A person who seems reserved may be deciding whether the room is safe enough to relax in.

Quietness gets read as coldness, disapproval or arrogance far too quickly. Often a person is simply reading the room, working out who is safe, what the rules are, whether their kind of humor lands, whether the last group like this went badly. That assessment takes time and happens silently. Reserve is usually a question rather than a verdict.

Give a quiet person something easy and low-stakes to answer, then let a pause exist. Resist filling their silence, and notice who arrives twenty minutes later.