Primary Location of Difficulty in the Processing of Thai and English Relative Clauses

We investigated the processing of Thai and English subject and object-extracted relative clauses (SRC and ORC) with native Thai and English speakers using a self-paced reading paradigm. Although both Thai and English exhibit post-nominal RCs, Thai uses neither determiners nor inflectional morphemes which warrants further investigation. The advantage of the SRC over the ORC was predicted and confirmed. The primary location of difficulty was predicted with either the Locality-based Integration or Surprisal-based models. For English, the results indicated that the primary source of difficulty was at the OR embedded verbs. Although a similar pattern of findings was obtained for Thai, with significant differences between the ORC and SRC embedded verbs, there was a tendency for the occurrence of primary difficulty at the ORC embedded nouns. The absence of determiners in Thai is likely to account for the difference in the primary location of difficulty in the processing of Thai and English relative clauses. The English results are similar to findings in prior studies with phrase-by-phrase segmentation. The results with Thai appear to favor the role of word-type frequency. We recommend that studies on post-nominal RCs in other languages be conducted to ascertain this role in initial sentence processing.