Listening effort across non-native and regional accents: a pupillometry study

Previous work has shown that L2 accented speech incurs a processing cost even when accurately understood. It remains unknown, however, whether an online processing cost is found when listeners process speech produced in L1 accents that are not their own. In this study, we examine this question by using comparative pupil dilation as a measure of cognitive load. Participants from the South of England heard sentences produced in four different accents: Southern British English (the listeners’ own familiar accent), American English (a standard L1-accent widely used in media), Glaswegian English (a less-familiar regional L1 accent), and Mandarin Chinese-accented English (an L2 English accent). Results show that Chinese-accented speech elicited significantly larger pupil dilation responses compared to Southern British English. Participants also showed larger pupil dilation when they heard relatively less-familiar L1 American and Glaswegian accents. Interestingly, pupil dilation was higher when listeners heard American English compared to Glaswegian English, despite self- reporting that they were more familiar with American English and found it less effortful to comprehend. The results show that accurately perceived and highly intelligible, L1 accents (e.g., American English) also incur a cognitive cost in perception, but to a smaller extent compared to L2 accented speech. We discuss the implications of our findings for the relationship between exposure, subjective effortfulness measures and pupil dilation responses.