The development of complexity in second language acquisition - A dynamic systems approach

Student thesis: Doctoral Thesis


In the past few decades, the notion of complexity has raised significant interest in many disciplines (e.g. physics, biology, mathematics and artificial intelligence). More recently, this cross- disciplinary endeavor has reached linguistics, and scholars of various theoretical backgrounds have been keen to test its relevance to language. It is, however, still unclear what complexity actually means in linguistics and what yardstick can be used to measure complexity, especially in comparing language and interlanguage varieties. Moreover, it is often assumed that complexity and development go hand in hand, particularly in the context of second language acquisition, even though this assumption lacks empirical underpinning. Therefore, this dissertation aimed (a) to contribute to the definition and operationalisation of L2 complexity, and (b) to investigate how the complexity of L2 writing develops over time in a group of ten young Dutch-speaking beginner learners of L2 English. An additional aim was (c) to explore the possibilities and limitations of DST-inspired approaches towards the study of L2 complexity and L2 complexity development.
Our study identified several problems with regard to the definition and operationalisation of L2 complexity in SLA research. First, we stressed the importance of defining L2 complexity independently from related constructs such as difficulty, developmental timing, advancedness, (writing or speaking) quality and proficiency level, mainly with a view to avoiding circular reasoning. We advocated a more restricted definition and interpretation of L2 complexity as an essentially quantitative property of L2 systems, L2 samples or L2 structures characterisable in terms of the number and nature of (a) constituent components and (b) relationships between components. Next, we argued that L2 complexity is a multidimensional, multilayered and multicomponential construct, a fact which is still insufficiently acknowledged in L2 studies. We proposed a taxonomy of complexity constructs in an attempt to elucidate this multifaceted nature, and to provide a common descriptive-analytic framework for future research on L2 complexity. We then discussed the often problematic operationalisation of complexity in L2 studies and pointed out that this raises questions as to the validity and generalisability of the results of empirical studies. We argued that at the current state of understanding, it is important to include a sufficiently wide selection of complexity measures in L2 studies in order to provide a comprehensive overview of L2 complexity. Also, we were able to confirm that, given the minimally required timeframe (i.e. a period of four months, and in most cases one year), certain complexity measures (especially MLTU and SCR) perform adequately as indices of development, especially when mean group scores are considered. In addition, we showed that it is worthwhile to explore the adequacy of measures that combine different complexity measures and complexity components as indices of development, since such hybrid and aggregate measures appear to be more robust and stable as indicators of progress over time.
Next, adopting a DST-approach, we analysed the development of L2 complexity over time on the basis of a longitudinal learner corpus consisting of eleven creative writing samples collected over a period of nineteen months from ten beginning Dutch-speaking learners (age 11-13) of L2 English, using fourteen quantitative measures targeting various aspects of syntactic, lexical and morphological complexity. The results of our analyses appear to confirm that (a) different complexity components can be measured separately, (b) selective components of the complexity of the L2 writing of beginner learners indeed increase over time (i.e. lexical richness, length of syntactic units and clausal subordination), (c) at the group level the increase in L2 complexity is fairly linear but at the level of the individual learners there is a high degree of variability, (d) a complex interplay exists between the different complexity measures, and possibly also between the complexity components they are meant to quantify (e.g. clausal subordination and phrasal complexity, which were identified as connected but competing growers), (e) individual learners follow different developmental paths that in many cases do not coincide with the observed mean group trends, even though some common patterns emerge for the development of several complexity components, (f) it is fruitful to combine complexity measures to yield a more comprehensive picture of L2 complexity, particularly for the purpose of measuring overall L2 development, and (g) it is instructive to combine longitudinal with group studies, since longitudinal data allow to investigate actual individual development, and the combination of different case studies permit the identification of generalisable patterns. Finally, we argued that even though DST-approaches to the study of L2 development have for the most part been restricted to metaphorical applications, they can provide novel insights into the dynamics of the developmental process L2 learners go through.
Date of Award26 Aug 2013
Original languageEnglish
SupervisorAlexis Housen (Promotor)


  • second language acquisition
  • complexity
  • linguistic complexity
  • dynamic systems theory

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