A Meta-Analysis and Meta-Regression of Incidental Second Language Word Learning from Spoken Input

We meta-analysed the effectiveness of incidental second language (L2) word learning from spoken input. Our sample contained 105 effect sizes from 32 primary studies employing meaning-focused word learning activities, with altogether 1,964 healthy participants. The random-effects meta-analysis yielded an average effect size of g = 1.05, reflecting generally large vocabulary gains from spoken input in meaning-focused tasks. In addition, a meta-regression with three substantive and two methodological predictors revealed that adult learners outperform children in terms of word learning, and that interactive learning tasks are more efficient than non-interactive ones. Furthermore, learning scores are higher when measured with recognition than with recall tests. Methodologically, the use of a no-input control group seems to protect against an overestimation of learning effects, as was visible in smaller effect sizes. Finally, whether or not a pre-post design was used did not influence effect sizes. All data, and the analysis script, are publicly available.