THE ROLE OF “FAMILIAR STRANGERS.” “The researchers classified human relationships into four types: in-roles (who include colleagues, classmates, and others who we are acquainted with and see on a regular basis), friends (those who we are acquainted with, but do not see regularly), strangers (those who we are neither acquainted with nor see regularly), and familiar strangers (those who we see regularly but are not acquainted with). . . . They found that strangers made up the largest percentage of relationships, followed by familiar strangers. Both types of strangers greatly surpassed the percentage of social acquaintances, with in-roles being the third most common relationship type, followed by friends.”