Others have mentioned that DeepSeek R1 also noticed this “problem”. I believe there are two things going on here. One, the model is no longer being trained to

Others have mentioned that DeepSeek R1 also noticed this “problem”. I believe there are two things going on here. One, the model is no longer being trained to output likely tokens or tokens likely to satisfy pairwise preferences. So the model doesn’t care. You have to explicitly punish the model for language switching, which dilutes the reasoning reward. Two, I believe there has been some research on models representing similar ideas in multiple languages in similar areas. Sparse autoencoders have shown this. So if the translated text makes sense, I think this is why. If not, I have no idea.