Scholars have argued that comprehensibility (i.e., ease of understanding), not nativelike performance, should be prioritized in second language learning, which inspired numerous studies to explore factors affecting comprehensibility. However, most of these studies did not consider potential interaction effects of these factors, resulting in a limited understanding of comprehensibility and less precise implications. This study investigates how pronunciation and lexicogrammar influences the comprehensibility of Mandarin-accented English. A total of 687 listeners were randomly allocated into six groups and rated (a) one baseline and (b) one of six experimental recordings for comprehensibility on a 9-point scale. The baseline recording, a 60 s spontaneous speech by an L1 English speaker with an American accent, was the same across groups. The six 75-s experimental recordings were the same in content but differed in (a) speakers' degree of foreign accent (American, moderate Mandarin, and heavy Mandarin) and (b) lexicogrammar (with errors vs. without errors). The study found that pronunciation and lexicogrammar interacted to influence comprehensibility. That is, whether pronunciation affected comprehensibility depended on speakers' lexicogrammar, and vice versa. The results have implications for theory-building to refine comprehensibility, as well as for pedagogy and testing priorities.
Keywords: Comprehensibility; listening; speaking; speech perception.