How could you visually determine, given a student in the class, if he or she is concentrating on the topic being taught in the classroom?
It is possible for an uninterested student to stay still and look focused during the class. Similarly, some students who seem to be fidgeting may actually be concentrating in the class lecture.
How do you differentiate from the two? Are there more features to consider than just attention towards the lecturer or the board? Are there any extensive studies done with respect to this problem?