Social trust and political participation are crucial indicators for examining the operation of a democracy. According to the traditional argument, social networks, including personal contact and group participation, are the main sources encouraging social trust and political participation. However, the accumulation of social trust and political participation might become more difficult along with the decrease in social networks in a changing society. Can the Internet become a new source for social trust and political participation?

This study investigates how ideological extremism is portrayed in online and offline communications by using the case of South Korea. We evaluate whether any forms of ideological biases are observed among Twitter users in Korea. We also examine how users are ideologically distinguished from one another in terms of their online political behavior. While most of the existing literature has relied heavily on survey data, we address these questions by means of both survey data analysis and Twitter data analysis using 13,500 tweets during the 2012 Korean presidential election. We find that 1.