A familiar stranger is an individual who is recognized from regular activities, but with whom one does not interact. First identified by Stanley Milgram in the 1972 paper The Familiar Stranger: An Aspect of Urban Anonymity, it has become an increasingly popular concept in research about social networks.
Somebody whom one observes frequently but with whom one does not otherwise communicate is an example of a familiar stranger; it is a visual and nonverbal relationship in which both parties maintain anonymity. These are people who aren't totally unknown to us but aren't acquaintances either. If such individuals meet in an unfamiliar setting, for example while travelling, they are more likely to introduce themselves than would be perfect strangers, as they have a background of shared experiences.
The Proceedings of the National Academy of Sciences of the United States of America (PNAS) published an article which analyzed the phenomenon of familiar strangers and noted the social implication of metropolitan patterns due to daily encounters. It notes that familiar strangers are a result of an individual's encounter capability which is rooted in daily, behavioral regularity. Findings suggested that these repeated encounters established a strong connection over time, resulting in a large and imperceptible small world contact network across the metropolitan area. Furthermore, deriving the specific encounter pattern and identifying this large-scale contact network play a large role in understanding these social acquaintances and collective human behaviors.
The 1972 paper was based on two independent research projects conducted in 1971, one at City University of New York and the other at a train station. Psychology Today published a second paper on the subject by Milgram, Frozen World of the Familiar Stranger, in 1974.
In 1972 Stanley Milgram and some of his students conducted an experiment to test the phenomenon of familiar strangers. His students took photographs of about 30 people waiting at a subway platform and developed them. They returned to the same platform a week later around the same time and distributed the photos, asking recipients to label anyone they either recognized or to whom they had spoken. Eighty nine percent of the people recognized at least one of the individuals shown in the photos. Circumstances surrounding familiar strangers have slightly changed since the 1970s.
In 2004, researchers at the Berkeley Intel Research Laboratory decided to revisit Milgram's study. Their goal was to observe changes in familiar stranger relationships since the initial study; they wanted to study how familiarity can affect an individual's recognition of their surroundings. Society's way of communication has changed since 1972 and due to that change today nearly everyone carries a cellphone around with them; the question is how much has that impacted the familiar strangers relationship. This study took place at Constitution Plaza located in downtown Berkeley. Constitution Plaza in the shape of a rectangle with one end being Berkeley's primary underground light-rail station and the other the central bus transfer point. There is a continuous flow of people walking in and out of the plaza, however there are individuals who stop to make a call, eat, smoke or rest on the benches. Based on what they were seeing they separated their test subjects into potential familiar strangers groups; one being workers and students who stop to rest and the others commuters waiting for transportation. They took photographs of the groups during their busiest hours; noon for the workers and students and 5pm for commuters. A week later they returned at the same times and distributed each group the same photos and asked them to identify anyone, they also handed out a questionnaire. The questionnaire focused on questions such as, what affiliations do they have to the plaza and their general stance on public areas. The participants were offered a chance to win a hundred dollar gift certificate to their local bookstores if they completed the questionnaire. As a results of their study they found less familiarity than Milgram's study. In Milgram's study eighty nine percent of the participants recognized some of the individuals in the photos and for Berkeley seventy eight percent recognized someone.
Georg Simmel wrote an article discussing the stranger in society. He states that the phenomenon of the “stranger” is the unity of liberation and the fixation of space; physical conditions are the condition and the symbol for human relationships. He wanted to talk about the stranger form the perspective of them being someone who comes today and stays tomorrow rather than a person who comes today and is gone tomorrow. In the organization of the human relations Simmel says that the unison of nearness and remoteness is an important factor. It all comes down to distance, someone who is close to you is really far way and someone who is far from you is actually close by. Simmel feels that the stranger is close to us to an extent; we share a connection with each other. Our human nature brings us together so to say, it holds similar national social and occupational features.
Social identity theory
Social identity theory is a social psychological phenomenon that discusses the individual’s self-perception in group interactions. This phenomenon tackles topics, such as, ethnocentrism, stereotyping, prejudice, group cohesiveness, conformity, crowd behavior, etc. The idea is that two people in the same place and time can be part of a group as long as they share a social identity. An example would be, two Americans named Allison and Javi are in Paris; they feel act American, therefore they belong to the "American" group not "Allison and Javi". In a social identity model it is stated that if an individual is aggressive and angry it is a result of the group they are apart of, all group share attributes. Self-enhancement and self-esteem are human motives in creating a social identity.
Conformity is a factor in the group being formed, people self-categorize and believe that each group is drastically different from the other. Therefore, familiar strangers exist in all these groups. Despite not having interacted, they share attributes with each other, as a result these groups separated by attributes contains familiar strangers. Moreover, the expansion of the social network world has made search ability easy; you can find anyone with just the click of a button. Social identity theory assists with search ability with social networking.
Social networks are ubiquitous factors in society. People are unaware of all the familiar strangers they have in their virtual life. Connections that are formed between people online can vary between a few individuals to a mass quantity and in most cases they are all unknown to each other. A social network is a world all in itself that is immensely intricate and contains various sets of human relations. Human interaction through social media occurs in numerous ways such as blogs, online friendship networks, wikis, instagram, twitter, yik yak, social media websites and tags on any given website. As the technological age continues to grow more familiar strangers will be found on social networks.
Blogosphere is a more commonly used blogging website that allows bloggers to post in single or community blog sites. Most blogs are linked to smaller blogger groups however each group is separate to one another; familiar strangers can share the same patterns and have similar blogging activities as these other groups. Familiar strangers are separated into three levels, the community level, networking site level and blogosphere level. In the community level its two bloggers in the same community post on a similar topic, however they are not involved in each other’s social network. Networking site level is when bloggers in two different communities post and communicate on the same blog despite not being in each other’s social network. Familiar strangers in the Blogosphere level are bloggers in similar communities that are on different social networking sites. 
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- Simmel Georg. "The Stranger". The Sociology of Georg Simmel. By Kurt Wolff, New York: Free Press, 1950, pp 402 - 408
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- Agarwal, Nitin, et al. "A Social Identity Approach to Identify Familiar Strangers in a Social Network." ICWSM. 2009 May 17.
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- Eric Paulos and Elizabeth Goodman. "Familiar Stranger Project". University of California, Berkeley. Retrieved 2008-10-05.
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