Processing difficulty in comprehension and production of relative clauses by learners of English as a second language

This study tested the predictions of three major hypotheses of relative clause acquisition in second language acquisition: Keenan and Comrie's (1977) Noun Phrase Accessibility Hierarchy (NPAH), Kuno's (1974) Perceptual Difficulty Hypothesis (PDH), and Hamilton's (1994) SO Hierarchy Hypothesis (SOHH). These hypotheses are based on different rationales and make different predictions on the difficulty order of different relative clause sentence types. Analyses of the data collected from 61 learners of English as a second language in three different elicitation tasks found mixed support for the NPAH and the SOHH and full support for the PDH. Generally, the results suggest a complementary relationship between the NPAH and the PDH. Some differences observed in different tasks point to the importance of examining learners' processing problems in multiple tasks in different modalities.