neural tracking of speech at specific frequencies, even in passive, quiet settings. This study highlights the sensitivity of frequency-specific neural tracking methods for elucidating subtle accent-related variations in speech, offering a foundation for future work on accent processing across more diverse speaker and listener populations.