As a concept of social interface theory, social interface is defined by Long (1989, 2001). In 2001 his revised definition was:
|“||"a social interface is a critical point of intersection between different lifeworlds, social fields or levels of social organization, where social discontinuities based upon discrepancies in values, interests, knowledges and power, are most likely to be located."||”|
In other words, interfaces are the areas in which social friction can be experienced and where diffusion of new technology is leading to structural discontinuities (which can be both positive or negative), the interface is where they will occur. Long continues to say that:
|“||" ... the concept implies face-to-face encounters between individuals or social units representing different interests and backed by different resources."||”|
As practical concept of social interface design, social interface is seen in the studies of human-computer interaction (in particular, its computer interface aspect). The basic thesis is that where a computer interface is more akin to another human, it can facilitate correct responses from users during human-to-computer interaction. Software that can provide such humanizing cues often does it by creating interface with human-like quality (such as giving recognizable gender to a software agent). Studies are often concerned with how should such agents (like the Microsoft Agent) be designed to make them more appealing (is having facial expressions efficient, should the agent be anthropomorphic, and so on). 
- For old 1989 definition, see Long, Norman, ed. 1989. Encounters at the Interface: a Perspective in Social Discontinuities in Rural Development, Wageningse Sociologische Studies 27. Wageningen: Wageningen Agricultural University. For new 2001 definition, see Print, p.243 in Norman Long, Development Sociology: Actor Perspectives, Routledge, 2001, ISBN 0-415-23535-9,
- Long, N. 1992. From paradigm lost to paradigm regained; the case of actor-oriented sociology of development. Pages 16-43 in N. Long and A. Long, editors. Battlefields of knowledge: the interlocking of theory and practice in social research and development. Routledge, New York, New York, USA.
- Arce, A., and N. Long. 1992. The dynamics of knowledge: interfaces between bureaucrats and peasants. Pages 211-245 in N. Long and A. Long, editors. Battlefields of knowledge: the interlocking of theory and practice in social research and development. Routledge, London, UK.
- Douthwaite, B., N. C. de Haan, V. Manyong, and D. Keatinge. 2001. Blending "hard" and "soft" science: the "follow-the-technology" approach to catalyzing and evaluating technology change. Conservation Ecology 5(2): 13. [online] URL: http://www.consecol.org/vol5/iss2/art13/
- Tourangeau R.; Couper M.P.; Steiger D.M., Humanizing self-administered surveys: experiments on social presence in web and IVR surveys, Computers in Human Behavior, Volume 19, Number 1, January 2003 , pp. 1-24(24), 
- Michael A. Cusumano, Richard W. Selby, Microsoft Secrets: How the World's Most Powerful Software Company Creates Technology, Shakes Markets and Manages People. Simon and Schuster, 1998, ISBN 0-684-85531-3, Google Print, p.178