Training courses in China (example)

"Due to my working focus on the computer sector, I also hold computer training courses in China. I always ask the participants repeatedly during the courses whether they have understood everything, so that I can carry on with the material. They all answer ‘yes’. However, when I then ask a specific question, no one can answer it. I now assume that many participants have not understood the material, although they nod in reply to my question as to whether they have understood. This behavior on the part of the Chinese always surprises me. Why don’t the Chinese students admit that they haven’t understood something?"
Thomas 1996, translated and cited by Rost-Roth, M. (2007). Intercultural training. In: H. Kotthoff and H. Spencer-Oatey (eds.) Handbook of Intercultural Communication. Berlin: Mouton de Gruyter, pp. 491–517.