In support of a developmental sequence model of second language acquisition: Ellis, 2015

Researching Acquisition Sequences: Idealization and De‐idealization in SLA
Ellis, R. (2015)., Language Learning Early view

DSC04473This paper examines Long’s claim regarding developmental sequences in second language acquisition, or what R. Ellis terms “Long’s law:”

“learners of different ages, with and without instruction, in foreign and second language settings, follow similar developmental sequences for such items as English negation”

Ellis develops an epistemological framework drawing on idealisation theory in the philosophy of science (Leszek Nowak, Cliff Hooker, Michael Weisberg) which he then applies to four successive studies of L2 negation in the same dataset, from 1978 to 2011. While retaining an interest in variation both at the level of learner language and theory development, he concludes that research generally supports the developmental sequence model of second language acquisition.

What follows is my own summary of Ellis’ argument in this 2015 Language Learning article.  The references are his; I haven’t included dates in the text.

Early, cognitive models of SLA (Corder) based on developmental stages have been challenged by socio-cognitive theory (Watson-Gegeo, Lantolf), discourse/conversation analysis (Firth & Wagner), and dynamic systems theory (Larsen-Freeman, de Bot et al.).  Ellis argues that we should therefore “reevaluate the long-held claim that the acquisition of L2 grammatical features involves predictable and universal stages of development” (p. 2).

Research in interlanguage variation (Ellis, Tarone) shows that such stages are an idealisation. Order of acquisition studies (Dulay & Burt), work on sequences of acquisition (Dulay, Burt & Krashen), and developmental sequence research (Pieneman & colleagues) have variously measured the emergence and stabilisation of morphemes and syntactic forms in learner language.  Variation in the production of these forms has been related to factors such as context (Tarone, Ellis), form-function mapping (Schachter), and creative speech versus formulaic chunks (N. Ellis).  This research appears to call into question “the existence of clearly delineated stages of acquisition and also emphasize the differences in the L2 development of individual learners.” The alternative term  “trajectories of learning” is preferred to “sequences of acquisition.”

Epistemological framework

To judge these different types of research, R. Ellis asks

  1. What exactly is a theory?
  2. What is the process by which theories are developed?
  3. What constitutes robust empirical evidence?

He reviews the investigation of developmental sequences in L2 acquisition by researchers using “set-of-laws theory,” or “research-then-theory” (as opposed to “axiomatic-causal theory,” or “theory-then-research”).  Following Long, this work has focused on selecting a phenomenon such as negation, examining samples of learner language to identify systematic patterns, and then proposing generalisations about the acquisition of this interlanguage feature.  These generalisation are idealisations, being accurate, though simplified, theoretically tenable, intelligible, and empirically verifiable (Hooker).  An idealisation neglects secondary factors (Nowak) and intentionally distorts, for pragmatic reasons, or as a minimalist model  (Weisberg). For Hooker, idealisation can have a positive effect (“simplifying,” when based on correctible quantitative error) or a negative effect (“degenerate,” based on conceptual error).

Weisberg argues for multiple models to achieve greater generality, accuracy, precision and simplicity and Ellis concurs, since “theories (and the idealizations that constitute them) can only be judged in terms of the specific domain they address.”  He takes a relativist stance, following Schumann’s position that “all knowledge is subjective and reality is multiple.”  He further argues that theories can be de-idealised without abandonment.

L2 negation studies

Applied to the question of acquisitional sequences, Ellis reviews four approaches to Cancino et al.’s 1978 data from six naturalistic learners of English in their first year after arrival in the US, involving both spontaneous and elicited oral production from two young, two adolescent and two adult Spanish speakers collected over a 10-month period.

  • Cancino et al’s original analysis discarded memorised chunks (e.g. I don’t know) and calculated frequency of types of negation over time to produce a universal developmental sequence.  Not all subjects had reached the end of the sequence by the end of the study, and one was considered to have stopped developing (fossilised; Alberto).
  • Schachter then reanalysed data from another of the six learners (Jorge) to relate different forms of negation to discourse function (e.g., rejection, affirmation).
  • In the third study, Berdan conducted a more sophisticated frequency analysis to show systematic use and development of negation in the learner originally considered to have fossilised.
  • Finally, Van Dijk et al took a dynamic systems approach and through statistical analysis highlighted the importance of interlearner variation which was related to age. This analysis also showed random variability in use of negation forms for one learner.

These results call into question Long’s claim that L2 learners follow similar developmental sequences.  They show it to be a simplifying idealisation which nonetheless holds up well in the four studies examined.  Ellis argues that these studies de-idealise the theory in helpful ways, particularly for those who seek to apply SLA research findings to instruction.  (In this respect, the dynamic systems analysis does not offer an improved model.)  Since the studies focused on untutored learners with the same L1/L2 pairing, the effects of instruction, and of other languages, must be verified.  In the meantime, however, R. Ellis suggests that his arguments drawn from the philosophy of science should militate against discarding Long’s developmental sequence “law.”

References (Ellis, 2015)

  • Berdan, R. (1996). Disentangling language acquisition from language variation. In R. Bayley & D. Preston (Eds.), Second language acquisition and linguistic variation (pp. 203244). Amsterdam: John Benjamins. CrossRef
  • Cancino, H., Rosansky, E., & Schumann, J. H. (1978). The acquisition of English negatives and interrogatives by native Spanish speakers. In E. Hatch (Ed.), Second language acquisition (pp. 207230). Rowley, MA: Newbury House.
  • Corder, S. P. (1967). The significance of learners’ errors. International Review of Applied Linguistics, 5, 161170. CrossRef,
  • de Bot, K., Lowie, W., & Verspoor, M. (2007). A dynamic systems theory approach to second language acquisition. Bilingualism: Language and Cognition, 10, 721. CrossRef,
  • Dulay, H., & Burt, M. (1973). Should we teach children syntax? Language Learning, 23, 245258.
  • Dulay, H., Burt, M., & Krashen, S. (1982). Language two. New York: Oxford University Press.
  • Ellis, N. C. (2002). Frequency effects in language processing: A review with implications for theories of implicit and explicit language acquisition. Studies in Second Language Acquisition, 24, 143188. CrossRef
  • Ellis, R. (1984). Classroom second language development. Oxford, UK: Pergamon.
  • Ellis, R. (1985). Sources of variability in interlanguage. Applied Linguistics, 6, 118131. CrossRef,
  • Ellis, R. (1995). Appraising second language acquisition theory in relation to language pedagogy. In G. Cook & B. Seidlhofer (Eds.), Principle and practice in applied linguistics: Studies in honour of H. G. Widdowson (pp. 7389). Oxford, UK: Oxford University Press.
  • Firth, A., & Wagner, J. (2007). Second/Foreign language learning as a local accomplishment: Elaborations on a reconceptualized SLA. Modern Language Journal, 91, 757772.
  • Hooker, C. (1994). Idealization, naturalism, and rationality: Some lessons from minimal rationality. Synthese, 99, 181231.
  • Lantolf, J. P. (2011). The sociocultural approach to second language acquisition. In D. Atkinson (Ed.), Alternative approaches to second language acquisition (pp. 2447). London: Routledge.
  • Larsen-Freeman, D. (2011). A complexity theory approach to second language development/acquisition. In D. Atkinson (Ed.), Alternative approaches to second language acquisition (pp. 4872). London: Routledge.
  • Long, M. H. (1985). Input and second language acquisition theory. In S. Gass & C. Madden (Eds.), Input in second language acquisition (pp. 377393). Rowley, MA: Newbury House.
  • Long, M. H. (1990). The least a second language acquisition theory needs to explain. TESOL Quarterly, 24, 649666.
  • Meisel, J., Clahsen, H., & Pienemann, M. (1981). On determining developmental stages in natural second language acquisition. Studies in Second Language Acquisition, 3, 109135. CrossRef
  • Nowak, L. (1992). The idealization approach to science: A new survey. Available at
  • Pienemann, M. (1984). Psychological constraints on the teachability of languages. Studies in Second Language Acquisition, 6, 186214. CrossRef
  • Pienemann, M. (1998). Language processing and second language development: Processability theory. Amsterdam: John Benjamins. CrossRef
  • Reynolds, P. (1971). A primer in theory construction. Indianapolis, IN: Bobbs Merrill.
  • Schachter, J. (1986). In search of systematicity in interlanguage production. Studies in Second Language Acquisition, 8, 119134. CrossRef
  • Schumann, J. H. (1993). Some problems with falsification: An illustration from SLA research. Applied Linguistics, 14, 295306.
  • Tarone, E. (1983). On the variability of interlanguage systems. Applied Linguistics, 4, 143163.
  • Tarone, E. (1988). Variation in interlanguage. London: Edward Arnold.
  • Van Dijk, M., Verspoor, M., & Lowie, W. (2011). Variability and DST. In M. Verspoor, K. de Bot, & Lowie, W. (Eds.), A dynamic approach to second language development (pp. 8598). Amsterdam: John Benjamins.
  • Watson-Gegeo, K. (2004). Mind, language, and epistemology: Toward a language socialization paradigm for SLA. Modern Language Journal, 88, 331350.
  • Weisberg, M. (2007). Three kinds of idealization. Journal of Philosophy, 104, 639659.

Peer observation: mutual support for language teachers

Perhaps one of the most direct ways of improving your teaching is through peer observation, where teachers watch colleagues in action in the classroom.

IMG_0046Peer observation can help teachers become more aware of the issues they confront in the classroom and how these can be resolved. Observation can also help narrow the gap between one’s imagined view of teaching and what actually occurs in the classroom. By engaging in nonevaluative classroom observations, the responsibility of professional development can also shift from others (supervisors, peers, etc.) to the individual teacher.

Richards & Farrell (2005, p. 94)

Many teachers dread observations.  Often evaluative observations take the form of inspections, organised in a spirit of quality control and with consequences for the teacher’s career (qualification, promotion, or pay).  But observations can also be much less formal, and involve individual teachers simply watching each other teach.  Sometimes a teacher educator or supervisor can oversee this process:

Instead of individual post-observation conferences between supervisor and teacher, the supervisor may lead a post-observation focus group to allow teachers to share their experiences observing colleagues’ classes.

Marshall & Young, 2009, p. 2

Teacher educators tend to agree that well-implemented peer observations can be more “benign and constructive” than traditional observations (Cosh, 1999, p. 24), as well as encouraging greater autonomy in professional development.


British Council (2012). Guide to continuing professional development: peer observations. PDF

Cosh, J. (1999). Peer observation: a reflective model. ELT Journal, 53(1). PDF

Davidson, G. (2013). Observation and your teaching staff. British Council webinar.

Marshall, B., & Young, S. (2009). Observing and providing feedback to teachers of adults learning English. CAELA Network. PDF

Richards, J. C., & Farrell, T. S. C. (Eds.). (2005). Professional development for language teachers: Strategies for teacher learning. Ernst Klett Sprachen.(Chapter 6)

Modèle multidimensionnel : le TBI en classe de langues (Acedle 2015)


Former à l’intégration des technologies en classe de langue : vers un modèle multidimensionnel


Les résultats de la recherche en apprentissage des langues médié par les technologies (ALMT) tendent à dresser un tableau quelque peu décevant de la classe de langue. Les occasions d’interaction au cours de véritables tâches communicatives manquent encore dans les classes dotées de technologies interactives ; de plus, l’appropriation de ces outils par les enseignants progresse lentement et de façon inégale selon les individus, le plus souvent en l’absence de transformation pédagogique. Se posent alors pour la recherche et pour la formation en didactique des langues les questions suivantes : (1) comment tirer profit des potentialités (affordances) des nouvelles technologies ? ; (2) comment rendre les apprenants plus actifs et autonomes ? ; (3) comment accompagner les enseignants dans ce sens ? Pour tenter de répondre à ces questions dans le contexte de l’appropriation du tableau blanc interactif (TBI) en classe de langue, nous adoptons un cadre théorique qui donne toute sa place à l’agentivité du praticien. L’enseignant doit être considéré comme acteur dans sa pratique de classe (Bandura, 2001) et comme collaborateur dans des activités de recherche-action (Burns, 2005). Le projet européen iTILT, axé sur la création de ressources éducatives libres pour la formation à l’enseignement-apprentissage des langues avec le TBI (Whyte et al., 2013), a fourni l’occasion de mettre en pratique ces principes au cours d’une étude longitudinale sur l’intégration du TBI par un sous-groupe d’enseignants. A partir d’un corpus d’enregistrements vidéo de séances au TBI en classe de langue (56 vidéos d’environ 3 minutes avec 9 enseignants d’anglais), nous utilisons des méthodes mixtes pour analyser les données complémentaires suivantes : – entretiens d’auto-confrontation avec les enseignants sur les séances enregistrées ; – entretiens de groupe avec les apprenants à la suite des séances enregistrées ; – questionnaires sur la pensée enseignante (attitudes, perception de vidéos de pratique au TBI) ; – contributions des enseignants à des discussions en ligne et en présentiel. La méthode de recherche permet de mettre en parallèle l’analyse de pratiques aux TBI (fonctionnalités, objectifs pédagogiques, organisation de la classe, choix et mise en place d’activités d’apprentissage) et le positionnement réflexif de l’enseignant par rapport à l’exploitation de cet outil dans l’enseignement-apprentissage des langues. A partir d’exemples concrets d’activités d’apprentissage et de commentaires d’enseignants, cette communication dessinera ainsi les étapes successives d’intégration de cette technologie interactive par les enseignants du projet, en démontrant les effets sur les interactions de classe. Cette analyse permet d’établir des profils types d’enseignant qui sous-tendent un modèle multidimensionnel de l’intégration du TBI comprenant une dimension pratique et technique, une dimension pédagogique ainsi qu’une dimension réflexive. Nous proposons ainsi des instruments de recherche (questionnaires et grilles d’analyse), ainsi que des résultats (effets de l’agir enseignant sur les interactions de classe) qui sont applicables à d’autres contextes d’ALMT et qui ont des retombées à la fois pour la formation des enseignants et pour les recherches en didactique des langues de manière plus large.

Références bibliographiques

Bandura, A. (2001). Social cognitive theory: An agentic perspective. Annual review of psychology, 52(1), 1-26. Brewer, S. S. (2008). Rencontre avec Albert Bandura: l’homme et le scientifique. L’orientation scolaire et professionnelle, 37(1), 29-56. Burns, A. (2005). Action research: An evolving paradigm?. Language teaching, 38(2), 57-74. Cutrim Schmid, E., & Whyte, S. (Eds.) (2014). Teaching languages with technology: communicative approaches to interactive whiteboard use. A resource book for teacher development. Advances in Digital Language Learning and Teaching (Series editors: Michael Thomas, Mark Warschauer & Mark Peterson). Bloomsbury. [link] Ellis, R. (2003). Task-based language learning and teaching. Oxford: Oxford University Press. Gibson, J.J. (1977). The theory of affordances. In R.E. Shaw & J. Brqnsford (Eds.), Perceiving, acting, and knowing. Hillsdale, NJ: Erlbaum.

Lave, J., & Wenger, E. (1991). Situated learning: legitimate peripheral participation. Cambridge: Cambridge University Press.

Macaire, D. (2007). Didactique des langues et recherche-action. Les cahiers de l’Acedle, 4, 93-120. Van den Branden, K., Van Gorp, K., & Verhelst, M. (Eds.) (2007), Tasks in action: Task-based language education from a classroom-based perspective. Cambridge Scholars Whyte, S. (sous presse). Implementing and Researching Technological Innovation in Language Teaching: The Case of Interactive Whiteboards for EFL in French Schools. New Language Learning and Teaching Environments. (Series editor: Hayo Reinders). Palgrave Macmillan. avril 2015 [descriptif] Whyte, S. (2014). Contextes pour l’enseignement-apprentissage des langues : le domaine, la tâche et les technologies. HDR, Université du Havre, novembre. Whyte, S., Beauchamp, G., & Alexander, J. (2014). Researching interactive whiteboard use from primary school to university settings across Europe: an analytical framework for foreign language teaching. University of Wales Journal of Education, 17, 30-52. [link] Whyte, S., Cutrim Schmid, E., van Hazebrouck, S., & Oberhofer, M. (2013). Open educational resources for CALL teacher education: the iTILT interactive whiteboard project. Computer Assisted Language Learning, 27 (2), 122-148.

CrowdWish lesson plan (Rachael Roberts)

A great example of a communicative lesson plan, using authentic resources to stimulate discussion. There is a grammar focus, but it comes from the topic and activities, rather than constituting the starting point of the lesson. Link to video and transcript provided, CC licence – what more could we ask?



A free downloadable lesson, about a new online service, CrowdWish, which invites people to post their wishes on their website. Every day people vote on the most popular wish, and CrowdWish will grant it!  Students start by discussing some wishes taken from the site, then read a short text about what the site aims to do (so don’t tell them at the start of the lesson!)  There is then a focus on some useful idioms, before going on to watch a video in which the founder of the site, ‘pitches’ his idea. Students then look at the grammar used with ‘wish’, particularly at the use of ‘would’ when you want someone else to change their behaviour. Finally the students come up with their own wishes and vote on them, like on the site. You could even try and grant the top wish if you’re feeling creative..

The lesson would be…

View original post 34 more words

Authenticity in the FL classroom

How can we offer an “authentic” experience to second language learners in a foreign context?  Is authentic language use at all possible for secondary school pupils in France, for example, who share French as a native language and have no special need to learn English beyond its presence in the curriculum?


I have talked about differences between pedagogical exercises and communicative tasks elsewhere.  But here are three other ideas worth considering:

Spontaneous language use

Authenticity can come from using language in an unplanned, spontaneous way.  Instead of practising language forms, memorising rules or words in isolation, simply using the language to communicate meaning can be a more natural, and so authentic approach.  Gavin Lamb discusses this in relation to language and then to music on his Leaky Grammar blog.  He has this quote:

“Improvisation can be considered the fifth skill — the skill which follows reading, listening, speaking, and writing. In many ways, it is the most important because it is the real test of whether students can use what they have learned without being told exactly what to do or say.” (Maurer, 1997)

Read more from here.

Content and language integrated instruction

If the meaning communicated by teachers and learners relates to learning new information in a particular discipline, then we are in the domain of CLIL, sometimes called CBI (Content-Based Instruction).  This type of teaching and learning brings its own problems, notably how to articulate the presentation and evaluation of new content and new language at the same time.  The advantage, however, is in providing a ready-made context for learning: learner needs, resources and activities related to the discipline in question.

I’m happy to see these Dutch Kennisnet CLIL videos are still accessible online: try this short video on pair and group work, for example.

Authentic texts

Finally, Genevieve White has an example of authentic texts and tasks for lower-level proficiency EFL learners.  She has the advantage of working with second language learners who need survival English to live in the UK, rather than the foreign language, school population learning English for No Obvious Reason (Medgyes, 1986).

FL teachers are used to adapting such tasks by simply pretending: planning a possible trip/visit/application … The authenticity here lies in the resources, not written specially for language learners, and in the design, implementation and evaluation of the activities.  It’s easy to trip up here and end up with exercises to practice language forms rather than communicative activities, so some caveats are worth mentioning.

I suggest the following: activities should be

  • worth doing in the native language,
  • set up to model and encourage actual collaboration (as opposed to minimal, unsupervised cooperation)
  • evaluated in terms of content, not just language accuracy.

Easier said than done, on the whole, but worth a try.

Going further

Erkan Kulekci’s blog has a good bibliography for this topic, and led me to Peacock (1997) and an impressive empirical study in Language Learning by Alex Gilmore, who conducted a 10-month study with some 60 Japanese university EFL learners, half of whom were taught from textbooks and half using authentic materials.

The results of this study strongly suggest that the authentic materials used with the experimental group in the investigation were better able to develop a range of communicative competencies in the learners than the two EFL textbooks used with the control group. This finding was predicted on the grounds that the authentic materials, with their associated tasks and activities, provided richer input for learners to work with in the classroom, which, in turn, allowed them to notice and then acquire a wider variety of linguistic, pragmatic, strategic, and discourse features. The consciousness-raising was therefore facilitated by (a) providing participants with rich input and (b) drawing learners’ attention to useful features through careful task design and follow-up practice activities

Gilmore used a battery of tests to measure subjects’ communicative competence and includes a very interesting discussion of each to tease out the effects of authentic materials on different aspects of language learning.  His conclusion, unsurprisingly, favours the use authentic materials, but is very sanguine about the difficulties of this approach.


Gilmore, A. (2011). “I Prefer Not Text”: Developing Japanese Learners’ Communicative Competence with Authentic Materials. Language Learning, 61(3), 786-819.

Kulekci, E. Relatively authentic. WordPress blog.

Maurer, Jay. (1997). Presentation, Practice, and Production in the EFL Class. The Language Teacher Online, 21 (9), 42-45.

Medgyes, P. (1986). Queries from a communicative teacher. ELT journal, 40(2), 107-112. PDF

Peacock, M. (1997). The effect of authentic materials on the motivation of EFL learners. ELT Journal, 51 (2), pp. 144–156. PDF

Whyte, S., & Alexander, J. (2014). Implementing tasks with interactive technologies in classroom CALL: towards a developmental framework. Canadian Journal of Learning and Technology, 40 (1), 1-26. PDF

Analysing learners’ language: a method to their madness

IMG_1995A lot of effort in language teacher education goes into making teachers aware that learners of a second language make errors that are not random or unprincipled, or indeed simply transfer from the first language, but rather obey a certain logic of their own.  Learners are not simply defective speakers of the target language, but are constructing their own interlanguage (Selinker, 1972), also referred to as learner language.  This means that the developmental stages of their language acquisition should be treated as necessary steps in the language learning process, rather than as strings of errors requiring remediation.

This idea has implications for the planning of language teaching, since it suggests that teaching should be tailored to learners’ in-built syllabus, rather than organised according to a separate, grammar-based syllabus.  If we accept the interactional hypothesis, for example, which claims that language is acquired through using the target language in the negotiation of meaning, we should allocate class time to communicative activities which engage learners in such language use, and support learners in participating in activities and reflecting on their engagement.

But the notion of learner language also has implications for the evaluation of language learning and teaching.  Teachers traditionally identify and correct learner production by underlining written errors, for example, or recasting oral errors of vocabulary, grammar or pronunciation.  But if we want to better understand learner language, more analytical methods are required.

Analysing errors: language accuracy

A CARLA resource on learner language explains that

“An error analysis – and teacher corrections – should ignore unsystematic performance slips (mistakes) and focus on errors, which are systematic violations of the rules to which the learners have been exposed; these tell us something about the learner’s current knowledge of the rules of the language being learned.”

Dyson (2010) distinguishes three different ways of studying errors (1):

  1. error analysis
    1. collect a sample
    2. identify grammatical errors
    3. record error frequencies
    4. explain errors
    5. repeat procedure with other morphemes
  2. obligatory occasion analysis
    1. select a morpheme
    2. identify and count obligatory occasions
    3. count suppliance of morphemes
    4. calculate accurate use as a percentage
    5. order devices implicationally in relation to other morphemes
  3. frequency analysis
    1. select a linguistic variable
    2. divide data into equal periods
    3. identify different devices used
    4. calculate frequencies
    5. identify dominant device at each point in time

More advice on error analysis is provided in the CARLA resource.  However, we should remember that accuracy is only one dimension of learner language: the complexity of a learner’s production is another important aspect.

Assessing complexity

Tarone and Swierzbin (2009) suggest measuring syntactic complexity by counting any of the following:

  • the number of sentences containing more than one verb
  • use of complex noun phrases
  • number of verb arguments
  • types of dependent clauses

For lexical complexity, variety can be analysed using type-token ratio: “the total number of different words (types) divided by the total number of words (tokens) in a given segment.” CARLA resource.


The fluency of a learner’s spoken production is perhaps harder to evaluate.  Different measures include

  • Breakdown fluency (e.g., time filled with speech, no. of pauses, filled pauses)
  • Speed fluency (e.g., speech rate measured as words per minute, syllables per minute)
  • Repair fluency (e.g. false starts, repetitions)

(See Skehan, 2009, cited in De Jong & Hulstijn, 2009)

Learner language can therefore be analysed in a number of ways, looking at its complexity, accuracy and fluency. We can look at several different learners, under different conditions of language production, or one learner at different points in time.  These measures are different from the kind of evaluations teachers constantly conduct, both formally and informally.  But they provide a different picture of learner language development, allowing teachers to take a step back from day-to-days concerns to see how their learners are really doing.

1. Another approach advocated by Dyson (2010) involves emergence analysis, based on Pienemann’s processability theory.  This approach is no doubt too complex to be useful for practitioner research.


Overview of Complexity of Learner Language

Overview on error analysis.

De Jong, N., & Hulstijn, J. (2009). Relating ratings of fluency to temporal and lexical aspects of speech. EALTA 2009 [slides]
Dyson, B. (2010). Learner language analytic methods and pedagogical implications.
Australian Review of Applied Linguistics, 33(3), 1-21. [PDF]
Selinker, L. (1972). Interlanguage. International Review of Applied Linguistics, 10, 209-241.
Skehan, P. (2009). Modelling second language performance: Integrating complexity, accuracy, fluency, and lexis. Applied Linguistics, 30(4), 510-532. doi: 10.1093/applin/amp047
Tarone, E. & Swierzbin, B. (2009). Exploring Learner Language. Oxford: Oxford University Press.