When ‘John broke up Mary’ becomes acceptable

This study investigates how the argument structure of shifting verbs in Mandarin is represented and processed during sentence comprehension. Shifting verbs — traditionally classified as intransitive but increasingly used in transitive frames — have been widely discussed in theoretical linguistics; however, their cognitive status remains underexplored. Addressing this gap, we examine whether shifting verbs have developed transitive argument structures and how they are processed in real time. Using self-paced reading and acceptability judgments, we compared shifting verbs to unaccusative verbs in transitive and intransitive contexts, where unaccusative, traditionally analyzed as intransitive, served as a baseline. Acceptability results showed that shifting verbs in transitive frames were readily accepted, unlike unaccusative verbs, which were consistently rejected in the same contexts. Reading time data revealed distinct processing profiles: Shifting verbs exhibited argument-structure flexibility, including possible coactivation of transitive and intransitive representations at the verb and target regions. In contrast, unaccusative verbs elicited substantial processing penalties in transitive frames. These findings show that argument structure representations can be shaped by usage. More broadly, results suggest that grammatical change can be observed not only in language use but also in real-time comprehension, offering insights into how evolving syntactic configurations are encoded and accessed in the mental lexicon.