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Complexity figures prominently in current science (Mitchell 2009), including the language sciences where it has received much attention from linguists working within functional and typological frameworks (Miestamo et al 2008).  Also in SLA research the notion of complexity has played an important role ever since the 1970s. In current SLA research, two strands of complexity research can be distinguished (Housen & Kuiken 2009). In the first strand, complexity figures as an independent variable, i.e., as a factor whose influence on some aspects of L2 performance or proficiency is investigated. Examples include studies of how the complexity of tasks affects L2 performance and development (Robinson 2011), or how the complexity of the target structure affects the effectiveness of instruction (e.g. Spada & Tomita 2010). In the second strand, complexity is investigated as a dependent variable, typically alongside fluency and accuracy, as a basic descriptor of L2 performance and proficiency. Here, the complexity of L2 learners’ performance is measured to demonstrate the effect of other variables, such as the effects of learner factors (e.g. age, aptitude) or of different types of instruction or of learning contexts (e.g. Kormos & Trebits in press; Norris & Ortega 2000). However, a review of the L2 literature shows that there is no consistency in terms of how complexity is defined, operationalised and measured in L2 research, which at least partly explains the inconsistency of complexity findings both across and within studies (Housen & Kuiken 2009; Housen, Kuiken & Vedder 2012).

The goals aimed at the Ailla REN COSELL are the following:

  • investigate the various strands of L2 research on complexity;
  • critically approach the definition and operationalisation of the complexity construct;
  • standardisation and validation of measures of complexity;
  • investigate the link between L2 complexity and other constructs in SLA and testing (e.g. developmental stages, learnability, ultimate attainment);
  • cross-linguistic approaches and perspectives on complexity;
  • pedagogical implications (e.g. complexity as skill or typical behaviour, complexity in L2 production and perception, task sequencing)

ReN conveners and contact

Folkert Kuiken, University of Amsterdam, Amsterdam


Ineke Vedder, Amsterdam

website :

Current members 


  1. Melissa Baralt, Florida International University, Miami
  2. Philip Choong, Columbia University, New York
  3. Daniel Jackson, University of Hawai’i  at Manoa, Honolulu
  4. Shawn Loewen, Michigan State University, Michigan
  5. John Norris, University of Hawai’i  at Manoa, Honolulu
  6. Lourdes Ortega, University of Hawai’i  at Manoa, Honolulu
  7. Sholo Sasayama, University of Hawai’i  at Manoa, Honolulu
  8. Mary Lou Vercellotti, University of Pittsburgh, Pittsburgh

 ABLA (Belgium)

  1. Bram Bulté, Free University Brussels, Brussels
  2. Alex Housen, VUB, Brussels
  3. Elke Peters, Katholieke Universiteit Leuven, Leuven

 AESLA (Spain)

  1. Roger Gilabert Guerrero, University of Barcelona, Barcelona

AFinLA (Finland)

  1. Raili Hilden, Helsinki University, Helsinki
  2. Lea Nieminen, University of Jyväskylä, Jyväskylä
  3. Nina Reiman, University of Jyväskylä, Jyväskylä
  4. Gabriele Pallotti, University of Modena and Reggio Emilia, Reggio Emilia
  5. Stefania Ferrari, University of Modena and Reggio Emilia, Reggio Emilia

AITLA (Italy)

ALAK (South Korea)

  1. Jay Kim, Korean National University of Education.  

ALANZ (New Zealand)

  1. Rebecca Adams, University of Auckland, Auckland

ANéLA (the Netherlands)

  1. Nel de Jong, Free University, Amsterdam
  2. Folkert Kuiken, University of Amsterdam, Amsterdam
  3. Rob Schoonen, University of Amsterdam, Amsterdam
  4. Ineke Vedder, University of Amsterdam, Amsterdam
  5. Nivja de Jong, University of Utrecht, Utrecht

ASLA (Sweden)

  1. Inge Bartning, Stockholm University, Stockholm
  2. Victorine Hancock, Stockholm University, Stockholm
  3. Rakel Österberg, Stockholm University, Stockholm
  4. Jonas Granfeldt, Lund University, Lund
  5. Marie Kallkvist, Lund University, Lund
  6. Petra Bernardini, Lund University, Lund
  7. Malin Ågren, Lund University, Lund


  1. Judit Kormos, University of Lancaster
  2. Andrea Revesz, University of Lancaster
  3. Anna Trebits, Eötvös University, Budapest

EAAL (Estonia)

  1. Annekatrin Kaivapalu, Tallinn University, Tallinn

GAL (Germany)

JAAL (Japan)

  1. Tomohito Ishikawa, Soka Women's College, Tokyo.
  2. Peter Robinson, Ayoama Gakuin University, Tokyo.

Activities (2011-2014) 

Conferences and events (2011)  

  • Bartning, I. & Hancock, V. took the initiative to set up a discussion group on Complexity in L2 at EuroSLA 21, Stockholm. September 9, 2011
  • Housen, A., Kuiken, F. & Vedder, I. Complexity in L2 performance. Definition, measurement and research. Colloquium at Eurosla 21, Stockholm. September 8, 2011
  • TBLT 2011. 4th Biennial Conference on Task Based Language Teaching. University of Auckland. November 18-20, 2011

Upcoming events

  • Workshops on Complexity and Idiomaticity in L2, June 8-9 2012, organizers: Fanny Forsberg & Victorine Hancock, Stockholm University, Stockholm
  • Eurosla 2012, Poznan, Poland, 5-8 September 2012
  • AILA 2014: organization of a symposium on complexity; special focus, design and participants of the colloquium still to be decided


  • Robinson (ed.) (2011). Second language task complexity: Researching the Cognition Hypothesis of language learning and performance. Amsterdam: John Benjamins
  • Housen, A., Kuiken, F. & Vedder, I. (eds) (2012, forthcoming) Dimensions of L2 performance and proficiency. Investigating complexity, accuracy and fluency in SLA. Amsterdam: John Benjamin