In an empirical study from 2006, Shen et al.  combined two important concepts - social presence and social identity - in order to investigate their effect on community participation. The structural model revealed that social presence is a decisive factor in creating social identity and that the influence of social presence and social identity on participation is bigger than the fulfillment of information needs (one of the primary reasons why people join a community).
1. Social presence theory , In “The social psychology of telecommunications” (1976), Short, Williams, and Christie analyzed the effect of telecommunications media on communication. They conceptualized social presence as the degree of salience between two communicators using a communication medium. Social presence varies with the type of communication media and plays an important role in how people interact. Some media have a higher degree of social presence (e.g., video, audio) others do not (e.g., text) - depending upon the extent to which nonverbal and relational cues common to face-to-face communication are filtred out. A medium with a high degree of social presence is perceived as being sociable, warm, and personal, whereas a medium with a low degree of social presence is seen as impersonal.
Subsequently, several other important conceptualizations were developed: for example social presence as:
- the degree to which a person is perceived as a real person in mediated communication (Gunawardena, 1995);
- the ability of participants in a community of inquiry to project themselves socially and emotionally, as real people (i.e., their full personality), through the medium of communication being used (Garrison et al., 2000);
- the degree of feeling, perception, and reaction of being connected by computer-mediated communication to another intellectual entity through a text-based encounter (Tu & McIsaac, 2002);
- a student’s sense of being in and belonging in an online course and the ability to interact with other students and an instructor (Picciano, 2002).
These definitions appear to be on a continuum between the feeling that someone is perceived as being present that is, simply there or real at one end and the existence of an interpersonal emotional connection between communicators at the other. The differences in how researchers define social presence have significant consequences on how they conceptualize it.
2. Social identity theory Whereas personal identity is an individual's concept of personal attributes that are not shared with others, an individual's social identity is developed on the basis of group membership and consists of a shared definition of what attributes the group has and how it differs from others.
The basis of social identity is social categorization, the continuous interplay between how we see ourselves, how we see others and how we are seen by them. Assigning others to a certain social category not just tells us things about them but we find out things about ourselves.
To identify with any given group of people, whether it is an ethnic group or an online organization, we look for similarities between the group members and ourselves. By categorizing ourselves as members of a specific group and identifying ourselves with it, we tend to accept the group’s influence on us and we comply to its norms. On the other hand, as active group members we try to make our influence to be felt in the group as well. Group norms not only prescribe attitudes and perceptions, they also influence behaviour.
If a group member strongly believes in the group she or he may even work harder to reach the group's goals instead of loafing. Members with a strong identification with the group may become very influential in the group and exert some kind of leadership because other member see them as very prototypical. On the other hand, less prototypical members have less influence and risk to stay on the fringes of the community.
3. The influence of social presence and social identity on participation As mentioned in the introduction, Shen et al. combine both concepts and analyze their effect on participation in four different virtual communities of interest. The content of these communities is mainly contributed and only accessed by registered members. The basic functions are browsing, searching, synchronous and asynchronous discussion, multi-media exchanging and voting. Members can attach animated icons (e.g., facial expressions) to better express their feelings, as well as audio and video to enrich their exchanges.
For each individual, they collect the total number of postings, the number of different threads where the postings were made, and the number of new threads created. The participation measures were gathered for a period of two weeks and were scaled by the averages of the associated communities.
The other variables were measured with an online survey using validated scales.
- For social presence, they used a reflective measurement which consists of 7-point bipolar items such as social - unsocial, sensitive - insensitive and warm - cold.
- As for social identity, they adapted the “organizational identity” instrument which consists of reflective items rated on a 7-point Likert scale, ranging from “strongly disagree” to “strongly agree”. A sample item is “when someone criticizes this forum, it feels like a personal insult”.
Social presence positively affects the social identity of community members: High social presence makes it more likely to build social relationships among members due to its capability to reduce discomfort, increase predictability and raise the level of affection toward others, thus increasing the possibility to develop attachment to the virtual community.
Social presence directly influences virtual community participation: According to Shen et al. some individual factors may mediate the effects of social presence on community participation, e.g., extrinsic and intrinsic motivation or satisfaction and trust. Furthermore, social presence may exert a direct influence on community participation - a strong sense of social presence makes a virtual community more similar to a real one, the salient social stimuli presented in the virtual community may activate the direct access processing of existing goals or trigger an automatic perceptual interpretation.
Social identity has a positive influence on virtual community participation: In order to maintain a positive self-defining relationship with other virtual community members, he or she will be motivated to engage in behaviors as the other members expected. For a virtual community, a large part of such behaviors is to actively participate in the social interaction and contribute to the community.
4. Managing an Online Community of InterestSocial classification as a prerequisite for social identification can be achieved quite easily in face-to-face communities. A scarf with the logo of a football team is sufficient. In virtual communities much depends on the already more active members. Their communication behaviour and the expressiveness of their profiles shape the perception of the level of social presence in the community and they are the basis for the decision of others to participate.
Interestingly, the influence of information fulfillment on participation is relatively low, even though information seeking is one of the primary reasons why people join a community. But: information fulfillment has a high impact on how social presence is perceived. Unfortunately, this point was not discussed any further in the study. My guess is that the perception of other community members as socially present increases with their willingness to provide information readily. Presumably, it is not even necessary that the information can be used immediately, it is more important that the individual member gets the impression that - if needed - it would get help quickly.
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 Code, J. R., & Zaparyniuk, N. E. (2009). Social Identities, Group Formation, and the Analysis of Online Communities. Handbook of research on social software and developing community ontologies. Google Scholar