UC Davis

Social media have become an essential part of day-to-day communication, adding to the spaces where citizens can gain information, participate in politics, mobilize actions, and influence over political agenda. The literature on agenda setting has long debated the direction of agenda setting dynamics, attempting to resolve the question of who influences whom. Although several studies examined inter-media agenda setting effects between social media and traditional news media, existing literature generates mixed results mainly because scholars paid little attention to the user dynamics in social media and their role as an agenda setter. In contrast with most existing research on inter-media agenda setting, the current study attempted to disentangle different Twitter users to understand how social media influence the news media agenda and how political and media elites and citizens interact in the decentralized social media sphere during a heightened political period when both journalists and citizens have access to information sources. A total of 247,600 Twitter messages on 3 different issues were examined, revealing that Twitter generally had agenda setting effects on news media. When the connectivity was considered, however, only the high-influence group by in-degree on Twitter shaped the media agenda. In other words, accounts with the most followers are likely to control the information flow between news media and Twitter. Media organizations predominantly were in the high-influence group and approximately 10% of the citizens belonged to the high-influence group. While the results demonstrated that social media play a critical role in setting the agenda, traditional media are yet highly influential within the Twitter network. The current study also found that citizens participate in the agenda setting process by producing a high volume of tweets on social media and effectively distributing them through their networks. Citizens’ efficacy is in its aggregate effect, which enables citizens to compete with traditional media’s singular agenda setting influence. Limitations and implications of the study were discussed.