This is most likely because the vast majority of the information the model absorbed during training was in Chinese. As a native Mandarin speaker, I frequently need to convert the prompt into English and output it in English in order to avoid that the model falls back into Chinese reasoning logic.

PS: Switching the thinking process from Chinese to English can also significantly circumvent certain self-censorship mechanisms built into the model.

Is the quality of the thinking better or it's just shorter since Mandarin is more compact?