I try to determine if any students are prone to non-participation because they feel bullied or because other students might make fun of them. I actually had an adult student who was very social with classmates and seemed to be an extrovert, but when asked to provide a verbal report to the class he practically fainted! This was a wake up call for me - I never would have believed that this student would become so stressed to present in front of other students! I thought he was joking! Many students aren't fond of speaking in front of others - I try to encourage this type of participation because you never know when a job interview will be in a group setting.