Operationalizing a theory of task-based learning requires a specification of the features of task design that can be manipulated and sequenced during the time-course of instructional language learning programs to promote both performance success (measured in terms of the degree to which tasks can be accomplished in the second language), as well as progress in second language development (measured in terms of progress learners make in the increasing accuracy, complexity and fluency of their language production and comprehension). This chapter describes a theoretically motivated framework for pedagogic task design and sequencing which is currently being implemented and researched to assess the extent to which it facilitates target task success and language development for learners performing sequences of pedagogic tasks following the design criteria it proposes.

This chapter presents theory and research that examine tasks in relation to the cognitive processes involved in L2 production in what we have called the Psycholinguistic Perspective. The chapter explores and critiques two models of task-based performance - the Limited Attention Capacity Hypothesis and the Cognition Hypothesis - which have informed a large body of research. The chapter reviews studies that investigated how task design and implementation variables impact on the complexity, accuracy, lexis and fluency of the learners’ production. The chapter also considers a key issue for TBLT, namely the relationship between task performance and L2 acquisition.

Individual learner factors play an important role in how a task is performed. This requires a perspective that draws on the theory and research that addresses the psychology of the learner – what we call the psychological perspective on TBLT. Chapter 5 surveys the large body of research on the role of cognitive aptitudes (including working memory) in mediating the effects of different instructional tasks on language performance and acquisition. The chapter will also discuss the influence of affective factors such as motivation and language anxiety on task performance and outcome. A key focus of this chapter is how these psychological variables mediate the performance of a task and the learning that results.