A familiar stranger is a stranger who is nonetheless recognized by another from regularly sharing a common physical space such as a street or bus stop, but with whom one does not interact. First identified by Stanley Milgram in the 1972 paper The Familiar Stranger: An Aspect of Urban Anonymity,[1] it has become an increasingly popular topic in research about social networks and technologically mediated communication.
Milgram specified that for a person to become a familiar stranger, they must be observed repeatedly over a certain amount of time but never interact with each other. Familiar strangers are more than complete strangers but do not rise to the level of an acquaintance. But if such individuals meet in a different setting, for example a different city or off the street, they are more likely to introduce themselves than would be perfect strangers, as they have a background of shared experiences.
Early experiments on familiar strangers by Milgram involved researchers visiting train stations and university campuses to survey people about who they recognized. They found that 89.5% of people knew at least one familiar stranger.[1] These experiments have been repeated at least once with similar results.[2] One aspect of research on familiar strangers that hampered research was lack of available data about these relationships. With the advent of widespread social media and urban analytics, researchers have used new datasets to understand familiar strangers, including public-transportation usage[3] and web blog networks.[4]