The new kid looks shy on day one. By week three, you might find out they were just scanning the room.

Quiet in a new room is usually caution rather than personality. Somebody who has just arrived is working out who is safe, what the jokes are and which table is which, and from outside that careful scanning looks like shyness. You end up reading a strategy as a trait, then treating the person as the trait you invented.

Give anybody new three weeks before you decide who they are. If there is someone you already filed as shy, start one ordinary conversation this week. Pay attention to how different they look on the second read.