SUMMARY
This study explores how relative clause (RC) constructions develop in the acquisition of English as a second language (L2). The acquisition of RC constructions has been the focus of much research in the field of language acquisition, but a majority of L2 studies in this area is experimental based on the Noun Phrase Accessibility Hierarchy (NPAH) (Keenan & Comrie, 1977). In this study, the spontaneous speech production by a Japanese primary school child, learning English in a naturalistic environment, was audio-recorded regularly over two years, and the development of RC constructions was compared with the acquisition of other English morphological and syntactic structures as represented within Processability Theory (PT) (Pienemann, 1998; Pienemann, Di Biase, & Kawaguchi, 2005; Pienemann & Keßler, 2011). Although PT predicts that subordinate clauses are acquired at the highest stage in processability hierarchy, the results in this longitudinal study show that some types of RC constructions emerge at earlier stages in L2 English acquisition. The results also show that RC constructions in the Japanese child’s English L2 develop in the similar way to those reported in L1 studies (e.g., Diessel, 2004).