Complex Dynamic Systems Theory (CDST), an instantiation in applied linguistics of complexity epistemology that transcends disciplinary boundaries, has gained much traction and momentum over the last decade, finding expressions in a fast-growing number of empirical second language developmental studies. However, the literature, while rapidly expanding, has displayed much confusion, notably oscillating between invoking CDST as a metatheory and as an object theory. Then, too, the metaphorical genesis of CDST—the metaphorical adoption of complexity epistemology from physical sciences—has seemed to invite miscellaneous interpretations, rendering CDST an ostensibly all-in-one conceptual prism. This article explores the epistemology of CDST, tracing its ontology and examining its role in second language developmental research. This enables a more nuanced understanding of CDST, while at once surfacing critical issues and directions for future research, as it moves toward a pluralistic approach to investigating CDST as a potentially unique lens on second language development.

Task-based language teaching (TBLT) is increasingly becoming known for its distinct edge in developing learners’ functional competence. Although its potential in promoting content learning has yet to be realized and explored, it should be high, given TBLT's primary attention to meaning. To what extent does the potential play out in foreign language teacher education, a domain involving much content learning, is both an intellectually stimulating and practically meaningful question. This article reports on a semester-long study investigating task-based learning in a Chinese language teacher-training program that promotes TBLT. The participants were three Chinese-speaking trainees, who, while being exposed to TBLT, performed ongoing tasks. Data from one task—writing weekly reading journals—were analyzed for both content and language, quantitatively (using robust automated tools) and qualitatively. The results show tangible gains on both counts—understanding TBLT (content) and the ability to articulate it (language). The conceptual and methodological implications of the findings are discussed for future research.

A founding concept in second language acquisition (SLA) research, fossilization has been fundamental to understanding second language (L2) development. The Fossilization Hypothesis, introduced in Selinker's seminal text (1972), has thus been one of the most influential theories, guiding a significant bulk of SLA research for four decades; 2012 marks its fortieth anniversary. This article revisits the Fossilization Hypothesis, starting with the earliest set of questions (still the most comprehensive) (Selinker & Lamendella 1978) and using them as a basis for updating the Hypothesis. The current understanding of fossilization is presented by introducing an alternative hypothesis, the Selective Fossilization Hypothesis (Han 2009) and, in the light of that alternative, reviewing a selection of fossilizable structures documented in the recent literature.