Individual differences in social traits such as the affiliation motive are closely linked to the formation and maintenance of social relationships. Most previous research focused on long-term characteristics or momentary assessments of social relationships (e.g., social network size, relationship quality), whereas theoretical accounts have emphasized the temporal dynamics, that is, how social interactions unfold over time. The present studies examined how social interactions unfold within days as well as between days, taking personality traits and situational affordances into account. In two multimethod studies (Study 1 :