An empirical study on parameters affecting the recoverability of deictic null subjects in Korean

Korean is a null subject language, allowing the omission of overt subjects in sentences. Within the framework of principle and parameter theory, Korean null subjects have traditionally been explained by the topic-drop parameter, which assumes that omitted subjects are recovered through topic chains linking them to an explicit discourse topic. However, this mechanism alone is insufficient to account for deictic null subjects, which primarily refer to the speaker or addressee and do not require a previously introduced topic. This study empirically and systematically evaluates the contribution of linguistic parameters within verbal complexes in resolving Korean deictic null subjects. A total of 208 heuristic rules were developed, integrating various morpho-syntactic and lexical features, and were incorporated into a unified null subject resolution system—the first attempt to comprehensively assess multiple parameters within a single system. The system was tested on 15,883 predicates containing null subjects, measuring the impact of each parameter in recovering discourse participant-referents. The system successfully identified 86% of discourse participant-related null subjects, achieving an accuracy rate of 99%. Additionally, an analysis of individual rule performance highlighted the crucial role of verbal suffixes in identifying and restoring deictic null subjects. These findings underscore the significance of explicit linguistic features in verbal complexes for the recoverability of deictic null subjects in Korean, particularly those linked to discourse participants.