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Wait, who said that?: Talker accent modulates neural processing of Mandarin-English code-switched speech
Poster Session E, Sunday, September 14, 11:00 am - 12:30 pm, Field House
This poster is part of the Sandbox Series.
Khushi N. Patil1, Philip J. Monahan1; 1University of Toronto
Code-switching, the act of using multiple languages in a single speech utterance, typically results in behavioural (Thomas & Allport, 2000; Costa & Santesteban, 2004; Fricke et. al, 2016; Olson, 2017) and neurophysiological costs (e.g., N400, LPC; Fernandez et. al, 2019; Yacovone et. al, 2021). That said, anticipatory phonetic cues reduce behavioral switch costs (Shen et. al, 2020). Additionally, foreign accented speech, which contains language-specific phonetic cues, modulates neurophysiological responses to otherwise unexpected speech patterns (Hanulikova et. al, 2011). Here, we ask whether bilingual listeners process code-switched sentences differently when speaker accent varies. Using EEG, we observe a sustained negativity to English-to-Mandarin code-switches in North American accented speech compared to Mandarin accented speech. More specifically, there was a contrast in the response to code-switched and unilingual speech to the North American talker, but no difference to the Mandarin talker. Participants (n = 15) listened to English sentences with and without Mandarin code-switches produced by a North American- or Mandarin-accented talker, while their neural activity was recorded using a 32-channel whole-head EEG. In half of all audio stimuli, the entire sentence was spoken in English, while in the other half, a sentence-medial noun was spoken in Mandarin, while the rest of the sentence was in English; for example, e.g., He did his homework on the school bus or He did his zuòyè (homework) on the school bus. We predicted an N400 and possibly a LPC for code-switched stimuli, but not for unilingual stimuli, consistent with switch costs seen in prior research (Fernandez et. al, 2019; Yacovone et. al, 2021). We expected Mandarin-accented sentences to induce relatively smaller N400 effects compared to Canadian English-accented ones, as listeners use cues available in the accent to anticipate the switch. Preliminary results show no clear N400s or LPCs. However, a sustained negativity (similar to Gosselin et. al, 2022) was observed in the Canadian English accented code-switched condition as compared to the Canadian English accented unilingual condition, possibly indexing a switch processing cost. In contrast, there was no ERP difference present between the Mandarin accented code-switched and unilingual conditions. We infer that the talker accent does influence switch processing, and that the Mandarin accent may ease English-to-Mandarin switch processing. Hence, talker accent modulates the neural processing of code-switched speech, indicating that accent helps bilingual listeners anticipate switches and ease processing demands. This supports a lack of associated switch cost in naturalistic settings, consistent with some recent code-switching research (Blanco-Elorrieta and Pylkkänen 2017). This research provides insight into the neurophysiological mechanisms underlying code-switching, deepening our understanding of phonetic variation and cross-linguistic interactions in the multilingual brain.
Topic Areas: Multilingualism, Speech Perception