Typological linguistics has made important contributions to our understanding of SLA processes, especially in the early days of SLA research (e.g., Eckman, 1977; Hyltenstam, 1977; Rutherford, 1984). In particular, the noun phrase accessibility hierarchy (NPAH), originally proposed as a generalization based on typological work by Keenan and Comrie (1977), has served as a basis on which many SLA studies are conducted. The NPAH predicts the ease of relativization as a function of the grammatical role of the head noun phrase (NP) modified by the relative clause (RC) observed in languages of the world: subject (SU) > direct object (DO) > indirect object (IO) > oblique (OBL) > genitive (GEN) > object of comparison (OComp). If a language can relativize on a position on the hierarchy, then it follows that any other higher position (or position to the left in the given schematic) can also be relativized on. For example, if a language has an OComp relative (e.g., the man who I am taller than), then it has a GEN relative (e.g., the man whose father I know) and all of the others higher on the hierarchy (i.e., OBL, IO, DO, and SU).

Although Keenan and Comrie's (1977) noun phrase accessibility hierarchy (NPAH) has been shown to predict the difficulty order of relative clauses (RCs) in SLA, most studies of the NPAH have been on European languages. This paper tests the prediction for Japanese. Study 1 analyzes RCs in an oral interview corpus from 90 learners of Japanese at four different levels of proficiency (first language = Mandarin Chinese, English, and Korean; N = 30 for each). Analysis of 1005 RCs from nonnative data and 231 RCs from 15 native speakers (NSs) of Japanese revealed that even lower proficiency learners used direct object (DO) and oblique (OBL) relatives, suggesting that subject (SU) relatives are not easier than DO or OBL relatives for second language learners of Japanese. The learners (except Korean NSs) also made strong associations between SU and animate heads and between DO/OBL and inanimate heads. Study 2 employed a sentence-combining experiment. Fifty NSs of Cantonese studying Japanese in Hong Kong took the test, which controlled for the animacy of head noun phrases and arguments of the verbs. Results revealed no significant difference between SU and DO, which were both easier than OBL, with only a minimal effect of animacy. However, errors of converting DO and OBL target items into SU relatives almost exclusively involved animate-head items. The results suggest that the NPAH does not predict the difficulty order of Japanese RCs, and that learners use different types of RCs based on the animacy of the head noun.This paper is based on a paper presented at the Workshop on the L2 Acquisition of Relative Clauses (January 28, 2005, Cornell University). We thank the participants at the workshop (in particular, Stephen Matthews and John Whitman), Kevin Gregg, Zoe Luk, William O'Grady, Wataru Suzuki, and the two anonymous SSLA reviewers for their invaluable comments and discussions. Study 1 is part of the first author's doctoral dissertation, submitted to Ochanomizu University, and has appeared in Japanese (Ozeki, 2005b). Study 2 was conducted at the Chinese University of Hong Kong, supported by a Direct Grant for Research from the university. We thank Alexis Chu, Yumi Inoue, Zoe Luk, and Chi-Ming Ho for their assistance in data collection and/or the construction of the test material and the statistical consultants at Cornell University (in particular, Freedom King) for their assistance.

This article reports on a crosslinguistic comparative study of the processing of Japanese relative clauses (RCs) by Chinese-, Sinhalese-, Vietnamese-, Thai-, and Indonesian-speaking second language (L2) learners. A robust finding in studies on the acquisition of RCs in L2 English and other European languages is that subject-gap RCs are easier than object-gap RCs, both in production and comprehension. However, in the case of L2 Japanese studies, the picture does not seem to be as clear as in the English case. This study identifies some factors that might contribute to this situation. The results of a listening comprehension test involving reversible and nonreversible test sentences show that the five groups of learners overall found subject-gap RCs easier to process than object-gap RCs, but that their performances are poor and vary for sentence types in which no semantic cue is available to help identify the grammatical function of the overt noun phrase in RCs, yielding inconclusive results with respect to the question of whether subject-gap RCs are easier than object-gap RCs. Results indicate that when RCs are too difficult for learners to process, first language properties such as head direction, word order, and the relative order of filler and gap affect the manner in which they are interpreted.I am grateful to Stephen Matthews, William O'Grady, Yasuhiro Shirai, and the anonymous SSLA reviewers for their valuable comments. I would also like to thank Chisako Umeda for her help in collecting data.

This quasi-experimental study explores the effects of three types of instruction (form-based, meaning-based, and form- plus meaning-based) on the learning of Japanese relative clauses (RCs) and postsecondary Japanese as a foreign language learners' ability to generalize different types of relativization, examined in comparison to the predictions of Keenan and Comrie's (1977) noun phrase accessibility hierarchy (NPAH). The study investigated whether instruction focused on a marked relativization type could facilitate the learning of other types. Results of comprehension and sentence-combination pretests and posttests showed that although the scores of all three groups increased, the form-based group outperformed the other two groups on both tests. Whereas the comprehension pretest results did not reflect the predictions of the NPAH, participants were able to generalize rules for other relativization types. This study suggests that learners' attention to detailed analysis of form facilitates the learning of RCs in this context, and that the teaching of marked items might inform effective syllabus development in second language relativization.I would like to thank Yasuhiro Shirai for giving me an opportunity to present this paper at the workshop on the SLA of relative clauses held at Cornell University on January 28, 2006. I greatly appreciate the insightful feedback that I received from the participants of the workshop (in particular, Stephen Matthews, James Mitchell, and Hiromi Ozeki) as well as the two anonymous SSLA reviewers, and Kiyoko Toratani, my colleague at York University. This paper is part of my doctoral dissertation to be submitted to the University of Toronto, and I would like to thank my thesis supervisor, Sharon Lapkin, as well as my thesis committee members, Nina Spada, Eunice Jang, and Yuki Johnson, for their continuous support and encouragement. I am also grateful to my former students in the Japanese course for agreeing to participate in this study.

This study examines how Keenan and Comrie's (1977) noun phrase accessibility hierarchy (NPAH) intersects with the typological characteristics of Korean in the acquisition of relative clauses (RCs). Korean has two types of RC constructions: head-external and head-internal. The head-external relative has its head to the right of the RC, whereas the head-internal relative has its lexical head in the RC and is marked by the complementizer kes. In first language development, it has been observed the head-internal type emerges earlier than the head-external type. The current study investigates how the use of the two types of RCs interacts with the NPAH, with a focus on subject (SU) and direct object (DO) RCs in Korean second language development. Oral production data were collected from 40 learners of Korean as a foreign language. The results showed that there was an advantage for SU over DO in the head-external RC and that the head-external construction was preceded by headless and head-internal constructions. The results suggest that a head-external RC in Korean involves the syntactic mechanism of linking the head and the gap relation, whereas this might not be the case for a head-internal RC.The authors would like to thank Yasuhiro Shirai, Stephen Matthews, Virginia Yip, and the anonymous SSLA reviewers for their valuable input and feedback on this paper. Any errors, of course, are our own.

Findings from a longitudinal study of bilingual children acquiring Cantonese and English pose a challenge to the noun phrase accessibility hierarchy (NPAH; Keenan & Comrie, 1977), which predicts that object relatives should not be acquired before subject relatives. In the children's Cantonese, object relatives emerged earlier than or simultaneously with subject relatives, and in their English, prenominal relatives based on Cantonese emerged first, with object relatives followed by subject relatives. These findings are discussed in light of findings on the typology and acquisition of relative clauses (RCs) and the underlying processing motivations of the NPAH. Prenominal object relatives in the bilingual children's Cantonese and English have the same word order as main clauses and can be analyzed as internally headed RCs. The reconceptualization of RCs as attributive clauses (Comrie, 1998a, 1998b, 2002) is supported by children's early RCs lacking a strict grammatical relationship between the head noun and the predicate. Furthermore, as observed by Diessel and Tomasello (2000, 2005) for English, bilingual children's earliest RCs consist of isolated noun phrases (NPs). The early object relatives produced by bilingual children are therefore essentially NPs with the linear order of a main clause, resulting in a configuration that is conducive to early production.We thank Yasuhiro Shirai for organizing the workshop on second language acquisition of RCs at Cornell University in January 2006, where this paper was presented, as well as for his valuable comments on earlier versions of this paper. We thank all the participants at the workshop and two anonymous SSLA reviewers for their comments. Additional feedback offered by William O'Grady, Salikoko Mufwene, and John Whitman is greatly appreciated and hereby acknowledged. We thank our children for their contributions to this paper and all of the members of our research team who have contributed to this work—in particular, Uta Lam for her technical assistance. This research has been fully supported by the Research Grants Council of the Hong Kong Special Administrative Region, China (project Nos. HKU336/94H, CUHK4002/97H, CUHK4014/02H, and CUHK 4692/05H) and direct grants from the Chinese University of Hong Kong (01/02, 03/04).

The articles that constitute the body of this journal issue present rich empirical evidence and theoretical reasoning that relate to the acquisition of relative clauses (RCs). Most are concerned with SLA, more specifically with the acquisition of East Asian languages (in particular, Japanese and Korean) by those who are already speakers of other languages, including European languages. The article by Yip and Matthews (this issue) is slightly different in that it documents the bilingual acquisition of Cantonese and English by children, with English being acquired with a slight lag relative to Cantonese, but, like the other articles, it also provides evidence of the confrontation of European and East Asian languages in the general area of language acquisition.

Why are crosslinguistic generalizations like the noun phrase accessibility hierarchy (NPAH) relevant to our understanding of language acquisition? The answer to this question relies on our view of language universals. In generative linguistics, it is commonly assumed that language universals are based on innate linguistic knowledge. In this approach, languages share some of their basic grammatical properties because the core of human grammar is innate (Crain & Pietroski, 2001). However, this view of linguistic nativism is incompatible with what we know about the neurological foundations of the human mind: Although language has genetic prerequisites, it is biologically implausible that these prerequisites consist of prespecified categories and constraints (Quartz & Sejnowski, 1997).

The purpose of this commentary is to discuss some of the findings and claims of the five articles contained in this special issue that deals with the relationship between the noun phrase accessibility hierarchy (NPAH), first proposed by Keenan and Comrie (1977), and the acquisition of relative clauses (RCs) in three Asian languages—Cantonese, Japanese, and Korean. This topic is of interest to SLA theory for at least two reasons. First, as Ozeki and Shirai (this issue) pointed out, there is significant literature proposing to explain facts about the SLA of RCs involving European languages. This raises the question of whether the NPAH has the same explanatory value for languages that are genetically unrelated and geographically separated. The second reason is that Comrie (1998, 2002) recently proposed that nominal-attributive clauses in some Asian languages differ from RCs in European languages in important ways that might have an impact on whether the NPAH holds true for the acquisition of RCs in these languages.

One of the authors of this commentary conducted her dissertation research (Gass, 1979) on relative clause (RC) acquisition and, with the exception of a pedagogical intervention study (Gass, 1982), has since then participated in the discussion of RC acquisition only from afar. Therefore, the opportunity to provide commentary is particularly welcome. The framework adopted in Gass' earlier work was the earliest formulation of the Keenan and Comrie (1977) noun phrase accessibility hierarchy (NPAH). In what follows, we build on and extend that earlier work within the context of SLA.

The articles in this special issue present very interesting data on the acquisition of relative clauses (RCs) in Japanese, Korean, and Cantonese. The errors and developmental patterns are partially different from those that have been observed in European languages, and they appear to go against predictions made by the Keenan and Comrie (1977) noun phrase accessibility hierarchy (NPAH).

The use of the noun phrase accessibility hierarchy (NPAH) as an explanation for the use, interpretation, or both of relative clauses (RCs) by second language (L2) speakers is one of the earliest examples of an attempt to offer a principled hypothesis about L2 development. Its explicit claims have allowed empirical testing that has produced important counterexamples, including the results of the studies reported in this special issue, which suggest that the hierarchy is not applicable to the SLA of languages like Cantonese, Japanese, and Korean. A weak version of the hypothesis that applies only to languages in which RCs express head-complement dependencies (i.e., postnominal relatives) is just as problematic. I suggest here that the time has come to consign this hierarchy to the history of SLA research and focus on other kinds of question about L2 speakers' knowledge of RCs.

This special issue has attempted to ascertain the universal applicability of the noun phrase accessibility hierarchy (NPAH; Keenan & Comrie, 1977) by extending previous research in this area, which has focused on English and a few other European languages, to East Asian languages. To this end, five empirical studies have been reported; these studies yielded mixed results with regard to their support for the NPAH. Overall, what is striking to me in these results is the fact that despite the expectation of some researchers to find robust counterevidence to the NPAH, many of these studies ended up finding at least partial support for the NPAH, even in East Asian languages.

The study of relative clauses (RCs) has been central to both theoretical linguistics and studies in acquisition. This thematic issue of Studies in Second Language Acquisition makes a very important new contribution in this area by highlighting recent developments in thinking on the structure of RCs crosslinguistically and by introducing new data on the acquisition of Japanese, Korean, and Cantonese as first languages (L1s) and second languages (L2s). In this commentary, I will focus on two themes that emerge from the articles: representation and processing of RCs.

A valuable perspective can be gained by examining whether claims about certain linguistic phenomena that were made largely based on observations from particular languages still hold for similar constructions in typologically different languages. This thematic issue contributes to SLA research in this respect by rethinking the putative universal influence of the noun phrase accessibility hierarchy (NPAH; Keenan & Comrie, 1977) on the acquisition of relative clause (RC) constructions in a second language (L2). The NPAH has been strongly supported by numerous studies in English and other European languages such as French, Italian, and Swedish; the articles in this special issue examine L2 RC acquisition in East Asian languages such as Japanese, Korean, and Chinese.

Publications received.