Meta-analysis of the effectiveness of task-based interaction in form-focused instruction of adult learners in foreign and second language teaching

Research into the effectiveness of task-based interaction in acquisition of specific grammatical structures of the target language has been scarce and sometimes has presented conflicting findings. Task-based interaction engages learners in focused face-to-face oral-communication tasks that predispose them to repeated use of the target structure in meaningful contexts.;Previous meta-analyses have provided some evidence of effectiveness of task-based interaction in learners' morphosyntactic development (Keck, Iberri-Shea, Tracy-Ventura, & Wa-Mbaleka, 2006; Mackey & Goo, 2007). The present meta-analysis adopts a somewhat different perspective from one or both of the previous meta-analyses through the following features: exclusion of studies that focus only on effects of corrective feedback, inclusion of both published and unpublished studies to expand the search domain, imposing of more stringent criteria for oral-communication tasks, focusing on adult learners and face-to-face, rather than computer-mediated interaction, and so forth.;This meta-analysis synthesized the results of 15 primary studies. On average, learners who received task-based interaction treatments through completing focused oral-communication tasks with native or nonnative interlocutors performed better than learners who received no focused instruction in the target structure and somewhat better than learners who received other types of instruction such as traditional grammar instruction, input processing activities, and so forth. The effect sizes were medium and small, respectively. Both the learners who received task-based interaction and those who received other instruction showed large within-group gains, whereas the gains demonstrated by the learners who received no instruction in the targeted form were insignificant or small based on Cohen's 1977 classification. The effects of task-based instruction were durable.;The analysis of the characteristics of tasks, target structures, educational settings, and so forth as moderator variables has identified statistically significant differences for some of these factors. The analog to the analysis of variance identified the complexity of the target structure, the nature of participant assignment to groups (nonrandom vs. random), and the difference between long-delay and short-delay posttests as factors that can account for variability in effect sizes. The meta-analytic findings expanded the scope of understanding of the effects of task-based interaction and were instrumental in formulating suggestions for future research in the domain.