MORE THAN A MEGAPHONE: THE IMPACT OF SOCIAL MEDIA ON POLITICAL LEADERS' FOREIGN AFFAIRS COMMUNICATION IN THE U.S. AND TAIWAN

This three-essay dissertation explores the impact of social media on international security, especially whether social media gives political leaders leverage to shape public opinion about foreign policy. The Democratic Peace Theory suggests public opinion is one of the main constraining factors of political leaders’ aggressive foreign policies. If social media empowers political leaders to shape public opinion, then social media may reduce political leaders’ potential costs of seeking a risky foreign policy. However, existing literature in International Relations has limited discussion on this urgent topic; this is the research gap that my dissertation bridged. To explore the influence of social media on political leaders’ control of public opinion about foreign policy, I used real-world social media data and conducted cross-national survey experiments in the U.S. and Taiwan. I find that social media’s settings and environment, especially those visible aggregate peer cues, give political leaders leverage to shape public opinion. I used the elaboration likelihood model of persuasion and the social contagion model to explain why people may be affected by seemingly peripheral information in social media posts. My research also finds that people were more willing to engage with a leader’s social media posts on foreign affairs with a positive tone than those with a negative tone—this finding is consistent with what the language expectancy theory has suggested. Besides, this research finds an organic nature of elite politicians’ social media communication—the persuasive effect of elite politicians’ social media posts can grow as the number of Likes increases. This research has several important contributions and implications. First, as far as the author knows, it is the first research in International Relations exploring how social media can provide leverage for political leaders to shape public opinion about foreign affairs. Second, it contributes to the discussion of the validity of the Democratic Peace Theory in the social media era—the findings suggest that democratic constraints may be weakened by social media. Finally, it provides a comparative insight into public opinion about foreign affairs by showing how malleable public opinion about foreign affairs can be in the West—as well as the East.