Appropriate complexity

One of the most widespread assumptions in SLA research is that complexity grows over time, so that increasing proficiency in a second language would imply that one's productions become more and more complex. However, this assumption needs to be qualified and further investigated. Firstly, complexity does not grow at the same rate in different linguistic sub-domains (e.g. lexicon, syntax, morphology). Secondly, linguistic complexity varies across tasks and modalities, so that it is not always the case that "the more, the better" -- there are adequate levels of complexity, and sometimes more can actually mean worse, at least for certain linguistic structures and sub-domains. This chapter presents results from a longitudinal four-year project involving adolescent learners, together with native speaker controls, performing a number of oral communicative tasks. The analysis looks at the complexity of telephone calls, demonstrating that the degree of syntactic complexity depends on the task's interactional requirements. More specifically, higher levels of syntactic complexity compete with the need to rapidly exchange turns and to direct the interlocutor's attention. As learners progress in the L2, their syntactic complexity in this task tends to decrease, while they develop more sophisticated pragmatic and interactional skills. Similar results are found using the conversation-analytic notion of Turn Constructional Unit (TCU) to compare syntactic complexity in telephone calls and in a narrative retelling task. The conclusion is that linguistic complexity must be interpreted, not just measured. Nowadays several tools are available to calculate dozens of complexity measures, and there is a risk of accumulating results with little reflection about how they should be understood in terms of language development and communicative adequacy. This has pedagogical implications, too, for language teachers must see complexity not as an objective in itself, but in a wider context of linguistic proficiency and functional appropriateness.