[Air-L] How long is a pause that is considered as a sign of break-down in students' conversations in virtual world classes ?

Dear all, Apologize for cross-posting! I am looking for literature that talks about pauses in students’ conversations especially in the virtual world classes. Does anybody know such kind of literature, and how long is a pause that is considered to be a break-down, 4 seconds, or something else? Thank you so much! Best, Airong WANG Doctoral Student in English Didactics Mid Sweden University Sweden