While speaking with a client of mine from Thailand recently, I raised my eyebrows at one point because I hadn't heard what she had said. Puzzlingly, shejust nodded. Then I said, "I'm sorry, I didn't understand the question." After she repeated the question, she told me that she had thought I was answering "yes." It led to some interesting dialogue about facial expression, cultural body language and meaning, and led me to several interesting articles regarding cultural gestures and norms. Here are a few that I found.
Body Language around the world