In the five-factor model of personality, the dimension that measures whether a person is quiet, reserved, passive, and a loner or whether a person is talkative, active, affectionate, and a joiner is called?

Extroversion.

Explanation:

Extroversion is a personality model that can be characterized as ease for sociability, expression of emotions, conversation and excitability.

Extrovert individuals often have a high sense of energy and assertiveness in social life, are excited, and less reserved people who are motivated to establish direct and easy contact with people and participate in social situations naturally, energetically and with excitement.