Studies looking into second language development have shown that findings about a group of learners cannot be transferred to individual learners. In this study, we explored ways to meaningfully group individuals starting from the data and investigated whether this grouping can give extra information about learning trajectories that goes beyond the…

Meta-analytic studies of second language (L2) learning typically employ a classic approach to meta-analysis. Although the classic approach can clarify findings, a multivariate, multilevel meta-analysis (3M) approach increases transparency by accounting for (a) dependencies in the evidence presented by primary studies, (b) methodological…