Florence Myles
email: florence.myles@ncl.ac.uk

Interlanguage corpora and second language acquisition research

This article presents a selective review of the work carried out recently in second language acquisition (SLA) research which makes use of oral learner corpora and computer technologies. In the first part, the reasons why the field of SLA needs corpora for addressing current theoretical issues are briefly reviewed. In the second part, recent literature on corpora and SLA is presented, as well as corpora currently available. The final part of the article demonstrates the way in which computerized methodologies can be used, by presenting a case study of a project whose aim was to construct a database of French Learner Oral Corpora, and by illustrating how the CHILDES tools have assisted in addressing a specific research agenda.

I Introduction

This article presents a selective review of the work carried out recently in second language acquisition (SLA) research which makes use of oral learner corpora and computer technologies. The impetus for One aim of the article is to assess if things have developed since then, and we report on recent efforts to use CHILDES tools in SLA research. The scope of this article is broader, however. In the first part, I briefly review the reasons why the field of SLA needs to make use of corpora for addressing current theoretical issues. In the second part, I present a brief review of recent literature on corpora and SLA (both written and oral), as well as of the corpora currently available. I concentrate on four texts that are representative of the field. One of these was published in 1992 and will serve as a benchmark to assess the progress the field has made since then. The final part of the article concentrates on demonstrating the way in which computerized methodologies can be used, by presenting a case study of a project whose aim was to construct a database of French Learner Oral Corpora, and by illustrating how the CHILDES tools have assisted in addressing a specific research question.

II Need for corpora in SLA

SLA research crucially depends on good datasets to work from. Researchers aim to build models of the underlying mental representations and developmental processes which shape and constrain second language (L2) productions. The language produced by learners, whether spontaneously or through various elicitation procedures, remains a central source of evidence for these mental processes, and the success of SLA research therefore relies on having access to good quality data. If we are to make generalizations about learner development, we need to be able to capture the various stages that learners go through. For this we either need longitudinal data of a number of learners over a lengthy period of time (as the acquisition of a L2 requires a considerable amount of time), or we need very large cross-sectional datasets, so that the number of learners in each well-defined stage is big enough for us to be confident that the results of the analysis are generalizable (or to capture what is variable in language development across learners for that matter).

In a field that is traditionally not very well funded, the cost of collecting such corpora is often prohibitive, and datasets tend to remain small and limited in scope (e.g., containing very focused data aiming to answer a specific research question). Moreover, these datasets are usually not accessible to the research community as a whole, for a number of reasons. However, it is now extremely easy to store and manage data digitally on any PC, and just as easy to make it available to other researchers on the web. The field of first language (L1) acquisition research has been doing this for some considerable time, and is consequently much more sophisticated than we are in its use of computerized methodologies.

For the purposes of fundamental SLA research, oral data is an important window into learners' underlying mental grammars, and may be relatively freer of metalinguistic interference than written data, which is complicated by additional layers of learnt knowledge and monitoring processes. This is not to say that written data is not highly suitable for some research agendas, for example in the fields of second language writing or literacy development, as well as to assist in the design of various pedagogical tools such as L2 dictionaries or L2 reference grammars, but it is less suitable for other kinds of research. For this reason, we only briefly review written corpora here, concentrating on the collection and analysis of oral corpora.

L2 written corpora, however, are much more readily available than oral ones. Part of the reason, of course, is that they are much easier and cheaper to collect, and therefore do not require as large an investment as oral corpora. Such corpora often consist of learner essays, which are usually part of the assessment the learners have to produce as part of their course, already in electronic form. The pioneering work done by Sylvianne Granger and her team in constructing the International Corpus of Learner English (ICLE; [START_REF] Granger | Learner English on computer[END_REF], or the extensive Longman Learners Corpus, are good examples of this. Oral corpora, on the other hand, remain rare.

Why is it imperative at the present time for SLA research to make use of new technologies, rather than to carry on handling data manually? The reasons are numerous. In its exploratory phase, the SLA research community has learnt a lot from detailed case studies or studies involving small numbers of learners. This has served its hypothesisbuilding endeavours very well, in the same way as in L1 acquisition, a somewhat older field of research, detailed descriptive case studies of individual children formed the starting point for hypothesis generating. Time has now come, though, to test some of the current hypotheses on larger and better constructed datasets, as has happened in L1 acquisition. Not only do we need large datasets in order to be able to generalize our findings, but some of the structures which are crucial for informing current debates are rarely found in learner data. They therefore either must be elicited specifically, or large datasets are needed in order to maximize their chance of being present. It is therefore now crucial that, as a field, we generate and make available to the research community a good range of well-constructed datasets.

Another reason for advocating the creation of electronic databases of oral corpora is that they become amenable to computerized analysis. As I demonstrate later on in this article, software tools allow us to manipulate the data in a number of ways, from the automatic morphosyntactic tagging of large datasets, to the carrying out of complex searches on batches of files. Having digitized sound files also allows us to use dedicated speech analysis software in order to address, e.g., research questions in language processing or phonology. An added, if incidental, benefit of sharing corpora across the research community, is that we will have to agree on procedures for so doing, from transcription conventions, to ethical codes of practice, for example, and thus we will become more rigorous in our practices. At present, for example, there are nearly as many transcription systems as there are researchers in SLA, which makes it difficult to share data, not to mention the fact that some coding systems might not meet expected standards.

III Corpora and SLA

In this section I present a brief review of four key texts dealing specifically with corpora in Applied Linguistics / SLA. The aim is to present a critical evaluation of how corpora have been used to enhance (or not, as the case may be) research in SLA.

I start with a book published in 1992, Computers in Applied Linguistics, an edited collection of papers presented at an international conference on this topic in 1987 (Pennington and Stevens, 1992). This enables me to assess any significant differences some 10-15 years later. A whole section of this book is dedicated to 'Research on applications of computers in second language acquisition', containing 4 chapters (out of the total of 13), the other two sections being devoted to 'Frameworks for computer-assisted language learning in the 1990s' (3 chapters) and 'Analysis tools for a new generation of language applications' (5 chapters, one on the computational analysis of language acquisition data). The volume overall is primarily about the use of computers in the classroom and on how to evaluate its efficiency. Even in the SLA section, only one chapter (by Catherine Doughty) reports an SLA study making use of computers both in the study design (in order to control the instructional context) and in order to assist with data analysis in an interesting if somewhat limited way. The chapter on 'Computational analysis of language acquisition data' (by Manfred Pienemann) presents the first software designed specifically for the analysis of L2 learner data, outlining promising developments in this area. This software, however, remained little used by the research community, and is no longer available. Overall, the focus of this book is quite explicitly on CALL, which of course was developing at a very fast rate at the time, and the application of computers to SLA research remained very limited.

Hunston's Corpora in Applied Linguistics was published in 2002, and explicitly focuses on English corpus linguistics in general, and on its application to teaching. In the whole book, only 6 pages are devoted to learner corpora and, even then, exclusively to advanced learner written English (the ICLE corpus). Although the ICLE corpus [START_REF] Granger | Learner English on computer[END_REF] is undoubtedly the best established learner corpus available to date, it remains limited in a number of ways (cross-sectional, written data, advanced learners only), and the view that emerges from this chapter is somewhat narrow in terms of the possibilities learner corpora can offer in this area. Given the almost exclusive focus of the book on the relevance of corpora to language teaching, no mention is made anywhere of the use of corpora in language acquisition research more generally (e.g., the huge impact of the CHILDES database in L1 acquisition research), and the immense possibilities offered for the analysis of many different aspects of language acquisition are not alluded to. This volume, if thin on SLA applications, nonetheless contains an excellent description of the different kinds of tools that have been used in corpus research, and is well worth reading by novices to this field. Granger, Hung and Petch-Tyson's volume (2002), after a critical evaluation of the field, is split into 2 sections: the first section contains three studies illustrating the use of corpus-based approaches to the analysis of learner language. The second section, comprising 5 chapters, is about the pedagogical relevance of learner corpus work, and need not concern us here.

Granger's excellent introductory chapter 'A bird's eye view of learner corpus research' gives a very good overview of learner corpus research to date, as well as very sound advice on how to design and exploit corpora. She stresses two main approaches to the linguistic analysis of L2 corpora: Contrastive Interlanguage Analysis (CIA), which compares learner productions to either native corpora or corpora of other learners (e.g., different levels, different L1s), or both, and computer-aided error analysis. The latter is undoubtedly of interest to teachers, but probably less so to SLA researchers who have moved away from looking at learner language in terms of its deviations, and have focused instead on analysing the linguistic system in its own terms. Various software tools available to researchers are then presented, from text retrieval to annotation (Part of Speech tagging and error tagging). Somewhat surprisingly, the CHILDES suite of software is not even given a mention here, in spite of its success in supporting a similar research agenda in L1 acquisition, and the fact SLA researchers have appealed for its use [START_REF] Rutherford | The child language data exchange system in research on second language acquisition[END_REF][START_REF] Ellis | Reflections on frequency effects in language processing[END_REF], or used it themselves, e.g., in the very volume Granger is introducing here [START_REF] Housen | A corpus-based study of the L2 acquisition of the English verb system[END_REF]. Also, one of the main research agendas in SLA, namely the documentation and explanation of learner development over time, for which longitudinal oral corpora are crucial, is not given a mention either.

The first two chapters presented in the volume are typical in many ways of current L2 research using corpora. Altenberg investigates the use of make in advanced learners of English (French and Swedish L1), using the ICLE corpus, comparing their written production to a corpus of native US English [START_REF] Altenberg | Using bilingual corpus evidence in learner corpus research[END_REF]. He suggests that transfer is taking place, and this is explained in terms of prototypicality.

The second study [START_REF] Aijmer | Modality in advanced Swedish learners' written interlanguage[END_REF] compares the use of key modal words in native English and in advanced L2 learners (L1 Swedish; some L1 German and French). It uses the ICLE corpus too, and makes interesting suggestions about possible pedagogical implications.

Both these chapters are good examples of the kind of studies that corpus linguistics have made much easier to carry out: they rely on large written corpora and focus on the use of discrete items in different cross-sectional populations (typically one or more L1s compared to native use). Concordancers and the availability of written corpora have made this kind of investigation very easy to carry out.

Housen's chapter in this volume is more ambitious [START_REF] Housen | A corpus-based study of the L2 acquisition of the English verb system[END_REF]. This is the only study that is about the acquisition process itself, and that relies on oral data produced by learners at different stages of development, combining a longitudinal dataset of 6 learners followed over 3 years to a cross-sectional dataset of 40 learners. The corpus used is the Corpus of Young Learner Interlanguage (CYLIL), consisting of English L2 data elicited from European School pupils from different L1 backgrounds (Dutch, French, Greek and Italian; 500,000 words). A control group of 8 native English-speaking children performing the same tasks was also used. The whole corpus has been transcribed, segmented, coded and annotated using the CHILDES range of software tools, enabling a very sophisticated analysis of the development of the verb system in these learners to be carried out. This study exemplifies very well the tremendous possibilities offered by the use of well developed software and good quality datasets. This is, however, atypical of the studies presented in this volume.

In the Aston et al. volume, Corpora and Language Learners (2004), a whole section is devoted to learner corpora (or corpora by learners, as they call them), totalling 6 out of 15 altogether, one of which is on the L1 acquisition of English, and which therefore will not be included in this discussion. This leaves 5 chapters. The range of L1s (Japanese, Swedish, Polish, German and Chinese) has grown when compared to other volumes. The target language, however, remains English in all cases. All the corpora used are written, except for one study which complements a large written corpus with a small spoken one. Two of the studies also include an L1 corpus for comparison purposes, and all studies except one use a native corpus of the target language, English. The British National Corpus (BNC) sampler is used for this purpose in two cases, ELT books in one case, and government reports in another case. All the learners investigated are advanced (although it is difficult to determine from the information given in the study by Tono), and a wide range of areas are investigated, as follows:

• subcategorization frames of verbs (Tono);

• L1 syntactic transfer, as evidenced by POS (Part of Speech) sequences (Borin and Prütz); • demonstratives (Lenko-Szymanska);

• support verb constructions (Nesselhauf);

• lexis (Flowerdew).

These studies employ of a range of software in order to assist the analysis. Two studies made use of the concordancer WordSmith [START_REF] Scott | WordSmith tools[END_REF], in one case complemented by APPRAISAL. Two studies made use of POS tagging or syntactic parsing, complemented in one case by pattern matching, ChaSen and the Comlex Lexicon. So, a wider range of L1s, of target structures, and of computerized tools are used in the studies presented in this volume, when compared with the earlier volumes reviewed here. However, the focus remains overwhelmingly on written advanced English L2 productions, with the limitations this implies.

To conclude this section, although the reasons why L2 corpora seem to be almost exclusively written and produced by advanced learners (ease of collection, and more readily comparable to equivalent native corpora than corpora from beginners), it still remains puzzling why so little use has been made in SLA research of oral corpora, or of tools such as CHILDES. Out of all the work reviewed in this section, only Housen capitalizes on it. Most of the studies using corpora make little use of software other than concordancing, and remain for the most part rather unambitious in their use of new technology. They also often remain rather descriptive, documenting differences between learner and native language rather than attempting to explain them, and the developmental dimension is almost totally lacking. Corpus-based L2 studies are also often not sufficiently informed by SLA theory, and tend to assume that finding out differences in use between learners and native speakers will have direct pedagogical implications, which is of course not necessarily the case. Such research is useful nonetheless, as we need to have good descriptions of learner language in order to inform our understanding of what shapes its development, but it is now time that corpus linguists and SLA specialists work more closely together in order to advance both their agendas.

IV The FLLOC database: a case study

The last section in this article briefly presents a current research initiative, which has led to the construction of a database of oral French L2 corpora, available from the internet and comprising transcripts, sound files, and morphosyntactically tagged transcripts. This database will be used to demonstrate the possibilities offered by such technology. After a brief presentation of the software and database, I illustrate how the various tools available in CHILDES can assist in investigating specific research questions, making the results more generalizable and reliable than would be the case with a small sample of learners. For more details of the database and its methodology, see, e.g., [START_REF] Myles | Using information technology to support empirical SLA research[END_REF].

The CHILDES system

In the early 1990s, a research team at the University of Southampton collected large amounts of data from classroom learners of French. The 'Progression Project' [START_REF] Mitchell | Progression in foreign language learning[END_REF] followed 60 children (12 to 14 year-olds) longitudinally for their first 27 months of learning French in the classroom, and includes some 650 transcripts, primarily of children engaged in 1:1 oral tasks with a researcher. In the context of a later project [START_REF] Myles | Linguistic development in classroom learners of French: a crosssectional study[END_REF], a cross-sectional study of classroom learners at the next stages of development, the team was acutely aware that the extremely rich data from the Progression Project was not exploited to its full potential, as it was not readily available to other researchers for further study, and only a relatively small subset of the database had been analysed manually [START_REF] Mitchell | Rote learning, creativity and 'understanding' in classroom foreign language teaching[END_REF][START_REF] Myles | Rote or rule? Exploring the role of formulaic language in classroom foreign language learning[END_REF][START_REF] Myles | Interrogative chunks in French L2: a basis for creative construction[END_REF]Myles, 2003;2005). The research team therefore decided to investigate the possibility of using computerized methodologies in helping them manage, store, share and analyse the data. Two attempts were made in the 1990s to develop analysis software specifically to deal with L2 data: COALA developed by [START_REF] Pienemann | a: Computational analysis of language acquisition data[END_REF] and COMOLA by [START_REF] Jagtman | Report -COMALA: a computer system for the analysis of interlanguage data[END_REF]. However, it seems these programs have been discontinued, and no POS tagging software is currently available that has been specifically designed for SLA data handling and analysis. By contrast, in the L1 acquisition field, software for the storage, management, sharing and analysis of L1 data (the CHILDES system), has been developed in an ongoing way since the early 1980s, and is now very widely used in L1 research. After investigating the various options, the team came to the conclusion that the CHILDES system was the most suitable option, with the proviso that some SLA-specific adaptations must be practicable. The reasons were many:

• It is a well developed and well supported system, used as standard within the L1 research community and constantly updated and refined. • It seemed relatively flexible and capable of being adapted to specific needs. • The policy of open access adopted by CHILDES makes accessibility and data sharing very straightforward.

CHILDES offers a suite of software options including word-based programs that can be used to carry out concordancing, frequency counts, etc. Most importantly, CHILDES also makes available POS taggers for a range of languages (currently 10 languages,1 with 4 more in preparation). The POS taggers are relatively easy to modify according to specific criteria and research needs. In its latest version, the CHILDES system is also now XML compatible.

The CHILDES set of tools was originally conceived for L1 acquisition research, but has also been used for research into language disorders and by some L2 researchers [START_REF] Paradis | The emergence of tense and agreement in child L2 French[END_REF][START_REF] Housen | A corpus-based study of the L2 acquisition of the English verb system[END_REF][START_REF] Malvern | Investigating accommodation in language proficiency interviews using a new measure of lexical diversity[END_REF]. CHILDES tools have been used in well over 1300 published studies ranging from L1 acquisition to computational linguistics, language disorders, narrative structures, literacy development, phonological analyses and sociolinguistics (MacWhinney, 2000a;2000b). All CHILDES tools are available free of charge on the internet (http://childes.psy.cmu.edu). CHILDES consists of three integrated components:

• A large and diversified database (TalkBank) consisting primarily of child speech recordings and transcriptions, but also including some language disorder data and bilingual data. It is a condition of using CHILDES tools that the data becomes part of the TalkBank database.

There are increasing numbers of second language acquisition datasets available in TalkBank; for example: -The Ionin corpus (Russian immigrant children learning English; 22 participants aged 2;4 to 12;5). -The Reading corpus (34 oral GCSE examinations taken by 16-yearold English learners of French within the UK education context). The speech recordings and transcripts from these corpora can be downloaded from TalkBank for further study. An online browsing facility should soon be available to locate data for further in-depth analysis. -The LIDES corpus (The Language Interaction Data Exchange System) is the database arising from the Language Interaction in Plurilingual and Plurilectal Speakers Project (LIPPS). The researchers involved have used their own list of coding conventions based on the CHILDES conventions. For example, they specifically tag each word/morpheme to indicate its language (http:// talkbank.org/data/LIDES/). The LIPPS research team have produced a coding manual which is available to other researchers. -Part of the FLLOC database (Progression project and Linguistic Development project, mentioned above) has now also been added to TalkBank, and the rest will follow soon.

• CHAT (Codes for the Human Analysis of Transcripts) are the transcription procedures that have been developed to be compatible with the analysis programmes.

• CLAN (Computerized Language Analysis) consists of about 40 core computer commands for carrying out searches and counts, along with a range of 'switches' that can be used to customize each command. This is a powerful and flexible software package that can carry out rapid and detailed analyses and is designed to recognize the tagging conventions of CHAT.

a Tiers: The CHAT transcription system is organized in tiers: the main speaker tier, starting with *, contains the language actually produced. In addition to this main tier, a limitless number of 'dependent tiers' can be added on separate lines, which always start with %, and contain any coding of the data. Examples of such tiers are the %err tier (on which errors are coded), the %mor tier (containing morphosyntax tagging) a %com tier (commentary) and a %pho tier (phonological coding).

The transcription conventions are specified in the CHILDES manual available on line (http://childes.psy.cmu.edu) and must be adhered to for the CLAN programs to run successfully on the data. It is, however, possible to add various adaptations, e.g., for SLA specific purposes. For details of how this has been achieved in the context of the case study database, see [START_REF] Marsden | Using CHILDES tools for researching second language acquisition[END_REF] and [START_REF] Rule | Constructing a database of French interlanguage oral corpora[END_REF].

b %mor tier: A particularly useful tool in CLAN (MOR) generates morphosyntactic tagging of the main line automatically. Versions of MOR have been produced for a range of languages (10 at present); the MOR parser for French was developed by Christophe Parisse in 2001. Below is an excerpt from a transcript with an added MOR tier from the Linguistic Development Corpus (see database content below). The extract comes from the file of a year 10 learner (a 15-year-old; 39-months of classroom French) carrying out an elicitation task focusing on the use of negation. *29N is the speaker line for the learner and *ELD the speaker line for the researcher. The %mor line can be generated very quickly on large batches of files, and other CLAN commands then enable searches to be carried out directly for morphosyntactic strings on this output.

CLAN commands

The range of CLAN tools aiming to assist analysis includes standard concordancing facilities as well as various searches on the different tiers. Depending how the data has been coded, lexical, morphosyntactic, discourse and phonological analyses, amongst others, can be carried out. CLAN programmes such as FREQ, KWAL and COMBO facilitate analyses of the frequency and linguistic context of interlanguage features. FREQ creates a file that provides the lexical range and frequency in a given file or group of files. KWAL operates like a concordancer and will search the data for specified words and outputs these keywords in context. FREQPOS does a frequency analysis by sentence position and MLU calculates the mean length of utterance. COMBO searches for specific words, word sequences or combinations of lexical items on the main tier, as well as directly on any of the dependent tiers, for example, for morphosyntactic or 'error' codes. In addition, the results of one analysis can be 'piped' through another analysis, allowing multiple analyses.

Using CLAN to address specific research questions

This section illustrates the use of CHILDES to answer specific research questions, by demonstrating how searches can be carried out directly on the morphosyntactic output (the %mor line). For example, you can search at the touch of a button for all instances of, say, masculine determiners followed by a feminine noun. You can do that for a specific learner over time (in the case of longitudinal corpora), or for batches of learners who share a given characteristic (e.g., school year; or performing a specific task). For details of how to carry out such searches, see e.g., [START_REF] Marsden | Using CHILDES tools for researching second language acquisition[END_REF]; [START_REF] Rule | Constructing a database of French interlanguage oral corpora[END_REF]; [START_REF] Myles | Using information technology to support empirical SLA research[END_REF].

A recent study (Rule and Marsden, in press) investigated the development of negatives in relation to finite and nonfinite verbs in the emerging grammars of early learners of French. Differences in negative placement in French and English are a result of the verb raising past the negative in French but not in English (strong vs. weak Infl): the French negative particle pas occurs after a finite lexical verb in French (1), but in English not cannot occur after a finite lexical verb (2) and the dummy auxiliary do needs to be inserted (3). The verb does not raise over negation if it is nonfinite (4) (for more details of verb raising in French, see [START_REF] Hawkins | Second language syntax: a generative introduction[END_REF].

1) Jean ne regarde pas la television. 2) Jean (ne) watches not the television. 3) John does not watch television. 4) Jean regarde la télévision pour ne pas s'endormir John watches television to not sleep, i.e., in order not to fall asleep Rule and Marsden therefore traced all occurrences of the following in the data:

• pas followed immediately by infinitive;

• pas followed immediately by verb in present;

• verb in present followed immediately by pas;

• infinitive followed immediately by pas.

This could be done extremely easily, across the whole corpus, using a COMBO directly on the %mor tier. For details, see [START_REF] Rule | French interlanguage corpora: recent developments[END_REF]; Rule and Marsden (in press). After this brief survey of the possibilities offered by the CHILDES system to assist L2 analysis, let us now turn to a brief description of the database which supported these analyses.

5 The database (www.flloc.soton.ac.uk)2

The French Language Learner Oral Corpora (FLLOC) website contains an electronic database freely available to the research community, in the form of digital sound files and transcripts formatted using CHILDES conventions. The database also comprises a search facility, which enables researchers to select the sound files and transcripts they wish to access, according to criteria such as the level of the learners, the elicitation task used, the sex of the participants, etc. The corpora included in the database have all been digitized and edited to ensure anonymity, and the transcripts have been (re)formatted according to the CHILDES system. Details of the CHILDES tools are given, and additional transcription conventions are specified in the context of each project. Additionally, most of the transcripts have been tagged using the French MOR program, and the resulting files, i.e., transcripts that have been tagged morphosyntactically, have been made available also.

The corpora included in the database come from diverse sources, but have all been donated for shared use by SLA researchers in the United Kingdom and in mainland Europe. There are 5 in total to date, representing instructed learners of L2 French from complete beginners to final year university undergraduates, undertaking a range of interactive and narrative tasks. The database currently includes 1375 transcripts and accompanying sound files, as well as tagged files in some cases, as follows:

• 60 learners in years 7, 8 and 9 in the UK context: beginners at outset of data collection; age 12-14; longitudinal over 27 months; range of 1:1 narrative and interactive tasks, e.g., story retelling, information gap, structured conversation, etc., 650 transcripts and sound files, approximately 10-15 minutes each; • 20 learners in each of years 9, 10 and 11 in the UK: post-beginners; age 14-16; cross-sectional; four 1:1 tasks each, some repeated from above project; 240 transcripts/sound files, around 10-15 minutes each; Each corpus is accompanied by a project description, which includes details of the learners and the tasks used, any additional transcription conventions used, plus an overview of the files contained in the database, and how each one is organized. Files (sound files, transcripts and tagged transcripts) can be directly downloaded for use by bona fide researchers who sign up to an explicit users' code.

V Conclusions

What can we conclude about the progress made in the last decade or so in the use of corpora in SLA? Some progress has undoubtedly been made, and there are now some L2 corpora available. My concern is that the kind of studies that are being undertaken are too closely dependent on what corpora are at hand, and what software tools are available. For reasons explored in Section I, the kind of corpora that are readily available are not necessarily those most suited to the investigation of SLA acquisition processes; they are nearly always written, crosssectional and overwhelmingly from advanced learners of English.

Although these corpora clearly have their place in the range of SLA studies the field needs to undertake -especially at the level of lexis, discourse and pragmatics at an advanced level -and are of interest to university teachers of such learners, the field needs to become much more ambitious in its use of new technologies, and in the kind of corpora it collects in order to address its current research agenda. For this purpose, we need good quality longitudinal oral corpora, in a range of different L1/L2 combinations, for the reasons outlined in Section II.

The possibilities offered by the computerized analysis of corpora are considerable, as I hope to have demonstrated. SLA researchers, however, need to make sure that not only the corpora they collect but also the computerized tools they use are adapted to their research agendas, rather than the other way round, i.e., adapting their research questions to the corpora or the tools readily available. Some sophisticated tools can be used, and it is high time that the pioneering work of L1 acquisitionists in this area is emulated by L2 researchers.

  • 34 learners: post-beginners; age 16; UK GCSE oral examination; 26 native controls; 60 transcripts; • 12 university undergraduate learners in the UK: intermediate to advanced; longitudinal; narrative and interactive tasks; 300 transcripts and sound files; approximately 5-10 minutes each; • 125 Dutch learners of French: intermediate; narrative task; 18-yearolds; 125 transcripts.

Cantonese, Danish, Dutch, English, French, German, Hungarian, Italian, Japanese and Spanish.

This project was supported by grants from the Economic and Social Research Council (RES000220070) and the Arts and Humanities Research Board (RE-AN9657/APN15456). I wish to thank the research team involved in these projects: Rosamond Mitchell, Sarah Rule, Emma Marsden, Vladimir Mircevski.

Appendix 1 List of corpora mentioned


Reading-time studies of second language ambiguity resolution

Despina Papadopoulou Aristotle University of Thessaloniki

This article provides a review of studies that have examined the ambiguity resolution strategies employed when processing a second language (L2). The way second language learners parse the L2 input has not yet been thoroughly investigated, although recently there has been an increasing interest in this area. The exploration of the mechanisms L2 learners use to parse ambiguous constructions allows us to examine not only aspects of L2 acquisition that still remain obscure, but also the validity of existing theories of parsing. The studies reported in this article look at three different types of ambiguous construction in the L2, and their results are discussed in relation to the L2 performance pattern. Most of the findings show that even advanced L2 learners are slower readers than native speakers and apply processing routines that depart from those best suited for processing the target language input. In addition, although L2 learners show sensitivity to lexical cues such as verb argument structure when processing the L2 input, they are less likely to rapidly employ structural information on line. The issues of the transfer of processing mechanisms from the first language (L1) to the second as well as the impact of L2 exposure on the adoption of the L2 processing routines are still unresolved and need to be further investigated.

I Introduction

One issue in second language (L2) acquisition that has not yet received a lot of attention is the way L2 learners process the second language Address for correspondence: Despina Papadopoulou, School of English, Department of Theoretical and Applied Linguistics, Aristotle University of Thessaloniki, Thessaloniki 540 06, Greece; email: depapa@enl.auth.gr input in real time. However, the construction of the target grammar has to be driven by the input, and the way people process sentences in real time is important to fully understand the development of the L2 grammar (for discussion of the relationship between input and grammar construction, see, for example, [START_REF] White | Second language competence v. second language performance: UG or processing strategies[END_REF]Fodor, 1999;[START_REF] Klein | Just parsing through: notes on the state of L2 processing research today[END_REF][START_REF] Klein | Investigating second language grammars: some conceptual and methodological issues in generative SLA research[END_REF]. Besides, many researchers in L2 acquisition [START_REF] Chaudron | Intake: On models and methods for discovering learners' processing of input[END_REF][START_REF] Fernández | Processing strategies in second language acquisition: some preliminary results[END_REF][START_REF] Klein | Just parsing through: notes on the state of L2 processing research today[END_REF][START_REF] Juffs | Parsing effects in second language sentence processing: subject and object asymmetries in wh-extraction[END_REF][START_REF] Crocker | Computational psycholinguistics[END_REF] have raised the question of whether the incomplete acquisition broadly observed in L2 learners is due to non-optimal parsing mechanisms employed by the learners. Hence, more recently research on L2 sentence processing has started to appear (for reviews on L2 sentence processing, see, for example, [START_REF] Harrington | Sentence processing[END_REF]Juffs, 2001) along with an increasing use of on-line experimental techniques in L2 research (for reviews of psycholinguistic methods used in L2 research, see Juffs, 2001;[START_REF] Marinis | Psycholinguistic techniques in second language acquisition research[END_REF].

One area that has been thoroughly investigated in the field of first language (L1) sentence processing is syntactic ambiguity resolution. Many studies have looked at globally or temporarily ambiguous constructions in order to examine what kind of strategies and what types of information native speakers use in order to resolve structural ambiguities on line. Broadly speaking, there are two classes of sentence processing models, which make different assumptions with respect to the way ambiguous material is disambiguated in real time. On the one hand, there are models such as the garden-path model [START_REF] Frazier | The sausage machine: a new two-stage parsing model[END_REF][START_REF] Frazier | Theories of sentence processing[END_REF] that give predominance to the use of purely syntactic information such as phrase-structure rules, at least during the initial processing stage. On the other hand, interactionist or constraintsatisfaction models (see, for example, MacDonald, 1997;[START_REF] Thornton | Accounting for crosslinguistic variation: A constraint-based perspective[END_REF]1999) assume that all kinds of information that are available to the parser interact with one another and affect even the initial analysis of ambiguous sentences. Another hot issue in the area of L1 syntactic ambiguity resolution is the universality of the human sentence processor. At one end, there are processing theories that argue for a universal parser (see for example, [START_REF] Frazier | The sausage machine: a new two-stage parsing model[END_REF][START_REF] Frazier | Construal[END_REF][START_REF] Frazier | Theories of sentence processing[END_REF][START_REF] Fodor | Learning to parse?[END_REF], whereas at the other end there are experience-based accounts that claim that the parsing decisions are determined by frequency records based on people's history of exposure to a specific language input [START_REF] Mitchell | Exposurebased models of human parsing: evidence for the use of coarse-grained nonlexical statistical records[END_REF]. 1 In this article, I review reading-time studies that have examined how L2 learners process ambiguous constructions on line. I use the term 'L2 learners' to refer to people who have learnt a second language during adulthood, and I do not present the results from studies with participants who grew up with two languages.2 As far as I am aware, existing studies on ambiguity resolution in the second language have investigated three types of ambiguous construction, namely main verb vs. reduced relative clause ambiguities, subject vs. object ambiguities, and relative clause attachment ambiguities.

The main research questions these studies have addressed are the following:

• Do L2 learners transfer parsing mechanisms from their first language to the second language? • Are L2 learners able to acquire the parsing mechanisms employed by native speakers of the target language? • Does consistent or prolonged exposure to the L2 input result in the adoption of native-like parsing routines? In what follows I first introduce the self-paced reading method used in the experiments to be reviewed. I then present a review of studies that have examined the aforementioned ambiguities in a second language, such that one section is devoted to reporting the findings for 1 An extensive review of the various parsing models lies beyond the purpose of the present article. For a detailed review of processing theories, the reader is referred to [START_REF] Pritchett | Garden-path phenomena and the grammatical basis of language processing[END_REF][START_REF]Parsing with grammar: Islands, heads, and garden paths[END_REF][START_REF] Macdonald | Probabilistic constraints and syntactic ambiguity resolution[END_REF]Mitchell, 1994;[START_REF] Gorrell | Syntax and parsing[END_REF][START_REF] Crocker | Computational psycholinguistics[END_REF][START_REF] Altmann | Ambiguity in sentence processing[END_REF][START_REF] Pickering | Sentence comprehension[END_REF][START_REF] Harrington | Sentence processing[END_REF] each type of ambiguity. In the final section, the results from all the studies are brought together, and some general conclusions are drawn with respect to the research questions raised above.

II The self-paced reading technique

Many studies in the field of sentence processing have used the selfpaced-reading (SPR) technique, the eye-tracking methodology or the cross-modal priming paradigm. SPR tasks yield on-line reaction time (RT) measures that provide a record of participants' reading performance during comprehension. Sentences are presented either in a word-byword or phrase-by-phrase fashion. The participants read sentences divided into segments on a computer screen, and the appearance of the next segment is triggered by the participants' pressing of a button. The time participants take to request the next word or phrase is measured. The visual presentation of the stimuli in SPR tasks can be either cumulative or noncumulative. The difference between the cumulative and the noncumulative presentation is that in the latter case the appearance of the next segment induces the disappearance of the previous one [START_REF] Just | Paradigms and processes in reading comprehension[END_REF], whereas in the former case the previous words remain displayed on the screen. The advantage of the noncumulative or 'moving window' technique is that readers cannot look back to the phrases or words they have previously read and are thus encouraged to keep up to date with their processing (Mitchell and Green, 1978: 610).

In eye-tracking experiments, participants' eye-movements are recorded in order to measure the time they take to read specific constructions. The data obtained are usually divided into first-pass reading times reflecting the initial reading of a particular word or phrase, and second-pass reading times reflecting regressions and rereads of the material (for a detailed description of the eye-tracking method and its use in psycholinguistic research, see [START_REF] Ferreira | The Independence of syntactic processing[END_REF][START_REF] Rayner | Eye movements in reading: A tutorial review[END_REF][START_REF] Rayner | Eye movements and on-line language comprehension processes[END_REF]. The cross-modal priming paradigm requires participants to listen to speech over headphones while simultaneously looking at a computer screen and to perform a lexical decision task on visually presented words. The cross-modal priming task has been widely used in the area of lexical ambiguity resolution as well as in studies seeking to test antecedent reactivation at gap positions. The studies presented and discussed in the following sections all employ the noncumulative SPR method.3

III The main clause vs. reduced relative clause ambiguity

The main verb vs. reduced relative clause (RC) ambiguity lies on the fact that in English there is often syncretism between the simple past tense and the passive participle verb forms. For example, in sentence (1) people usually analyse the word squeezed as a main verb so that encountering the word could induces a garden-path effect4 and forces the reanalysis of squeezed as a passive participle:

1) The elephants squeezed into the booth could not move.

Proponents of the garden-path model of sentence processing have attributed the preference for the main clause over the reduced relative clause analysis to the parsing strategy of Minimal Attachment [START_REF] Frazier | The sausage machine: a new two-stage parsing model[END_REF][START_REF] Frazier | Theories of sentence processing[END_REF]. According to Minimal Attachment, new incoming material is preferably attached in a way that the fewest necessary phrase structure nodes are postulated in accordance with the well-formedness rules of the language. In examples such as (1), the main clause interpretation results in fewer nodes than that of the reduced relative clause, as shown in (2a) and (2b): However, [START_REF] Macdonald | The lexical nature of syntactic ambiguity resolution[END_REF] -supporting the constraint-satisfaction approaches -have argued that the preference for the main clause reading can be overridden given the presence of specific cues. For example, according to MacDonald et al. the argument structure of the first verbnamely whether the verb is transitive or optionally transitive -will affect the interpretation of this verb form as a main verb or as a passive participle. Furthermore, the frequency of a verb form being used as a main verb or as a passive participle is assumed to guide the parser's analysis of the sentence. Juffs (1998a) investigated the main clause vs. reduced RC ambiguity with advanced learners of English and addressed the following questions:

1) Are L2 learners of English able to process sentences such as (1)? 2) Do they show sensitivity to morphological and syntactic cues as well as to the argument structure of the verbs? 3) Is there an impact of the first language on the way L2 learners parse temporarily ambiguous sentences such as (1)?

In order to address the second research question, Juffs (1998a) manipulated three variables:

• the morphology of passive participles (verb forms that are unambiguously marked as participles, like seen in ( 3) and ( 4) vs. ambiguous verb forms like criticised and watched in ( 5), ( 6) and ( 7), (8), respectively); • the plausibility of analysing the word following the first verb form as an object of a main verb (by adding adverbials providing misleading or 'bad' cues such as almost every day in (4), ( 6) and ( 8) vs. adverbials providing 'good' cues such as during the morning in (3), ( 5) and ( 7)); and • the argument structure of the first verb form (transitive verbs like criticize in ( 5) and ( 6) vs. optionally transitive verbs such as watch in ( 7) and ( 8)).

The manipulation of these variables resulted in six conditions exemplified below:

3) Unambiguous participle -good cue:

The bad boys seen during the morning were playing in the park.

4) Unambiguous participle -bad cue:

The bad boys seen almost every day were playing in the park.

5) Ambiguous participle -transitive verb -good cue:

The bad boys criticized during the morning were playing in the park.

6) Ambiguous participle -transitive verb -bad cue:

The bad boys criticized almost every day were playing in the park.

7) Ambiguous participle -optionally transitive verb -good cue:

The bad boys watched during the morning were playing in the park.

8) Ambiguous participle -optionally transitive verb -bad cue:

The bad boys watched almost every day were playing in the park.

In order to investigate a possible L1 influence on L2 parsing strategies, Juffs examined speakers of Romance languages in which RCs follow the head noun, as is also the case in English, and speakers of Chinese, Japanese and Korean, in which the RC precedes the head noun. Moreover, the parsing of RCs in Chinese and Japanese/Korean might involve the reanalysis from a main verb to a relative clause analysis, whereas in Romance languages, although reduced RCs are possible, morphological markers -at least in the written speech -usually disambiguate the verb form.

Juffs conducted an SPR task in which sentences like ( 3)-( 8) were presented word by word via the moving window technique. At the end of the sentence participants had to judge the grammaticality of the sentences they read, thus providing an additional off-line performance measure. The accuracy data from the grammaticality judgement task showed that the Romance speakers were better overall than the Chinese and the Japanese/Korean speakers, and did not significantly differ from the natives, which suggests that L1 grammatical properties can affect performance in a second language. Moreover, the L2 learners, and especially the Japanese/Korean group, were more likely to be misled in their judgements by the presence of 'bad cue' adverbials that followed an ambiguous verb form than were the native speakers.

The reading time data revealed that overall the L2 learners were slower than the native speakers. However, the Chinese learners of English were slower than the other L2 groups, especially when reading the disambiguating region, namely the main verb. In addition, the L2 learners' reading pattern differed from that of the native speakers on the region that contained the passive participle and the following constituent. More specifically, the L2 learners took longer to read sentences that contained a 'bad' adverbial cue -even with unambiguous participles -than sentences in which the adverbial supported the reduced relative clause analysis. This effect was more pronounced in the Chinese speakers, which might be due to the fact that participles are not morphologically marked in Chinese. The RTs on the disambiguating region showed that sentences such as ( 6) and ( 8) were read more slowly than sentences like (3) and ( 5), which shows that both the native speakers and the L2 learners were sensitive to the argument structure of the verbs and the type of constituent following the past participle.

With respect to the question of L2 learners' ability to employ nativelike parsing routines, the findings from this study provide a partially positive answer. This is because even though both L2 and L1 processing were found to be affected by morphological and syntactic cues as well as verb argument structure, the L2 learners differed from the native speakers in that a confusing post-ambiguity cue affected both the L2 learners' RTs and judgements. This finding is interpreted by Juffs as an indication of the fact that L2 learners, when processing L2 input on line, do not feel as confident as native speakers do so that their parsing ability is 'less robust' than that of native speakers (Juffs, 1998a: 133). Notice, however, that the issue of whether L2 learners transfer processing mechanisms from their native to the second language cannot be addressed here as nothing is known about how this kind of ambiguity is resolved in the participants' native languages. Furthermore, Juffs' study offers a dataset from both native speakers and L2 learners that argues against the predominance of Minimal Attachment. The fact that the interaction between verb argument structure and constituent type affected all groups' ambiguity resolution pattern could be taken as evidence against sentence processing models that assume that lexical information does not influence initial parsing decisions. Finally, Juffs' findings suggest that grammatical similarities between the first and the second language in the way (reduced) RCs are construed may influence the processing of these constructions in the L2.

IV The subject vs. object ambiguity

The subject-object ambiguity is illustrated in the following example: 9) Before Mary ate the pizza arrived from the local restaurant.

In (9) the verb of the pre-posed adverbial clause is optionally transitive, and therefore the noun phrase the pizza could be analysed either as its direct object, or as the subject of the following main verb. Studies on the processing of sentences such as (9) with native speakers (for a review, see Mitchell, 1994) have found that a garden-path effect is induced on the main verb, which suggests that the NP the pizza is initially analysed as the object of the subordinate clause verb. The observed preference for the object reading has been accounted for by the Late Closure parsing strategy [START_REF] Frazier | The sausage machine: a new two-stage parsing model[END_REF][START_REF] Frazier | Theories of sentence processing[END_REF], which dictates that new incoming material should be attached to the phrase currently being processed, that is, the VP incorporating the verb ate in examples like (9). Juffs and Harrington (1996) and Juffs (1998b) have investigated how L2 learners process constructions such as (9). 5Juffs and Harrington (1996) conducted an on-line grammaticality judgement experiment -similar to that carried out by Juffs (1998a)investigating L2 learners' processing of subject-object ambiguities, with sentences that involved four verb classes: 10) Optionally intransitive verbs:

After Bill drank the water proved to be poisoned.

11) Purely intransitive verbs:

After Mary died her husband married a woman from Toronto.

12) Verbs subcategorizing for two arguments: Ann warned her friends are unreliable.

13) Verbs subcategorizing for one argument: Ann knew her friends liked Jane.

The participants were very advanced Chinese-speaking learners and native speakers of English. The accuracy data on sentences such as (10)-( 13) showed that both the native speakers and the L2 learners were more likely to reject garden-path sentences such as (10) and ( 12) than they were to reject non-garden-path sentences. The analysis of the RT data revealed that both groups of participants were surprised when encountering the matrix verb in sentences like (10), or the embedded verb in sentences such as ( 12), which points to the conclusion that the L2 learners experienced similar processing difficulties at these points during processing, as did the native speakers. However, the L2 learners differed from the native speakers in the processing of the sentences involving purely intransitive verbs (example (11)). First, their judgements were less accurate on those sentences than the native speakers' and, secondly, they tended to pause on the main verbs longer than the English L1 group.

In a later study, Juffs (1998b) conducted a similar on-line grammaticality judgement task for sentences like ( 10)-( 11) with advanced Chinese, Korean/Japanese and Romance learners of English that replicated Juffs & Harrington's (1996) findings. Furthermore, in this study Juffs found that the Chinese and Japanese/Korean participants also seemed to be puzzled when encountering an NP following a purely intransitive verb in sentences like (11). This result was also present in Juffs and Harrington's study and seems to imply that the Chinese and Japanese/Korean L2 groups experience processing difficulties when they have to open a new clause immediately after an embedded verb (Juffs, 1998b: 415).

Taken together, the results from the above studies on the subjectobject ambiguity show that native speakers and L2 learners use the same parsing strategies for sentences such as ( 10) and ( 12), that is, they seem to employ Late Closure. Moreover, the fact that both groups were garden-pathed when the main verb is optionally transitive implies that they make use of the verb argument structure to parse constructions such as (9)-( 13). This finding also supports sentence processing models which assume that verb argument structure affects ambiguity resolution patterns. 6 In addition, the fact that the Chinese and Japanese/ Korean participants' RTs on the NPs following intransitive verbs were higher than the native speakers' -even though their grammaticality judgements were similar to the native speakers' judgements -indicates that grammatical knowledge and parsing mechanisms might not develop in parallel (see also Juffs, 1998b: 421).

V The RC attachment ambiguity

The RC attachment ambiguity is exemplified in (14) below, in which the RC who was having a glass of wine is preceded by a complex NP (the psychiatrist of the actress) and can potentially be attached to either of the two preceding NPs (i.e., to the psychiatrist or the actress):

14) The woman saw the psychiatrist of the actress who was having a glass of wine.

This particular type of ambiguity has received a lot of attention in the psycholinguistic literature because it seems to provide an example of parametric variation in parsing -the only one that has been clearly identified thus far. Native speakers' RC attachment preferences have been extensively investigated in a variety of languages (for a review, see [START_REF] Cuetos | Parsing in different languages[END_REF], and it has been found that there is cross-linguistic variation in the way constructions such as ( 14) are processed. More specifically, in languages like English, Swedish, Norwegian and Arabic people prefer to attach the RC to the second NP (i.e., the actress), whereas the reverse pattern has been observed in languages like Spanish, French, German, Dutch and Greek. Many parsing models have been put forward to account for RC attachment preferences. 7 In this article, I focus on two of these that are relevant to some of the studies that are reviewed below. [START_REF] Gibson | Recency preferences in the human sentence processing mechanism[END_REF] have proposed that the cross-linguistic variation observed in RC attachment preferences can be captured by the competition of two structural parsing strategies, Recency and Predicate Proximity. Recency, which is similar to Late Closure, is assumed to be universal and forces new material to be attached to the most recently processed phrase, that is, to the second NP in sentences such as ( 14). Predicate Proximity, on the other hand, which is argued to be parameterized, requires new material to be attached as close as possible to the IP node, that is, to the first potential antecedent NP in ( 14). Predicate Proximity is assumed to be 'strong' in languages that have a relatively flexible word order and which do not require adjacency between the verb and its complements (such as Spanish, German, Greek, French, etc.), resulting in an NP1 attachment preference. In languages like English, on the other hand, which require adjacency between the verb and its complements, Predicate Proximity is comparatively weak and is thus outweighed by Recency, which yields an NP2 attachment pref-erence. Furthermore, native speakers' RC attachment preferences are also guided by a lexical principle that requires new material to be attached within the currently processed thematic domain [START_REF] Frazier | Construal[END_REF]. Hence, in a sentence such as (15) the presence of the lexical preposition with signals the beginning of a new thematic domain, thus making the first NP a less accessible host for the RC:

15) The woman saw the psychiatrist with the actress who was having a glass of wine.

The thematic domain hypothesis correctly predicts the NP2 attachment preference that is exhibited across different languages (see, for example, De [START_REF] De Vincenzi | Some observations on the universality of the late-closure strategy[END_REF][START_REF] Gorrell | Syntax and parsing[END_REF][START_REF] Gilboy | Argument structure and association preferences in Spanish and English compound NPs[END_REF][START_REF] Hemforth | Syntactic ambiguity resolution in German[END_REF][START_REF] Traxler | Adjunct attachment is not a form of lexical ambiguity resolution[END_REF][START_REF] Baccino | Cross-linguistic studies of the Late Closure strategy: French and Italian[END_REF]Frenck-Mestre and Pynte, 2000;[START_REF] Papadopoulou | Cross-linguistic variation in sentence processing: evidence from relative clause attachment preferences in Greek[END_REF].

The fact that this particular ambiguity has been widely investigated in a number of different languages makes it a suitable example to test parsing preferences in a second language, because L1 and L2 ambiguity resolution strategies can be directly compared. Moreover, one can examine whether L2 learners transfer L1 sentence processing strategies to the second language, an issue that the studies reviewed in the previous sections were unable to address. On-line RC attachment preferences have been investigated in L2 learners of English, Spanish and Greek. 8Dussias (2001; 2003) tested advanced learners of English and Spanish who were all tested in Spanish. A monolingual Spanish group was also examined for control purposes. Dussias conducted an SPR task using sentences that were disambiguated either towards NP1 (see example ( 16)) or NP2 (see example ( 17)) attachment. The ambiguity was resolved via pragmatic information on the last segment.

16) NP1 disambiguation:

El perro mordió a, cuñada del maestro/que vivió en Chile/con su esposo. 'The dog bit the sister-in-law of the teacher-MASC who lived in Chile with her husband'.

17) NP2 disambiguation:

El perro mordió al cuñado de la maestra/que vivió en Chile/con su esposo. 'The dog bit the brother-in-law of the teacher-FEM who lived in Chile with her husband'.

The sentences were divided into three segments as indicated by the slashes in examples ( 16)-( 17). The RTs on the disambiguating (third) segment showed that, although monolingual native speakers of Spanish showed an NP1 attachment preference, the Spanish L2 learners took longer to read sentences that were disambiguated towards the first NP than the ones disambiguated towards the second. The results from the English L2 learners indicated only a trend for an NP2 attachment preference that was not statistically significant.

The hypothesis that L2 learners transfer ambiguity resolution strategies from their first to their second language cannot account for the English learners' behaviour, as one would have expected them to show a clear NP2 attachment preference. The English participants did not appear to have acquired the relevant Spanish processing strategy, either, as in this case they should have shown an NP1 attachment preference. Dussias (2003) accounts for her results from the English and Spanish learners in terms of Late Closure, which, given the cognitive pressure and memory load demands associated with housing two linguistic systems, is likely to be favoured by the processor. However, a possible alternative explanation -especially for the results from the Spanish learners -is that the participants' daily exposure to English has resulted in the adoption of native-like processing routines and has even shifted the attachment preferences in their first language (Dussias, 2001: 174 -75;[START_REF] Marinis | Psycholinguistic techniques in second language acquisition research[END_REF]. Such an explanation is in line with exposure-based processing models [START_REF] Macwhinney | Applying the competition model to bilingualism[END_REF]1997;2001;[START_REF] Mitchell | Exposurebased models of human parsing: evidence for the use of coarse-grained nonlexical statistical records[END_REF], which postulate that processing preferences are determined by the way temporary ambiguities have most frequently been resolved in the participants' past experience.

RC attachment preferences in English as a second language have been examined by [START_REF] Felser | The processing of ambiguous sentences by first and second language learners of English[END_REF], who conducted an off-line grammaticality judgement and an SPR task with advanced Greek-speaking and German-speaking learners of English. In the grammaticality judgement task, Felser et al. tested whether the L2 learners were able to accept sentences such as ( 14) and ( 15) as grammatical, and whether they were able to detect subject-verb agreement violations in such constructions. The results showed that the L2 learners' grammaticality judgements were similar to those of the native speakers. In the SPR task, Felser et al. investigated RC attachment preferences in sentences that contained complex NPs linked by the functional preposition of (see example ( 18)) and the lexical preposition with (see example ( 19)). The critical items were disambiguated towards either NP1 or NP2 attachment via number information on the auxiliary of the RC, as illustrated below:

18) The dean liked/the secretary of the professors/who/was (were)/reading a letter.

19) The dean liked/the professors with the secretary/who/were (was)/reading a letter.9

The way the sentences were divided into segments is indicated by the slashes in ( 18) and ( 19).

The reading times on the disambiguating auxiliary showed that both L2 groups preferred to attach the RC to the second NP when this was headed by the lexical preposition with, whereas they showed no attachment preferences for either NP in the of-conditions. The native speaker controls, on the other hand, showed a clear NP2 attachment preference for both conditions.

Parallel results were found in off-line and on-line experiments on RC attachment preferences with L2 learners of Greek reported in [START_REF] Papadopoulou | Parsing strategies in L1 and L2 sentence processing: a study of relative clause attachment in Greek[END_REF]. The L2 learners in this study were native speakers of Spanish, German and Russian who were highly proficient in Greek. In this study an off-line grammaticality judgement task, similar to the one conducted by [START_REF] Felser | The processing of ambiguous sentences by first and second language learners of English[END_REF], was also carried out. The results showed no differences between the native speakers and the L2 learners. The participants' RC attachment preferences were investigated using an SPR task, in which the sentences were divided into five segments (as indicated in (20) below). The experimental items were disambiguated via gender information on the passive participle in the RC, and involved complex NPs that incorporated (morphologically expressed) genitives and the lexical preposition me ('with'), as illustrated in the following example: 20) O kirios idhe/ton psihiatro tis ithopiu (ton psihiatro me tin ithopio)/pu itan/kathismen-os (-i)/ston kanape. 'The man saw/the psychiatrist-MASC of the actress (the psychiatrist with the actress)/who was/sitting-MASC (-FEM)/on the sofa.'

Table 1 presents the mean RTs on the critical disambiguating (4th) segment. The results indicate that the Greek native speakers' RC attachment preferences were divergent in the two conditions. More specifically, an NP1 attachment preference was obtained in the genitive condition, whereas in the me ('with') condition there was a preference to attach the RC to the second NP. The L2 learners, however, behaved similarly to those in Felser et al.'s study in that they showed an NP2 attachment preference in the me condition but no preference for either NP in the genitive condition.

The results from Papadopoulou and Clahsen are elucidating for the question of whether L2 learners transfer processing strategies from their native to the second language. In similar constructions to the ones tested in this study, the L2 learners' first languages all manifest NP1 attachment preferences with functional (of-type) prepositions. However, neither L2 group showed any preference for either of the two possible attachment sites in Greek. This finding suggests that the participants in these studies did not transfer their L1 processing routines to the second language.

Furthermore, the highly proficient L2 learners in Felser et al. and Papadopoulou and Clahsen's studies did not show native-like parsing patterns, either. Specifically, Felser et al. and Papadopoulou and Clahsen found that L2 learners' RC attachment preferences differed from those of native speakers in the genitive or of-conditions. According to these authors, this difference is attributed to differences in the types of information native speakers and L2 learners use during on-line processing. They suggest that, although RC attachment preferences in L1 processing are influenced by both phrase structure and lexical information, L2 learners over-rely on lexical cues when parsing the L2 input. Felser et al. and Papadopoulou and Clahsen -following [START_REF] Gibson | Recency preferences in the human sentence processing mechanism[END_REF] and [START_REF] Frazier | Construal[END_REF] -assume that RC attachment preferences in the L1 are influenced by two structural strategies -Recency and Predicate Proximity -as well as by lexical/thematic considerations. The latter result in the NP2 attachment preference exhibited by native speakers and the L2 learners in both English and Greek when the complex NP preceding the RC contains a lexical preposition. In the of or genitive conditions, on the other hand, both NPs are equally available for RC attachment as they both belong to the same thematic domain. In this case, English native speakers show an NP2 attachment preference, in accordance with the Recency principle. In contrast, Predicate Proximity is assumed to be strong in Greek, thus favouring NP1 attachment. As far as L2 learners are concerned, however, because there are no lexical cues that could be used to help resolve the ambiguity in the of or genitive conditions, the learners do not make any commitment to either analysis. According to Felser et al. and Papadopoulou and Clahsen, such a result suggests that even highly proficient L2 learners, while able to use lexical information, might not employ structural information in on-line processing to the same extent as native speakers do. Moreover, the results from Papadopoulou and Clahsen's study argue against exposure-based models of parsing. Both the learners' first (Spanish, German and Russian) and second (Greek) languages show an NP1 attachment preference when the complex NP preceding the RC contains a functional preposition. Despite the (likely) predominance of the NP1 attachment pattern in the learners' L1 and L2 input, they did not show any preference for attaching the RC to the first NP. This implies that language exposure cannot be the sole factor affecting parsing decisions.

Finally, it is worth mentioning that the results from the last two studies indicate that there might be a developmental dissociation between the processing mechanisms and grammatical competence of L2 learners. This is so because the L2 learners examined in these studies showed a native-like command of the relevant sentences in off-line grammaticality judgements, that contrasted with their non native-like processing performance.

VI Conclusions

The results from the studies reviewed above provide some tentative but still far from definite answers to the research questions they pursued. First, with respect to the issue of whether L2 learners are able to achieve native-like ambiguity resolution patterns, most studies showed that the L2 learners were slower and less confident about their parsing decisions than the native speakers. This finding demonstrates that there are differences between L1 and L2 sentence processing that may be indicative of L2 parsing being less automatized than L1 processing (see also [START_REF] Favreau | Second language reading in fluent bilinguals[END_REF]1983;[START_REF] Segalowitz | Skilled reading in the second language[END_REF]Fernández, 2003).

Moreover, even though L2 sentence comprehension is similar to L1 comprehension in that parsing decisions in both the L1 and the L1 are influenced by lexical cues such as verb argument structure or thematic information, L2 learners nevertheless seem to employ different parsing strategies. In some studies, the differences between the native and the L2 speakers are evident in L2 learners' tendency to attach the ambiguous material locally, whereas in other studies they appear as a reluctance to make a reliable commitment to a specific parsing decision. L2 learners' processing patterns have been attributed either to their preference for applying Late Closure as a default strategy in order to avoid processing overload, or to their reduced ability to use structural information on line. To test whether Late Closure is a universal strategy also employed by L2 learners, we need to investigate different types of ambiguity with participants from different language backgrounds and proficiency levels. In order to further examine the hypothesis that L2 learners over-rely on nonstructural information when parsing the L2 input, it may be worthwhile investigating how contextual cues affect their parsing preferences, especially in the light of L1 processing studies whose results indicate that native speakers' initial parsing decisions cannot be reversed by discourse factors.

With respect to the issue of transfer of processing routines from the first language, the evidence available to date is rather scarce. Results from several studies of learners' RC attachment preferences suggest that parsing strategies are not transferred from the native to the target language (but, for different outcomes, see Frenck-Mestre, 2002; this issue). No doubt more studies are needed; these studies should also help elucidate how processing strategies develop during the course of L2 acquisition, an issue that has not been addressed by the studies discussed in this article.

Another interesting finding obtained in several studies of L2 ambiguity resolution is that L2 learners' off-line grammatical knowledge of certain constructions does not necessarily imply that they are able to process these constructions in a native-like way. Such findings also indicate the need for further studies comparing L2 learners' grammatical competence and their processing behaviour. Some researchers have suggested that the non-native-like behaviour observed in several L2 acquisition studies should not necessarily be attributed to the UGaccess issue, but instead might reflect processing difficulties (see, for example, Juffs, 1998b: 422). However, the questions of how the L2 learners use their grammatical knowledge when parsing the L2 input, and whether their non-native-like performance is due to different parsing strategies rather than to different underlying grammatical representations as compared to native speakers' require further investigation.

The role of the exposure to the second language has been tackled by some studies, but the results are rather inconclusive. One set of findings suggests that the daily exposure to the L2 might have an influential role on the processing routines used, whereas another set argues against it. As Dussias (2003) notes, in order to further explore the role of exposure to L2 processing it would be useful to examine L2 learners who actually live in a predominantly L2 environment, vs. people who do not. A comparison between these two groups might shed light on this issue.

With respect to sentence processing models, the findings from the L2 studies on ambiguity resolution point to two directions. The first one is that parsing decisions are affected by lexical/thematic cues. The second one is that processing strategies like Minimal Attachment and Late Closure (or Recency) do not seem to apply universally. These two points remain unresolved in L1 sentence processing, too. Research in the area of L2 parsing could provide useful evidence to clarify these issues.

A final comment needs to be made with respect to some methodological issues. Although most of the L2 learners who participated in these studies are reported to be highly advanced, the way the participants' proficiency level was measured varies from study to study. This might have resulted in participants with different degrees of proficiency being grouped together, or in unbalanced comparisons. Moreover, there are differences in the way L2 ambiguity resolution patterns were measured. For example, some studies have used grammatical disambiguation, whereas others have used pragmatic disambiguation. In some studies the ambiguity was not resolved until the very end of the sentence, whereas in others it was resolved comparatively early. While in some studies sentence segments were presented in a word-by-word fashion, others used phrase-by-phrase presentation. Such methodological issues have long been known to play a role in L1 ambiguity resolution research, and may well have contributed to the divergent results reported in this article. Hence, I think that this is an additional reason for continuing to investigate L2 ambiguity resolution using a variety of experimental techniques before any firm conclusions can be drawn with respect to the processing strategies employed in the L2.

  2) a. Main clause reading: [IP [DP [D the] [NP elephants]] [IЈ [I] [VP squeezed]] b. Reduced relative clause reading: [IP [DP [D the] [NP [NP elephants] [IP [PRO] [IЈ [I] [VP squeezed]]]]]

Table 1

 1 Reaction times on the disambiguating segment

	Conditions	Native speakers	Spanish	German	Russian
		of Greek	participants	participants	participants

For bilingual sentence processing, see[START_REF] Dussias | Sentence parsing in fluent Spanish-English bilinguals[END_REF] Fernández, 2003.

For further information on eye-tracking experiments in the L2, the reader is referred to Frenck-Mestre (this issue). A brief summary of the cross-modal priming paradigm and its application in antecedent reactivation studies can be found in[START_REF] Marinis | Psycholinguistic techniques in second language acquisition research[END_REF].

 4 In the psycholinguistic literature, the term 'garden-path' effect refers to the processing disruption caused by a reader's or listener's realization that their initial analysis was wrong, forcing them to backtrack and reanalyse the sentence. In on-line experiments, this effect is evident from elevated RTs on the regions that force reanalysis.

[START_REF] Frenck-Mestre | Syntactic ambiguity resolution while reading in second and native languages[END_REF] have also investigated the subject/object ambiguity in L2 learners of English and French. However, as their study used the eye-tracking methodology, their results are not reviewed here. The reader is referred to Frenck-Mestre (2002; this issue) instead.

Notice, however, that only very strict syntax-first parsing models would predict garden-path effects even with intransitive verbs. Thus far such an effect has been obtained in studies with English native speakers[START_REF] Mitchell | Lexical guidance in human parsing: locus and processing characteristics[END_REF] and children[START_REF] Traxler | Plausibility and subcategorization preference in children's processing of temporarily ambiguous sentences: Evidence from selfpaced reading[END_REF].

For an extensive review of parsing models that aim to account for the RC attachment preferences, see[START_REF] Cuetos | Parsing in different languages[END_REF],Fernández (2003), and[START_REF] Papadopoulou | Cross-linguistic variation in sentence processing: evidence from relative clause attachment preferences in Greek[END_REF], among others.

See[START_REF] Frenck-Mestre | An on-line look at sentence processing in the second language[END_REF] this issue) for eye-tracking experiments on RC attachment preferences with learners of French.

The order of the two NPs was reversed in the with conditions to make the sentences sound more natural in English (for more details on this issue, see[START_REF] Felser | The processing of ambiguous sentences by first and second language learners of English[END_REF].

Acknowledgements

I am grateful to Harald Clahsen and the psycholinguistic research group at Essex University for providing me with insightful advice on various aspects of psycholinguistic research. I also thank Claudia Felser and an anonymous Second Language Research reviewer for helpful comments and discussions.