Joining an academic social event means you have to interact with other people and internationals, get to know them better, and share academic insights as the direction of conversation permits. And I noticed that people with the same interests could also share the same energy towards certain activities, such as socialization.
While others can still stretch their energy levels further and continue with the socialization, some could appear to have exhausted their reserves and settled with courteous nods and smiles rather than chime in the discussion.
Give them a momentary isolation and maybe sleep, and you’ll find them ready to mingle again.