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

Abstract

We investigated the processing of Thai and English subject- and object-extracted relative clauses (SRCs and ORCs) 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 processing advantage of the SRC over the ORC was predicted and confirmed, while the primary location of difficulty was predicted by the Locality-based Integration or Surprisal/Expectation models. For English, the results indicated that the primary source of difficulty was at the ORC embedded verbs, consistent with predictions from the Locality-based Integration account. Although a similar pattern of findings was obtained for Thai, with significant differences between ORC and SRC at the embedded verbs, there was a tendency for the primary difficulty to occur at the ORC embedded nouns, which aligns more with the Surprisal/Expectation account. Thus, the absence of determiners (e.g., articles) in Thai appears to account for differences in the primary location of difficulty in the processing of Thai and English relative clauses. The English results are consistent with prior studies using phrase-by-phrase segmentation. The results with Thai, particularly from the by-item analysis, indicate a tendency toward an effect of word category frequency. We recommend that future studies investigate post-nominal RCs in other languages to shed light on language-specific properties (such as bare NPs in Thai) and to ascertain the role of word category frequency in initial sentence processing.