a lot of research on the efficacy and cognitive effects of generative language models is just, uh, bad science https://www.404media.co/nature-retracts-paper-on-the-benefits-of-chatgpt-in-education/
from what we've seen (we try to dig into these things with our friends when we have time), that's true kind of regardless of whether the authors think they're making a statement for or against the things. lots of statistical sloppiness and conclusions that the methodology can't support
