|Thesis abstract: |
Social media have a strong impact on the way users interact and share information. The literature makes a distinction between influencers and influence. The former are social media users with a broad audience. For example, influencers can have a high number of followers on Twitter, or a multitude of friends on Facebook, or a broad array of connections on LinkedIn. The term influence is instead used to refer to the social impact of the content shared by social media users. The majority of these studies has focused on the role of influencers. Our claim is that while the information shared by influencers has a broader reach, the content of messages plays a critical role and can be a determinant of the social influence of the message irrespective of the centrality of the message's author. According to this perspective, influence is the actual impact of messages, which depends not only on the structure of the network, but also on the ability of message content to raise attention. This thesis provides a conceptual framework and related software tools to assess influence. The assessment of influence is performed in two steps. First, an empirical analysis is conducted in order to verify the assumption that content can have an impact on influence. This analysis is performed on a per-post basis and by characterizing content in terms of sentiment, inclusion of multimedia and specificity. This focus at a post level is important to make a clear separation between influence and influencers and measure the impact of content without a bias from the content's author. Then, we make an effort to translate our post-level findings into guidelines to be adopted by authors to maximize their influence. This is performed in two steps. First, we describe an empirical analysis investigating the relationship between content and influence by approaching content measures at an author's level and, thus, searching for the rules that tie author-level behavioural variables and authors' influence. Second, we attempt the application of these rules in a practical case to create and promote a brand. To support both steps we have developed and continuously improved a software suite that supports assessment.