How effective is second language incidental vocabulary learning? A meta-analysis

Incidental learning may commonly be perceived to be learning without intention. This may be owing in part to the fact that incidental learning is frequently contrasted with intentional learning (e.g., Hulstijn, Reference Hulstijn and Robinson2001; Laufer, Reference Laufer2003; Webb & Nation, Reference Webb and Nation2017). Defining incidental learning as learning without intention in research is problematic, however, because intention to learn is likely to vary among learners as well as within an individual from moment to moment (Webb, Reference Webb and Webb2020). For example, during meaning-focused learning our attention may be oriented solely towards comprehension or move between understanding and learning unfamiliar language features when they are of interest or necessary for comprehension. Therefore, in research, incidental learning is commonly defined as either: (a) learning as a byproduct of a meaning-focused task (e.g., Chen & Truscott, Reference Chen and Truscott2010; Ellis, Reference Ellis1999), or (b) learning without knowledge of a forthcoming test (e.g., Hulstijn, Reference Hulstijn and Robinson2001).