Introduction: Complementarity in Research Syntheses

This special issue of Applied Linguistics has two primary goals: The first is to examine the complementarity of two types of research synthesis—traditional narrative reviews and meta-analysis. The second is to accumulate information from primary studies on the role that instruction plays in second language learning. The topics addressed in the six articles come from the field of SLA: two were relatively broadly defined (language aptitude and L2 pronunciation instruction) and one more narrowly (Processing Instruction). In this introduction, I will focus on the complementarity of the methodology of these two ways of conducting research synthesis. Research synthesis serves as a cover term for any attempt to review the literature related to a specified topic, either narrowly or broadly defined. In the context of this special issue, complementarity refers to how two different approaches to conducting a research synthesis can in combination provide a more complete explanation of a phenomenon than either approach by itself. In other words, if we want to know what research has told us about the role of instruction in language learning, we will benefit most from a combination of narrative and meta-analytic syntheses.