Herb's lab had a visiting scientist for many months. However, their spoken English was poor. I think it this situation, Herb should have insisted, as part of the arrangement, that the person also take intensive conversational English courses while here. The person was very bright and had great ideas, but their limited English hindered collaboration and even just regular lab meetings sometimes. It seems like a missed opportunity for Herb, the visiting scientist, and the lab.
*This person came with funding from their home country, so it was a situation with low financial investment for Herb.