The opening keynote at #VAR4LCR is by none other than the master of register variation, Doug Biber, on "Grammatical complexity in L2 writing development: Contrasting oral versus literate complexity across registers and
developmental levels", himself introduced by the doyenne of learner corpus research, Sylviane Granger. Doug showed us lots of heat maps illustrating bottom-up patterns of co-occurrences of complexity features in English L2 writing based on recent work by himself, Tove Larsson and Greg Hancock, e.g., https://doi.org/10.1515/cllt-2025-0017.