[6]: 39 The boundaries of what people or groups are considered strangers varies according to circumstances and culture, and those in the fields of sociology and philosophy in a variety of broader contexts.
According to sociologist and philosopher Zygmunt Bauman, every society produces its own strangers, and the natures of "strangeness" is "eminently pliable [and] man-made".
A familiar stranger is an individual who is 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,[10] it has become an increasingly popular topic in research about social networks and technologically-mediated communication.
The term was coined by Karen L. Fingerman and further developed by Melinda Blau, who collaborated with the psychologist to explore and popularize the concept.
[5]: 29 With the conglomeration of populations into large cities, people now have a historically high propensity to "live among strangers".
[15]Infants will generally be receptive to strangers until after they achieve object permanence and begin forming attachments.
According to one estimate, "classic stranger abductions" accounted for only 0.014% of total missing children annually in the United States, or about 14 per 100,000.
[25][26] This has led to calls to de-emphasize stranger danger, as Nancy McBride of NCMEC told NBC News, "let's take stranger-danger and put it in a museum.
"[23] This was echoed by sociologist, and director of the Crimes Against Children Research Center, David Finkelhor, writing in The Washington Post: We'd do much better to teach them the signs of people (strangers or not) who are behaving badly: touching them inappropriately, being overly personal, trying to get them alone, acting drunk, provoking others or recklessly wielding weapons.
[27]: 408 Among environmental factors, physical uncomfortably, such as presence in a room that is hot and crowded, have been shown to increase negative attitudes toward strangers.
[28]: 177 Laboratory evidence has indicated that individuals are likely to behave less modestly when meeting face-to-face with strangers, when no friends or acquaintances were present.
This may be influenced by the temporary nature of their relationship, and the knowledge that the stranger themselves have no access to an individual's wider social circle.
[29] As one author put it, the phenomenon is ironically best described by the words of travel writer Paul Theroux, saying: The conversation, like many others I had with people on trains derived an easy candour from the shared journey, the comfort of the dining care, and the certain knowledge that neither of us would see each other again.
There is a concept in sociological literature of the "professional stranger", the person who intentionally maintains an intellectual distance from the community in order to observe and understand it.