Task-based language teaching (TBLT) approaches have been growing into a fruitful area of second language (L2) research since the mid-1990s. The use of “tasks” in these approaches is predicated on the notion that tasks are effective when meaning is made central, learning outcomes are met, and real-world language is used. However, a task can be considered appropriate for a TBLT curriculum only when learners who carry out the task show improvement in their short-term performance and their long-term development. Toward this end, the editor of this volume presents a series of empirical studies that investigate how task design variables impact the oral performance of language learners within the framework of Skehan’s tradeoff hypothesis. The tradeoff hypothesis predicts that there will be necessary “tradeoffs” in different performance areas due to competing processing demands. The research presented has the goal of exploring how learners can overcome the limitations of their finite cognitive resources and maximize their oral development.

In the first chapter of the volume, Skehan provides an overview of the debate between the tradeoff and cognition hypotheses, two opposing views, and clarifies the current status of the tradeoff hypothesis. The editor also specifically addresses the constructs and framework used to investigate tasks in the volume, defining complexity-accuracy-fluency-lexis (CAF-lexis) performance measures, task characteristics, and Levelt’s theoretical model of first language speaking, which is used as the basis for the L2 speaking model. The first chapter not only contextualizes the empirical studies in the volume within a larger research agenda but also models a consistent standard for performance measurements across the studies in the volume.

The next six chapters empirically investigate how the circumstances surrounding a task (task condition) or the qualities of a task (task characteristics) impact L2 oral development, specifically the CAF-lexis performance measures. Four studies focus on the effect of task condition, including online versus offline planning (Wang), planning versus “readiness” (Gavin), the factors that contribute to effective or ineffective planning (Pang & Skehan), and the use of transcriptions as a posttask activity (Qian). Two studies investigate the effect of task characteristics: One study explains how improved accuracy and complexity may be due to task structure and time perspective rather than evidence of the cognition hypothesis (Wang & Skehan), whereas the other explores the effect of structure and processing constraints (Skehan & Shum).

In the final chapter of the volume, the editor positions the findings within a broader research context and then discusses the pedagogical implications of the research for TBLT. According to Skehan, the results of these studies show that task conditions or task characteristics, such as (a) “overly ambitious” (Skehan, p. 246) learner planning (after which concepts or forms cannot be accessed during the actual task), (b) unstructured tasks (in which the speaker has no footholds to help maintain parallel processing), and (c) substantial processing pressure (in which the quantity or speed of the input overburdens the learner’s resources), may unduly tax a L2 speaker, making it difficult to return to parallel processing. The section in the latter part of the chapter discusses suggestions for tasks within lesson plans and the research that informs task sequencing.

This volume, on the whole, presents a focused set of exceptionally well-designed studies that investigate task design variables and their major processing benefits for L2 speakers. A major contribution of this volume is Skehan’s proposed finer-grained definition for the construct of “planning,” which includes the traditional concept of planning, along with newer additions of readiness—task-internal properties, such as content familiarity and task. Moreover, the consistency of the CAF-lexis performance measures across the volume is a valuable model which, if adopted, could contribute to the validity and reliability of future studies. One area for improvement would be a fuller exploration of proficiency levels; the editor readily admits that this volume only contributes to our understanding of intermediate learners. In addition, the pedagogical implications are highly theoretical and would benefit from more concrete examples. The volume assumes prior knowledge of several important theoretical concepts, such as serial versus parallel processing, rendering it somewhat inaccessible for a nonexpert audience. Nevertheless, this research significantly contributes to a theoretical understanding of task design, its impact on performance measures, and the manner in which L2 speakers can overcome the limitations of their finite cognitive resources.