Wright State University CORE Scholar The Ohio Center of Excellence in Knowledge- Kno.e.sis Publications Enabled Computing (Kno.e.sis) 2012 On the Role of Social Identity and Cohesion in Characterizing Online Social Communities Hemant Purohit Wright State University - Main Campus Yiye Ruan David Fuhry Srinivasan Parthasarathy Amit P. Sheth Wright State University - Main Campus, [email protected] Follow this and additional works at: https://corescholar.libraries.wright.edu/knoesis Part of the Bioinformatics Commons, Communication Technology and New Media Commons, Databases and Information Systems Commons, OS and Networks Commons, and the Science and Technology Studies Commons Repository Citation Purohit, H., Ruan, Y., Fuhry, D., Parthasarathy, S., & Sheth, A. P. (2012). On the Role of Social Identity and Cohesion in Characterizing Online Social Communities. https://corescholar.libraries.wright.edu/knoesis/619 This Report is brought to you for free and open access by the The Ohio Center of Excellence in Knowledge-Enabled Computing (Kno.e.sis) at CORE Scholar. It has been accepted for inclusion in Kno.e.sis Publications by an authorized administrator of CORE Scholar. For more information, please contact [email protected]. On the Role of Social Identity and Cohesion in Characterizing Online Social Communities ∗ ∗ H. Purohit Y. Ruan , D. Fuhry, y z A. Sheth S. Parthasarathy Kno.e.sis Center Dept. of Comp. Sci. & Eng. Wright State University, USA Ohio State University, USA ABSTRACT Keywords Two prevailing theories for explaining social group or com- Community sustainability, Social cohesion, Social identity, munity structure are cohesion and identity. The social cohe- Activity-Influence-Diffusion (AID) identity sion approach posits that social groups arise out of an aggre- gation of individuals that have mutual interpersonal attrac- 1. INTRODUCTION tion as they share common characteristics. These character- Online social networks allow Internet users all over the globe istics can range from common interests to kinship ties and to share information, exchange thoughts, and work collab- from social values to ethnic backgrounds. In contrast, the oratively. All of those activities involve more than a single social identity approach posits that an individual is likely to user, consequently, making questions on dynamics of online join a group based on an intrinsic self-evaluation at a cog- social groups worthy of study. Especially, what factors in- nitive or perceptual level. In other words group members fluence an online social group's formation, its growth, and typically share an awareness of a common category mem- its sustainability? bership. Prevalence of online social networks in the last decade has In this work we seek to understand the role of these two enabled computer scientists to answer questions of group contrasting theories in explaining the behavior and stabil- sustainability and evaluate their solutions with large-scale ity of social communities in Twitter. A specific focal point experiments [2, 25, 7, 20]. Despite the research progress of our work is to understand the role of these theories in made to date on community structure and group dynamics, disparate contexts ranging from disaster response to socio- there are at least three open questions to be answered: political activism. We extract social identity and social co- hesion features-of-interest for large scale datasets of five real- world events and examine the effectiveness of such features • What is the relation between the findings of past re- in capturing behavioral characteristics and the stability of search on group sustainability using structural charac- groups. We also propose a novel measure of social group teristics and socio-psychological theories of group dy- sustainability based on the divergence in group discussion. namics? Our main findings are: 1) Sharing of social identities (espe- • How can existing theories on social group behavior cially physical location) among group members has a posi- guide us in identifying relevant features to model on- tive impact on group sustainability, 2) Structural cohesion line social group sustainability? (represented by high group density and low average short- est path length) is a strong indicator of group sustainability, • Online social group's sustainability not only depends and 3) Event characteristics play a role in shaping group on group size, but also on the divergence of its dis- sustainability, as social groups in transient events behave cussion content. How do we quantify this notion and differently from groups in events that last longer. what are the social group characteristics pertaining to it? ∗Joint First Authors y Email: fhemant,[email protected] Over decades of study, social psychologists have proposed zEmail: fruan,fuhry,[email protected] diverse explanations about the dynamics of a social group and its behavior. Two main frameworks among others are the social identity approach and social cohesion approach. Social Identity Approach: Social identity approach in- cludes two closely related theories: social identity theory [26] and self-categorization theory [28]. In [26], Tajfel defines the concept of social identity as \the individual's knowledge that he belongs to certain social groups together with some emo- tional and value significance to him of this group member- ship". Therefore, group membership is the result of \shared self-identification" rather than \cohesive interpersonal re- We represent social cohesion by structural features of the lationship", and such shared identity leads to cohesiveness group's static friendship/follower network. These features and uniformity, among other features [27]. One commonly- incorporate guidance of the two theoretical approaches to cited evidence for social identity approach is team sports, capture users' social behavior from both physical and online where teammates are representing the same organization (a world, and therefore, help us better understand the role of school, a club, or a country) and they are well aware to sus- these theories in group behavior. tain the reputation of their associated identity. We refer to this approach as \(social) identity" in the following sections. Furthermore, we propose a novel measure of social group sustainability, topic divergence, based on the divergence of Social Cohesion Approach: Social cohesion approach each individual member's discussion from the group's main views social groups from a different perspective. Its hy- line of discussion. Our two main hypotheses regarding group pothesis is that the necessary and sufficient condition for sustainability are: individuals to work as a group is the cohesive social re- lationships between individuals. While social relation- ships exist for different reasons (e.g., kinship ties, or similar Hypothesis 1.1. The more structurally cohesive a social social values), we focus on a group's structural cohesion, group is, the lower topic divergence the group has. the collective result of those social relationships. Here, we adopt the definition by Lott and Lott [11] that interprets co- hesiveness as mutual attraction between individuals, which Hypothesis 1.2. The more similar in identities a social is slightly different from that used in [5]. In accordance with group's members are, the lower topic divergence the group this definition, the positive correlation between group cohe- has. sion and group's performance has been reported on various types of groups [14, 3]. We will denote this structural cohe- sion approach as \(social) cohesion" from now on. From experiments on five real-world datasets, we observe that 1) Sharing of social identities (especially regional iden- As noted above, social identity and social cohesion attribute tity) among group members has a positive impact on group group formation and sustainability to different factors. Iden- sustainability, 2) Structural cohesion (represented by high tity approach posits that a social group is the result of mem- group density and low average shortest path length) is a bers' collective awareness of some type of category member- strong indicator of group sustainability, 3) At least on Twit- ship. In contrast, the conjecture of cohesion approach is ter, features based on the assumption of uni-directional in- that mutual attractions among individual pairs make them terpersonal attraction have statistically equal explanatory a group, implying that structural cohesion of member con- power as features based on the assumption of mutual at- nections determines the sustainability of a social group. traction, and 4) Event characteristics affect online social group sustainability. Notably, during transient events like To study the sustainability of social groups, a multitude disasters, structurally cohesive social groups are less likely of predictive models have been established to answer the to exist, therefore, social identity of users can be utilized to question \How many users will a social group have in the create stable groups for help in the relief efforts. future?". While group size and growth rate are intuitive measures, using them alone overlooks other important as- 2. RELATED WORK pects in defining a social group's sustainability. One draw- Social network analysis has received greater attention in back, for example, is they do not capture the stability of the last decade as online social networks have been evolv- group membership. Imagine that a group had five mem- ing faster than ever. Most of the studies took the path bers previously,