Does isomorphism boost heritage speakers' sentence processing? A case of Korean active transitive and suffixal passive constructions

This study investigates the role of isomorphism in sentence processing by Korean heritage speakers in the United States. Employing acceptability judgement and self-paced reading tasks, we examine how Korean heritage speakers comprehend two Korean clausal constructions expressing transitivity: active transitive and suffixal passive. Results reveal a nuanced interplay between isomorphism, construction-specific cues, and task demands in sentence processing. While Korean heritage speakers' acceptability ratings are largely comparable to those of monolingual Korean speakers, they spend more time reading critical regions and less time reading spill-over region than monolingual Korean speakers. Notably, there are no significant reading-time differences (i) across all critical and spill-over regions within identical grammaticality conditions and (ii) in the verb and post-verb regions across grammaticality pairs within the same construction and canonicity conditions. General proficiency in Korean does not substantially affect heritage speakers' performance across the tasks. These findings advance our understanding of heritage language (processing) and sentence-processing architectures, also highlighting the unique linguistic experiences and challenges encountered by heritage language speakers.