Introduction

In this chapter I describe a theoretical rationale for and, where possible, empirical research into criteria to be adopted when progressively increasing the cognitive demands of second language (L2) tasks. These criteria, I argue, provide a basis for decisions about sequencing tasks in a task-based syllabus as well as a framework for studying the effects of increasing L2 task complexity on production, comprehension and learning. I distinguish task complexity (the task dependent and proactively manipulable cognitive demands of tasks) from task difficulty (dependent on learner factors such as aptitude, confidence, motivation, etc.) and task conditions (the interactive demands of tasks), arguing that these influences on task performance and learning are different in kind, and have not been sufficiently distinguished in previous approaches to conceptualizing the options in, and consequences of, sequencing tasks from the syllabus designer's perspective. My focus in this chapter is on the issue of task complexity, which I argue should be the sole basis of prospective sequencing decisions since most learner factors implicated in decisions about task difficulty can only be diagnosed in situ and in process, so cannot be anticipated in advance of implementation of a syllabus and therefore can be of no use to the prospective materials and syllabus designer. Those learner factors which can be diagnosed in advance of syllabus implementation (e.g., aptitude and cognitive style) have not to date been shown to have stable effects on task performance at the different levels of complexity proposed here.