這份研究以第二語言習得框架下的「原則與參數理論」中的「參數設定理論」為切入點，去探討：以英語為母語，中文為第二語的語言學習者在中文中零主詞的習得，並著手解釋，以中文為母語者，和以英文為母語者，其習得上的差異性。在現下的研究中，根據一個關於中文零主詞語料的傾向測試中發現，第二語言習得者，趨於使用零主詞的頻率和語言程度的優劣成正比。那些研究也顯示，以中文為第二語的語言習得者，包含程度較高者，在習得從屬子句中的零主詞所遇到的困難度，比在學習主要子句中的零主詞要高。這樣的研究結果支持了Tsimpli 和Roussou 在1991 年與Smith 和Tsimpli 在1995 年的研究中所聲稱的：與功能性範疇相關的語言參數值，對於年齡超過「關鍵時期」的第二語學習者之第二語言重新建構是無效的。在本研究中更強調，「主題冠」，一個普遍化的語言屬性，可能會嘉惠於第二語言習得者。

This study looks at the interpretation of null subjects in L2 Chinese by adult L1 English speakers and sets out to explain the divergence between non-native speakers and native speakers in relation to parameter-resetting in SLA within the framework of Principles and Parameters. Findings in the current study, based on a preference test of null subject-related Chinese properties, show that second language speakers’ use of null arguments increases with proficiency. They also suggest that L2 Chinese learners, advanced speakers included, have difficulty with the acquisition of null embedded subjects more so than with null matrix subjects. The results support the claim made by Tsimpli and Roussou (1991) and Smith and Tsimpli (1995) that parameter values associated with functional categories are inaccessible to L2 learners after the critical period. It is argued that the “topichood” being a generalised property may have contributed to the L2 divergence found in the study.