High proficiency learners showed a larger N100 effect to open-class content words compared to closed-class function words, while low proficiency learners did not show a significant N100 difference between open- and closed-class words.
— ERPs Recorded During Early Second Language Exposure Predict Syntactic Learning
- feels like a dangerous conclusion given how "low down" this neuro measurement stuff is, but interesting
- also I'm not sure they're making a point of the causality direction here