Replication data: Puncturing the Knowledge Illusion Does Not Reduce Policy and Political Extremism

Understanding the formation of and changes in citizens' extreme views on complex public policies is an important task in our increasingly polarized world. Behavioral sciences offer insights on cognitive processes and potential mechanisms to mitigate extremity in policy preferences and develop more realistic models that underprint political attitudes. About a decade ago, Fernbach et al. (2013) offered a simple cognitive intervention to reduce political extremism: Confront people with their lack of procedural policy knowledge such that their overestimation of knowledge is shattered. We conducted three high-value replications and extensions to examine the applicability of Fernbach's proposed theory among a sample of 5,139 citizens in postconflict Hong Kong. Our results suggest the opposite: Positional extremity is higher when citizens articulate their understanding of policy. Our study, which is larger in scale, draws on different time periods and extended interventions and examines more controversial policy issues has epistemological and cognitive implications for future research on the political psychology of extremism.