Relative Marker Omission in Thai: Evidence from Native Speakers’ Acceptability Judgments and Language Transfer

Relative clauses are a well-studied phenomenon in linguistics, giving rise to discoveries about human language. In this study, we consider thîi-less relative clauses in Thai, in which a relative marker may be omitted under certain circumstances. The objectives of the study are to identify native speakers’ conditions of thîi omission and to explore whether knowledge of the conditions is transferred to their relative marker omission in English. Two parallel acceptability judgment tasks in Thai and English were conducted: 437 students from various faculties at Kasetsart University judged the acceptability of thîi-less relative clauses while 233 non-English major students and 83 English major students at the same university judged the acceptability of English marker-less relative clauses. Results showed the most favorable condition for thîi omission is a subject relative clause that modifies a general head noun and contains a non-eventive predicate. Such a structure of a thîi-less relative clause resembles the basic construc­tion of nominal modification, i.e., a noun modified by a phrase. Results also showed the transfer of the thîi omission pattern into English, particularly among students with lower English proficiency. With L1 and L2 supporting data, the study demonstrated that syntax and semantics are determinants of relative marker omission in Thai