Recent years have seen an increase in the use of Interest-based social networks such as Pinterest,
ChimeIn and Twitter. While classic online social networks like Facebook or LinkedIn offer a social utility that deepens social connectivity with our existing social graphs, in interest-based social networks people form social ties based on their interest with people that they don’t already know. The information diffusion in such interest-based social networks has only been marginally researched. Twitter offers a promising natural laboratory to study such networks,because the social ties, interactions and exchanged information in this network are public. This offers the possibility to study the influence of social ties and thematic interest on information
diffusion in such interest-based communities. In this work, the theory of social capital was employed to study this subject. The theory of social capital explains why individuals receive retweets in networks as a result of their social ties. The operationalization of the social capital concept for Twitter uses the publicly available data traces of Twitter users. Social ties express
the structural and relational dimension of social capital, whereas the interest of a user expresses this cognitive dimension. By studying the retweet traces in 166 Interest-based networks, this study finds that in Twitter the structural and cognitive dimension of social capital positively influence information diffusion. This influence has been studied on an individual and group level for bonding and bridging social capital resulting in four perspectives on the phenomenon. The study of the influence of individual bonding social capital on information diffusion shows that highly central individuals who share a group’s interests receive more retweets from members of their own interest group. Individuals that build up a high individual bridging social capital by positioning themselves structurally between interest groups and who express a high number of different interests, receive a high number of retweets from members of other interest
groups than their own. In the group bonding social capital perspective the work shows that the internal group structure in terms of clustering, density and short paths between the actors of the group positively influences the information exchange among group members. However, a high
reciprocity of social ties does not positively influence information exchange between group members. Interest groups that are located in the center of the Twitter ecosystem and whose members have a high number of diverse interests possess a high group bridging social capital. This helps them obtain many retweets from other groups. Studying the interdependencies between bonding and bridging social capital showed that when groups primarily build up
group bonding social capital, they decrease their chances of receiving retweets from other groups. However, groups that build a high bridging social capital do not harm their internal information exchange. At the individual level, the study showed that individuals with a high bonding social capital receive less retweets from people outside the group and that individuals with a high bridging social capital receive less retweets from people within the group (i.e.,
group members).
