This book addresses the topic of cognitive task complexity as it has been investigated in second language (L2) task-based research. This interest is premised on the notion that communication tasks may differ systematically in the types and amounts of cognitive complexity they present to L2 learners, and these differences may have predictable effects on L2 performance, learning, and other outcomes. Adopting a research synthetic approach, the authors pursued the first ever comprehensive review of experimental and quasi-experimental studies, published over the first 30 years of relevant research, that drew comparisons between tasks designed to differ in levels and types of cognitive complexity. Findings from included studies (N = 296) illuminated critical patterns and gaps in the tasks, cognitive complexity operationalizations, outcome measures, and moderating variables investigated. Meta-analytic comparisons of the most replicated variables identified substantial beneficial as well as detrimental effects between a few task designs and certain measures of performance, uncovering heretofore unknown patterns of cause and effect. The book concludes with a detailed consideration of what is now known about L2 cognitive task complexity as well as the ways in which research should be improved, providing an essential interpretive benchmark and a foundation for future investigations.

This book addresses the topic of cognitive task complexity as it has been investigated in second language (L2) task-based research. This interest is premised on the notion that communication tasks may differ systematically in the types and amounts of cognitive complexity they present to L2 learners, and these differences may have predictable effects on L2 performance, learning, and other outcomes. Adopting a research synthetic approach, the authors pursued the first ever comprehensive review of experimental and quasi-experimental studies, published over the first 30 years of relevant research, that drew comparisons between tasks designed to differ in levels and types of cognitive complexity. Findings from included studies (N = 296) illuminated critical patterns and gaps in the tasks, cognitive complexity operationalizations, outcome measures, and moderating variables investigated. Meta-analytic comparisons of the most replicated variables identified substantial beneficial as well as detrimental effects between a few task designs and certain measures of performance, uncovering heretofore unknown patterns of cause and effect. The book concludes with a detailed consideration of what is now known about L2 cognitive task complexity as well as the ways in which research should be improved, providing an essential interpretive benchmark and a foundation for future investigations.